Serial electrodiagnostic testing: Utility and indications in adult neurological disorders

Although existing guidelines address electrodiagnostic (EDX) testing in identifying neuromuscular conditions, guidance regarding the uses and limitations of serial (or repeat) EDX testing is limited. By assessing neurophysiological change longitudinally across time, serial electrodiagnosis can clarify a diagnosis and potentially provide valuable prognostic information. This monograph presents four broad indications for serial electrodiagnosis in adult peripheral neurological disorders. First, where clinical change has raised suspicion for a new or ongoing lesion, EDX reassessment for spatial spread of abnormality, involvement of previously normal muscle or nerve, and/or evolving pathophysiology can clarify a diagnosis. Second, where diagnosis of a progressive neuromuscular condition is uncertain, electrophysiological data from a second time point can confirm or refute suspicion. Third, to establish prognosis after a static nerve injury, a repeat study can assess the presence and extent of reinnervation. Finally, faced with a limited initial study (as when complicated by patient or environmental factors), a repeat EDX study can supplement missing or limited data to provide needed clarity. Repeat EDX studies carry certain limitations, however, such as with prognostication in the setting of remote or chronic lesions, sensory predominant fascicular injury, or mild axonal injury. Nevertheless, serial electrodiagnosis remains a valuable and underused tool in the diagnostic and prognostic evaluation of neuromuscular conditions.