peripheral neuropathy
DESCRIPTION
PERIPHERAL NEUROPATHY. PHYSIOLOGY. Pain and temperature sensation : unmyelinated and small myelinated A d fibers, Vibratory sense, proprioception, and the afferent limb of the tendon reflex : large myelinated A a and A b fibers. Light touch : both large and small myelinated fibers. - PowerPoint PPT PresentationTRANSCRIPT
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PERIPHERAL NEUROPATHY
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PHYSIOLOGY• Pain and temperature sensation :
unmyelinated and small myelinated Ad fibers,
• Vibratory sense, proprioception, and the afferent limb of the tendon reflex : large myelinated Aa and Ab fibers.
• Light touch : both large and small myelinated fibers.
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FIVE QUESTION APPROACH
2. Pattern of distribution
3. Temporal course
1. Fiber type
4. Key features
5. Pathology
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• 1.What is the fiber type involved? (motor, large sensory, small sensory, autonomic,
combination)• 2. What is the pattern of distribution?(distal or proximal, symmetric or asymmetric)• 3. What is the temporal course? (acute, chronic, progressive, stepwise, relapsing
remitting)• 4. Are there any key features pointing to a specific
etiology? (toxic/nutritional/malignancy)• 5. What is the pathology? (axonal, demyelinating)
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Pathological Process• (1) Wallerian degeneration, which is the
response to axonal interruption; • (2) Axonal degeneration or axonopathy; • (3) Primary neuronal degeneration or
neuronopathy; • (4) Segmental demyelination
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Wallerian degeneration• Any type of mechanical injury that
causes interruption of axons leads to wallerian degeneration (degeneration of axons and their myelin sheaths) distal to the site of transection.
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Axonal degeneration• Most common pathological reaction of
peripheral nerve• Caused by :Systemic metabolic disorders,
toxin exposure, and some inherited neuropathies
• Also called dying-back or length-dependent neuropathy:
• The myelin sheath breaks down along with the axon in a process that starts at the most distal part of the nerve fiber and progresses toward the nerve cell body.
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Dying-back neuropathy• Clinically, presents with symmetrical, distal
loss of sensory and motor function in the lower extremities that extends proximally in a graded manner.
• The result is sensory loss in a stocking-like pattern, distal muscle weakness and atrophy, and loss of ankle reflexes
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Neuronopathy• Primary loss or destruction of nerve cell bodies with
resultant degeneration of their entire peripheral and central axons.
• Either lower motor neurons or dorsal root ganglion cells may be affected.
• When anterior horn cells - poliomyelitis or motor neuron disease: focal weakness without sensory loss
• Sensory neuronopathy, or polyganglionopathy :damage to dorsal root ganglion neurons - inability to localize the limb in space, diffuse areflexia, and sensory ataxia.
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Segmental demyelination
• The term implies injury of either myelin sheaths or Schwann cells, resulting in breakdown of myelin with sparing of axons
• This occurs in immune-mediated demyelinating neuropathies and in hereditary disorders of Schwann cell/myelin metabolism.
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Demyelinating neuropathies
• Relative sparing of temperature and pinprick sensation +
• 1.Early generalized loss of reflexes, 2.disproportionately mild muscle atrophy 3.presence of proximal and distal weakness, 4.neuropathic tremor
5. palpably enlarged nerves
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Diagnostic Clues from the History • 1.motor 2.sensory 3.autonomic disturbances. Seek both positive and negative symptoms.• A. Motor:• Positive : Muscle cramps, fasciculations, myokymia, or
tremor • Negative : early distal toe and ankle extensor weakness,
resulting in tripping on rugs or uneven ground
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Sensory symptomsPositive :• prickling, searing, burning, and tight bandlike
sensations.• Paresthesia: Unpleasant sensations arising
spontaneously without apparent stimulus• Allodynia: perception of nonpainful stimuli as
painful. • Hyperalgesia: Painful hypersensitivity to noxious
stimuli • Neuropathic pain: cardinal feature of many
neuropathies.
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Autonomic dysfunction• Orthostatic lightheadedness,• Fainting spells, • Sweating reduced or excessive, • Heat intolerance, • Bladder, Bowel, and Sexual dysfunction. • Anorexia, early satiety, nausea, and vomiting
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TEMPORAL CLUES• Onset, duration, and evolution of symptoms • Tempo of disease : acute, subacute, or chronic• Course: monophasic, progressive, or relapsing • Acute presentations: Guillain-Barré syndrome
(GBS), acute porphyria, vasculitis, toxic neuropathies.
• Relapsing course : (CIDP), acute porphyria, Refsum's disease, hereditary neuropathy with liability to pressure palsies (HNPP), familial brachial plexus neuropathy, and repeated episodes of toxin exposure.
