LE 1 NEURO 2024 Flashcards

Question

Which microorganism causes acute bacterial meningitis with rapid onset, associated with rash and shock? A. Haemophilus influenzae B. Neisseria meningitidis C. Streptococcus pneumoniae D. Pseudomonas aeruginosa

Answer 1

B. Neisseria meningitidis Rationale: Neisseria meningitidis is known for causing acute bacterial meningitis, which often presents rapidly with symptoms including a characteristic rash and can progress to shock, especially in cases of meningococcemia.

Answer 2

D. Pseudomonas aeruginosa Rationale: Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis are common causes of bacterial meningitis. Pseudomonas aeruginosa is not typically associated with bacterial meningitis in otherwise healthy individuals.

Answer 3

A. 10-14 days Rationale: The typical duration for antibiotic treatment of acute bacterial meningitis is 10-14 days, though it can vary based on the causative organism and clinical response.

Answer 4

A. Infection spread to the cavernous sinus Rationale: Infections in the "danger triangle" of the face (from the corners of the mouth to the bridge of the nose) can spread to the cavernous sinus via venous connections, leading to cavernous sinus thrombosis.

Answer 5

A. Meningitis Rationale: Cryptococcus neoformans commonly causes cryptococcal meningitis, particularly in immunocompromised individuals such as those with HIV/AIDS.

Answer 6

A. Frontal lobe Rationale: Oligodendrogliomas most commonly occur in the frontal lobe of the brain. This location is typical for these types of tumors and aligns with clinical and radiological findings.

Answer 7

B. Mesial Temporal Lobe and Insula Rationale: HSV encephalitis commonly affects the mesial temporal lobe and insular regions of the brain, leading to symptoms such as fever, headache, seizures, and focal neurological deficits.

Answer 8

A. Acyclovir Rationale: Acyclovir is the first-line treatment for HSV encephalitis. It is an antiviral medication that is effective in reducing the viral load and improving clinical outcomes if administered promptly.

Answer 9

B. Glioblastoma Multiforme Rationale: Glioblastoma Multiforme (GBM) is the most common and aggressive primary brain tumor in adults. It is a high-grade astrocytoma and is characterized by rapid growth and poor prognosis.

Answer 10

B. Pilocytic Astrocytoma Rationale: In children, pilocytic astrocytoma is a common brain tumor, especially in the posterior fossa, presenting with symptoms such as headache and vomiting due to increased intracranial pressure. Glioblastoma Multiforme is rare in this age group.

Answer 11

A. Oligodendroglioma Rationale: Oligodendrogliomas are typically located in the supratentorial region of the brain, especially in the cerebral hemispheres. Medulloblastomas and Schwannomas are commonly found in the infratentorial region.

Answer 12

B. Wallerian Degeneration Rationale: Wallerian Degeneration is a process where the part of the axon distal to the site of injury degenerates, often described as a "dying forward" phenomenon.

Answer 13

D. Sudden loss of vision in one eye Rationale: Acute stroke can present with sudden onset of neurological deficits, including loss of vision in one eye (amaurosis fugax), which may be due to embolism or other vascular events. Other options do not typically present suddenly as stroke symptoms do.

Answer 14

A. The overall prevalence is 10% Rationale: Febrile seizures are the most common type of seizure during childhood, reportedly occurring in 2-5% of children aged 6 months to 5 years. The statement that the overall prevalence is 10% is incorrect, as the actual prevalence is significantly lower.

Answer 15

B. Continuous multifocal spikes and slow waves of large amplitude Rationale: West Syndrome, or Infantile Spasms, is characterized by a specific EEG pattern called hypsarrhythmia, which includes continuous multifocal spikes and slow waves of large amplitude.

Answer 16

A. Right subthalamic nucleus Rationale: The patient's symptoms of sudden onset forceful, flinging movements (hemiballismus) of the left arm and leg suggest a lesion in the right subthalamic nucleus. Hemiballismus is typically caused by a lesion in the contralateral subthalamic nucleus, which results in involuntary, violent movements on the opposite side of the body. This fits with the patient's clinical presentation and history of transient weakness, indicating a possible vascular event affecting the subthalamic nucleus.

