Electromyoneurographic findings in patient with congenital muscular dystrophy

Abstract

Congenital muscular dystrophies (CMD) are a clinically and genetically heterogeneous group of inherited muscle disorders defined by early onset of hypotonia and muscle weakness. They are the second most common myopathic cause of floppy infant syndrome, following the group of congenital myopathies. The main CMD are classified by involved protein function and gene in which causative mutations occur. Merosin-negative muscle dystrophy is the most common CMD, characterized by early onset hypotonia, delayed motor milestones, contractures, normal cognitive abilities and diffuse brain white matter changes. Some forms of CMD are characterized by mental retardation, eye involvement, epileptic seizures and structural brain abnormalities. The diagnosis of CMD is based on clinical findings, elevated muscle enzymes, brain imaging, muscle biopsy histology and immunohistochemical staining and molecular genetic testing. The vast majority of patients have myopathic findings on electromyography (EMG). Slowed motor and sensory nerve conduction velocities could be found in patients with merosin deficiency. Electromyography has a significant role in the primary assessment of patients with muscle weakness. Myopathic EMG findings ruled out other causes of floppy infant syndrome and led to a muscle biopsy and focused genetic tests. An associated demyelinating neuropathy could focus the investigation on primary or secondary merosin deficit.