Idiopathic Hypersomnia with long sleep time:

Essential Features
Constant and severe sleepiness with prolonged naps
Unrefreshing naps of up to 3 or 4 hours
Prolonged major sleep episode (typically 12 to 14 hours)
Difficulty awakening from nap or in morning
Few or no nocturnal awakenings
Post – awakening confusion (sleep drunkenness) often reported

Associated Features:
Sleep drunkenness
Use special procedures to wake up
Symptoms of autonomic nervous system dysfunction
Orthostatic hypotension with syncope
Peripheral vascular complaints (Raynaud’s type phenomena)
Unpredictable response to stimulants
Lack of drug efficacy, tolerance and side effects common
Timing of drug to relieve sleep drunkenness problematic

Ratio 1:10 (Narcolepsy)?

Predisposing and Precipitating Factors
Familial predisposition
No HLA association
Possible autosomal-dominant mode of inheritance
No consistent precipitating factors
Familial Patterns
Autosomal-dominant mode of inheritance suggest
Onset, Course and Complications
Onset usually before age 25
Stable in severity and long lasting
Few with spontaneous improvement
Social and professional complications

Pathology and Pathophysiology
Normal hypocretin-1 levels in CSF
Histamine transmission may be decreased
Polysomnography and Other Objective Findings
Normal sleep of prolonged duration
Increase in slow wave sleep may occur
MSLT 6.2 + 3.0 < 2 SOREMPs
Consider 24 – hour continuous PSG

Diagnostic Criteria
Complaint of EDS almost daily for at least 3 months
Prolonged nocturnal sleep (more than 10 hours) documented
Nocturnal PSG excluded other causes of EDS
PSG demonstrates short sleep latency and sleep period greater than 10 hours
If MSLT performed , mean latency < 8 minutes, < 2 SOREMPs
Hypersomnia not better explained by another condition

Differential Diagnosis
Idiopathic Hypersomnia without long sleep time
Sleep disordered breathing
Narcolepsy without cataplexy
Hypersomnia not due to substance or known physiological condition (personality or psychiatric condition)
Hypersomnia due to drug or substance
Hypersomnia due to medical condition
Posttraumatic hypersomnia
Chronic fatigue syndrome
Behaviorally induced insufficient sleep syndrome

Use of Somnolytics; Modafinil (Provigil), Armodafinil (Nuvigil)
Use of psychostimulants; Methylphenidate (Ritalin), Amphetamine-Dextroamphetamine salts (Adderall)