In neonates with myotonic dystrophy, EMG may show myotonic discharges. These discharges may occur spontaneously or be elicited by moving the recording needle or percussion on the muscle. Muscle biopsy may shows an arrest of fetal muscle maturation. Mothers with myotonic dystrophy have characteristic facies, clinical or EMG myotonic responses, and a minimal degree of mental delay may be present. Clinical myotonia is readily elicited in the mother (inability to open eyes quickly after they have been briefly closed or inability to extend the fingers after a handshake). The diagnosis is established by DNA testing. The abnormal site is at 19q13.3. The likelihood of giving birth to another infant with neonatal myotonia in subsequent pregnancy is about 30%. Treatment is supportive. Arthrogryposis should be managed nonsurgically in the neonatal period. Surgical management of joint deformities may be necessary later on.

Neonatal Fascioscapular Humeral Dystrophy
Neonatal fascioscapular humeral dystrophy is a rare condition. It is encountered in two situations: (1) in a neonate who has weakness and hypotonia that spares the extraocular movements and the lower extremities, who also has a family history of facioscapular humeral dystrophy; or (2) in a neonate with facial and shoulder girdle weakness and a muscle biopsy that exhibits inflammatory changes. Serum creatine phosphokinase is moderately elevated. Treatment is supportive.

Congenital Muscular Dystrophy
Congenital muscular dystrophies are a group of disorders that affect the muscles. They produce elevated serum creatine phosphokinase and a characteristic muscle biopsy pattern. The characteristic muscle biopsy changes are replacement of muscle by fat and connective tissue and evidence of muscle fiber necrosis and regeneration.