Denny has been diagnosed with narcolepsy, and suffers from cataplexy and the occasional episode of sleep paralysis. Denny has:

Dyssomnia

Explanation:

Dyssomnia is a broad term used to refer the sleeping disorders in which the person remains asleep and causes excessive sleepiness during the daytime.

The dyssomnia shows its symptoms in the form of narcolepsy is a sleep disorder in which the person feels excessive sleepiness, hallucinations and cataplexy in which the muscle tone is lost for a brief period of time due to the strong emotions.

Thus, dyssomnia is the correct answer.