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A 76-year-old man had taken up gardening. A few days after a particularly tiring day he suddenly developed a right-sided foot-drop. There were no other muscle weaknesses. He had not used chemical garden sprays. His medical history included treatment for asthma with inhaled steroids and a successful resection of the colon for carcinoma.
He was suspected to have a metastatic tumour in the upper sacral or lower lumbar region, affecting the sciatic nerve, and was referred to the local oncology clinic. X-Rays and an abdominal computed tomography scan showed no abnormality, apart from minor osteo-arthritis of the vertebral column.
- What further investigations would you advise?
- What is the likely diagnosis?
- What treatment is indicated and what is the prognosis?
A detailed history and physical examination should have preceded the request for investigations. The patient had knocked the lateral side of his knee while carrying a heavy rolled-up garden hose. No bruise developed at any time, and the discomfort from the injury subsided within 24 hours. Apart from the loss of dorsiflexion at the ankle, eversion of the foot and extension of the toes were reduced. There was an anaesthetic area on the dorsum of the foot. No other neurological signs were present.
The patient had injured the peroneal nerve (synonym: lateral popliteal nerve) at the point where it curves round the neck of the fibula. The sciatic nerve divides into medial and lateral popliteal nerves in the lower thigh. The lateral division or peroneal nerve then curves round the neck of the fibula, where it is only covered by subcutaneous tissue and skin. It is easily palpable at this site. Further down it innervates the tibialis anterior muscle, the peroneal muscles and the long extensors of the toes. It supplies the skin of the dorsum of the foot. The peroneal nerve was compressed at the neck of the fibula.
Nerve stimulation studies may be performed to ascertain whether the nerve is completely divided. If it is not divided, recovery usually is complete in 4–6 months, as occurred in this patient.
A recent letter in The Lancet 1 describes injuries to the peroneal nerve at the neck of the fibula due to ski injuries. The authors state “This type of peroneal injury has rarely been reported and its cause is widely ignored ...” Many of their patients did not recover completely, even with immediate microsurgical repair. They advocate prevention with protective pads on the lateral aspect of the ski pants.
A series of 302 patients with peroneal nerve lesions seen in 30 years at the Department of Neurosurgery in Louisiana, USA, includes injuries to this nerve by sharp lacerations, gunshot wounds and tumours.2 If the nerve is divided they advise surgical repair or nerve graft. If spontaneous recovery of a compressed nerve has not occurred in about 6 months, neurolysis is advised. In their series 45% of patients made an acceptable recovery.
Compression of the peroneal nerve at the neck of the fibula.