title: Repetitive compound muscle action potentials in electrophysiological diagnosis of congenital myasthenic syndromes: a case report and review of literature.
abstract: Congenital myasthenic syndromes (CMSs) are a heterogeneous group of disorders, characterized by dysfunction of neuromuscular junction (NMJ) transmission. These syndromes are genetically inherited and are present since birth. Some have characteristic clinical or electrodiagnostic features but in many cases determination of the specific form requires genetic studies or specialized morphological and electrophysiological studies on muscle tissue. We report a case of a 4-year-old boy with progressive ptosis and limitation of ocular movements who was diagnosed as slow-channel CMS based on the characteristic electrodiagnostic features. Repetitive compound muscle action potentials (R-CMAPs) were recorded after single nerve stimulus, with decremental response after repetitive trains performed at 3 Hz. CMSs are at times clinically difficult to distinguish from acquired myasthenia. The characteristic clinical and electrodiagnostic features help in the diagnosis and enable rational therapy. In this article we discuss the characteristics of synaptic R-CMAPs.
authors.affiliation: Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India. drshivakumar1995@yahoo.co.in
authors.forename: R Shiva
authors.initials: RS
authors.lastname: Kumar
authors.forename: Abraham
authors.initials: A
authors.lastname: Kuruvilla
references.citation: Electroencephalogr Clin Neurophysiol Suppl. 1987;39:91-102
references.pmid: 2443341
references.citation: J Neurol Sci. 1980 Jul;47(1):35-48
references.pmid: 7411162
references.citation: Muscle Nerve. 1996 Sep;19(9):1127-33
references.pmid: 8761268