Neurology Flashcards

Question

What changes in the biceps, triceps, and brachioradialis reflexes are expected after damage to the anterior horn cells supplying the C6 nerve root?

Answer 1

The biceps reflex, which is regulated by fibers from C5 and C6, will be moderately diminished secondary to diminished lower motor neuron input. The triceps reflex is regulated primarily by C7 and should thus be unaffected by a C6 lesion. The brachioradialis reflex is primarily regulated by C6 and will thus be markedly diminished after a C6 lesion.

Answer 2

- The hallmark lesion for **craniopharyngioma** is a suprasellar, cystic, calcified mass. The differential diagnosis for a suprasellar mass includes optic gliomas, meningiomas, pituitary adenomas, and metastases. - Other causes of short stature can arise from endocrine disorders including Cushing syndrome, growth hormone deficiency, hypothyroidism, and gastrointestinal disorders including malabsorption syndromes such as celiac disease, lactase deficiency, or inflammatory bowel disease.

Answer 3

Craniopharyngiomas are rare tumors derived from the Rathke pouch. The Rathke pouch is an invagination of ectoderm lining the primitive mouth that develops into the adenohypophysis.

Answer 4

CT scan or MRI of the head can visualize the cystic calcified suprasellar mass characteristic of craniopharyngioma. Plain radiographs of the skull can detect advanced cases. Testing of the pituitary axis and optic pathways can determine if the tumor has affected these structures.

Answer 5

**Craniopharyngiomas** - Epidemiology: Craniopharyngiomas exhibit a bimodal distribution, with one peak among children and the second among patients 55–65 years of age. It is the third most common intracranial tumor in children. - Clinical manifestations: Craniopharyngiomas are slow-growing tumors with a highly variable clinical presentation. Symptoms occur because the tumor involves the pituitary gland or the optic chiasm. Patients may present with growth hormone deficiency, hypothyroidism, or central diabetes insipidus. Visual disturbances and headaches are common.

Answer 6

- This patient underwent surgery for hyperthyroidism. Damage to the recurrent laryngeal nerve may occur as the surgeon is ligating the inferior thyroid artery, which is adjacent to the nerve. - The recurrent laryngeal nerve is a branch of the vagus nerve (CN X). - The recurrent laryngeal nerve innervates all intrinsic muscles of the larynx except for the cricothyroid, which is innervated by the external laryngeal nerve (also a branch of CN X).

Answer 7

The left recurrent laryngeal nerve branches off the vagus nerve at the level of the aortic arch, wraps posteriorly around the aorta, and ascends superiorly to the larynx (Figure 10-8). The right recurrent laryngeal nerve branches off the vagus at the level of the right subclavian artery and vein and wraps around the artery to ascend posteriorly to the larynx. Because the left recurrent laryngeal nerve has a long course arising from the vagus in the superior mediastinum, it is prone to injury from abnormal structures, such as enlarged lymph nodes, aneurysm of the arch of the aorta, a retrosternal goiter, or a thymoma.

Answer 8

- Surgical technique focuses on preservation of the parathyroid glands, and hypoparathyroidism can occur after surgery. For this reason surgeons often remove the parathyroid gland and reimplant it elsewhere in the neck. - Left atrial enlargement (eg, from mitral regurgitation) and tumor in the apex of the right upper lobe of the lung can impinge on and injure the recurrent laryngeal nerve. Injury of the left recurrent laryngeal nerve may also result in compression by abnormal structures in the superior mediastinum, as described above.

Answer 9

Weakness of the quadriceps muscles and hip flexors (which are innervated by the femoral nerve) and lack of patellar reflex suggests femoral neuropathy (L2–L4). The cause of the neuropathy in this case is a hematoma (secondary to trauma) compressing the nerve. Because both the hip flexors (L2–L3) and the quadriceps muscles (L3–L4) are involved, the nerve is affected above the inguinal ligament. If the compression had affected the nerve distal to the inguinal ligament where the nerve branches into anterior and posterior divisions, a deficiency in either the hip flexors (anterior) or the quadriceps muscles (posterior), but not both, would be expected.

Answer 10

The femoral nerve innervates the skin of the anterior and medial thigh; thus, light touch sensation is decreased in these areas. The lateral aspect of the thigh is innervated by the lateral femoral cutaneous nerve (L2–L3) and is spared in an isolated femoral neuropathy. The saphenous nerve is a cutaneous branch of the femoral nerve that arises from the femoral nerve in the femoral triangle. It innervates the skin of the anteromedial knee, leg, and foot to the medial side of the big toe. Because this lesion is above the femoral ligament, the saphenous nerve distribution is also involved.

Answer 11

The femoral nerve is the largest branch of the lumbar plexus and, after forming in the abdomen, runs posterolaterally to the inguinal ligament. It crosses under the inguinal ligament lateral to the psoas muscle and enters the femoral triangle. In the femoral triangle (bounded by the sartorius muscle, inguinal ligament, and adductor longus), it runs lateral to the femoral artery, which is lateral to the femoral vein. The vessels are enclosed within the femoral sheath and the nerve is outside it.

Answer 12

The major muscles responsible for thigh adduction are the adductor longus, adductor brevis, adductor magnus, and the gracilis, which are innervated by the obturator nerve (L2–L4). Because this is a peripheral neuropathy, not pathology of the nerve root, the obturator nerve is spared and so is thigh adduction.

Answer 13

1. Diabetic vasculitic damage. 2. Direct penetrating trauma. 3. Hip fracture. 4. Iliac aneurysms. 5. Incorrect placement of the femoral line. 6. Prolonged hip flexion during gynecologic or urologic procedures. 7. Tumor.

Answer 14

- Open-angle glaucoma is the most common form of glaucoma in the United States (90%) and presents as progressive, painless visual loss. Closed-angle glaucoma is painful and can cause additional symptoms such as seeing halos around lights and red eye. - Open-angle glaucoma is caused by elevated intraocular pressure resulting from obstruction of flow of aqueous humor through the normal outflow channels (Figure 10-9).

Answer 15

The direct cholinergic agonists pilocarpine and carbachol are used to treat open-angle glaucoma. These agents act by stimulating ciliary muscle contraction, thereby relieving tension in the suspensory ligament. Cholinomimetics also stimulate the sphincter pupillae of the iris, which widens the canal of Schlemm and constricts the pupil (miosis). Adverse effects include nausea, vomiting, diarrhea, salivation, sweating, vasodilation, and bronchoconstriction.

Answer 16

Pilocarpine is an M3/M2 muscarinic receptor agonist. Cardiac cells have M2 receptors that, when activated, stimulate a G protein that inhibits adenyl cyclase and increases potassium conductance. Pilocarpine stimulation decreases the heart rate and the force of contraction (negative inotrope).