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Constitutional symptoms
• DM• hypothyroidism • chronic renal failure • liver disease• intestinal malabsorption • malignancy • connective tissue diseases
• [HIV] • drug use • Vitamin B6 toxicity• alcohol and dietary habits• exposure to solvents,
pesticides, or heavy metals.
•Weight loss, malaise, and anorexia.
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Mononeuropathy
• Focal involvement of a single nerve and implies a local process:
• Direct trauma• compression or entrapment • vascular lesions• neoplastic compression or infiltration
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Mononeuropathy multiplex• simultaneous /sequential damage to multiple
noncontiguous nerves.• Ischemia caused by vasculitis • Microangiopathy in diabetes mellitus • Less common causes : Infectious,
granulomatous, leukemic, or neoplastic infiltration, Hansen's disease (leprosy) and sarcoidosis.
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Polyneuropathy• Characterized by symmetrical, distal motor and
sensory deficits that have a graded increase in severity distally and by distal attenuation of reflexes,
• Rarely predominantly proximal:(E.g: acute intermittent porphyria).
• The sensory deficits generally follow a length-dependent stocking-glove pattern
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Motor deficitsDominate the clinical picture in• 1. AIDP/CIDP
• 2. Hereditary motor and sensory neuropathies,
• 3. Neuropathies associated with osteosclerotic myeloma, porphyria, lead and organophosphate intoxications, and hypoglycemia.
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Pattern of weakness• Asymmetrical motor weakness without
sensory loss suggests motor neuron disease or multifocal motor neuropathy with conduction block
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Neuropathies with Facial Nerve Involvement
• Guillain-Barré syndrome
• Chronic inflammatory polyradiculoneuropathy • Lyme disease
• Sarcoidosis
• HIV
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Predominant Sensory
• Diabetes• Carcinoma;• Sjögren's syndrome; • Dysproteinemia; • AIDS • vitamin B12
deficiency
• Celiac disease • Toxicity with cisplatin,
thalidomide, or pyridoxine
• Inherited and idiopathic sensory neuropathies
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Autonomic dysfunction
• GBS
• Diabetes
• Amyloid sensorimotor polyneuropathy
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Small-Fiber Neuropathies • Idiopathic small fiber neuropathy• Diabetes mellitus • Amyloid neuropathy • HIV-associated distal sensory neuropathy• Hereditary sensory and autonomic neuropathies
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Large-fiber• Areflexia
• Pseudoathetosis
• Loss of joint position and vibration sense
• Positive Romberg's sign
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Electrodiagnostic studies
• (1) Confirming the presence of neuropathy,
• (2) Locating focal nerve lesions,
• (3) Nature of the underlying nerve pathology
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Distal motor latency prolonged
Nerve conduction velocity slow
Reduced action potential
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Nerve biopsy• In vasculitis, amyloid neuropathy, leprosy, CIDP,
Inherited disorders of myelin, and rare axonopathies
• The Sural nerve is selected most commonly • The superficial peroneal nerve –
alternative; :advantage of allowing simultaneous biopsy of the peroneus brevis muscle through the same incision.
• This combined nerve and muscle biopsy procedure increases the yield of identifying suspected vasculitis
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Neuropathies + Serum Autoantibodies
Antibodies against Gangliosides• GM1 : Multifocal motor neuropathy • GM1, GD1a : Guillain-Barré syndrome • GQ1b : Miller Fisher variant
Antibodies against Glycoproteins• Myelin-associated glycoprotein : MGUS
Antibodies against RNA-binding proteins• Anti-Hu, antineuronal nuclear antibody 1: Malignant
inflammatory polyganglionopathy
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SUMMARY• A. Clinical pattern of neurologic findings
Polyneuropathy, Neuronopathy, Mononeuropathy, Multiple mononeuropathy, Plexopathies
• B. Functional disturbance: Motor, Sensory, Autonomic, Mixed
• C. Mode of onset :• 1.Acute 2.Subacute 3.Chronic
4.Relapsing •
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• D. Pathological and electrophysiological criteria:
• 1.Demyelinating disease vs Axonopathy • 2.Wallerian degeneration - trauma • 3.Dying back neuropathy - toxic,
metabolic
• E. Etiology: • Metabolic, immune mediated, toxic,
vasculitis, dysproteinemic, inherited, Nutritional deficiency
•
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• F. Diagnosis • 1.Clinical data• 2.Electrophysiologic test : NCS, EMG• 3.Biochemical test : metabolic,
nutritional, toxic
• 4.CSF study • 5. Nerve & muscle biopsy • 6. Measurement of Ig & anti-neural
antibody • 7. Genetic study