Segmental Innervation and Nerve Lesions

Most vulnerable sites for nerve damage

Close to skin - penetrating injury, between skin and bony projection - crushing injury, between retinacula and bone - squashing injury, on bone - from fracture

Common effects of nerve lesion

Paralysis or paresis - loss or weakened movement, loss of sensation seen distal to lesion

Lesions of peripheral nerves

Motor loss, sensory loss, functional motor loss, deformity

Segmental innervation

Distribution of motor and sensory neurons of the spinal nerve

Myotome

Group of muscles supplied by one spinal nerve via both dorsal and ventral rami, often described in terms of the movement that these muscles cause

Dermatome

An area of skin supplied by one spinal nerve, usually long elongated strip of skin, have overlap and variation which makes it less clinically reliable than myotomes