Spinal Muscular Atrophy: Survival Pattern and Functional Status

• Published in: Pediatrics (Evanston) 2004-11, Vol.114 (5), p.e548-e553
• Main Authors: Chung, Brian H.Y, Wong, Virginia C.N, Ip, Patrick
• Format: Article
• Language: English
• Subjects: Activities of Daily Living; Actuarial Analysis; Adolescent; Child; Female; Hong Kong - epidemiology; Humans; Infant; Male; Spinal Muscular Atrophies of Childhood - classification; Spinal Muscular Atrophies of Childhood - mortality; Spinal Muscular Atrophies of Childhood - physiopathology; Survival Analysis; Walking
• ISSN: 0031-4005; 1098-4275
• DOI: 10.1542/peds.2004-0668

Spinal muscular atrophy (SMA) is common. The prevalence of SMA in southern Chinese is 1 in 53,000. The clinical course is variable. The traditional classification of SMA includes age of onset, age of death, achievement of motor milestones, and ambulatory status as criteria. There was a lack of inclusion of the best lifetime functional status of any child with SMA. With the advances in medical care, the life expectancy and ambulatory status of patients with SMA have improved. The objective of this study was to assess the survival pattern, ambulatory status, and functional status of children with SMA. Patients with SMA were recruited from the neuromuscular clinic of the Duchess of Kent Children's Hospital, which is a university-affiliated hospital, and the Families of SMA in Hong Kong. By September 2002, 102 SMA cases had been registered in the Duchess of Kent Children's Hospital neuromuscular clinic and Families of SMA registry, and 83 patients were analyzed. Among them, 39 were recruited for the administration of Functional Independence Measure for Children (WeeFIM), an assessment tool for functional status that has been previously validated by us for Chinese children. The diagnosis of SMA was made from clinical history, serum muscle enzyme, electromyography, muscle biopsy, and, recently, by molecular studies. In Hong Kong, molecular tests of the survivor motor neuron gene was available since 1995. A total of 36 in our cohort of 83 patients had the diagnosis confirmed with molecular analyses. We adopted the classification of SMA from previous studies in which the criteria were based on the International SMA consortium (1992) with modifications according to the 59th European Neuromuscular Center International Workshops. As only SMA patients with childhood onset were studied, we did not include any type IV patients in our study. Parents were interviewed and records were reviewed for demographic and clinical data, including age of onset, gender, family history, motor milestones, disease progression, loss of motor function, and involvement of respiratory or bulbar muscles. We define the age of disease onset as the age in which the first abnormalities were obvious from the medical records or from the descriptions of the parents about the first signs of weakness, eg, age of achievement of certain motor milestones or loss of functions. For the ambulatory status, we define "being ambulatory" as having the ability to walk for 100 meters, either with assistance such