Flashcards in CN LANGE - Sensory Disorders I Deck (126):
The sensory pathway between peripheral tissues (eg skin or joints) and the cerebral cortex involves ...?
3 neurons and 2 central synapses.
Relatively specialized for particular sensations:
1. Free endings --> Pain, itch.
2. Meissner corpuscles + Merkel corpuscles + Hair cells --> Touch.
3. Krause end-bulbs --> Cold.
4. Ruffini corpuscles --> Heat.
Other fibers that mediate touch and those subserving pain, temp, and itch appreciation in the limbs and trunk synapse on neurons in the ...?
Posterior horns of the spinal cord --> Particularly in the substantia gelatinosa.
Fibers that mediate facial touch and pressure sensation project from the main trigeminal sensory nucleus via the ...?
Fibers that convey facial pain, itch, and temperature project from the spinal trigeminal nerve nucleus via the ...?
Trigeminothalamic tract to the IPSILATERAL thalamus.
In the thalamus, medial lemniscal and spinothalamic fibers synapse in the VPL nucleus - Spinothalamic fibers also synapse in the ...?
VPI (ventral posteroinferior) + ILa (intralaminar) nuclei.
In addition some 2nd-order spinothalamic sensory neurons send collaterals to ...?
The reticular formation.
Fibers from the VPL, VPI, and VPM travel primarily to ...?
Primary somatosensory cortex in the postcentral gyrus.
--> Fibers from ILa also project to:
2. Cingulate gyrus.
3. Prefrontal cortex.
History - Sensory disturbances may consist of ...?
1. Loss of sensation.
2. Abnormal sensations.
Abnormal spontaneous sensations, such as burning, tingling, or pins and needles.
Any unpleasant sensation produced by a stimulus that is normally painless.
The term numbness is often used by the patients to describe a sense of ...?
in part of the body.
--> Sometimes to signify any sensory impairment.
Anesthesia --> Complete loss of touch appreciation.
Hypesthesia --> Partial loss.
Hyperesthesia --> Incr. sensitivity.
--> Corresponding terms for pain --> Analgesia/Hypalgesia/Hyperalgesia or hyperpathia.
Misperception of a trivial tactile sensation as pain.
Primary sensory modalities - Deep pressure is evaluated ...?
By pressure on the tendons, such as the Achilles tendon at the ankle.
Vibration - Many healthy elderly patients have impaired ...?
Appreciation of vibration below the knees.
Joint position - Patients with severe impairment of joint position sense may exhibit ...?
Slow, continuous movement of fingers (pseudoathetoid movement) when attempting to hold the hands outstretched with eyes closed.
For clinical purposes, both joint position sense and the ability to appreciate vibration are considered to depend on fibers carried in the posterior columns of the spinal cord, although ...?
This is NOT strictly true for vibration.
The ability to distinguish simultaneous touch at 2 neighboring points depends on the integrity of ...?
1. CNS and peripheral NS.
2. The degree of separation of the 2 points.
3. The part of the body that is stimulated.
Threshold for 2 point discrimination approximates ... at the fingertips, and may be several ... on the back.
4mm --> Fingertips.
Several cm --> On the back.
When peripheral sensory function is intact, impaired 2-point discrimination suggests a disorder affecting the ...?
Agraphesthesia implies a lesion involving ...?
The CONTRALATERAL PARIETAL lobe.
--> Same is true for astereognosis, and abarognosis.
Bilateral sensory discrimination:
In some patients with apparently normal sensation, simultaneous stimulation of the 2 sides of the body reveals an APPARENT NEGLECT of (or inattention to) sensation from one side, usually because of an underlying CONTRALATERAL cerebral lesion.
Failure to find clinical evidence of sensory loss in patients with sensory symptoms should ...?
NOT imply that the symptoms necessarily have a psychogenic basis.
--> Sensory symptoms often develop well before the onset of sensory signs.
Peripheral nerve lesions - Mononeuropathy - Compressive lesions tend to affect ...?
Preferentially the LARGE FIBERS subserving touch.
What is the characteristic feature of polyneuropathy?
Sensory loss is generally symmetric and is greater DISTALLY than PROXIMALLY.
Polyneuropathy - What is Tangier disease?
