Fatigue in Parkinson's disease patients.

Nonmotor features of Parkinson's disease (PD) have only recently been getting the attention they deserve. Dementia, depression, and psychosis are often more devastating than motor dysfunction. Fatigue affects about half of all PD patients and has a major impact on quality of life. Fatigue is the single most important reason cited for medical disability insurance claims by PD patients in the United States. PD patients suffer from both physical and mental fatigue, described as both qualitatively and quantitatively different from the fatigue experienced prior to disease onset. Although fatigue is an early symptom and may be associated with depression, most PD patients with fatigue are not depressed. It is not associated with motor dysfunction but seems to worsen with disease progression. No physiologic differences have been found between fatigued and nonfatigued PD patients. The mechanism of fatigue in PD is unknown. It does not respond to treatment of the motor symptoms. Unlike physical fatigue in normal patients, PD patients often report that their fatigue improves with exercise. No treatment is known to be effective. Methylphenidate was reported to be beneficial in one study, whereas modafinil was not. My own approach to treating fatigue is to look first for other causes that may be treatable, such as sleep dysfunction, depression, or medical disorders. If one is not found, or if it is not treatable, I then institute a course of a low-dose stimulant if there is no cardiac or psychiatric contraindication. I use either amphetamine salts (starting at 10 mg), or methylphenidate (5 mg) taken in the morning and early afternoon, and increased weekly by one dose in the morning or afternoon. Some patients may take their doses unevenly, with more or less for the morning dose. Patients who tend to go to bed late at night may take their doses three times daily.