diseases of the peripheral nerves

Question 1

what 6 principle mechanisms cause nerve malfunction

Answer 1

demyelination
axonal degeneration e.g. due to toxin
wallerian degeneration following nerve section
infarction (in arteritis)
infiltration by inflammatory cells e.g. sarcoid

Question 2

mononeuropathies

Answer 2

affects a single nerve
acute compression where nerves exposed anatomically or entrapment where nerve passes through a tight passage eg carpal tunnel
direct damage eg trauma / surgery

Question 3

carpal tunnel syndrome

Answer 3

most common entrapment neuropathy

pressure on median N as it passes through the carpal tunnel

Question 4

causes carpal tunnel syndrome

Answer 4

idiopathic usually
hypothyroidism
DM 
pregnancy
obesity
RA
acromegaly - when body makes too much growth hormone

Question 5

clin features carpal tunnel syndrome

Answer 5

• pain and paraesthesiae (tingling and prickling) in the hand - worse at night
• wasting of thenar muscles
• sensory loss of palm and palmer aspects of radial 3.5 fingers
• tapping on carpal tunnel may reproduce the pain

Question 6

management carpal tunnel syndrome

Answer 6

nocturnal splints
local steroid injections
surgical decompression

Question 7

polyneuropathy

Answer 7

acute or chronic
symmetrical
diffuse
motor, sensory & autonomic Ns

Question 8

polyneuropathy sensory symptoms

Answer 8

numbness
tingling
pins and needles
pain in the extremities and unsteadiness on the feet

Question 9

polyneuropathy motor symptoms

Answer 9

weakness

Question 10

polyneuropathy autonomic symptoms

Answer 10

postural hypotension
urinary retention 
erectile dysfunction
diarrhoea (or occasionally constipation)
diminished sweating
cardiac arrhythmias

Question 11

egs of polyneurophathies where autonomic feautures predominate

Answer 11

guillain barre
DM
amyloidosis

Question 12

first line investigations polyneuropathy

Answer 12

FBC
ESR
vit B12 
blood glucose
U + E
liver biochem

Question 13

guillain-barre syndrome?

Answer 13

most common acute neuropathy
inflammatory demyelinating usually
life threatening resp failure

Question 14

guillain-barre pathogenesis

Answer 14

triggered by infection - campylobacter, jejuni, EPV, cytomegalovirus
infectious organism shares epiptopes with antigen in peripheral N tissue leading to autoantibody mediated N cell damage formation

Question 15

clinical features guillain-barre

Answer 15

progressive onset of limb weakness - symmetrical - over 4 weeks
reflexes lost early
sensory symps- paraesthesias
mild to severe resp and facial muscle disability
autonomic - postural hypotension, cardiac arrhythmias, ileus & bladder

Question 16

Miller fisher sydrome

Answer 16

related variant of guillain-barre that affects the cranial Ns to the eye muscles

Question 17

investigations guillain-barre

Answer 17

clinical diagnosis
confirmed by nerve conduction studies showing slowing of motor conduction
CSF protein elevated
MRI to exclude cord compression

Question 18

management guillain-barre

Answer 18

vital capacity monitored 4hrly, fall below 80% predicted = transfer to ITU
ECG monitoring for cardiac dysrhythmias 
rx - IV immunoglobulin 
supportive - heparin, physio, PEG feed
recovery within 6w