P.18.11 Nerve conduction alterations in Mexican patients with myotonic dystrophy type 1

Abstract

Myotonic dystrophy type 1 (DM1) is an autosomal dominant disorder with multisystemic clinical features. It is the most common type of muscular dystrophy in adults. The clinical phenotype varies with the age of presentation showing muscle weakness, wasting, myotonia, cardiac problems, cataracts, and central nervous system altetration. The peripheral nervous system involvement in the DM1 pathogenesis has not been clearly defined. To explore nerve conduction studies in DM1 Mexican patients and establish a relation with their clinical phenotype. A clinical, transversal, non-randomized study of consecutive cases was designed. Patients with molecular diagnosis of DM1 admitted between January 2010 and October 2012 with glycemic levels lower than 110 mg/dl and without concomitant diseases were part of the study. We documented the age, age at presentation and time of evolution. A nerve conduction study was performed in all patients recording motor and sensitive nerve conduction and F waves in the median, ulnar, tibial, peroneal and sural nerves of 4 extremities. We studied 39 patients, 25 male (64.1%) and 14 female (35.9%) between 6 and 57 years old. 35.9% classic, 28.2% early, 17.9% infant and 7.7% congenital DM1 form. A normal sensitive conduction was observed in 84.6% of the patients. Peroneal nerve was the most affected with decreased amplitude in 18 patients (42%). Median nerve showed prolonged latency in 3 patients (33%). Peroneal was the most affected nerve showing F waves with low persistence in 35.9% of patients, 25.6% had no response and 2.6% had prolonged latency. Tibial nerve showed alteration only in 12.9% of patients. DM1 patients presented electrophysiological data of motor neuropathy with axonal degeneration, mostly in peroneal nerve. These must be caused by muscular atrophy or neuropathic alteration. Sensitive nerve conduction abnormalities are infrequent.