Diagnostic Value of Sensory Nerve Conduction Studies in Acute Inflammatory Demyelinating Polyradiculoneuropathy

Objective: The diagnosis of acute inflammatory demyelinating polyradiculoneuropathy (AIDP) is based mainly on motor nerve conduction studies (NCSs), which may lead to inconclusive results, especially early in the course of the disease. The present study aimed to evaluate sensory NCSs as an additional tool to aid the identification of this illness. Materials and Methods: We retrospectively evaluated the sensory and motor nerve conduction findings of patients with AIDP and compared them with laboratory controls. The sensitivity and specificity of the NCS parameters and sural sparing pattern (SSP) were also assessed. The NCS patterns were categorized as normal, abnormal, and no response. The association of sensory nerve action potential (SNAP) amplitude patterns and effect of the timing of the electrodiagnostic examination on sensory and motor NCS patterns were analyzed.Results: The most sensitive sensory nerve conduction findings were reduced ulnar (79.3%) and median (75.9%) SNAP amplitudes, which were more sensitive than the compound muscle action potential amplitudes and forearm motor nerve conduction velocities of these nerves. Employing ulnar SNAP for SSP identification was more useful than using the median SNAP. The timing of the electrodiagnostic studies did not affect the patterns of the sensory nerve conduction parameters.Conclusion: The reduction in the median and ulnar SNAP amplitudes along with SSP, with the ulnar SNAP amplitude used for comparison, is beneficial for diagnosing AIDP regardless of the timing of the electrodiagnostic examination.