A recessive trait characterized by the near absence of HDL.
Spinal cord lesions - Keep in mind the physiologic areas of increased sensitivity:
1. At the costal margin.
2. Over the breasts.
3. In the groin.
The level of sensory deficit affecting the trunk is best determined by careful sensory testing over ...?
The back rather than the chest and abdomen.
Spinal cord lesion - Central cord lesion:
Syringomyelia, trauma, with certain tumors --> Loss of pain and temperature appreciation with SPARING of other modalities.
Central cord lesion - May be accompanied by ...?
1. LMN weakness in the muscles supplied by the affected segments.
2. Sometimes by a pyramidal + posterior column deficit below the lesion.
Anterolateral spinal cord lesion - The spinothalamic tract is laminated:
1. Intramedullary lesions often spare SACRAL fibers.
2. Extramedullary lesions tend to involve sacral fibers.
Posterior column lesion:
A patient with posterior column lesion may complain of a tight or bandlike sensation in the regions corresponding to the level of spinal involvement.
--> Sometimes also of paresthesias (like electric shocks) radiating down the extremities on neck flexion (Lhermitte sign).
Hemisection of the spinal cord - The contralateral loss of pain and temp appreciation begins ...?
2 or 3 segments below the lesion.
Hemisection of the spinal cord - Other feature:
HYPERALGESIA + spontaneous pain are sometimes prominent IPSILATERALLY.
Brainstem lesions - Sensory disturbances may be accompanied by ...?
1. A motor deficit.
2. Cerebellar signs.
3. Cranial nerve palsies.
Brainstem lesions - When such a lesion is MEDULLARY, it also typically involves the ...?
Spinal trigeminal nucleus, impairing pain and temperature sensation on the SAME side of the face as the lesion.
--> CROSSED SENSORY DEFICIT = Ipsilateral face + contralateral limbs.
Brainstem lesions - Spinothalamic lesions above the spinal trigeminal nucleus affect ...?
The face, limbs, and trunk CONTRALATERAL to the lesion.
May lead to loss or impairment of all forms of sensation on the contralateral side of the body, and this may have a distribution that differs from the area of symptomatic involvement.
Any form of cutaneous stimulation can lead to painful or unpleasant sensations.
--> Can also occasionally result from lesions of the white matter of the parietal lobe or from spinal cord lesions.
Lesions of the sensory cortex:
Disease limited to the sensory cortex impairs discriminative sensory function on the opposite side of the body.
Lesions of the sensory cortex - Patients may be unable to ...?
1. Localize stimuli on the affected side.
2. Recognize the position of different parts of the body.
3. Astereognosis, abarognosis etc.
Cortical sensory disturbances are usually more conspicuous in the ...?
Hands than in the trunk or proximal portions of the limbs.
Peripheral nerve lesions - The term mononeuropathy simplex:
Signifies involvement of a single peripheral nerve.
The term mononeuropathy multiplex:
Several individual nerves are affected, usually AT RANDOM + NONCONTIGUOUSLY.
Main categories of causes of peripheral neuropathy:
1. Idiopathic inflammatory neuropathies.
2. Metabolic and nutritional neuropathies.
3. Infective and granulomatous neuropathies.
4. Vasculitic neuropathies.
5. Neoplastic and paraproteinemic neuropathies.
6. Drug-induced and toxic neuropathies.
7. Hereditary neuropathies.
8. Entrapment neuropathies.
The term polyneuropathy denotes a disorder in which the ...?
Function of several peripheral nerves is affected at the SAME TIME.
Polyneuropathies - Classification:
1. Distal axonopathies (axonal neuropathies).
2. Myelinopathies (demyelinating neuropathies).
Distal axonopathies (axonal neuropathies):
The axon is the principal target - Most polyneuropathies fall into this category.
Myelinopathies (demyelinating neuropathies):
Involve the myelin sheath surrounding the axon.
Mention some myelinopathies:
1. Acute idiopathic polyneuropathy (Guillain-Barre).
4. Certain paraneoplastic and paraproteinemic states.
5. Various hereditary conditions including: Metachromatic leukodystrophy, Krabbe, types 1 and 3 Charcot-Marie-Tooth hereditary motor and sensory neuropathy (CMT-1 and 3).
