What leads you to suspect that a foot drop is secondary to a myopathy rather than a neuropathic process?  

Factors suggesting that a foot drop is due to a myopathy include: Clinical factors (slow progression (myopathy but also seen in CMT) versus acute or sub-acute onset (usually neurogenic), absence of sensory findings, absence of pes cavus, signs of facial or shoulder girdle weakness (FSHD can cause...

Distal myopathies are much less common than distal neuropathies but I have seen patients followed for years as CMT when they had an hereditary distal myopathy. The red flag was the lack of any sensory symptoms or signs. However, some of these myopathies can also have sensory signs due to an associat...

There are a couple of clinical exam clues I have found quite helpful in distinguishing a myopathic from a neurogenic foot drop: The bulk and strength of the EDB muscle at the foot. In most distal myopathies, the EDB muscle bulk is relatively preserved, and often patients can still extend their gr...

I agree. EMG/NCS is a critical differentiating factor, and if there is even a concern for a more diffuse process, the protocol should be expanded to be comprehensive. I have seen EMGs done that are limited, despite these symptoms, and they can be inconclusive in those results. As an old attending of...