Answer 17

Other drug classes used to treat open-angle glaucoma include the following: 1. Adrenergic agonists such as epinephrine. 2. β-Blockers and acetazolamide (a carbonic anhydrase inhibitor), which decrease aqueous humorsecretion. 3. Prostaglandins, which increase the outflow of aqueous humor.

Answer 18

- Glioblastoma multiforme (GBM), the most common primary brain tumor. GBM represents almost 20% of all primary intracranial tumors. - Glioblastomas are found supratentorially in the cerebral hemispheres and often cross hemispheres via the corpus callosum (“butterfly glioma”) (Figure 10-10).

Answer 19

- Glioblastomas are composed of highly malignant astrocytes that are visualized with a glial fibrillary acidic protein stain. Histology of glioblas- tomas shows pseudopalisading tumor cells surrounding focal areas of necrosis (Figure 10-11). - Treatment is largely palliative and only moderately increases survival time. Treatment may include surgical resection, radiation, and chemotherapy. - Glioblastoma is an aggressive tumor; without treatment, most patients die within 3 months of diagnosis. With treatment, the median survival time is 1 year, and < 10% of patients survive 5 years.

Answer 20

The most common cause of brain tumors in adults is metastases, and their presentation depends on location. Meningiomas derive from dura mater or arachnoid and are usually benign, but severity depends on location. Astrocytoma arises in brain parenchyma, has a better prognosis than GBM, and presents with seizures, headaches, and focal deficits.

Answer 21

Guillain-Barré syndrome (GBS), or acute inflammatory demyelinating polyradiculoneuropathy, is characterized by symmetric ascending muscle weakness or paralysis that begins in the lower extremities. Hyporeflexia or areflexia is invariable but may not be present early in the course of disease.

Answer 22

GBS often occurs 1–3 weeks after a gastrointestinal or upper respiratory tract infection, vaccination, or allergic reaction. Common associated infections include Campylobacter jejuni and herpesvirus. Although a preceding event is present in most patients, approximately one third of patients with GBS report no such events during the preceding 1–4 weeks.

Answer 23

GBS is thought to be an autoimmune reaction that develops in response to a previous infection or other medical condition. This process results in aberrant demyelination of peripheral nerves and ventral motor nerve roots. Cranial nerve roots can also be affected.

Answer 24

Cerebrospinal fluid (CSF) reveals a markedly elevated protein concentration with a normal cell count, commonly referred to as albuminocytologic dissociation. This contrasts the increased cell counts typical of CNS infection. Increased CSF protein can lead to papilledema.

Answer 25

The first element of GBS management is supportive care and treatment of the underlying condition with either IVIG antibody or plasmapheresis. Pulmonary function should be monitored with peak flow studies to assess for respiratory failure. Rehabilitation may be required to restore function.

Answer 26

Chronic inflammatory demyelinating polyradiculopathy is a chronic, progressive, or chronic progressive counterpart of GBS that often presents with similar symptoms.

Answer 27

**Horner syndrome** Horner syndrome results from a disruption in the sympathetic innervation of the face and subsequent uninhibited parasympathetic activity, which produces the classic symptoms: ipsilateral Ptosis (slight drooping of the eyelid), Anhidrosis (absence of sweating), and Miosis (pupillary constriction) (mnemonic: PAM).

Answer 28

The first neuron of the sympathetic pathway begins in the hypothalamus and synapses in the intermediolateral column of the spinal cord near T1 (Figure 10-14). The second, preganglionic, neuron travels to the superior cervical ganglion. The third and final neuron of the pathway innervates the pupil, the sweat glands of the face, and the smooth muscle of the eyelid.

Answer 29

Wallenberg syndrome results from a stroke in the lateral medullary region supplied by the posterior inferior cerebellar artery. It can present with ipsilateral Horner syndrome, nystagmus to the side of the lesion, ipsilateral limb ataxia, and vertigo. Another distinguishing feature is impaired pain and temperature sensation in the ipsilateral face and contralateral hemibody.

Answer 30

Any pathology that interrupts the described pathway can cause Horner syndrome. These include Pancoast tumor, neck trauma, carotid dissection, cervical cord lesions, and multiple sclerosis. Many cases of Horner syndrome are idiopathic.

Answer 31

Pancoast tumor is a carcinoma that usually occurs in the apex of the lung. It can cause Horner syndrome and ulnar nerve pain.

Answer 32

Hydrocephalus is defined as an excessive volume of cerebrospinal fluid (CSF) within the ventricles of the brain. Because CSF is trapped within the ventricular system, this case is an example of a noncommunicating hydrocephalus. A communicating hydrocephalus can occur in states of excess CSF production. CT scan of the head shows a dilated ventricular system (Figure 10-15) with dilated atria of the lateral ventricles (arrowheads) and rounded third ventricle (arrow). Other causes of disproportionally large head size or growth include trauma, Canavan disease, and Hurler syndrome.

Answer 33

- CSF is produced by the choroid plexus epithelium within the cerebral ventricles (Figure 10-16). The lateral ventricle communicates with the third ventricle via the foramen of Monro. The third ventricle communicates with the fourth ventricle via the aqueduct of Sylvius. The fourth ventricle communicates with the subarachnoid space via the foramen of Luschka (laterally) and the foramen of Magendie (medially). - Arachnoid villus cells, which are located in the superior sagittal sinus, return CSF to the bloodstream within vacuoles (through a process called pinocytosis).

Answer 34

Capillary and choroid endothelial cells form the blood-brain barrier. Tight junctions of capillary endothelium within the brain impede the passage of water and solutes. Within the choroid plexus, the choroid endothelium regulates the transport of water and solutes.

Answer 35

Hydrocephalus results from a mismatch of CSF production and reabsorption in which the rate of production exceeds reabsorption. Causes of hydrocephalus include the following: 1. Excess CSF production (eg, choroid plexus papilloma). 2. Impaired CSF reabsorption (due to obstruction or disruption of arachnoid villi). 3. Blockage of the flow of CSF.

Answer 36

Treatment is surgical and involves a ventriculoperitoneal shunt, which allows for reabsorption of fluid in the peritoneum.

Answer 37

Huntington disease is characterized by dementia, choreoathetoid movements of the face and extremities, and early death. Huntington disease has an autosomal dominant inheritance. Other causes of early-onset dementia include early-onset Alzheimer disease, multiple sclerosis, HIV infection, or Creutzfeldt-Jakob disease (much rarer).

Answer 38

- A mutation in chromosome 4 results in expansion of trinucleotide CAG repeats, which may decrease transcription of a striatal neurotrophic factor (brain-derived neurotrophic factor). - Patients with Huntington disease have marked atrophy of the striatum, including the caudate and putamen, representing degeneration and loss of γ-aminobutyric acid–ergic and cholinergic neurons.

Answer 39

1. Sydenham chorea in rheumatic fever 2. Tardive dyskinesia 3. Wilson disease are among other diseases associated with choreoathetoid movements.

