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N36 Neurology
Peripheral Neuropathies Toronto Notes 2019
Denervation on EMG
Fibrillations, positive sharp waves, complex repetitive discharges
Reinnervation on EMG
Increased amplitude and duration of motor units
Treatment
• riluzole(modestlyslowsdiseaseprogression) • symptomaticrelief
■ spasticity/cramping: baclofen, tizanidine (Zanaflex®), regular exercise, and physical therapy
■ sialorrhea: TCA (i.e. amitriptyline), sublingual atropine drops, parotid/submandibular Botox® (rare) ■ pseudobulbar affect: dextromethorphan/quinidine, TCA, SSRI
• non-pharmacologic:highcaloricdiet,ventilatorysupport(especiallyBiPAP),earlynutritionalsupport (i.e. PEG tube), rehabilitation (PT, OT, SLP), psychosocial support
Prognosis
• mediansurvival3yr;deathduetorespiratoryfailure
Other Motor Neuron Diseases
• degenerative
■ progressivemuscularatrophy(progressivebulbarpalsy):onlyLMNsymptomswithasymmetric
weakness, later onset than ALS, 5-10% of patients in ALS centres
■ primary lateral sclerosis (progressive pseudobulbar palsy): UMN symptoms, later onset, not fatal,
variable disability; 5-10% of patients in ALS centres
■ spinalmuscularatrophy:pediatricdiseasewithsymmetricLMNsymptoms
• infectious
■ post-polio syndrome
■ West Nile infection: residual asymmetric muscle weakness, atrophy
Peripheral Neuropathies
Diagnostic Approach to Peripheral Neuropathies
1. Differentiate: motor vs. sensory vs. autonomic vs. mixed
2. Pattern of deficit: symmetry; focal vs. diffuse; upper vs. lower limb; cranial nerve involvement
3. Temporal pattern: acute vs. chronic; relapsing/remitting vs. constant vs. progressive
4. History: PMH, detailed FHx, exposures (e.g. insects, toxins, sexual, travel), systemic symptoms
5. Detailed peripheral neuro exam: LMN findings, differentiate between root and peripheral nerves,
Diabetic Neuropathies
• Peripheral neuropathy: pain or loss
of sensation in a glove and stocking distribution (hands and feet affected before arms and legs)
• Autonomic: anhidrosis, orthostatic hypotension, impotence, gastroparesis, bowel and bladder dysfunction
• Mononeuropathy multiplex: nerve infarct or compression
• Cranial neuropathy: CN III (pupil sparing) > IV>VI
• Lumbosacral plexopathy
cranial nerves, respiratory status
Tinel’s Sign
Tap lightly over the median nerve at the wrist; the patient’s symptoms of carpal tunnel will be elicited in a positive test
Phalen’s Test
Hold both wrists in forced flexion (with the dorsal surfaces of the hands pressed against each other) for 30-60 s; test is positive if symptoms of carpal tunnel are elicited
DDx of Demyelinating Neuropathy
GBS, CIDP, paraproteinemia, diphtheria, amiodarone, Charcot-Marie-Tooth, storage diseases,pressurepalsypredisposition, paraneoplastic
polyneuropathy mononeuropathy mononeuropathy radiculopathy (peroneal) (multiplex) (C6)
Figure 23. Pattern of distribution for peripheral neuropathies
Classification
• monoradiculopathy:dermatomaldeficitduetosinglenerverootlesion ■ due to disc herniation or root compression causing radicular pain
■ little tactile anesthesia, as dermatomes overlap
plexopathy (brachial)
• polyradiculopathy: multiple dermatome deficits due to multiple nerve root lesions (e.g. one type is cauda equina syndrome (lumbosacral roots))
• plexopathy:deficitmatchingdistributionofanerveplexus ■ brachial plexopathy
◆ upper (C5-C7): LMN Sx of shoulder and upper arm muscles (Erb’s palsy)
◆ lower (C8-T1): LMN Sx and sensory Sx of forearm and hand (Klumpke’s palsy)
◆ DDx: trauma, idiopathic neuritis, tumour infiltration, radiation, thoracic outlet syndrome (i.e.
cervical rib)
■ lumbosacralplexopathy(rare,especiallyunilateral)
◆ DDx: idiopathic neuritis, infarction (i.e. DM), compression