A 4 year old child who had complex partial seizures alternating with sleep that presented as episodic hypersomnolence is reported from the Mayo Clinic, Rochester, MN. The hypersomnolence lasting 24-72 hrs was preceded by irritability and hyperkinesia for 48-96 hrs. The intervals between episodes ranged from 10-60 days. The EEG showed left occipital spikes in sleep. Prolonged recording during hypersomnolence showed right temporal seizure discharges. Phenytoin controlled the episodic hypersomnolence, with no recurrence at 19 yr follow-up. Complex partial seizures followed by postictal somnolence occurred occasionally between 5 and 11 yrs of age. CT was normal. Behavioral problems required special education and methylphenidate. He graduated from high school and has a manual labor job. 
COMMENT. The EEG recording showing right temporal seizure discharges during the period of hypersomnolence. and the excellent response to phenytoin suggest that the episodic sleep disorder may be regarded as a seizure phenomenon. Lennox WG refers to “sleeplike episodes” and somnambulism as forms of epilepsy, but does not describe a case similar to the above report. (Epilepsy and Related Disorders. Boston, little, Brown, 1960).
A young man presented with episodes of unexplained hypersomnolence lasting 24-48 hrs in my own practice. An EEG between episodes showed occasional temporal sharp waves. CT and metabolic studies were normal. An EEG recording during an attack could not be obtained. A trial of phenytoin was successful in this case, and attacks recurred when treatment was discontinued. A seizure disorder was suspected but not proven.
Sleep disorders with central hypoventilation syndrome and seizures is reviewed in Progress in Pediatric Neurology II, Chicago, PNB Publ, 1994, pp 192-4.