Parkinsonism with excessive daytime sleepiness--a narcolepsy-like disorder?

Parkinsonian patients with excessive daytime sleepiness (EDS), hallucinations, REM sleep behavior disorder (RBD), short mean sleep latencies, and sleep-onset REM periods (SOREMP) on multiple sleep latency tests (MSLT) have been reported. In these patients a narcolepsy-like pathophysiology of sleep-wake disturbances has been suggested.

We studied 14 consecutive patients with Parkinsonism and EDS. Standard studies included assessment of duration and severity of Parkinsonism (Hoehn & Yahr score), Epworth sleepiness score (ESS), history of "REM-symptoms" (RBD/hallucinations/sleep paralysis/cataplexy-like episodes), polysomnography (PSG), MSLT, and measurement of cerebrospinal fluid (CSF) levels of hypocretin-1 (orexin A).

There were 12 men and 2 women (mean age 69 years; range 54-82). The mean duration and the Hoehn&Yahr score were 6.3 years and 2.2, respectively. Diagnoses included idiopathic Parkinson's disease (IPD, n = 10), dementia with diffuse Lewy bodies (n = 3), and multisystem atrophy (n = 1). The ESS was > or = 10 in all patients (mean 12; range 10-18). "REM-symptoms" were reported by all but two patients (hallucinations: n = 9; RBD: n = 9). None of the patients reported cataplexy-like symptoms or sleep paralysis. On PSG sleep apnea (apnea hypopnea index > 10/h, n = 7), periodic limb movements during sleep (PLMS-index > 10/h, n = 6), and features of RBD (n = 5) were found. On MSLT mean sleep latency was < 5 minutes in 10 patients, and SOREMP were found in two patients. When compared with controls (n = 20, mean 497 pg/ml; range 350-603), CSF hypocretin-1 levels were normal in 8 patients and low in 2 patients (221 and 307 pg/ml, respectively).

These findings do not support the hypothesis of a "final common pathway" in the pathophysiology of narcolepsy and Parkinsonism with EDS. Sleep apnea and PLMS may play a so-far underestimated role in the pathogenesis of EDS in Parkinsonian patients.