Answer 40

Expansion of trinucleotide repeats over successive generations leads to earlier manifestations of disease in offspring; this is called anticipation. The patient’s father died at age 45 years and likely developed Huntington disease many years earlier. If this patient had the genetic mutation, he might already be expected to show symptoms.

Answer 41

Fragile X syndrome, myotonic dystrophy, and spinocerebellar ataxia types I and II are also associated with trinucleotide repeats.

Answer 42

- The Amsler grid assesses the degree of central vision loss (Figure 10-19A). In this assessment, patients cover one eye and, with the open eye, focus on the dot at the center of the grid. Patients with vision deficits in their macula see a distortion of the grid (Figure 10-19B). - Age-related macular degeneration (ARMD), in which central vision is blurred, is a significant cause of vision loss in the elderly. By contrast, glaucoma typically affects peripheral vision while sparing central vision. Central vision loss can also be caused by optic neuritis and cataracts.

Answer 43

There are dry and wet forms of macular degeneration. The dry form (85% of cases) typically progresses more slowly and occurs earlier in the disease process. The wet form, although rarer (% of cases), causes the majority of significant blindness in patients.

Answer 44

Drusen are extracellular protein and lipid deposits in the retina, which appear on funduscopic examination as yellow or white spots in the eye (Figure 10-18). Irregularity and, in later stages, atrophy of the retinal pigmented epithelium also occur. In wet ARMD, new vessels from the choroid may grow into the subretinal space, causing metamorphopsia (a wavy distortion of vision), hemorrhage, and scarring.

Answer 45

The macula, which is located temporal to the optic disc, is the area of the retina that is specialized for fine- detail vision. The center of the macula is the fovea, which has the highest density of cone photoreceptor cells in the retina and the smallest amount of convergence to bipolar cells. This provides for exquisite detail in visual perception.

Answer 46

The defect is a right homonymous hemianopia likely caused by a stroke. The patient’s symptoms suggest that he has experienced a number of transient ischemic attacks (TIAs). The classical definition of a TIA is a vascular event that causes neurologic deficits that last < 24 hours. Clinically, it is defined as a neurologic deficit that lasts < 1 hour in the absence of abnormal imaging findings.

Answer 47

Photoreceptors (rods and cones) synapse on bipolar cells that synapse on ganglion cells in the retina, which form the optic nerve. The optic nerve travels posteriorly and merges to form the optic chiasm where nasal (medial) retinal fibers from both eyes cross. The nasal hemiretina fibers are responsible for the temporal visual fields. Once past the chiasm it is known as the optic tract, which synapses on the lateral geniculate nucleus (LGN) of the thalamus. Axons exiting the LGN fan out posteriorly through the white matter. The inferior radiations carry information from the inferior retina or superior visual field, travel through the temporal lobe, and are known as the Meyer loop. The superior radiations carry information from the superior retina or inferior visual field and travel through the parietal lobe. The optic radiations synapse in the visual cortex of the occipital lobe near the calcarine fissure. The superior radiations synapse superior to the calcarine fissure and the inferior radiations inferior to the fissure (Figure 10-21).

Answer 48

A lesion in the left optic tract, posterior to the chiasm and anterior to the lateral geniculate nucleus, may be the cause, as may a large lesion affecting the upper and lower optic radiations or a lesion in the left visual cortex.

Answer 49

The inferior optic radiations (Meyer loop) travel through the temporal lobe. A lesion to this area shows a left upper quadrantic anopia (“pie in the sky”) as indicated by lesion J in Figure 10-21.

Answer 50

The history suggests **medulloblastoma**, a highly malignant tumor most often found in the cerebellum. The majority of patients are 4–8 years of age, and males are affected more than females. In children, 70% of intracranial tumors are infratentorial, whereas in adults 70% are supratentorial. Although medulloblastoma is the most common pediatric brain tumor, astrocytoma, brain stem glioma, and ependymomas are also common. Astrocytomas can occur anywhere in the hemispheres and the brain stem. In children, ependymomas typically occur in the fourth ventricle and are characterized by pseudorosettes, in which cells are arranged around vessels with ependymal processes directed toward the vessel wall.

Answer 51

Lesions can occur in either the vermis or the hemispheres. Cerebellar lesions in the hemispheres cause ipsilateral limb ataxia and loss of muscle tone. Superior vermis lesions are characteristic of Wernicke encephalopathy and alcoholic cerebellar degeneration, presenting with the classic triad of gait or truncal ataxia, ophthalmoplegia, and confusion.

Answer 52

On MRI of the head, medulloblastomas are heterogeneous enhancements located in the cerebellum, often extending into the fourth ventricle (Figure 10-22).

Answer 53

The association of inherited colonic syndromes with brain tumors is named Turcot syndrome. Patients with autosomal dominant familial adenomatous polyposis are at risk for medulloblastomas and gliomas. Patients with hereditary nonpolyposis colorectal cancer are at risk for gliomas only.

Answer 54

Medulloblastomas are rapidly growing, well-circumscribed friable tumors found exclusively in the cerebellum. Microscopically, Horner-Wright rosettes, described as circular patterns of tumor cells surrounding a center of neutrophils, can be seen.

Answer 55

Treatment consists of complete or near-complete surgical excision followed by radiation and chemotherapy. Current treatment protocols are designed to minimize damage to adjacent structures and prolong survival.

Answer 56

- The location of the lesion on MRI scan is typical of a meningioma. Meningiomas are usually benign, slow- growing tumors arising from the arachnoid cells penetrating the dura. They are the second most common primary brain tumor. - Meningiomas are found along the dura, most often in the sylvian region, superior parasagittal region, and cerebellopontine angle. Other diseases that commonly involve the dura include lymphoma, metastatic carcinoma, and tuberculosis.

Answer 57

Meningiomas display psammoma bodies and elongated spindle cells arranged concentrically in a whorled pattern. Psammoma bodies are laminated, concentric calcified concretions formed by meningiomas (head), papillary adenocarcinomas of the thyroid (neck), malignant mesothelioma (thorax), and serous papillary cystadenocarcinoma of the ovary (pelvis).

Answer 58

For small, slow-growing, and asymptomatic tumors, careful observation is appropriate. Surgical resection is indicated for symptomatic tumors or quickly growing tumors. Complete resection is often curative; however, tumors can recur if incompletely resected.

Answer 59

Because of their slow growth, many meningiomas are detected incidentally after neuroimaging for other reasons. However, large tumors may displace normal brain tissue and cause focal neurologic deficits such as visual disturbances, hearing loss, mental status changes, extremity weakness, obstructive hydrocephalus, and/or seizures.

Answer 60

Acute otitis media. The bulging, red tympanic membrane is a sign of middle ear infection. The clinical course suggests a viral upper respiratory infection leading to secondary involvement of the middle ear due to inflammation and congestion of the eustachian tube. The eustachian tube connects the middle ear to the nasopharynx.