Answer 17

A. Early fecal and urinary incontinence Rationale: Cauda equina syndrome typically presents with gradual onset of symptoms, including areflexia, severe radicular pain, and gradual and unilateral numbness and weakness of the lower extremities. Early fecal and urinary incontinence is not typical of cauda equina syndrome and usually occurs later in the disease progression.

Answer 18

A. The treatment for vasogenic edema is the use of steroids. Rationale: Vasogenic edema, which is due to the breakdown of the blood-brain barrier, is often treated with steroids to reduce inflammation. Interstitial edema is usually due to hydrocephalus and managed with measures like mannitol or hypertonic saline to reduce intracranial pressure. Large infarcts typically present with cytotoxic edema, not vasogenic. Space-occupying lesions like tumors usually cause vasogenic edema, not interstitial edema.

Answer 19

D. All of the above. Rationale: Diffuse axonal injury (DAI) results from widespread mechanical disruption or shearing of axons, most commonly affects the corpus callosum, and can explain persistent coma or vegetative state after closed head injury. All statements provided are true.

Answer 20

A. Arsenic Rationale: Arsenic poisoning can cause a neuropathy that mimics Guillain-Barré Syndrome, presenting with symptoms like weakness and sensory loss.

Answer 21

B. Colchicine Rationale: Colchicine disrupts microtubules and impairs axonal transport, leading to potential neurotoxic effects.

Answer 22

D. All of the Above Rationale: Coordination can be assessed using the Heel to Shin Test, Finger to Nose Test, and Rapid Alternating Movements. All these tests evaluate different aspects of cerebellar function and coordination.

Answer 23

C. Middle Cerebellar Peduncle Rationale: The middle cerebellar peduncle, also known as the brachium pontis, connects the cerebellum to the pons and carries fibers from the contralateral cerebral cortex.

Answer 24

A. Oligoclonal bands in the CSF Rationale: Oligoclonal Ig bands (OCBs) of the cerebrospinal fluid (CSF) are a hallmark of multiple sclerosis (MS). These bands indicate an abnormal immune response within the central nervous system and are used as a diagnostic marker for MS. While oligoclonal bands can also be found in the CSF of patients with Neuromyelitis optica (Devic's disease), their presence is most closely associated with multiple sclerosis. The options regarding chromosomal markings and "None of the above" are not correct in this context.

Answer 25

A. All of the above Rationale: Most intradural mass lesions in adults result from metastases to the adjacent vertebral column, and the thoracic spinal column is the most commonly involved region. While primary intradural tumors can be benign, metastases are more common in adults.

Answer 26

B. Loss of reflexes without neuropathy Rationale: Subacute Combined Degeneration, often due to vitamin B12 deficiency, is characterized by loss of position and vibration sense, and predominant involvement of the posterior and lateral tracts. Loss of reflexes is typically associated with neuropathy, which is contrary to the nature of this condition.

Answer 27

A. Early fecal and urinary incontinence Rationale: According to Harrison's Principles of Internal Medicine, cauda equina syndrome typically presents with gradual onset of symptoms such as severe radicular pain, areflexia, and unilateral numbness and weakness of the lower extremities. Fecal and urinary incontinence can occur, but they are not early symptoms; they develop as the syndrome progresses.

Answer 28

**C. Spinal cord, lower thoracic level**. Rationale: 1. **Lower Extremity Numbness and Weakness**: Severe weakness (0/5 strength) in both lower extremities suggests a lesion affecting the motor pathways to the legs, which are located in the lower thoracic or lumbar spinal cord. 2. **Urinary Retention**: This indicates involvement of the spinal cord segments responsible for autonomic control of bladder function, typically found in the lower thoracic and upper lumbar regions. 3. **Sensory Level at the Nipple Area (T4)**: While a lesion at the T4 level would traditionally present with a sensory level at or below T4, a lesion in the lower thoracic region could cause ascending symptoms affecting higher dermatomes over time. 4. **Bilateral Babinski and Clonus**: These upper motor neuron signs suggest a lesion affecting the corticospinal tracts, which can be seen in spinal cord lesions involving the thoracic region. Although the sensory level at T4 initially seems to indicate a higher lesion, the constellation of symptoms including severe bilateral lower extremity weakness, urinary retention, and upper motor neuron signs aligns with a lower thoracic spinal cord lesion. **Correct Answer: C. Spinal cord, lower thoracic level**

