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Can an entrapment neuropathy of the superficial peroneal nerve cause foot drop?Posted on August 29, 2010
Of the 26 medical doctors I have met in the last couple of years, about 10 of them had this question before them in some way. All of them answered “no.” I am very confident this tiny sample set extrapolates – I doubt there is a doctor who would not say no.
They are all wrong.
Entrapment neuropathy of the superficial peroneal nerve is not a common condition, but one which I had after an ankle inversion sprain. The entrapment was 10cm proximal to the lateral malleolus at the deep fascia exit behind the peroneal muscles.
In order to achieve resolution of this problem, I had to publish an essay with citations and present it to several surgeons. My citations include every case study of this condition that currently exists and several orthopaedic text books.
My insistence that this was causing a significant problem and that I also had incomplete foot drop was met with deep scepticism. After all, the superficial peroneal nerve (SPN) is a cutaneous nerve that does not supply motor control. I knew this too of course, but I had no explanation. It is the deep peroneal nerve (DPN) which supplies motor control – the guy next door. Foot drop is often caused by an entrapment below and behind the knee before the nerve splits into these two branches, but I knew this was not the cause.
A marcaine/steroid injection into the SPN entrapment site immediately (within seconds) relieved some amount of foot drop. This too, was met with scepticism (?placebo), but I was adamant – there was an effect including a functional improvement.
An entrapment neuropathy of the superficial peroneal can cause foot drop by extending the nerve, and placing traction on the L5 nerve root. This will result in the expected fibrillation of the foot extensor muscles. Further, this is an extremely painful and distressing condition resulting in symptoms that can be very distracting from the actual etiology.
I am not a medical expert, just an independent thinker who owns too many medical text books.