Answer 61

The tympanic membrane derives from the first pharyngeal membrane. The pharyngeal membranes constitute the tissue between the pharyngeal groove, or cleft, and the pharyngeal pouch. Only the first pharyngeal membrane is retained in the adult; the rest are obliterated during development.

Answer 62

The three bones located in the middle ear (auditory ossicles) are the malleus, incus, and stapes (Figure 10-25); together, they transmit sound from the tympanic membrane to the internal ear. The malleus, which articulates with the tympanic membrane, derives from the first branchial arch. The incus, which lies between the malleus and the stapes, derives from the first branchial arch. The stapes, which articulates with the oval window of the inner ear, derives from the second branchial arch.

Answer 63

The tensor tympani inserts on the malleus and dampens the amplitude of the tympanic membrane oscillations, which prevents damage to the inner ear from loud sounds. Innervation is by the mandibular nerve (CN V3). The stapedius inserts onto the neck of the stapes and dampens movement of this ossicle. It is innervated by the facial nerve (CN VII). A lesion denervating the stapedius causes hypersensitivity to sound.

Answer 64

In order of prevalence, common bacteria that cause middle ear infection are Streptococcus pneumoniae, Haemophilus influenzae (although rarely type B since the introduction of the conjugated vaccine), and Moraxella catarrhalis. Appropriate antibiotic coverage involves a β-lactamase such as amoxicillin. Less common organisms are group A streptococci, Staphylococcus aureus, Pseudomonas, and in newborns, gram-negative bacilli. Approximately 15%–20% of middle ear infections are due to viruses, including respiratory syncytial virus, rhinovirus, influenza viruses, and adenovirus.

Answer 65

- Metastatic brain tumor from her small cell lung cancer. Brain metastases are more prevalent than primary central nervous system tumors. - The differential diagnosis includes a primary brain tumor, metastatic tumor from a second primary brain tumor, infection, cerebral infarct, or radiation necrosis.

Answer 66

Lung, Breast, Skin (melanoma), Kidney (renal cell carcinoma), and Gastrointestinal (mnemonic: Lots of Bad Stuff Kills Glia) tumors can spread hematogenously to the brain.

Answer 67

Metastases are supratentorial, located at the gray-white matter junction, where the arterial vessels narrow sufficiently for tumor cells to lodge (Figure 10-26). They are also found at watershed areas, or vascular territories situated between two supplying arteries (eg, middle cerebral artery and anterior cerebral artery).

Answer 68

Symptoms include headaches, seizures, stroke, nausea, vomiting, cognitive dysfunction such as personality changes, and focal neurologic deficits such as aphasia or weakness.

Answer 69

MRI is the imaging modality of choice because of its superior sensitivity for soft tissue. Biopsy of the lesion is often indicated to confirm the diagnosis before a definitive treatment plan is chosen.

Answer 70

The most common paraneoplastic syndromes are the syndrome of inappropriate antidiuretic hormone secretion and the syndrome of ectopic adrenocorticotropic hormone; however, small cell lung cancer can also cause variable nonspecific neurologic symptoms.

Answer 71

Migraine headache.

Answer 72

1. **Maintenance agents** include β-blockers, calcium channel blockers, tricyclics, and anticonvulsants. 2. **Abortive agents** include non steroidal anti-inflammatory drugs, acetaminophen, triptans, andergotamine agents. 3. **Antiemetics** are often used for control of associated nausea and vomiting.

Answer 73

Neurofibromatosis type 1 (NF1), or von Recklinghausen disease, is a common neurocutaneous disorder. NF1 has complete penetrance with variable expression. Diagnosis is made on clinical criteria. Although neurofibromatosis type 2 (NF2) can present with skin lesions, NF2 most commonly causes bilateral acoustic neuromas and eye lesions; approximately 50% of affected patients develop lesions in the spinal cord, cranial nerves, and meninges.

Answer 74

The hallmark finding is six or more hyperpigmented mac- ules called café-au-lait spots. In addition, neurofibromas, multiple soft fleshy tumors, usually develop during adoles- cence (Figure 10-27). Freckling is also present in the axilla and groin. Although NF2 often demonstrates neurofibro- mas, café-au-lait spots are rare in this condition.

Answer 75

Lisch nodules, which are raised, pigmented, hamartomas, are found on the iris (Figure 10-28). Optic gliomas may arise anywhere along the optic tract, particularly in the optic nerve or chiasm. Patients are also at increased risk for other central nervous system tumors such as astrocytomas and other gliomas. Peripheral neurofibromas can undergo malignant transformation into neurofibrosarcomas.

Answer 76

Multiple sclerosis (MS). The arrowheads in Figure 10-29 show the lesions of MS.

Answer 77

Risk factors for MS include the following: 1. Age 20–50 years (mean age of onset is 30 years). 2. Female gender (female/male ratio is 1.77:1.00). 3. Having grown up in a temperate climate. 4. Family history of MS.

Answer 78

A medial brain stem lesion involving cranial nerves VI, VII, and XII (Figure 10-30) leads to the constellation of facial droop, tongue deviation, and lateral gaze weakness. The intention tremor indicates cerebellar involvement.

Answer 79

Oligoclonal bands are seen in 85%–95% of cases. The presence of these immunoglobulins reflects the autoimmune nature of the disease. Oligoclonal bands are not specific to MS and can be elevated in Lyme disease, lupus, syphilis, Sjögren syndrome, and neurosarcoidosis. Similarly, the IgG index is elevated in > 90% of patients with definite MS. The total CSF WBC count is normal in most patients, but an elevated WBC count is nonspecific.

Answer 80

Multiple demyelinating plaques are usually present in the brains of patients with MS, especially in the periventricular region, corpus callosum, and centrum semiovale.

Answer 81

Acute attacks are treated with high-dose corticosteroids; however, these drugs do not change the course of the disease. Interferon-β1b is the most common disease-modifying treatment. Supportive care including neurorehabilitation is important in preserving activities of daily living. Interferon-β binds a receptor and induces a transcriptional response that reduces T-cell proliferation and antigen presentation and alters cytokine levels.

Answer 82

- Myasthenia gravis. Differential includes Lambert-Eaton syndrome, which is a paraneoplastic syndrome associated with small cell lung cancer involving muscle weakness; however, strength improves if a contraction is maintained. In myasthenia gravis, symptoms worsen as activity progresses. Lambert-Eaton syndrome also typically spares the extraocular muscles. - Myasthenia gravis is more commonly seen in women than in men, and most patients are older than 50 years of age when diagnosed.

Answer 83

Patients may present with a variety of findings, including ptosis, diplopia, dysarthria, difficulty chewing, and difficulty swallowing. Proximal muscle weakness is usually greater than distal muscle weakness. Weakness increases with use of the muscles.