Answer 29

**D. Vascular Parkinsonism**. Rationale based on Harrison's Principles of Internal Medicine: 1. **Gait Difficulty and Lack of Arm Swing**: Vascular Parkinsonism often presents with prominent gait disturbance, which can include difficulty in walking and a shuffling gait. The lack of arm swing on the affected side is also a common feature. 2. **Asymmetrical Symptoms**: While typically, Vascular Parkinsonism can present with more symmetrical symptoms, asymmetry can occur depending on the location of the cerebrovascular lesions. 3. **Constipation**: Although constipation is a common non-motor symptom in Idiopathic Parkinson Disease (IPD), it can also be present in Vascular Parkinsonism due to overall autonomic dysfunction. 4. **History of Falls and REM Sleep Behavior Disorder**: While REM sleep behavior disorder is more characteristic of IPD, patients with Vascular Parkinsonism can also experience sleep disturbances and falls. 5. **Absence of Tremor**: Tremor is less common in Vascular Parkinsonism compared to IPD, which aligns with this patient's lack of tremor. 6. **Risk Factors and History**: Vascular Parkinsonism is often associated with cerebrovascular disease and risk factors such as hypertension, diabetes, and previous strokes. The gradual progression of symptoms over the years can be due to cumulative cerebrovascular damage. 7. **Neuroimaging Findings**: Although not provided in the case, neuroimaging in Vascular Parkinsonism typically shows cerebrovascular lesions, particularly in the basal ganglia or other areas involved in motor control. In summary, Vascular Parkinsonism is the most likely diagnosis for this patient given the chronic progression of gait difficulty, unilateral symptoms, lack of tremor, and the presence of non-motor symptoms like constipation and sleep disturbances. The absence of a classical resting tremor and the context of progressive symptoms without a sudden onset fits the pattern of Vascular Parkinsonism.

Answer 30

D. Dysmetria Rationale: Harrison's notes that posterior circulation strokes can lead to symptoms such as dysmetria, which is a lack of coordination involving the cerebellum. Other options like astereognosis, apraxia, and aphasia are typically associated with anterior circulation strokes.

Answer 31

B. Haloperidol 1 mg 1 to 3 times per day Rationale: Harrison's suggests that for the chorea associated with Huntington's disease, antipsychotic medications such as Haloperidol can be useful in managing the involuntary movements.

Answer 32

B. Treatment includes low copper diet Rationale: Wilson's disease is managed by reducing copper intake and enhancing copper excretion. According to Harrison's, a low copper diet is an essential part of treatment. The disease is autosomal recessive and involves a mutation in the ATP7B gene.

Answer 33

C. Female gender Rationale: Harrison's indicates that severe COVID-19 infection, pre-existing lung disease, and advanced age are predictors for post-COVID-19 interstitial lung disease and fibrosis. Female gender is not listed as a specific risk factor.

Answer 34

B. Anisocoria Rationale: Harrison's describes uncal herniation as causing compression of the oculomotor nerve, resulting in anisocoria (unequal pupil sizes) due to impaired parasympathetic innervation on the affected side.

Answer 35

D. All of the above Rationale: Miller Fisher Syndrome, a variant of Guillain-Barré Syndrome, is characterized by a triad of ataxia, ophthalmoplegia, and areflexia, as described in Harrison's.

Answer 36

A. Carbamazepine Rationale: According to Harrison's Principles of Internal Medicine, benign epilepsy of childhood with centrotemporal spikes (also known as Rolandic epilepsy) is a type of focal epilepsy that typically presents with nocturnal seizures and has a good prognosis. Carbamazepine is one of the first-line treatments for this condition. It is effective in controlling focal seizures and is generally well-tolerated in children. While other antiepileptic drugs like valproic acid and lamotrigine can also be used, carbamazepine is often preferred for its efficacy and safety profile in this particular type of epilepsy.

Answer 37

A. Reduction in the number of acetylcholine receptors at the neuromuscular junction Rationale: Myasthenia gravis is an autoimmune disorder characterized by antibodies directed against acetylcholine receptors on the postsynaptic membrane of the neuromuscular junction. This results in a reduction in the number of functional acetylcholine receptors, leading to impaired neuromuscular transmission and muscle weakness.

