Pregnancy associated with Friedreich ataxia.

The pregnancy of a woman with Friedreich ataxia was complicated by the onset of preterm labor and preeclampsia. Administration of magnesium sulfate (MgSO4.7H2O) in the usual intravenous dosage resulted in the dramatic development of profound motor weakness and respiratory distress. Magnesium acts to antagonize the action of acetylcholine at the motor end plate of the neuromuscular junction and may operate synergistically with underlying neuromuscular disorders. Therefore, the use of magnesium sulfate in patients with Friedreich ataxia and other similar neurodegenerative diseases is contraindicated.