Congenital myasthenic syndrome: presentation, electrodiagnosis, and muscle biopsy.
We report 10 children with congenital myasthenic syndromes diagnosed by clinical features, electrodiagnostic studies, and response to acetylcholinesterase inhibitors. Age at diagnosis (mean = 4.4 years; range 0.2-10 years) correlated with age fatigue was recognized. Symptoms at presentation included mild gross motor development delay (7/10), speech articulation difficulty (5/10), and respiratory and feeding difficulties resulting in poor growth in 7 of 10 children. None of the five children with possible presynaptic abnormalities had decremental compound muscle action potential responses to 2 Hz repetitive nerve stimulation. Instead, electrodiagnostic studies showed a more than 100% increment of compound muscle action potential amplitude during 50 Hz repetitive nerve stimulation in two children and sustained compound muscle action potential decrement to 2 Hz repetitive nerve stimulation after depletion (10 Hz stimulation for 10 min) in four children. Muscle biopsies (n = 7) showed mild to severe variation in fiber size. Our experience suggests that many children with congenital myasthenic syndromes might be undiagnosed because of atypical presentation and because additional electrophysiologic studies are required.
Gurnett
Christina A
CA
Department of Neurology, Washington University School of Medicine, Saint Louis, MO 63110, USA.
Bodnar
Judy A
JA
Neil
Jeffrey
J
Connolly
Anne M
AM
D001323:Autoantibodies / Q000097:blood; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D002800:Cholinesterase Inhibitors / Q000627:therapeutic use; D003937:Diagnosis, Differential; D004558:Electric Stimulation; D004576:Electromyography / Q000187:drug effects; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D018737:Hand Strength; D006801:Humans; D007223:Infant; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology; D020294:Myasthenic Syndromes, Congenital / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D009460:Neurologic Examination / Q000187:drug effects; D010543:Peroneal Nerve / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D011729:Pyridostigmine Bromide / Q000627:therapeutic use; D011950:Receptors, Cholinergic / Q000276:immunology
D001323:Autoantibodies; D002800:Cholinesterase Inhibitors; D011950:Receptors, Cholinergic; D011729:Pyridostigmine Bromide