Foot drop

Foot drop is a common and distressing problem where there is a weakness of the dorsiflexion muscles in the foot resulting in difficulty in walking and an increased risk of falling (1,2)

The most common cause of foot drop is peroneal neuropathy.

• less often it may be due to L5 radiculopathy or polyneuropathy and much less often by sciatic neuropathies, lumbar plexopathies, mononeuritis multiplex, or myopathies.
• rarely it can be due to central causes (such as cerebral ischaemia), anterior horn cell diseases, cauda equina compression, and muscle dystrophy - usually these produce other symptoms (1,2)

If a patient has a foot drop, then a clinical indicator to the underlying pathology can be achieved by testing the ankle jerk. If the ankle jerk is absent then an L5 lesion is likely. A normal ankle jerk indicates a possible common peroneal palsy. The ankle jerk will be increased in an upper motor neurone lesion.

Notes:

• bilateral foot-drop has been reported as a possible presentation of diabetes mellitus (1)

Reference:

• (1) Stevens F, Weerkamp NJ, Cals JW.Foot drop. BMJ. 2015;350:h1736
• (2) Stewart JD. Foot drop: where, why and what to do? Pract Neurol. 2008;8(3):158-69
• (3) Shahani B, Spalding JM. Diabetes mellitus presenting with bilateral foot-drop. Lancet. 1969 Nov 1;2(7627):930-1.