Answer 84

Patients develop antibodies against acetylcholine receptors. Because of a higher threshold of activation by acetylcholine, signal transmission across the neuromuscular junction is decreased. This process leads to muscle weakness. The Tensilon test assesses the response to edrophonium to distinguish myasthenia gravis from cholinergic crisis; because edrophonium is an anticholinesterase it will improve myasthenia gravis but worsen a cholinergic crisis.

Answer 85

Myasthenia gravis has been associated with an increased frequency of thymomas. It is thought that the thymus is the site of production of autoantibodies against acetylcholine receptors. Even in patients with no thymus neoplasm, thymectomy has been shown to improve symptoms in 85% of cases.

Answer 86

Anticholinesterase drugs are the mainstay of treatment. Pyridostigmine is the most common drug prescribed; however, neostigmine may still be used. Prophylactic thymectomy is indicated in patients younger than 60 years of age. Corticosteroids and azathioprine are used in refractory cases. Plasmapheresis and IVIG can provide temporary relief.

Answer 87

- Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder whose hallmark is bilateral acoustic neuromas. Perforation of the eardrum, ototoxic medication, otosclerosis, or Ménière disease can also cause acquired hearing loss in children. - Mutation of the gene merlin found on chromosome 22 (mnemonic: type 2 = 22). Merlin codes for a protein involved in cytoskeleton components responsible for contact inhibition of tumor progression.

Answer 88

Blurry or cloudy vision due to juvenile cataracts is also seen in NF2. Patients may also present with skin findings similar to those seen in neurofibromatosis type 1, such as café-au-lait spots.

Answer 89

- **Conductive hearing loss** involves the ear canal, tympanic membrane, middle ear, and ossicles. - **Sensorineural hearing loss** involves the innerear (cochlea), vestibulocochlear nerve, or central processing centers in the brain.

Answer 90

- Parkinson disease typically presents with the following symptoms: Tremor that is worse at rest, Rigidity, Akinesia or bradykinesia, and Postural instability (mnemonic: TRAP). - Parkinson disease is marked by significant neuronal loss in the substantia nigra, which decreases dopaminergic input into the basal ganglia. Characteristic findings include depigmentation of neurons in the substantia nigra and concentric eosinophilic cytoplasmic inclusions called Lewy bodies (Figure 10-32).

Answer 91

The Parkinson plus syndromes and their associated symptoms are as follows: 1. **Dementia with Lewy bodies**: Fluctuating cognition and visual hallucinations 2. **Multiple system atrophy**: Autonomic instability 3. **Progressive supranuclear palsy**: Early postural instability, loss of voluntary eye movements, and dysarthria 4. **Corticobasal degeneration**: sensory loss, apraxia, aphasia, myoclonus, dementia

Answer 92

Dopamine produced by the substantia nigra activates the direct pathway and inactivates the direct pathway in the basal ganglia. In the direct pathway, dopamine activates the caudate nucleus; this inhibits the globus pallidus internus, which in turn inhibits the ventral lateral thalamus nucleus resulting in frontal motor stimulation. In the indirect pathway, dopamine inhibits the caudate, which inhibits the globus pallidus externus, which in turn inhibits the subthalamic nucleus resulting in stimulation of the globus pallidus internus (the opposite end result as the direct pathway) (Figure 10- 33). In both, decreased dopamine results in inhibition of the frontal motor cortex and bradykinesia.

Answer 93

As the disease progresses, shuffling gait, masked facies, and dementia are likely to occur.

Answer 94

Carbidopa can be used with levodopa to treat Parkinson disease. Carbidopa, a peripheral dopa decarboxylase inhibitor, reduces peripheral conversion of levodopa. This augments its action in the central nervous system and reduces its action outside the central nervous system (where levodopa can cause arrhythmias and dyskinesias). Pramipexole and bromocriptine, which are direct dopaminergic agonists, can also be used to augment dopamine signaling. Catechol-O-methyltransferase increases the half-life of Sinemet. Anticholinergic drugs, amantadine, and monoamine oxidase-B inhibitors are also used in Parkinson disease.

Answer 95

Typical antipsychotic agents have antidopaminergic activity. Thus, patients taking these medications for schizophrenia can exhibit Parkinson-like symptoms. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine and antiemetic agents can also induce Parkinson-like symptoms.

Answer 96

- Hyperprolactinemia from a prolactin-secreting anterior pituitary adenoma. Classic symptoms in females are amenorrhea, infertility, and galactorrhea. - Hyperprolactinemia also occurs in patients on antipsychotic medication. Because dopamine inhibits prolactin production, the dopamine inhibitors cause hyperprolactinemia. - The differential diagnosis includes pituitary adenoma, pituitary hyperplasia, craniopharyngioma, meningioma, germ cell tumor, chordoma, primary lymphoma, cyst, abscess, or arteriovenous fistula of the cavernous sinus.

Answer 97

Dopamine secreted from the hypothalamus travels to the anterior pituitary where it inhibits prolactin secretion. A mass in the pituitary may compress the infundibulum, causing a “stalk effect,” in which dopamine cannot reach its target. Thus, prolactin is continuously secreted. Physiologic hyperprolactinemia may occur during pregnancy. Pregnancy must always be ruled out in any female who presents with amenorrhea.

Answer 98

Adrenocorticotropic hormone, thyroid-stimulating hormone, growth hormone, luteinizing hormone, and follicle-stimulating hormone are also secreted. Although prolactinomas are the most common hyperfunctioning tumor, a pituitary adenoma may secrete any of the above hormones.

Answer 99

Reduction in tumor size, suppression of prolactin secretion, and return of menses are usually accomplished with a dopamine agonist such as bromocriptine or cabergoline. Both are ergot derivatives that act directly on dopamine receptors in the hypothalamus to decrease prolactin secretion. When medical management is no longer effective or the mass is very large, transsphenoidal surgery with resection of a large hyperfunctioning sellar mass is typically indicated.

Answer 100

Bitemporal hemianopia results when the growing pituitary tumor impinges on the optic chiasm (Figure 10-34).

Answer 101

Seizure. Involvement of the left motor cortex is implicated because the seizure started with right-handed motor activity. In this patient a metastasis is the likely culprit. Seizures can also be caused by infection, ischemia, drug exposure or withdrawal, certain ion imbalances including hypoglycemia and hyponatremia, and trauma.

Answer 102

This is a simple partial seizure with motor signs secondarily generalizing into a tonic-clonic seizure. During the first 10 seconds, the patient maintained consciousness, pointing to a simple seizure (complex seizures require a loss of consciousness). After the first 10 seconds, her simple partial seizure evolved into a generalized tonic-clonic seizure. The tonic phase is characterized by the immobile contraction of all muscles, and the clonic phase is characterized by the bilateral rhythmic jerking of the extremities.

