P85-F The utility of MVRCs in detection of early axonal involvement in GBS

The initial diagnosis of Guillain Barre Syndrome (GBS) may be difficult since electrophysiological changes are usually first seen 2–3 weeks after disease onset. We aimed in this study to examine whether Muscle Velocity Recovery Cycles (MVRCs) may detect early changes in GBS and differentiate demyelinating (Acute Inflammatory Demyelinating Polyneuropathy-AIDP) and axonal (Acute Motor Axonal Neuropathy-AMAN) types. Twelve GBS patients (7 AIDP, 4 AMAN, 1 acute CIDP (chronic inflammatory demyelinating polyneuropathy)) and 24 age-matched healthy controls (HC) were included. In addition to conventional nerve conduction studies (NCS) and electromyography, MVRCs in the anterior tibial muscle were done in the 1st week of symptom-onset. A 4th-week examination by NCS/electromyography was done in all patients and MVRC in 6 (4 AIDP and 2 AMAN). Of MVRC parameters, muscle relative refractory period was significantly prolonged and early and late supernormality were reduced in patients compared to HC (t-test, p < 0.001), however abnormality was only seen in AMAN and acute CIDP whereas AIDP patients were normal. EMG was normal in the 1st week while on the 4th week, profuse denervation activity was seen in 6 patients including the 4 AMAN. None of the MVRC parameters changed significantly from 1st to 4th week (paired t-test, p > 0.05). Changes in MVRCs already in the 1st week of symptoms before presence of denervation activity may suggest early detection of axonal involvement in GBS. Additionally, MVRC could distinguish AIDP from AMAN, however this could also be due to severity of the disease in these patients.