Answer 38

A. Normal pupil Rationale: The clinical manifestations of myasthenia gravis include muscle weakness and fatigue that worsens with activity and improves with rest. Pupillary function is typically normal in myasthenia gravis, which means that pupils remain normal in size and reaction. While the table in the screenshot mentions various aspects of myasthenic crises, tachycardia, increased secretion, and pale color skin are not typical primary manifestations of myasthenia gravis itself. Tachycardia can be a feature of myasthenic crisis, but the question asks about the typical clinical manifestations of myasthenia gravis. Therefore, the correct answer is that the pupils are normal.

Answer 39

A. Weakness evolves over hours to days with tingling dysesthesias in extremities Rationale: Guillain-Barre syndrome (GBS) is an acute inflammatory demyelinating polyneuropathy characterized by rapid-onset muscle weakness and tingling dysesthesias that progress over hours to days. This weakness often starts in the legs and can ascend to affect the arms and upper body.

Answer 40

A. Group of interconnected nuclei located deep within the cerebral hemisphere Rationale: The basal ganglia are a group of interconnected subcortical nuclei located deep within the cerebral hemispheres. They play a critical role in regulating voluntary motor movements, procedural learning, routine behaviors, and emotions.

Answer 41

A. Hypo- or bradykinesia, resting tremor, gait dysfunction, rigidity Rationale: Parkinson's disease is characterized by motor symptoms including bradykinesia (slowness of movement), resting tremor, gait dysfunction, and rigidity. These symptoms result from the degeneration of dopaminergic neurons in the substantia nigra.

Answer 42

A. Regional dissociated sensory loss and areflexic weakness in the upper limbs Rationale: Syringomyelia is a disorder where a cyst or cavity forms within the spinal cord. This can lead to a characteristic pattern of dissociated sensory loss (loss of pain and temperature sensation with preserved light touch and proprioception) and areflexic weakness, particularly affecting the upper limbs.

Answer 43

A. Common radicular pain and ascending progression of paresthesias Rationale: Extramedullary spinal cord lesions often cause radicular pain (pain radiating along the nerve pathway) and can lead to ascending progression of paresthesias (abnormal sensations). This pattern is due to the compression and irritation of nerve roots and spinal cord segments.

Answer 44

A. Treatment includes low copper diet Rationale: Wilson’s disease is a genetic disorder resulting in excessive accumulation of copper in tissues. Treatment involves a low copper diet, along with medications such as chelating agents to remove excess copper and zinc to block copper absorption.

Answer 45

B. Warfarin Rationale: In the acute phase of ischemic stroke due to atherothrombosis, antiplatelet agents like aspirin are preferred. Warfarin is an anticoagulant used primarily for cardioembolic strokes, not typically for atherothrombotic strokes. Mannitol may be used to manage cerebral edema in cases of large infarctions.

Answer 46

A. Schwannoma Rationale: Schwannomas are typically found in the peripheral nervous system, often associated with cranial nerves, such as vestibular Schwannomas on the 8th cranial nerve. In contrast, astrocytomas, oligodendrogliomas, and germinomas can occur in the supratentorial region of the brain.

Answer 47

A. Carotid bifurcation Rationale: According to Harrison's Principles of Internal Medicine, the carotid bifurcation is a common site for the formation of atherosclerotic plaques, which can lead to artery-to-artery emboli. These emboli can travel to the brain and cause ischemic strokes.

Answer 48

C. Diffuse axonal injury Rationale: Diffuse axonal injury (DAI) is a type of traumatic brain injury characterized by widespread shearing and tearing of axons in the brain's white matter. It is often caused by rapid acceleration or deceleration forces, such as those experienced in motor vehicle accidents.

Answer 49

A. 3rd generation cephalosporin + Vancomycin (with or without Ampicillin) Rationale: The recommended first-line empiric treatment for acute bacterial meningitis in adults includes a third-generation cephalosporin (such as ceftriaxone or cefotaxime) combined with vancomycin to cover for Streptococcus pneumoniae, with the addition of ampicillin for coverage of Listeria monocytogenes in certain populations (e.g., the elderly or immunocompromised).

Answer 50

B. Memantine Rationale: Memantine is not considered the first-line treatment for Lewy Body Dementia. Cholinesterase inhibitors, such as rivastigmine, donepezil, and galantamine, are typically preferred for managing cognitive symptoms in Lewy Body Dementia. Memantine is more commonly used for Alzheimer's disease but is not as effective for Lewy Body Dementia.

