Segmental evaluation of the peripheral nerve using tibial nerve SEPs for the diagnosis of CIDP

SEPs can evaluate the proximal portion of the peripheral nerve, including the nerve root, which is preferentially involved in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We retrospectively investigated the utility of tibial nerve SEPs for the diagnosis of CIDP.

Subjects were 12 clinically-defined CIDP patients and 17 patients with diabetic polyneuropathy (DPN). We segmentally evaluated the entire peripheral nerve using the N8, P15, and N21 components. We defined findings suggestive of proximal-dominant involvement (proximal-dominant findings), and investigated their frequency in both groups.

Ten out of 12 CIDP patients showed at least one of the proximal-dominant findings, whereas none of the DPN patients did, when appropriate parameters were selected. The sensitivity was higher than conventional electrodiagnostic criteria such as the European Federation of Neurological Societies/Peripheral Nerve Societies criteria (definite in 8/12). Both a proximal-dominant involvement in CIDP patients and a distal-dominant involvement in DPN patients were evident by the Z-score plots.

Tibial nerve SEPs were highly sensitive and specific, at least in comparison with DPN, measures for the diagnosis of CIDP.

Segmental evaluation of the peripheral nerve using tibial nerve SEPs is expected as a promising tool to document proximal-dominant involvement in CIDP.