Nerve conduction studies of sensory nerves with proven vasculitic neuropathy often show an absent electrical response.

Introduction/aims: In vasculitic neuropathy (VN), it is not known whether nerve conduction studies (NCSs) showing low amplitude sensory nerve action potentials (SNAPs) or those with absent responses have a higher yield in detecting appropriate nerves for pathological confirmation. Our goal was to describe NCS findings of nerves prior to biopsy in patients with VN.

Methods: We performed a retrospective study between January 2000 and April 2021 in patients with VN who either met pathological definite criteria for VN or criteria for clinically probable VN and had NCS of the sural or superficial radial sensory nerves prior to biopsy of the same nerve.

Results: We included 61 patients with VN. The pathological findings showed 37 (60.7%) definite, 14 (23%) probable, and 2 (3.3%) possible VN; eight (13%) samples did not meet Peripheral Nerve Society pathological criteria. Most patients who met definite (20 out of 37, 54%) and probable (9 out of 14, 64%) VN pathological criteria had absent SNAPs. Only three out of eight (37.5%) patients without VN pathological findings had absent SNAPs. There was no statistically significant correlation between pathological diagnosis and SNAP amplitude (χ² = 1.98, p = .58). Additionally, no association was found between VN pathological criteria and use of immunomodulatory treatment (p = .67) or corticosteroids (p = .52).

Discussion: Most nerves with pathological VN findings showed no response on NCS. In patients with suspected VN, sural or superficial radial sensory nerves with absent responses on NCS are adequate biopsy targets as compared to nerves in which SNAPs can be recorded.