Vulpian-Bernhardt syndrome. Its frequency and clinical and electrophysiological features in a tertiary care centre in Mexico

Vulpian-Bernhardt syndrome (VBS) is an atypical rare clinical phenotype of amyotrophic lateral sclerosis (ALS) that causes a significant delay in diagnosis, and thus it is important to recognise its clinical and electrophysiological features. Retrospective cross-sectional study. We reviewed the clinical records of patients diagnosed with ALS in the period from January to December 2019. Those meeting criteria for VBS were included so as to describe their frequency as well as their clinical and electrophysiological features. Twenty patients (15.8%) met criteria for VBS; 55% were female; age at onset of symptoms was 46.6 ± 12.9 years; 40% were smokers; median delay in diagnosis was 24 (12-96) months; median time to involvement of the second body segment was 24 (12-132) months, which was lumbosacral in 65%; mean Revised Amyotrophic Lateral Sclerosis Functional Rating Scale score was 27 ± 7 points; 45% met the El Escorial criteria for ALS defined at diagnosis and 58.8% met the Awaji criteria. There were 19 nerve conduction studies and 17 electromyograms, and an abductor digiti minimi-abductor pollicis brevis (ADM/APB) ratio < 0.6 was found in 63% (split hand). There is a significant delay in the diagnosis of motor neuron diseases in general and more particularly in VBS. Calculating the ADM/APB ratio and applying the Awaji criteria in the electrophysiology study can be a valuable aid to increase diagnostic certainty in this clinical entity.