Differential Diagnosis of Neuropathies and Compression Dr Ashwin Pinto Consultant Neurologist Wessex 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 1 st DIO with ADM
Peripheral neuropathy common causes include diabetes, alcohol and druginduced 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, 1 st 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