Certain disorders, termed neuronopathies, principally affect nerve cell bodies in the anterior horn of the spinal cord or dorsal root ganglion. Examples are:
1. Type 2 CMT.
2. Pyridoxine-induced neuropathy.
3. Some paraneo syndromes.
Sensory disturbances - Involvement of sensory fibers can lead to ...?
2. Impaired sensation.
3. Abnormal spontaneous sensations, such as pain and paresthesias.
4. Perverted sensations such as hyperpathia (amplified response to a normally painful stimulus).
Pain is a conspicuous feature of certain neuropathies, especially if ...?
Small fibers within the nerves are affected. (not precisely known why).
Polyneuropathies associated with pain include:
8. Dominantly inherited sensory neuropathy.
9. Paraneoplastic sensory neuroNOpathy.
Dissociated sensory loss:
Impairment of some sensory modalities, such as pain and temperature, with preservation of others, such as light touch, vibration, and joint position sense.
Where is dissociated sensory loss commonly found?
In spinal cord lesions.
Dissociated sensory loss ALSO occurs in peripheral neuropathies when there is ...?
Selective involvement of peripheral nerve fibers of a CERTAIN SIZE --> Amyloid neuropathy, leprous neuritis, or hereditary sensory neuropathy.
Small fiber disease is commonly associated with:
1. Disproportionate impairment of pain and temperature appreciation.
2. Spontaneous pain.
3. Autonomic dysfunction.
Large fiber disease by contrast, results in ...?
1. Defective touch, vibration, and joint position sense.
2. Early loss of tendon reflexes.
3. Prominent motor symptoms.
Which reflex is usually the first to be lost in polyneuropathy?
The ankle reflex - May also be absent in HEALTHY elderly subjects.
Autonomic disturbances are associated with:
3. Renal failure.
5. Certain paraneo disorders.
Palpably enlarged nerves raise the possibility of:
3. Hereditary motor and sensory neuropathies.
4. Refsum disease.
What is often the first manifestation of an occupationally-related polyneuropathy?
Peripheral neuropathy may be related to metabolic disorders such as:
3. Liver disease.
6. Metachromatic leukodystrophy.
Peripheral neuropathy due to diabetes is particularly important and may take the form of:
1. Entrapment mononeuropathy.
2. Acute ischemic mononeuropathy.
3. Distal sensorimotor polyneuropathy.
4. Subacute proximal motor polyradiculoplexopathy (diabetic amyotrophy).
5. Thoracoabdominal radiculopathy.
6. Autonomic neuropathy.
Connective tissue disorders may be associated with mononeuropathy multiplex or, less commonly, polyneuropathy or cranial neuropathy:
4. Granulomatosis with polyangiitis.
Polyneuropathy is more common in which connective tissue disease?
AIDS and polyneuropathy?
Commonly associated with a distal, symmetric, primarily sensory polyneuropathy.
Less common polyneuropathies associated with AIDS:
1. Acute or chronic inflammatory demyelinating polyneuropathy.
3. Mononeuropathy multiplex.
4. Autonomic neuropathy.
Peripheral neuropathies - DDx - The preservation of sensation + tendon reflexes distinguishes the motor deficit of ... from that caused by peripheral nerve involvement.
1. Pure pyramidal lesions.
2. Spinal muscular atrophies.
4. Disorders of neuromuscular transmission.
Respiratory function must be monitored particularly in which polyneuropathies?
1. Acute idiopathic polyneuropathy.
3. Diphtheritic neuropathy.
Patients with sensory disorders may suffer from especially severe pain, which can impair quality of life. Treatment of this pain is important:
4. Phenytoin, carbamazepine, mexiletine.
5. Amitriptyline - If the pain is constant, burning, or dysesthetic.
7. Topiramate, Valproate, Lamotrigine (caution with skin rashes and other complications).
Guillain-Barre - Forms:
BOTH demyelinating and axonal forms occur --> Distinctive clinical and electrophysiologic features.
Guillain-Barre form MC in USA:
The demyelinative form is more common - An axonal variant is encountered occasionally (acute motor sensory axonal neuropathy).
Guillain-Barre - Patients generally present with ...?