Answer 103

The patient is likely responding to acidosis. A respiratory acidosis can develop from the loss of coordinated respirations during the seizure, and a metabolic acidosis can develop as muscles contract under anaerobic conditions and produce lactic acid.

Answer 104

Popular antiseizure medications include valproic acid, phenytoin, phenobarbital, primidone, and carbamazepine. Many antiseizure medications work by enhancing γ-aminobutyric acid (GABA) binding on chloride channels. GABA binding allows chloride ions to flow into neurons, thereby inhibiting neuronal firing. Barbiturates act on the same chloride channels and enhance GABA signaling by increasing the duration of chloride channel opening. Benzodiazepines act on the same channels and enhance GABA signaling, but they do so by increasing the frequency of chloride channel opening.

Answer 105

Stroke. Figure 10-35 shows extensive hemorrhage in the thalamus (left arrow) and its extension into the third (top arrow), ipsilateral (bottom arrow), and lateral (right arrow) ventricles.

Answer 106

- The combination of fluent but nonsensical speech and poor comprehension is characteristic of Wernicke aphasia (sensory aphasia). These patients also display poor repetition and naming ability. Other findings commonly associated with Wernicke aphasia include contralateral visual field cut (due to ischemia of optic radiation) and anosognosia (unawareness of one’s deficit). - The inferior frontal gyrus controls motor aspects of speech. A stroke in this area causes Broca aphasia (motor aphasia), which is characterized by nonfluent, agrammatic speech. Because of the proximity of the primary motor cortex for the face and arm, dysarthria (difficulty in articulating words) and right face and arm weakness are often associated with Broca aphasia. Comprehension is intact in these patients.

Answer 107

This constellation of symptoms suggests infective endocarditis, which is characterized by splinter hemorrhages, Osler nodes on the pads of the fingers and toes, and Roth spots on the retina. Infective endocarditis can lead to the release of thrombi from the valvular vegetations, resulting in embolic events.

Answer 108

1. Musculoskeletal conditions (eg, muscle strain, osteoarthritis, compression fracture, or ankylosing spondylitis). 2. Disk herniation. 3. Metastases. 4. Osteomyelitis. 5. Referred pain from visceral disease (eg, gallstones or kidney stones, pancreatitis, or aortic aneurysm).

Answer 109

The patient’s history of breast cancer raises concern for the development of metastases resulting in epidural spinal cord compression. Her leg weakness, hyperreflexia, and positive Babinski signs indicate upper motor neuron lesions, which are likely the cause of her weakness as well. Her pain at rest and lack of sciatica argue against disk herniation.

Answer 110

As in this patient, upper motor neuron lesions are characterized by spastic paralysis, hyperreflexia, and a positive Babinski sign. By contrast, lower motor neuron lesions are associated with flaccid paralysis, muscle atrophy, muscle fasciculations and fibrillations, and hyporeflexia.

Answer 111

The most common sources of bone metastases are cancers of the breast, prostate, lung, and kidney (renal cell carcinoma).

Answer 112

Treatment options include steroids such as dexamethasone, radiation therapy, and surgical decompression. Spinal cord compression is an oncologic emergency because neurologic dysfunction, if present, may become permanent if it is not immediately addressed.

Answer 113

Sturge-Weber syndrome is a rare neurocutaneous congenital disorder with unknown etiology. The disorder manifests vascular malformations of the skin (port-wine stain; see Figure 10-36) and leptomeninges (leptomeningeal angiomatosis).

Answer 114

MRI is most useful for identifying a leptomeningeal angioma. Often, these tumors are ipsilateral to the port-wine stain. These lesions are responsible for the seizures, hemiparesis, and mental retardation in Sturge-Weber syndrome.

Answer 115

Many patients may also have glaucoma. Heterochromia of the iris (different-colored irises), visual field defects, and vascular malformations of the choroid may also be present.

Answer 116

Treatment is aimed at alleviating symptoms. Port-wine stains may be treated with laser therapy. Seizures can be managed with anticonvulsants. Patients with seizures refractory to pharmacotherapy may undergo surgical resection of the lesion, often involving a hemispherectomy of the affected side.

Answer 117

- Subarachnoid hemorrhage (arrows in Figure 10-37). The classic presentation is a complaint of “the worst headache in my life” after a “thunderclap” sensation marking the onset of severe pain. Hypertension is the most common risk factor. - Most spontaneous subarachnoid hemorrhages occur as the result of the rupture of a berry aneurysm in the circle of Willis. Other causes are trauma or an arteriovenous malformation. The risk is increased by a history of hypertension. The most common location of a berry aneurysm is the anterior communicating artery, followed by the posterior communicating artery and then the middle cerebral artery.

Answer 118

The murmur on cardiac examination is characteristic of mitral valve prolapse, which is commonly seen in Marfan syndrome. Berry aneurysms have been associated with Marfan syndrome, Ehlers-Danlos syndrome, adult polycystic kidney disease, and coarctation of the aorta.

Answer 119

After a subarachnoid hemorrhage, CT scan of the head will show blood, in the subarachnoid space if the scan is performed within 24 hours of the bleed. The diagnostic finding in the CSF is xanthochromia, a yellow supernatant caused by bilirubin release from the breakdown of hemoglobin. There may also be gross blood in the fluid, but since this can also be due to a traumatic tap it is not considered a diagnostic finding unless there is a steady elevation in CSF red blood cell count over subsequent lumbar punctures.

Answer 120

- Vomiting is a common sign of increased intracerebral pressure, which, in this patient, is secondary to the hemorrhage. - Patients who have recently suffered a subarachnoid hemorrhage are prone to cerebral vasospasm, especially during the first week after the hemorrhage. Prophylaxis is typically achieved with nimodipine, a calcium channel blocker that improves outcomes in SAH.

Answer 121

- The temporary loss of consciousness followed by gradual mental status change over the course of days or even weeks is the classic history of a subdural hematoma. The diagnosis is confirmed by CT scan, which shows a crescent-shaped area of hemorrhage that crosses cranial suture lines (Figure 10-38). - Subdural hematomas result from head trauma that causes venous bleeding, most commonly from rupture of bridging veins within the dura, which then bleed into the space between the arachnoid and dura mater. The elderly and alcoholics are more prone to subdural hemorrhage due to cortical atrophy and subsequent increased tension on the bridging veins.

Answer 122

Venous bleeding results in a slowly expanding blood accumulation and gradual compression of the cerebrum. Symptoms result from the compression of cortical and subcortical structures and therefore are variably delayed depending on when specific intracranial areas are affected by the compression.

Answer 123

An immediate “lucid interval,” or temporary conscious state, after a head trauma followed by rapid decline in function is more consistent with an epidural hematoma. Unlike subdural hematomas, epidural hematomas are due to arterial bleeding and thus cause a dramatic decline in mental status after an initial period of intact function. The CT scan of an epidural hematoma (Figure 10-39) shows a subosteal blood accumulation in the shape of a biconcave disk that does not cross suture lines.

