- Discussion:
- disease of infancy and childhood, however, severity of disease is variable in its severity and progression;
- transmitted as an autosomal recessive trait;
- there is degeneration of the
anterior horn cells of spinal cord w/ associated muscle weakness and atrophy;
- its most severe form, Werdnig-Hoffman disease, may be noted at birth or in early infancy and usually
leads to death within months;
- Clinical Findings:
- condition presents with hypotonia, areflexia, and motor dysfunction;
- sensation remains intact;
- although these patients may sit, severe muscle weakness causes to joint contractures,
bony abnormalities, and scoliosis;
- most striking finding is muscle weakness;
- patients will have minimal leg leg movement;
- weakness progresses to upper limbs and finally to muscles of respiration;
- death is due to respiratory compromise;
- Kugelberg-Welander disease;
- some children have less severe clinical picture;
- this disorder usually manifests itself late in first decade of life;
- it is clinically similar to muscular dystrophy, w/ slowly progressive weakness and
wasting of the proximal limb muscles;
- ability to walk is lost either late in the first decade of life or in teenage years, or pt is able to
walk w/ limited ability but is never able to run effectively;
- this form may be associated with a slight rise in the level of serum "muscle" enzymes;
- EMG:
- nerve-conduction velocities are normal in patients who have spinal muscular atrophy;
- findings on electromyography and muscle biopsy are characteristic of
neuropathic disorder, showing muscle denervation;
- nerve-conduction velocities are normal;
- Labs:
- in spinal muscular atrophy, creatine phosphokinase and aldolase muscle
enzymes in the blood are either at normal levels or are slightly elevated;
- Classification:
- there are
three forms of SMA;
- Type I: (Werdnig Hoffmann)
- appears between birth and 6 months of age;
- prognosis for survival is guarded;
- Type II:
- appears between 6 months and 5 years;
- Type III:
- appears between 2 and 17 years;
- Treatment:
- many w/ this disorder will survive well into adulthood;
- however, other pts manifest w/ severe hypotonic & have considerable problems
with eating and breathing;
- here, treatment is limited to daily ROM exercises for joints;
- deterioration leads to death, and orthopaedic intervention is not warranted;
- marked hypotonia can be associated with fractures at birth;
- Deformity of the Hip:
- valgus deformity of the proximal part of the femur, which tends to lead to subluxation of the hip;
- unilateral dislocations are assoc w/ pelvic obliquity;
- treatment consists of passive stretching exercises and soft-tissue releases of contracted hip muscles;
- varus osteotomy may occassionally be needed;
-
Scoliosis:
- scoliosis is common, esp in pts who cannot walk;
- scoliosis almost always begins in the first decade of life as a result of severe truncal weakness;
- progression of scoliosis correlates w/ severity of the muscle weakness;
- Bracing:
- bracing is poorly tolerated & curves tend to progress over time;
- for pts who do not walk, a soft anterior-opening orthosis, a wheelchair contoured back and a
seating cushion, thigh & chest seat belts, & head rest, are helpful;
- Operative Correction of Scioliosis:
- surgery may prevent progression of curve & may improve sitting comfort;
- indications:
- patients who are > ten years old;
- flexible curve of > 40 degrees;
- forced vital capacity of > 40 per cent;
- patients w/ SMA may use diaphragm and anterior abdominal muscles for
respiration and hence,
anterior approaches are contraindicated;
- posterior arthrodesis: options:
- two Luque rods
- Harrington distraction rod on concave side & Luque rod on convex sides;
- arthrodesis to the sacrum;
- bone may be too weak for sublaminar wires;
Spinal deformities in patients with spinal muscle atrophy: a review of 36 patients.
