Synopsis
Localise common focal nerve lesions from motor, sensory and provoking patterns, distinguish them from root and plexus disease, and select urgent decompression, conservative care, neurophysiology or surgery appropriately.
- Localise before naming: identify every weak movement, reflex change and sensory territory, then compare muscles supplied by the same root through different peripheral nerves.
- Carpal tunnel syndrome causes nocturnal paraesthesia in thumb, index, middle and radial ring fingers with later thenar weakness; sensation over the thenar eminence is often spared because the palmar cutaneous branch travels outside the tunnel.
- Anterior interosseous neuropathy is motor only, weakening flexor pollicis longus and index flexor digitorum profundus so the patient cannot make a round thumb-index OK sign.
Key red flags
Deficit after fracture, dislocation, deep laceration, tourniquet or expanding painful swelling requires immediate orthopaedic, plastic or vascular assessment.
Investigation priorities
Distinguish named nerve, branch, root and plexus lesions before testing.
Management branches
A patient presents with focal hand weakness, wrist drop or foot drop.
- Establish onset, pressure, posture, injury, weight loss, surgery, pregnancy, diabetes and neck or back pain, noting progression and any sphincter or systemic symptoms.
- Test each affected movement, reflex and autonomous sensory zone, then test same-root muscles supplied by other nerves to distinguish mononeuropathy from radiculopathy.
Key medicines
Local corticosteroid for carpal tunnelA trained clinician uses the locally approved corticosteroid and dose, commonly with local anaesthetic, after confirming anatomy, consent and contraindications.
ParacetamolUse the current BNF adult oral regimen for short-term associated musculoskeletal pain, reducing the maximum for low body weight or liver risk.