Examine this patient's legs.
Test this patient's gait.
· History of trauma to the nerve, particularly where it winds around the neck of the fibula where it is protected by only skin and
· Whether the symptoms occur after sitting cross-legged for prolonged periods.
· Recent weight loss, particularly in those who have been confined to bed (nerve more vulnerable because the protective fat and
muscle is lost).
· Plaster around the knee.
· History of diabetes, polyarteritis nodosa, collagen vascular diseases (all causes of mononeuritis multiplex, p. 165).
· Wasting of the muscles on the lateral aspect of the leg, namely the peronei and tibialis anterior muscle.
· Weakness of dorsiflexion and eversion of the foot.
· High-stepping gait.
· Loss of sensation on the lateral aspect of the leg and dorsum of the loot. If the deep peroneal branch is affected, the sensory
loss may be limited to the dorsum of the web between the first and second toes.
Proceed as follows:
· Test the ankle jerk:
- Absent ankle jerk: suspect an S 1 lesion.
- Normal jerk: common peroneal nerve palsy.
- Brisk jerk: suspect an upper motor neuron lesion.
· Comment on calliper shoes by the bedside (if any).
This patient has wasting of the lateral aspect of the leg and sensory loss (lesion) due to common nerve palsy caused by trauma to
the head of the fibula (aetiology), and has to wear callipers (functional status).
Mention a few causes.
· Compression resulting from application of a tourniquet or plaster of Paris cast. The nerve is vulnerable at the head of the fibula,
where it lies on the surface of the hard bone and is covered only by skin.
· Direct trauma to the nerve.
· Leprosy (commonest cause worldwide).
· Ganglion arising from the superior tibiofibular joint may compress the nerve.
· Compression of the nerve by the tendinous edge of the peroneus longus.
How would you manage such a patient?
· Nerve conduction studies: there may be a local conduction bh)ck or slowing in the region of the head of the fibula. There may
be denervation in the tibialis anterior and extensor digitorum profundus.
· If the intact nerve is severed: surgery.
· If the nerve is intact and concussed: 90 degree splint at night, calliper shoes with a 90 degree stop, and galvanic or faradic
stimulation to maintain the bulk of the muscle until the nerve recovers.
What other types of nerve injury do you know?
· Neurapraxia, i.e. concussion of the nerve after which a complete recovery occurs.
· Axonotmesis, in which the axon is severed but the myelin sheath is intact; recovery may occur.
· Neurotmesis, in which the nerve is completely severed and the prognosis for recovery is poor.
What are the other causes of foot-drop?
· Peripheral neuropathy (see pp 164-6).
· L4, L5 root lesion.
· Motor neuron disease
· Sciatic nerve palsy.
· Lumbosacral plexus lesion.