Answer 51

A. Romberg's Rationale: The Romberg test primarily assesses proprioception and vestibular function, not cerebellar function. The heel to shin test, finger to nose test, and alternate pronation supination are direct tests of cerebellar function, evaluating coordination and fine motor control.

Answer 52

A. 4 vessel angiogram Rationale: A 4-vessel angiogram is considered the gold standard for diagnosing subarachnoid hemorrhage (SAH) and identifying the source of bleeding, such as an aneurysm or arteriovenous malformation. While CT scans are often the first step in evaluating suspected SAH, angiography provides detailed visualization of the cerebral vasculature.

Answer 53

A. Creutzfeldt-Jakob disease Rationale: Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, fatal neurodegenerative prion disease. It presents with a combination of cognitive decline, pyramidal and extrapyramidal symptoms, visual and cerebellar dysfunction, myoclonus, and eventually akinetic mutism.

Answer 54

A. Acyclovir Rationale: Acyclovir is the first-line treatment for herpes simplex virus (HSV) encephalitis. It is an antiviral medication that significantly improves outcomes if administered early in the course of the disease.

Answer 55

A. Arsenic Rationale: Arsenic poisoning can cause a neuropathy that resembles Guillain-Barre syndrome (GBS), characterized by progressive weakness and sensory disturbances. Other listed drugs do not typically cause neuropathy with a similar presentation to GBS.

Answer 56

C. Pseudomonas aeruginosa Rationale: Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae are common pathogens that have a predilection for causing meningitis. Pseudomonas aeruginosa is not typically associated with meningitis and is more commonly involved in infections of other body sites, particularly in immunocompromised patients.

Answer 57

A. The treatment for vasogenic edema is the use of steroids Rationale: Vasogenic edema, which is due to the disruption of the blood-brain barrier, is often treated with steroids to reduce inflammation and edema. Cytotoxic edema, resulting from cellular injury and swelling, is not effectively treated with steroids. Steroids can be ineffective in some forms of cerebral edema, and vasogenic edema can respond to treatment with steroids.

Answer 58

A. Urinary Tract Rationale: Genitourinary TB primarily affects the urinary tract, which includes the kidneys, ureters, bladder, and urethra. While genitourinary TB can involve multiple structures within the urinary system, the term "urinary tract" encompasses all these organs and structures. It is important to note that genitourinary TB can involve one or more specific structures within the urinary tract, but the overall term "urinary tract" represents the primary site of infection for this condition.

Answer 59

C. Fallopian tubes and endometrium Rationale: In women, genitourinary tuberculosis most commonly affects the fallopian tubes and the endometrium. These are the primary sites where the infection is likely to spread, leading to complications such as infertility.

Answer 60

D. Spine Rationale: Skeletal tuberculosis, or Pott's disease, most commonly affects the spine in about 40% of cases. This form of TB can lead to significant morbidity due to vertebral involvement and potential spinal deformities.

Answer 61

C. Ulnar nerve Rationale: In type I (reversal) reactions of leprosy, the ulnar nerve is the most commonly affected nerve trunk. This results in neuropathy with sensory loss and muscle weakness, often leading to characteristic claw hand deformities.

Answer 62

E. All **Rationale:** When evaluating a patient with symptoms suggestive of acute viral hepatitis, it is important to order a panel of serologic tests to determine the specific viral cause. The recommended serologic tests for evaluating acute viral hepatitis include: A. **HBsAg (Hepatitis B surface antigen):** This test detects the presence of the hepatitis B virus (HBV) surface antigen, indicating an active HBV infection. B. **IgM anti-HAV (IgM antibody to hepatitis A virus):** This test detects the presence of IgM antibodies specific to the hepatitis A virus (HAV), indicating an acute HAV infection. C. **IgM anti-HBc (IgM antibody to hepatitis B core antigen):** This test detects the presence of IgM antibodies specific to the hepatitis B core antigen, indicating an acute HBV infection. D. **Anti-HCV (Antibody to hepatitis C virus):** This test detects the presence of antibodies to the hepatitis C virus (HCV), indicating a past or current HCV infection. Since the patient in the scenario presented with symptoms of acute viral hepatitis, it would be appropriate to request all of the serologic tests (A, B, C, and D) to evaluate for the most common causes of acute viral hepatitis, which are hepatitis A, B, and C. Therefore, option E, All, is the correct choice in this case.

