Pediatric motor neuron disease

1. What is the pathophysiology behind spinal muscular atrophy?
2. What is another name for SMA I, when does it present, and what muscles are spared?
3. What weakness is characteristic of SMA type II?
4. What is another name for SMA III, what is the onset, and what is the prognosis?
5. What is the inheritance of Friedreich's ataxia and what protein is abnormal?
6. What is the most effective treatment of progressive scoliosis?

Answers:
1. Inherited disorders characterized by weakness and muscle wasting, secondary to degeneration of anterior horn cells and brain stem motor nuclei. There are three subtypes.
2. Severe SMA or Werdnig-Hoffman disease presents within first few months of life with severe hypotonia and weakness, with respiratory problems, sucking and swallowing difficulties. Extraocular and cardiac muscles are spared.
3. SMA II is intermediate and results in predominent leg weakness so that patient may sit unsupported but not stand.
4. Mild SMA or Kugelberg-Welander syndrome has onset >18 mo, with walking limitations, but good long-term survival depending on respiratory function.
5. Autosomal recessive, liked to chromosome 9q21, with abnormal Frataxin protein.
6. Spinal arthrodesis prior to curvature of 35 deg and prior to VC below 35%. Bracing can be used to improve sitting balance in nonambulatory patients.