Early electrophysiological findings in Fisher-Bickerstaff syndrome

The term Fisher-Bickerstaff syndrome (FBS) has been proposed to describe the clinical spectrum encompassing Miller-Fisher syndrome (MFS) and Bickerstaff brainstem encephalitis. The pathophysiology of FBS and the nature of the underlying neuropathy (demyelinating or axonal) are still subject to debate. This study describes the main findings of an early neurophysiological study on 12 patients diagnosed with FBS. Retrospective evaluation of clinical characteristics and electrophysiological findings of 12 patients with FBS seen in our neurology department within 10 days of disease onset. Follow-up electrophysiological studies were also evaluated, where available. The most frequent electrophysiological finding, present in 5 (42%) patients, was reduced sensory nerve action potential (SNAP) amplitude in one or more nerves. Abnormalities were rarely found in motor neurography, with no signs of demyelination. The cranial nerve exam revealed abnormalities in 3 patients (facial neurography and/or blink reflex test). Three patients showed resolution of SNAP amplitude reduction in serial neurophysiological studies, suggesting the presence of reversible sensory nerve conduction block. Results from cranial MRI scans were normal in all patients. An electrophysiological pattern of sensory axonal neuropathy, with no associated signs of demyelination, is an early finding of FBS. Early neurophysiological evaluation and follow-up are essential for diagnosing patients with FBS. El término síndrome de Fisher-Bickerstaff (SFB) ha sido propuesto para describir el espectro clínico que engloba el síndrome de Miller-Fisher y la encefalitis de Bickerstaff. Su fisiopatología y las características de la neuropatía subyacente, axonal o desmielinizante son todavía objeto de debate. En este estudio describimos los principales hallazgos del estudio neurofisiológico realizado de forma precoz en 12 pacientes diagnosticados de SFB. Se han evaluado de forma retrospectiva las características clínicas y los hallazgos electrofisiológicos de 12 pacientes con diagnóstico de SFB y estudio realizado en los primeros 10 días de evolución. El estudio electrofisiológico de control ha sido evaluado en los pacientes en los que estaba disponible. El hallazgo electrofisiológico más frecuente fue una reducción de la amplitud del potencial de acción nervioso sensitivo (PANS) en uno o más nervios, presente en 5 (42%) pacientes. La neurografía motora presentó hallazgos aislados y poco frecuentes, ninguno de ellos