Answer 63

B. Lepromatous leprosy Rationale: According to Harrison's Principles of Internal Medicine, lepromatous leprosy is characterized by symmetric, multiple infiltrated nodules and plaques. This form of leprosy has a high bacterial load and affects the skin diffusely.

Answer 64

B. Ulnar nerve Rationale: The ulnar nerve is the most commonly affected nerve in leprosy. Damage to this nerve leads to sensory loss and muscle weakness in the hand, commonly resulting in the characteristic claw hand deformity.

Answer 65

A. Tuberculoid leprosy Rationale: Tuberculoid leprosy is characterized by one or more asymmetric macules or plaques with a tendency toward central clearing and elevated borders. This form of leprosy has a lower bacterial load and involves a strong immune response that leads to more localized lesions.

Answer 66

B. Plantar ulceration Rationale: Lepromatous leprosy is associated with several complications due to its chronic nature and extensive involvement of the skin, nerves, and other tissues. One of the most common complications is plantar ulceration, which occurs as a result of sensory loss and repeated trauma to the feet. The lack of sensation leads to unrecognized injuries and subsequent ulcers, particularly on weight-bearing areas like the soles of the feet. This complication is more frequent than other issues such as blindness, foot drop, or clawing of the fingers in the context of lepromatous leprosy.

Answer 67

A. Dapsone, rifampicin, clofazimine Rationale: The standard multidrug therapy for lepromatous leprosy includes dapsone, rifampicin, and clofazimine. This combination effectively reduces the bacterial load and prevents the development of drug resistance.

Answer 68

A. True Rationale: AIDS was first recognized in 1981 in the United States when the CDC reported unexplained cases of Pneumocystis pneumonia and other opportunistic infections in previously healthy homosexual men in Los Angeles, New York, San Francisco, and other cities.

Answer 69

C. Condition in which underlying circulatory and cellular/metabolic abnormalities leads to increased mortality risk Rationale: Septic shock is a severe and potentially fatal condition that arises from sepsis, which is a dysregulated response to infection leading to life-threatening organ dysfunction. Septic shock specifically refers to a subset of sepsis cases characterized by underlying circulatory and cellular/metabolic abnormalities that result in increased mortality risk. This includes persistent hypotension requiring vasopressors to maintain mean arterial pressure (MAP) ≥ 65 mm Hg and serum lactate level > 2 mmol/L despite adequate fluid resuscitation, indicating profound abnormalities in perfusion and metabolism.

Answer 70

D. Reversal reaction Rationale: Reversal reactions, also known as type 1 reactions, occur after the initiation of therapy and are characterized by an increase in cell-mediated immunity. This leads to a more tuberculous histology with increased inflammation and may result in nerve damage.

Answer 71

B. Erythema nodosum leprosum Rationale: Erythema nodosum leprosum (ENL) is a type of immune-mediated reaction seen in leprosy, particularly in lepromatous leprosy. It presents with painful erythematous papules or nodules that can resolve spontaneously but often recur. It is an immune complex-mediated reaction.

Answer 72

B. False Rationale: While HIV is predominantly a sexually transmitted infection, in developing countries, heterosexual transmission is often the most common mode. Male homosexual transmission is more commonly associated with higher prevalence in Western countries.

Answer 73

A. True Rationale: In Western countries, male homosexual transmission is a significant mode of HIV transmission, contributing largely to the epidemic in these regions.

Answer 74

A. True Rationale: These are all opportunistic diseases that can involve the central nervous system (CNS) in patients with HIV infection. They are commonly seen in the context of advanced immunosuppression.

Answer 75

A. Cryptococcosis Rationale: Cryptococcosis, caused by Cryptococcus neoformans, is the leading infectious cause of meningitis in patients with AIDS. It is a significant opportunistic infection in this population.

Answer 76

A. JC Virus Rationale: Progressive multifocal leukoencephalopathy (PML) is an opportunistic infection caused by the JC virus, a human polyomavirus. It leads to demyelination of the central nervous system in immunocompromised patients, including those with AIDS.