Answer 124

Treatment for both acute subdural and epidural hematomas is decompression and evacuation of the blood via a craniotomy.

Answer 125

The primary differential for syncope is divided into cardiogenic and noncardiogenic causes. Cardiogenic causes include arrhythmias, aortic stenosis, tamponade, and aortic dissection. Noncardiogenic causes include orthostatic hypotension and vasovagal, or neurogenic, syncope, which is a reflex drop in blood pressure caused by activation of the vagus nerve.

Answer 126

Orthostatic hypotension, tachycardia, tachypnea, dry mucous membranes, and decreased skin turgor are signs of volume depletion evident on physical examination.

Answer 127

Late-stage diabetes mellitus can be associated with orthostatic hypotension. This is due to autonomic neuropathy and is one of the microvascular complications of diabetes mellitus. The autonomic nervous system dysfunction causes a diminished compensatory response to decreased blood pressure.

Answer 128

Mechanoreceptors in the heart react to the decrease in blood pressure and compensate by increasing sympathetic tone, decreasing vagal tone and causing release of antidiuretic hormone. This results in increased peripheral vascular resistance (increasing venous return) and an increase in cardiac output, thereby minimizing the drop in blood pressure.

Answer 129

Transient ischemic attack (TIA). Classically, TIA has been defined as strokelike symptoms that resolve within 24 hours. However, increasingly sensitive imaging techniques have helped refine the definition of TIA; now it is defined as focal neurologic symptoms that last < 1 hour with no evidence of ischemic changes on radiologic studies.

Answer 130

Signs of cerebral edema include: 1. Loss of the gray matter–white matter junction 2. Loss of prominence of sulci 3. Evidence of a mass effect, such as midline shift, decreased size of the lateral ventricle on the affected side, and uncal herniation.

Answer 131

The anterior cerebral, middle cerebral, and posterior cerebral arteries are the three major vessels supplying the cortex. The anterior cerebral artery branches off the internal carotid artery and supplies the medial portion of motor cortex, the sensory cortex, and the majority of the frontal lobe. The middle cerebral artery also stems from the internal carotid artery and supplies the lateral portion of the motor cortex, temporal lobe, and the somatosensory cortex. The posterior cerebral artery stems from the basilar artery and supplies the visual cortex as well as the posterior parietal lobe (Figure 10-40).

Answer 132

Stroke symptoms correspond to the vascular distribution of each artery. A stroke of the anterior cerebral artery results in lower extremity deficits; a stroke of the middle cerebral artery results in face and upper extremity deficits; and a stroke of the posterior cerebral artery results primarily in visual deficits.

Answer 133

Tuberous sclerosis, an autosomal dominant syndrome manifested by numerous benign neoplasms of the brain, skin, heart, and kidney. Tuberous sclerosis demonstrates complete genetic penetrance but highly variable expressivity. Most cases arise from a sporadic mutation, but offspring of an affected individual will inherit the mutation in an autosomal dominant pattern.

Answer 134

1. Ash-leaf spots, which are elliptical hypopigmented macules, may develop. In fair-skinned individuals, they can be visualized with a Wood’s lamp (Figure 10-41). 2. Adenoma sebaceum, which are small angiofibromas typically distributed in a malar fashion on the face, are also seen (Figure 10-42). 3. Shagreen patches, which are firm, reddish, raised lesions with a leathery texture, are commonly found on the lumbar area of the back. 4. Retinal hamartomas, which appear as gray or yellow lesions on funduscopic examination, may also be present.

Answer 135

Patients classically present with cardiac rhabdomyomas that often regress spontaneously in the first few years of life. Renal manifestations include bilateral angiomyolipomas and cysts.

Answer 136

Cortical tubers and subependymal nodules are common, and both are considered hamartomas. Subependymal nodules can undergo malignant transformation to subependymal giant cell astrocytomas. Consequences of cortical hamartomas are seizures and mental retardation.

Answer 137

1. **Neurofibromatosis** I is characterized by café-au-lait spots, neurofibromas on the skin, Lisch nodules, and optic gliomas. This condition is associated with astrocytomas and pheochromocytomas. 2. **VonHippel–Lindau syndrome** is characterized by hemangiomas of the skin and retina, hemangioblastomas in the central nervous system, and bilateral renal cell carcinoma. The inheritance pattern for all three conditions is autosomal dominant.

Answer 138

Ulnar neuropathy due to nerve compression. Ulnar nerve injuries often present with acute onset of numbness/tingling in the fourth and fifth digits and weakness of wrist and fourth/fifth finger flexion. If severe, ulnar injury can present as a partial clawlike deformity known as the “Pope’s blessing” (Figure 10-43).

Answer 139

Injuries that cause ulnar neuropathy include direct trauma or prolonged pressure on the nerve. Symptoms occur when there is destruction of the myelin sheath or damage to axons sufficient to hinder nerve conduction. The most common site of ulnar nerve injury is at the elbow, because the nerve lies superficially in the groove between the medial epicondyle and the olecranon. A blow to the medial epicondyle often hits the nerve, causing tingling in the territory of the ulnar nerve and the so-called funny bone sensation.

Answer 140

Medial epicondylitis, or “golfer’s elbow,” is an overuse injury affecting the muscle origins at the medial epicondyle, often due to repetitive swinging motions at the elbow joint. It causes medial elbow pain. It can result in irritation of the ulnar nerve.

Answer 141

Anti-inflammatory agents such as corticosteroids and nonsteroidal anti-inflammatory drugs are used to treat ulnar neuropathy due to nerve compression and medial epicondylitis. Patients can also benefit from braces or casts that reduce movement at the elbow joint to decrease chronic inflammation.

Answer 142

Multi-infarct dementia, also known as vascular dementia. Vascular dementia is the second most common cause of dementia after Alzheimer disease. It can be broadly categorized as either large vessel or small vessel in origin. Large-vessel disease results from recurrent infarctions or hemorrhage in the vessels that supply the cortical territories and is usually due to chronic atherosclerotic disease. It is characterized by a stepwise decline in cognitive, executive, and motor or language function. By contrast, small-vessel disease results from recurrent infarctions in subcortical and white matter regions of the brain and is usually due to poorly controlled hypertension. The stepwise decline in these patients can be subtle and may lack major defining events.

Answer 143

History of stroke, advanced age, hypertension, vascular disease, diabetes, smoking, and dyslipidemia are all risk factors for vascular dementia. Treatment is aimed at any of these underlying causes. Antiplatelet therapy, especially aspirin and clopidogrel, may be used to prevent further cerebrovascular accidents.

Answer 144

MRI is the best imaging choice to diagnose vascular dementia. The T2-weighted MRI shown in Figure 10-44 of a patient with diffuse white matter disease demonstrates numerous periventricular and corona radiata lesions.