1. Ascending weakness that is symmetric.
2. Usually begins in the legs.
3. Often more marked PROXIMALLY than distally.
4. May be life-threatening if muscles of respiration or shallowing are involved.
Guillain-Barre - Sensory complaints?
Also frequent, although usually less marked than motor symptoms.
Guillain-Barre - Deep tendon reflexes?
Guillain-Barre - CSF:
Often shows CYTOALBUMINOLOGIC dissociation --> Incr. protein concentration but normal cell count.
--> Abnormalities may NOT occur in the first week.
Diagnostic criteria for Guillain-Barre syndrome - 2 required for diagnosis:
1. Progressive weakness of more than one limb.
2. Distal areflexia with proximal areflexia or hyporeflexia.
Diagnostic criteria for Guillain-Barre - Supportive of diagnosis:
1. Progression for up to 4 weeks.
2. Relatively symmetric deficits.
3. Mild sensory involvement.
4. CN involvement (especially VII).
5. Recovery beginning within 4 weeks after progression stops.
6. Autonomic dysfunction.
7. NO FEVER at onset.
8. Incr. CSF protein after 1 week.
9. CSF WBC
Diagnostic criteria for Guillain-Barre - 4 against diagnosis:
1. Markedly asymmetric weakness.
2. Bowel or bladder dysfunction (at onset or persistent).
3. CSF WBC >50 or PMN count >0.
4. Well-demarcated sensory level.
Diagnostic criteria for Guillain-Barre - Excluding diagnosis:
1. Isolated sensory involvement.
2. Another polyneuropathy that explains the picture.
Guillain-Barre - Treatment:
2. IV Ig.
--> 2 Therapies are NOT ADDITIVE.
Guillain-Barre - Corticosteroids?
NO - May affect the outcome adversely or delay recovery, and are NOT INDICATED.
Guillain-Barre - Prognosis:
Symptoms and signs cease to progress by approx. 4 weeks into the illness.
--> 70% recover completely, 25% are left with mild neurologic deficits, and 5% die.
Guillain-Barre - The prognosis is poorer when ...?
1. There is evidence of preceding C.jejuni infection.
2. Advanced age.
3. The need for ventilatory support.
4. More rapid onset of symptoms.
Chronic inflammatory demyelinating polyneuropathy:
Clinically similar to Guillain-Barre, except that it follows a chronic progressive course, or a course characterized by relapses, and no improvement is apparent within the 6 months after onset.
CIDP - CSF:
Findings resemble those in Guillain-Barre.
CIDP - Treatment:
1. Often responsive to treatment with corticosteroids --> May be required on a long-term basis.
2. IV Ig.
3. Plasma exchange --> More difficult to administer.
Main clinical features of CIDP:
1. Weakness, hyporeflexia, or areflexia --> 94%.
2. Sensory deficit on examination --> 83% distal lower extremity.
3. Paresthesia --> 79% upper extremity.
4. Pain --> 15%.
5. Dysarthria --> 9%.
6. Dysphagia --> 9%.
7. Impotence --> 4%.
8. Incontinence --> 2%.
Neuropathies associated with diabetes:
2. Mononeuropathy simplex/multiplex.
4. Thoracoabdominal radiculopathy.
MC manifestation of diabetic neuropathy:
Distal polyneuropathy --> May be mixed (sensorimotor + autonomic 70%) or predominantly sensory 30%.
How can diabetic polyneuropathy be diagnosed presymptomatically?
By the presence of depressed tendon reflexes and impaired appreciation of vibration in the legs.
Due to radiculoplexopathy, polyradiculopathy, or polyradiculoneuropathy.
--> Pain, weakness, and atrophy of pelvic girdle and thigh muscles are typical with absent quadriceps reflexes and little sensory loss.
Diabetic neuropathy - CSF protein:
Typically increased in diabetic polyneuropathy and mononeuropathy multiplex.
Diabetic amyotrophy - Prognosis:
Usually improves spontaneously.
Main problem with hypothyroidism and polyneuropathy?
1. Polyneuropathy may be mistakenly diagnosed in patients with proximal limb weakness caused by hypothyroid myopathy.
2. Delayed relaxation of tendon reflexes --> Independent of neuropathy.
Acromegaly and polyneuropathy?
