Craniofacial morphology of spinal muscular atrophy

Spinal muscular atrophy (SMA) is the second most common neuromuscular disease of childhood. It is the most common fatal recessive neuromuscular disease. This study is the first to evaluate the craniofacial growth of SMA patients. The results pertain to a sample of 25 SMA patients, between 5 and 32 y of age, who were case matched with unaffected normal controls. Group differences for 25 measures, derived from tracings of standardized cephalometric radiographs, were evaluated using multivariate analysis of variance. The SMA group showed excessive vertical development, particularly of the lower face. They demonstrated relatively larger anterior than posterior facial heights, due in part to a smaller cranial base angulation and a more anteriorly positioned mandibular ramus. Anteroposterior skeletal discrepancies of SMA patients, due to the combined effects of a protrusive maxilla and a retrusive mandible, were moderate. The interincisal angle of the SMA group was smaller than normal, due primarily to proclined maxillary incisors. Relative to palatal length, the SMA group had smaller anterior cranial base and mandibular corpus lengths. These results suggest abnormal craniofacial growth patterns of SMA patients. The etiology of the observed abnormalities seems to be complex and multifaceted, but attention to the treatment of malocclusion may be important for optimal nutrition and respiratory function.