Sleep apnea in association with neurologic disease is uncommon, and its documentation with nocturnal polysomnography (PSG) is rare. Two patients with posterior fossa neurologic disease had obstructive and central sleep apnea on PSG. The first was a 40-year-old woman who experienced a respiratory arrest ten days after neurosurgical decompression of a cervical syrinx associated with syringobulbia. Nocturnal PSG demonstrated obstructive sleep apnea. Tracheostomy was performed and a second nocturnal PSG showed no sleep apnea. The second patient was a 76-year-old woman with daytime hypersomnolence, nocturnal choking spells, progressive spastic paraparesis, and left-sided cerebellar tremor. Neurologic evaluation led to the diagnosis of olivopontocerebellar degeneration. Nocturnal PSG showed multiple episodes of central and obstructive apnea. These cases support the hypothesis that central and obstructive sleep apnea can originate from a central mechanism.