Taking an accurate history and a thorough clinical examination are important. A trapped nerve in the upper lumbar spine (L4/L5) can cause similar symptoms but in contrast to the peroneal palsy often causes pain (sciatica).
Electrophysiological tests (EMG and nerve conduction test) will be able to show the cause. It is, however, important to know that the changes of these tests usually take 3-4 weeks to develop and therefore the test is unreliable if performed too early.
An MRI scan of the lumbar spine is indicated if there is a clinical doubt or if the electrophysiological tests do not confirm the peroneal palsy. In cases of progressive symptoms an MRI scan of the region just below the knee is indicated to see whether there is an underlying lesion.
Non-surgical treatment often means support of the foot with a calliper or foot support to avoid tripping over the foot. Physiotherapy will also help to strengthen the muscles. Surgery exploring and decompressing the nerve is only indicated in a very few cases where conservative treatment has failed and the patient is significantly disabled from this. If an underlying tumour is found, it should be surgically explored.
The majority of cases improve with time, in particular when the paralysis is incomplete (mild to moderate weakness).