Isha, a 39-year-old woman, presents with a three-month history of disturbed sleep. She reports waking, thrashing and screaming within two hours of falling asleep.

Her sleep duration has increased from around seven to at least 10 hours. After waking, she easily returns to sleep which is unfragmented for the rest of the night.

She commutes by train and feels sleepy during travel. She will nap during the day when possible, however naps are unrefreshing.

There are no associated sudden episodes of sleepiness, loss of consciousness or muscle tone.