Answer 145

The etiologies of dementia can be broadly categorized as reversible or irreversible. The irreversible causes constitute the majority of cases; however, reversible causes should be sought out since treating them can significantly improve the patient’s quality of life (Figure 10-45).

Answer 146

Delirium is characterized by an acute, rapid decrease in attention span with a waxing and waning level of consciousness. The patient may be difficult to arouse and classically has changes in mental status with visual hallucinations. The EEG in delirium shows nonspecific slowing. By contrast, dementia is more gradual in onset with no changes in level of consciousness. The EEG is usually normal in dementia.

Answer 147

This patient has sensorineural hearing loss. The recent hospital course suggests antibiotics, most commonly aminoglycosides, as the likely culprit. Sensorineural hearing loss is often associated with tinnitus. The otologic examination reveals a normal external ear canal and visualizes a normal tympanic membrane on the affected side. Weber testing lateralizes to the opposite ear, whereas Rinne testing in the affected ear is normal.

Answer 148

Hearing loss can also be conductive in nature. This occurs when there is an obstruction of the ear canal (cerumen impaction) or mechanical dysfunction of the middle ear apparatus (due to an inflammatory process such as otitis media or otitis externa) that helps transmit sound waves to the cochlea.

Answer 149

In conductive hearing loss, the Weber test lateralizes to the affected ear. This is due to the reverberation and accentuation of sound caused by entrapment of sound waves behind the occlusion or site of dysfunction. The Rinne test results in greater bone conduction of sound in the affected ear because air conduction is obstructed.

Answer 150

- This presentation likely represents a viral meningitis. - The most common causative organism of viral meningitis is echovirus, which is part of the Enterovirus subgroup of the Picornaviridae family. Enterovirus outbreaks tend to occur during the summer and are often associated with summer camps. Other causative organisms include coxsackievirus (another enterovirus), adenovirus, HIV, cytomegalovirus, Epstein-Barr virus, and herpes simplex virus.

Answer 151

Reverse transcriptase is essential in this modified PCR. Because enteroviruses are RNA viruses, detection proceeds with reverse transcription PCR (RT-PCR). Normal transcription is the synthesis of RNA from DNA; this process is the reverse. Viral RNA is reverse transcribed into the complementary DNA (cDNA), and that cDNA can then be amplified using the standard PCR DNA amplification strategy.

Answer 152

As with most cases of viral meningitis, CSF glucose concentration is typically normal (two-thirds of plasma glucose level) and CSF protein concentration is typically normal to slightly increased. CSF cell count reveals a lymphocytosis. This is in contrast to CSF findings in bacterial meningitis, in which protein is increased glucose is decreased and CSF cell count reveals a predominance of polymorphonuclear leukocytes (Table 3-1 in Chapter 3 for a comparison of CSF findings in bacterial, viral, and fungal meningitis).

Answer 153

Acyclovir targets viral DNA polymerase. Herpesviruses are DNA viruses that are sensitive to acyclovir because they contain the viral thymidine kinase required to phosphorylate acyclovir. The phosphorylated acyclovir is a nucleic acid analog and will then be incorporated by viral DNA polymerase, disrupting replication. Picornaviruses, however, are RNA viruses that do not contain DNA polymerase, and therefore they are not sensitive to acyclovir.

Answer 154

The cell is a lymphocyte, which is characterized by its small size; most of the cell volume is occupied by the darkly stained and round nucleus. Lymphocytes play a key role in cellular immunity, particularly in combating infection. Lymphocytosis of the CSF is common in viral meningitis.

Answer 155

- Von Hippel–Lindau (VHL) disease is characterized by diffuse hemangioma formation, commonly in the retina and central nervous system, as well as by an increased incidence of renal cell carcinoma (RCC). - VHL disease is inherited in an autosomal dominant fashion in 75% of cases. It is associated with deletion of the VHL gene, a tumor suppressor gene on the short arm of chromosome 3. Approximately 25% of cases occur sporadically. In the United States, the incidence of VHL disease is approximately 1:36,000.

Answer 156

RCC, predominantly the clear cell type, is the leading cause of death in patients with VHL; some case series report prevalence rates as high as 40%–75% at autopsy. In patients with VHL, RCC develops from malignant degeneration of renal cysts and is usually bilateral. The average age for development of RCC in patients with VHL is 44 years. Because of the high incidence of renal cysts and RCC in patients with VHL, periodic imaging of the kidneys is indicated in patients and at-risk relatives.

Answer 157

Patients with VHL disease are at risk for developing multiple cysts in the liver, epididymis, pancreas, and kidneys. Pheochromocytomas, rare pancreatic carcinomas, and endolymphatic sac tumors are also within the spectrum of VHL. Hemangioblastomas are typically in the cerebellum or medulla but may also occur in the spinal cord. In a significant number of patients, the hemangioblastomas release erythropoietin; these patients can present with polycythemia. Hemangiomas of the skin, mucous membranes, and retina are common.

Answer 158

- Excessive alcohol abuse is the primary culprit of Wernicke-Korsakoff syndrome. Wernicke encephalopathy presents as the triad of nystagmus, ataxia, and confusion. This may progress to Korsakoff syndrome, which consists of irreversible memory loss, confabulation, and personality changes. - Patients with Wernicke-Korsakoff syndrome usually suffer from anterograde amnesia, which is characterized by an inability to form new memories but a general preservation of long-term memories. This is in contrast to retrograde amnesia, in which only long-term memories that precede the precipitating event are lost.

Answer 159

This disease is seen in alcoholics with thiamine deficiency due to poor nutrition and absorption. Thiamine deficiency results in degeneration in a symmetric pattern in multiple cerebral areas, including the cerebellum, brain stem, and bilateral mammillary bodies (Figure 10-48; arrows show abnormal enhancement of the mammillary bodies).

Answer 160

Thiamine (vitamin B1) is needed in glycolysis as a cofactor for pyruvate dehydrogenase; in the tricarboxylic acid cycle as a cofactor for α-ketoglutarate dehydrogenase; in the hexose monophosphate shunt as a cofactor for transketolase; and in the breakdown of amino acids as a cofactor for branched-chain amino acid dehydrogenase.

Answer 161

Glucose repletion in an alcoholic patient must always be accompanied by thiamine administration. Since thiamine is a cofactor in glycolysis, administration of glucose further depletes thiamine stores. This can lead to worsening of the Wernicke-Korsakoff syndrome.

Answer 162

Beriberi is also caused by a deficiency of thiamine secondary to malnutrition. There are two forms of beriberi: dry and wet. Dry beriberi is characterized by peripheral neuropathy and symmetrical muscle wasting due to axonal loss. Wet beriberi is characterized by edema and high-output cardiac failure due to dilated cardiomyopathy.

Neurology Flashcards

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