A case of Kleine-Levin syndrome arising during chemotherapy: efficacy of oral L-carnitine

A woman in her 50 s with Kleine-Levin syndrome (KLS) was referred to our sleep clinic for recurrent episodes of sleep hypersomnia lasting for two to 3 days, despite attempts to remain awake. These episodes were unaccompanied by anxiety or depression, increased appetite, increased sex drive, irritability, or hallucinations, and had first appeared during chemotherapy for malignant lymphoma. Video polysomnography revealed mild obstructive sleep apnea syndrome (apnea-hypopnea index 7.9/h), but no other abnormalities. All blood tests and brain imaging investigations, including brain MRI and A I-123-ioflupane SPECT, yielded normal results. Oral L-carnitine was found to be effective for shortening the period of hypersomnolence, reducing the degree of hypersomnolence, and prolonging the inter-episode period. Since it has been reported that alkylating agents may induce carnitine deficiency, the present observations appear to support the involvement of carnitine in the onset of KLS.