Abstract:

Objective To investigate the clinical and electrophysiology features of infantile spinal muscular atrophy, and explore the clinical significance of genetic diagnosis. Methods The clinical data of 13 infants suffering from infantile spinal muscular atrophy were analysed. The serum creatine phosphokinase was examined, and nerve conduction velocity was tested in median nerve, ulnar nerve, tibial nerve and peroneal nerve. The parameters such as distal motor latency, motor nerve conduction velocity and amplitude of compound motor active potential were analysed. Electromyography was performed in no less than four muscles, and the insertion potential, spontaneous potential and motor unit action potential were observed. Deletion of exon 7 in SMN1 gene was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results All these infants were characterized by progressive flaccid paralysis in limbs. In all cases, amplitude of muscle response was significantly decreased, with prolonged distal latency and slowed conduction velocity. Electromyography demonstrated motoneuron degeneration. Deletion of exon 7 in SMN1 gene was detected in all 13 infants. Conclusion There are unique clinical and electrophysiology features for infantile spinal muscular atrophy, and electromyography may play an important role in the diagnosis. Prenatal genetic diagnosis may help to avoid the birth of this kind of infants.

Key words: spinal muscular atrophy, infant, motor nerve conduction, electromyography, gene