Spinal muscular atrophy 4 years prospective, multicenter, longitudinal study (168 cases)

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterised by motoneuron degeneration in the anterior horn of the spinal cord and in the bulbar nuclei. The various types of SMA are linked to the 5q13 locus in 95 % of cases. In the absence of an effective specific treatment, orthopaedic and respiratory management can significantly improve the prognosis. To study the contemporary natural history of SMA and to identify clinical and non invasive prognostic criteria, 168 patients with SMA were recruited in 6 hospital units (Lille, Lyon, Marseille, Paris) during a 4-year prospective m ulticen ter follow-up study (1998-2002). Follow-up has now lasted at least 4 years in 151 cases (90%), and24 of thesepatients have died. Disease outcome was appraised by using three criteria : muscle strength, the sum of the motor function and examination index (IFM), the respiratory muscleparalysis index (IMR), and the dorsal decubitusforced vital capacity/theoretical index (XV/CT). Statistical analysis showed a significant worsening (about 20 %) of the three criteria during follow-up. The motorfunction and examination index (IFM) is particularly interesting: the difference between initial andfinal status was significant in all age groups and in all three types of the disease. The IFMmay thus be useful as the main outcome measure during therapeutic trials.