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Juvenile spinal muscular atrophy, characterized by slowly progressive muscular weakness as a result of degeneration of anterior horn cells (spinal motor neurons). Onset is between the ages of 2 and 17 years. Early symptoms consist of atrophy and weakness of the proximal muscle of the extremities (mainly legs), followed by thoracic muscles. Should not be confused with muscular dystrophy syndromes.

Kugelberg-Welander Syndrome; Juvenile type of Muscular Atrophy Syndrome; Neurogenic Familial Girdle type of Muscular Atrophy, type K-W; Spinal Muscular Atrophy type III; Juvenile Spinal Muscular Atrophy.

Neurological disorder resulting from degeneration of anterior horn cells. Kugelberg-Welander Spinal Muscular Atrophy is the least severe of the three forms of spinal muscular atrophy.

1:15,000 live births; genetic carrier prevalence is 1:80. Both sexes affected, but more severe in males.

Mostly autosomal recessive; some families with autosomal dominant inheritance; very rarely, X-linked transmission. Gene map location (usually) is 5q13.

Degeneration of anterior horn cells.

Blood DNA analysis, electromyography, and muscle biopsy.

Onset at the age of 3 to 4 years, with progressive muscular dystrophy involving, at first, the proximal muscles. Progressive weakness of the axial muscles, pharyngeal control, and swallowing. Decreased or absent tendon reflexes and muscular fasciculations. Progressive respiratory failure as a result of muscular weakness. Cardiac involvement seems to be significant and includes atrial hyperexcitability, atrioventricular blocks, and right-sided heart failure as a result of pulmonary hypertension. Congestive biventricular failure has also been reported.

Check pulmonary functions before induction. Numerous postoperative pulmonary infections. Need intensive care unit stay after operation, and may need several days postoperative ventilation. Check ECG for signs of right cardiac overload; echocardiography may be useful. Cardiovascular status and intravascular fluid volume should be evaluated.

Very poor vascular access. Maintain intravascular volume. Perioperative cardiac monitoring is necessary. Intracardiac stimulation should be available in operating room in case of severe sudden conduction block.

Avoid succinylcholine. Exaggerated response to neuromuscular blockers (complete muscular blockade with 20 to 30% of the usual dose), titration is indicated and the use of neuromuscular monitoring highly recommended. Avoid drugs that could trigger cardiac dysrhythmias.

Other variants of spinal muscular atrophy including type 1 (Werdnig-Hoffman disease, the most severe form); type 2 (chronic spinal muscular atrophy, juvenile spinal muscular atrophy, or intermediate spinal muscular atrophy); and type 4 (adult spinal muscular atrophy) need to be considered.

Fehlings DL, Kirsch S, McComas A, et al: Evaluation of therapeutic electrical stimulation to improve muscle strength and function in children with types II/III spinal muscular atrophy. Dev Med Child Neurol 44:741, 2002.  [PubMed: 12418614]
Nicole S, Diaz CC, Frugier T, et al: Spinal muscular atrophy: Recent advances and future prospects. Muscle Nerve 26:4, 2002.  [PubMed: 12115944]
Veen A, Molenbuur B, Richardson FJ: Epidural anaesthesia in a child with possible spinal muscular ...

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