Ct. Carter et al., PROFILES OF NEUROMUSCULAR DISEASES - SPINAL MUSCULAR-ATROPHY, American journal of physical medicine & rehabilitation, 74(5), 1995, pp. 150-159
Forty-five individuals with spinal muscular atrophy (SMA) types II and
III were evaluated prospectively over a 10-yr period to develop an im
pairment and disability profile. SMA II subjects showed marked weaknes
s and progressive decline of strength. Mean manual muscle test (MMT) s
core for all muscles combined was 2.3 +/- 0.6, with a decline in stren
gth of -0.24 MMT units per decade. SMA III individuals had a relativel
y static or very slowly progressive course and were far stronger. Mean
MMT score for all muscles combined was 3.8 +/- 0.7, and the decline i
n strength per decade was not significant. In both types proximal weak
ness was greater than distal, but there was greater involvement of the
lower extremities and the extensor muscle groups only in SMA II. Cont
ractures, progressive scoliosis, and restrictive lung disease (RLD) we
re present in most of the SMA II individuals, but these complications
were rare in SMA III. Maximal expiratory pressures were affected earli
er and to a greater degree than vital capacity. Seventy-eight percent
of those with SMA II had scoliosis with a mean Cobb angle of the prima
ry curve of 62 +/- 37 degrees. Forty-one percent had severe RLD, and 1
7% had moderate RLD. In both types, 63% had abnormal electrocardiogram
s although most had minor findings. Timed motor performance and functi
onal evaluations indicated that muscle weakness translated to substant
ial disability in both SMA II and III, with more severe impairment not
ed in SMA II. Neither type was associated with abnormal mean scores on
intellectual and neuropsychologic test batteries.