Peripheral neuropathies

Peripheral neuropathies

1. Hereditary motor sensory neuropathies

   • -> symmetrical slowly progressive distal muscular wasting
   • type I
     • aka peroneal muscular atrophy (Charcot-Marie-Tooth disease)
     • dominantly inherited
     • commonest type
     • affected nerves hypertrophy
       • due to demyelination fb attempts @ remyelination
         • so nerve biopsy shows 'onion bulb formation'
     • onset
       • 1st decade
         • presentation
           • distal atrophy
           • pes cavus
           • legs> arms affected
           • distal sensory loss & diminished reflexes
             • rare
           • loss of walking ability is rare
           • initial presentation of Friedreich ataxia can be similar
     • chronic course

2. acute post-infectious polyneuropathy (Guillain-Barre syn)

   • presentation
     • 2-3 weeks ff
       • upper resp tract infection
       • campylobacter gastroenteritis
     • fleeting abnormal sensory sx in legs
     • prominent feature
       • ascending symmetrical weakness
         • w/ loss of reflexes
           • & autonomic involvement
     • sensory sx in distal limbs
     • bulbar mm involvement
       • difficulty chewing & swallowing
       • risk of aspiration
     • max mm weakness
       • occurs 2-4 weeks after onset of illness
   • full recovery expected in 95% of cases
     • may take up to 2 years
   • Ix
     • CSF protein
       • sig raised
         • characteristic
         • may not be seen till 2nd wk of illness
     • CSF WCC
       • not raised
     • nerve conduction velocities
       • reduced
   • Mx
     • supportive
       • respiration
         • ventilator
     • NOT USEFUL
       • corticosteroids
     • immunoglobulin infusion
       • reduce time on ventilator
       • if unsuccessful
         • use plasma exchange

3. Bell palsy & facial nerve palsies

   • Bell's palsy
     • isolated lower motor neurone paresis of CN7
       • -> facial weakness
     • aetiology unclear
       • but probably post-infectious
         • assoc w/ herpes simplex in adults
     • Mx
       • Rx
         • corticosteroids
           • to reduce oedema in the facial canal during the 1st week
         • NO USE
           • aciclovir
     • recovery may take several months
     • complications
       • conjunctival infection
         • caused by incomplete eye closure on blinking
           • eye protection or tarsorrhaphy
     • differential diag
       • features of Bell's + sx of CN7 paresis
         • compressive lesion in cerebellopontine angle
           • most likely diag
         • painful vesicles on tonsillar fauces, external ear
           • due to HSV invading geniculate ganglion
           • Rx = aciclovir
       • hypertension
         • cos assocn btw Bell's palsy and coarctatin of aorta
       • if facial weakness bilat
         • sarcoidosis
         • Lyme disease