Somnolence and other sleep disorders in Parkinson's disease: The challenge for the practicing neurologist

Sleep dysfunction occurs in up to 98% of patients who have PD. Among these patients, up to 51% experience EDS. Although there still is no consensus on whether or not SOS is a unique physiologic entity or an extreme manifestation of EDS, several studies using the ESS confirm that EDS is a class effect of all dopaminergic agents, including levodopa. Disease severity and duration may also be important factors leading to EDS and SOS, although the contributions of these factors are frequently confounded by the polypharmacy of patients who have PD. Management of somnolence as a comorbid condition of PD is a clinical and therapeutic challenge. The clinician must be vigilant for signs of somnolence to accurately diagnose the condition, and patient counseling is an important part of an overall treatment plan. All concomitant medications that could be soporific must be reviewed and possibly adjusted, as should the patient's dopaminergic therapy, because the presence of somnolence seems to correlate with increasing doses of levodopa and dopaminergic agents. To exclude intrinsic treatable sleep disorders, it is advisable to conduct a PSG for patients in whom no clear cause of EDS is identified. Whether or not the ESS is the best means of screening patients for EDS and SOS or if new, more practical, accurate, and cost-effective tools can be developed is a subject for future research.