1. Carpal tunnel more often, not polyneuropathy.
2. Many acromegalic patients are also diabetic --> Difficult to determine which is primarily responsible for polyneuropathy.
Uremia and neuropathy:
A symmetric, sensorimotor polyneuropathy - Predominantly AXONAL in type - may occur in uremia.
Polyneuropathy due to uremia - May improve markedly with ...?
In patients on chronic hemodialysis, polyneuropathy often relates ...?
To amyloidosis and the accumulation of β2-microglobulin.
Liver disease and polyneuropathy:
1. PBC may lead to a sensory neuropathy that is probably of the axonal type.
2. A predominantly demyelinative polyneuropathy can occur with chronic liver disease.
Polyradiculopathy, polyneuropathy, and myelopathy may follow ...?
Bariatric surgery --> Nutritional deficiencies, including but NOT limited to vitB12.
Infective and granulomatous neuropathies - Involvement of peripheral nerves is seen at autopsy in approx. ...% of patients with AIDS.
AIDS neuropathy may be a consequence of ...?
1. HIV infection.
2. Secondary infection with other organisms (eg CMV, VZV, T.pallidum).
3. Immunologic basis.
4. Nutritional deficiency or medication.
MC neuropathy associated with HIV-1 infection:
Distal symmetric sensorimotor or predominantly sensory polyneuropathy.
--> Axonal > Demyelinating.
6 neuropathies associated with AIDS:
1. Sensorimotor polyneuropathy.
2. Inflammatory demyelinating polyneuropathy.
3. Lumbosacral polyradiculopathy.
4. Mononeuropathy multiplex.
5. Mononeuropathy simplex.
6. Autonomic neuropathy.
Sensorimotor polyneuropathy in AIDS:
1. Early or late HIV-1 infection.
2. Immunocompetent or immunosuppressed.
3. Symmetric, distal, LOWER > upper limbs.
Inflammatory demyelinating polyneuropathy in AIDS:
1. Early HIV infection.
3. PROXIMAL > DISTAL limbs.
Lumbosacral polyradiculopathy in AIDS:
1. Late HIV infection.
3. Proximal lower limbs, sphincters.
Mononeuropathy multiplex in AIDS:
1. Early or late infection.
2. Immunocompetent or immunosuppressed.
3. Cranial nerves (eg facial), peripheral nerves (eg fibular).
Mononeuropathy simplex in AIDS:
1. Early HIV infection.
3. Cranial (eg facial nerve), peripheral (eg fibular nerve).
Autonomic neuropathy in AIDS:
1. Early or late HIV infection.
2. Immunocompetent or immunosuppressed.
Medication-related neuropathy in AIDS - Mention 3 drugs:
1. Zalcitabine (ddC).
2. Didanosine (ddI).
3. Stavudine (d4T).
--> After approx. 4 months.
Medication-related neuropathy in AIDS - Characteristics:
Axonal sensory neuropathy, characterized by tingling, numbness, and pain.
Leprosy - Tuberculoid - Sensory problems:
1. Hypopigmented macule or papule over which sensation is impaired, with pain/temp most affected.
2. Anhidrosis occurs with involvement of the autonomic fibers.
Tuberculoid leprosy - Sensory deficits occur most often in the distribution of the ...?
4. Posterior auricular nerves.
Tuberculoid leprosy - Motor findings:
Involvement of the ulnar or fibular nerve.
--> Involved nerves are often ENLARGED.
1. Primarily sensory polyneuropathy that disproportionately affects pain and temperature sense.
2. Distinctive distribution --> Exposed areas of the body are preferred.
3. UNLIKE most polyneuropathies --> Leprosy tends to spare the tendon reflexes.
C.diphtheriae infects tissues of the URT and produces a toxin that causes DEMYELINATION of peripheral nerves.
Diphtheria - Usual presenting complaint:
Diphtheria - Delayed syndrome 2-3months after the primary infection:
Takes the form of a symmetric distal sensorimotor polyneuropathy.
--> Most recover completely.
Sarcoidosis - Neuropathy:
Commonly --> Mononeuropathy.
In some instances --> A small-fiber neuropathy leads to pain, dysesthesias, and autonomic involvement.
Sepsis and multi-organ failure:
Critical illness polyneuropathy.