Mononeuropathies

•    Median nerve (carpal tunnel syndrome):

o    Features: numbness/tingling in radial 3½ fingers, worse at night.

o    Thenar wasting, weak thumb opposition.

o    Tinel’s (tapping) and Phalen’s (flexion) tests positive.

o    Risk factors: diabetes, hypothyroidism, pregnancy, repetitive wrist use.

•    Ulnar nerve:

o    Lesion at elbow (cubital tunnel) or wrist (Guyon’s canal).

o    Features: weakness of finger abduction/adduction, hypothenar wasting, sensory loss in ulnar 1½ fingers.

•    Radial nerve ("Saturday night palsy"):

o    Compression in spiral groove (e.g., sleeping on arm).

o    Features: wrist drop, finger drop, sensory loss over dorsum of hand.

•    Peroneal (common fibular) nerve:

o    Compression at fibular head (crossed legs, prolonged squatting).

o    Features: foot drop, weak dorsiflexion and eversion, sensory loss over lateral shin and dorsum of foot.

Polyneuropathy

•    Typical features:

o    Symmetrical distal sensory > motor symptoms ("glove and stocking").

o    Loss of vibration, proprioception early if large-fibre involvement; pain and temperature if small-fibre.

•    Common causes:

o    Diabetes mellitus: most common in UK; sensory predominant ± autonomic features.

o    Alcoholism: nutritional deficiency (B1, B12), direct neurotoxicity.

o    Vitamin deficiencies: B12 (subacute combined degeneration), B6, B1.

o    Drugs/toxins: chemotherapy (vincristine, cisplatin), isoniazid, amiodarone.

o    Paraproteinaemias (e.g., myeloma, amyloidosis).

o    Hypothyroidism, CKD (uraemic neuropathy), HIV.

•    Investigations:

o    Bloods: glucose, HbA1c, B12/folate, TFTs, renal and liver function, paraprotein screen.

o    Nerve conduction studies (NCS): demyelinating vs axonal.

Guillain–Barré Syndrome (GBS)

•    Features:

o    Rapidly progressive ascending weakness, often starting in legs.

o    Areflexia (universal finding), possible sensory symptoms (paresthesia).

o    Cranial nerve involvement (e.g., bilateral facial weakness).

o    Autonomic dysfunction: arrhythmias, BP swings, urinary retention.

•    Preceding infections:

o    Campylobacter jejuni most common (diarrhoea history).

o    CMV, EBV, Mycoplasma.

•    Investigations:

o    LP: albuminocytologic dissociation (↑ protein, normal or few cells).

o    NCS: demyelination (↓ conduction velocity, conduction block).

•    Management:

o    IV immunoglobulin or plasma exchange.

o    Monitor vital capacity (risk of respiratory failure).

o    Supportive: DVT prophylaxis, autonomic monitoring.

Extra Revision Pearls

•    Claw hand → ulnar nerve; wrist drop → radial nerve; ape thumb → median nerve.

•    B12 deficiency → subacute combined degeneration (posterior columns + corticospinal tracts).

•    GBS → always check forced vital capacity regularly (consider intubation if <15 mL/kg).

•    Diabetes → can cause distal symmetric neuropathy, mononeuropathy (CN III palsy sparing pupil), or radiculoplexopathy.

•    Small-fibre neuropathy → pain and autonomic symptoms, normal NCS (needs skin biopsy or thermal threshold testing).