Risk of sudden death during sleep in syringomyelia and syringobulbia.

Clinical, respiratory, and polysomnographic findings in three patients with syringomyelia and syringobulbia who developed severe respiratory complications are described. Neurological examination showed evidence of IXth and Xth cranial nerve involvement with dysphagia and dysphonia, but there were no complaints of serious sleep difficulties. Two patients died during sleep and the other was resuscitated during a nap. All patients showed moderate restrictive ventilatory defects with reduced maximal buccal pressures and one also showed a low ventilatory response to CO2 rebreathing. Protracted central, obstructive, and mixed apnoeas and hypopnoeas were commonly observed during sleep. There were no changes in heart rate during these events. A combination of respiratory and cardiovascular mechanisms might have been responsible for the severe complications described.