Electrodiagnostic Studies

Nerve conduction and electromyography are an exten­sion of the clinician’s physical examination and a use­ful tool for the localization of lesions within the lower motor neuron. In addition, electromyogramy (EMG) and nerve conduction studies help guide further studies, such as muscle biopsy, by providing information about the most appropriate muscle site for biopsy.

Figure 12.8 Trendelenburg or “gluteus medius” gait pattern in a male with Duchenne muscular dystrophy. Note the lateral lean over the stance side due to hip abductor weakness; ankle dorsiflexion weakness necessitates swing phase in circumduction for clearance.

muscular atrophy, an electrodiagnostic evaluation can allow the clinician to defer muscle biopsy and proceed with molecular genetic studies of the survival motor neuron gene. Electrodiagnostic studies in patients with CMT help to categorize the neuropathy as either pri­marily demyelinating or axonal, and such information may help focus subsequent molecular genetic analyses for a more cost-effective approach. In patients with sus­pected CMT and positive family histories with geneti­cally confirmed diagnoses, the diagnosis of CMT may be confirmed in the clinic by a simple, reliable, and relatively inexpensive nerve conduction study.

A thorough discussion of the role of electrodiag­nosis and neuromuscular disease is provided in the chapter on pediatric electrodiagnosis.