Differential Diagnosis of Neuropathies and

CompressionDr Ashwin Pinto

Consultant NeurologistWessex Neurological Centre

Outline of talk

●Mononeuropathies●median and anterior interosseous nerve●ulnar nerve●Radial and posterior interosseous nerve

●“Polyneuropathies”●vasculitic neuropathy●brachial neuritis●cervical radiculopathy●peripheral neuropathy●syringomyelia●motor neurone disease●hereditary neuropathy with liability to pressure palsies

Anterior interosseous syndrome

●around 1% of all median nerve lesions●marked weakness of FPL and FDP -> F2●pinch sign●no sensory symptoms●test pronator teres

causes: overuse of pronator muscles brachial neuritis

Deep motor branch of ulnar nerve

●Typical ulnar nerve compression at elbow●weakness of intrinsics plus FDP -> F5●sensory deficit

●Deep motor branch of ulnar●distal to Guyon’s canal -> weakness of DIO, PIO, AP and ADM●no sensory loss

Posterior interosseous nerve

●“dropping fingers without dropping hand”●weakness of EDC and EI

●preservation of wrist extension from ECR

●DIO and PIO may appear weak unless strength assessed with the fingers extended

●Mimics – C8 radiculopathy, brachial neuritis

Vasculitic polyneuropathy

●associated with systemic vasculitis●Rheumatoid arthritis●Churg-Strauss syndrome●microscopic polyarteritis●polyarteritis nodosa●Wegener’s granulomatosis●mixed essential cryoglobulinaemia●Sjogren’s syndrome

●vasculitis restricted to the peripheral nervous system

Clinical Features

●systemic symptoms (may be absent in isolated vasculitis)

●weight loss●low grade fever●arthralgia●rash

●painful motor and sensory polyneuropathy●stepwise progression – often rapid●often asymmetric affecting individual peripheral nerves (mononeuritis mulitplex)●may be symmetric (confluent)

Investigations

●vasculitic screen●inflammatory markers and complement levels●RhF, ANCA, ANA, cryoglobulins, hepatitis serology

●peripheral neurophysiology●NCS – absent sensory nerve action potentials, reduced CMAPs●EMG – acute denervation

●document end-organ damage●CXR●urine microscopy for casts, 24hr urine collection for creatinine clearance and protein

Management

●diagnosis should be confirmed by histology of affected organ if possible (eg nerve and muscle biopsy)

●prednisolone 40-60mg daily

●pulsed monthly iv cyclophosphamide for 6 months

●maintenance – low dose prednisolone with steroid sparing agent (eg azathioprine)

Brachial Neuritis

●Parsonage-Turner syndrome (“Neuralgic Amyotrophy” Lancet, 1948)

●Strenuous exercise often preceded onset of symptoms by 1-7 days

●Other recognised precipitants include vaccination, surgery, childbirth and infection

Clinical Features

●Pain (96% of cases)●shoulder, neck and upper arm●nocturnal●typically lasts 4 weeks

●Patchy weakness●long thoracic nerve (serratus anterior)●suprascapular nerve●anterior interosseous nerve●lateral cutaneous nerve of the forearm

Management and Prognosis

●Prednisolone 1mg/kg for 1/52 in severe cases●NSAIDs +/- opioids●physiotherapy

●Recovery to 80-90% of pre-attack strength●however residual shoulder weakness is common

Cervical Radiculopathy

●Neck, shoulder and arm pain (brachialgia)●C5/6 -> shoulder pain●C7/8 -> interscapular pain

●Weakness●C5/6 – deltoid and biceps●C7 – triceps●C8 – EDC and 1st DIO with ADM

Peripheral neuropathy

●common causes include diabetes, alcohol and drug-induced

●length-dependent process●symptoms in toes/feet slowly progress proximally●symptoms in fingers only when the sensory loss has reached below the knee

●physical signs●sensory symptoms and signs often predominate●loss of tendon reflexes●distal loss of sensation to PP, VS (JPS often relatively preserved)●may develop distal weakness and wasting in hands and feet

Case presentation

25 year old female●weakness triceps, wrist extensors, 1st DIO, ADM and APB on left●sensory symptoms C8●loss of spinothalamic sensation left hand but normal JPS and VS●areflexia

Investigations

●Neurophysiology●preserved sensory nerve action potentials in the left hand●EMG –> chronic denervation suggestive of loss of anterior horn cells●reduced or absent F waves

Neuroradiology

Syringomyelia

●Typically associated with Chiari type 1 malformation (cerebellar ectopia)

●weakness and wasting of intrinsic hand muscles with areflexia in upper limbs

●dissociated sensory loss in upper limbs●loss of pain and temperature sensation with preserved dorsal column sensation

Motor Neurone Disease

●neurodegenerative condition●degeneration of upper and lower motor neurones●typically absent sensory symptoms and signs

●typically presents with painless progressive wasting and weakness in one hand

●Look for fasciculations in muscles outside of the affected hand

●Best clue – combination of UMN and LMN signs in the same myotome (eg wasting, weakness and fascics in triceps with brisk triceps reflex)

Hereditary neuropathy with liability to pressure palsies

●Autosomal dominant condition●allelic with CMT1A (PMP22 deletion)

●painless foot drop or ulnar palsy after trivial pressure (eg sitting squatting or kneeling)

●recovery is the rule but may be incomplete

HNPP

●Neurophysiology●mild to moderate slowing in nerves not

clinically affected●conduction block at ulnar groove or at fibular

head

●Decompressive surgery is best avoided

Summary

●Unusual mononeuropathies●anterior and posterior interosseous nerves●deep motor branch of ulnar nerve

●“polyneuropathies”●Is it pure motor or mixed motor-sensory●Is the pattern mononeuritis multiplex, patchy brachial plexus or multiple cervical roots●Are the sensory signs dissociated?●Are there unexpected UMN signs