Answer 77

A. 2.5 ng/kg BW Rationale: According to Harrison's Principles of Internal Medicine, the minimal lethal dose of tetanospasmin (the toxin produced by Clostridium tetani) in humans is approximately 2.5 ng/kg body weight. This extremely potent toxin interferes with neurotransmission, leading to the characteristic muscle spasms and autonomic dysfunction seen in tetanus.

Answer 78

A. Puncture wound Rationale: The most common mode of transmission of tetanus in adults is through puncture wounds. These types of wounds provide an anaerobic environment that is conducive to the growth of Clostridium tetani spores, which release the toxin causing tetanus.

Answer 79

C. Persons >60 years old because antibody levels decrease over time Rationale: Persons over 60 years old are at greater risk of tetanus because their antibody levels decrease over time, especially if they have not received booster vaccinations. This age-related decline in immunity increases their susceptibility to tetanus infection.

Answer 80

B. Presynaptic inhibitory nerves Rationale: The clinical presentation of tetanus occurs after the tetanus toxin (tetanospasmin) has reached the presynaptic inhibitory nerves. The toxin blocks the release of inhibitory neurotransmitters (such as GABA and glycine), leading to unopposed muscle contraction and spasm.

Answer 81

A. True Rationale: Botulism toxin is recognized as a potential bioterrorism agent due to its extreme potency and lethality. It has been considered for use by governments and terrorist groups for its ability to cause widespread harm with small quantities.

Answer 82

A. True Rationale: In cases of foodborne botulism, gastrointestinal symptoms such as nausea, vomiting, and abdominal pain can precede or follow the onset of paralysis. These symptoms are due to the ingestion of food contaminated with Clostridium botulinum toxin.

Answer 83

D. None Rationale: There is currently no widely available or routinely recommended vaccination for botulism for the general public, including women of childbearing age or as a booster every 10 years.

Answer 84

B. False Rationale: The cornerstone treatment for botulism includes meticulous intensive care and administration of antitoxin, not botox. Supportive care is crucial, particularly mechanical ventilation if respiratory failure occurs, and the antitoxin helps neutralize circulating toxin.

Answer 85

C. Taenia saginata Rationale: Taenia saginata, also known as the beef tapeworm, is contracted through the ingestion of insufficiently cooked beef containing larval cysts.

Answer 86

C. Neuromuscular junction Rationale: Botulinum toxin primarily affects the neuromuscular junction, where it inhibits the release of acetylcholine, leading to muscle paralysis. It does not typically affect preganglionic parasympathetic nerve endings or peripheral serotonergic nerve terminals.

Answer 87

C. Benzodiazepine Rationale: Benzodiazepines are the drug of choice for controlling tetanus spasms. They act as muscle relaxants and help manage the muscle rigidity and spasms associated with tetanus.

Answer 88

**Answer: B. Penicillin is the drug of choice** **Rationale:** While the correct answer according to current guidelines is B, let’s clarify why establishing a secure airway is not the incorrect choice: 1. **A. Establishing a secure airway is the first priority in severe tetanus:** This statement is true. In cases of severe tetanus, airway management is crucial due to the risk of laryngeal spasms and respiratory failure. Ensuring the patient has a secure airway, often through tracheostomy or intubation, is a priority. 2. **B. Penicillin is the drug of choice:** This statement is no longer accurate as metronidazole has become the preferred antibiotic over penicillin for tetanus treatment due to its efficacy and lower risk of adverse effects, such as seizures. 3. **C. Antitoxin is given to deactivate the circulating tetanus toxin:** This is true. Administration of tetanus immunoglobulin (antitoxin) is critical to neutralize the toxin that has not yet bound to nerve tissue. 4. **D. Wound debridement is important to prevent further toxin production:** This is true. Proper wound care, including debridement, is essential to remove the source of Clostridium tetani bacteria and prevent further toxin production. Thus, the statement about penicillin being the drug of choice is the exception.

Answer 89

B. Cercaria Rationale: Cercariae are the infective stage of Schistosomiasis. They are released by freshwater snails and penetrate the skin of humans who come into contact with contaminated water.

Answer 90

C. Small venules of the portal and perivesical system Rationale: Adult Schistosoma worms are most commonly found in the small venules of the portal and perivesical systems. For example, Schistosoma mansoni primarily resides in the mesenteric veins draining the small intestine, while Schistosoma haematobium is found in the venous plexus of the bladder.