ABSTRACT
Whatever the age of onset, the clinical features consist of symmetrical muscle weakness (more proximal than distal) associated with muscle atrophy, absence or marked decrease of deep tendon reflexes, fasciculations of the tongue, and tremor of hands. There is no evidence of sensory or upper motor neuron involvement. Electromyographic studies show a pattern of denervation with neither sensory involvement nor marked decrease of motor nerve conduction velocities. Finally, muscle biopsy, which has been recendy replaced by genetic testing for diag nosis, provides evidence of skeletal muscle denervation with groups of atrophic and hyper trophic fibers or fiber type grouping most often found in chronic cases (Types II and III).
