Pseudo-conduction blocks in a case with polyarteritis nodosa

A 43-year-old female was referred to our clinic for an electromyographic (EMG) examination due to weakness in both the lower extremities. Conduction blocks were indicated through nerve conduction studies (NCS). Because of demyelinating polyneuropathy findings and elevated protein levels in the cerebrospinal fluid (CSF), the patient was diagnosed with acute inflammatory demyelinating polyneuropathy (AIDP) and was treated with intravenous immunoglobulin. In the follow-up examination, a distal quadriparesis was found that was markedly pronounced in the lower left extremity, and a second EMG examination showed asymmetrical worsening. These findings combined with the lack of demyelination suggested axonal degeneration, and the partial conduction blocks observed during the first NCS were determined to be pseudo-blocks. Vasculitic syndromes were considered and the associated laboratory tests were performed. Following a sural nerve biopsy, non-infectious necrotizing arteritis was found and the patient was diagnosed with polyarteritis nodosa (PAN). Therefore, clinicians should be aware that conduction blocks observed in nerve conduction studies may potentially be pseudo-blocks and an indication of vasculitic neuropathy.