Peripheral neuropathies

Question 1

what is the definition of peripheral neuropathies?

Answer 1

Mono or poly
Mono - one nerve (carpal tunnel = median nerve, ulnar neuropathy = cubital tunnel, peroneal neuropathy = fibular head, cranial neuropathy (III or VII palsy)
Poly - multiple nerves (either small or larger fibres, chronic or acute, axonal damage or demyelination)

Question 2

what is the aetiology of peripheral neuropathies?

Answer 2

Axonal PN - systemic disease (diabetes, CD, renal disease, alcohol, hypothyroidism), inflammatory (immune mediated = acute), infection (hep, HIV, lyme), ischaemia (vasculitis), metabolic (fabry’s, porphyria), hereditary (CMT, HLPP), toxins (pharmaceuticals, environment, B6)
Chronic idiopathic axonal PN - not aetiology identified, follow up yearly
Chronic demyelinating - CIDP, multifactorial motor neuropathy, charcot-marie-tooth disease
Acute PN - guillain barre, demyelinating, axonal motor, axonal sensorimotor, rapid ascending paralysis and sensory deficits, infection (campylobacter, needs immediate treatment (IVIG infusion or plasma change - ITU admission

Question 3

what are the key presentations of peripheral neuropathies?

Answer 3

Pain - c-fibres
Ataxia (cerebelar) - poor balance, loss of proprioception, WORSE IN DARK/EYES CLOSED
Motor symptoms - cramps, weakness, fasciculations, atrophy ( small muscle of feet, high arches of feet)
Symmetrical - length dependent (longer fibres affected first), tingling numbness and burning pain in toes, most common
Asymmetrical sensory - patches of numbness, dorsal root ganglia affected, uncommon, e.g. sjogren’s, paraneoplastic, coeliac disease
Asymmetrical sensorimotor - motor neuritis multiplex, very uncommon (vasculitis)

Question 4

what is the first line and gold standard investigations for peripheral neuropathies?

Answer 4

History taking
Clinical examination - reduced or absent tendon reflexes, sensory deficits, weakness (muscle atrophy in advanced disease)
Neurophysiological examination NCS / QST - demyelinating = slow conduction velocities, axonal damage = reduced amplitude of potentials

Question 5

how are peripheral neuropathies treated?

Answer 5

Pain - amitriptyline, gabapentin, pregabalin
Cramps - quinine
Balance - physio, walking aids

Question 6

which nerve is affected in carpal tunnel syndrome?

Answer 6

median nerve