Narcolepsy in midbrain structural lesion.

A 59-year-old Caucasian man presented with a 2-year history of excessive daytime sleepiness associated with sudden and irresistible bouts of sleep occurring up to five times per day. Moreover, he reported occasional episodes of cataplexy that were triggered by strong emotional stimuli, especially anger and surprise. He had a depressed mood and was exhausted from his symptoms that caused him great difficulty in maintaining concentration while at work and had even led to a car crash. There was no relevant family history or any other previous sleep disorder. He was overweight [body mass index (BMI 29)] and used to take no medication. His past medical history was unremarkable; in particular, he denied any history of vivid dream-like images or hallucinations. He used to drink 4-5 cups of coffee throughout the day and one glass of wine most evenings and denied any use of illicit drugs. Neurological evaluation did not show any pathological finding. Epworth sleepiness scale score was 18 and all the laboratory tests, including thyroid function, were within normal values. The nocturnal polysomnogram did not show significant sleep-disordered breathing or periodic limb movement activity, while a multiple sleep latency test (MSLT) confirmed the suspected diagnosis of narcolepsy. Magnetic resonance imaging (MRI) of the brain revealed a midbrain T2-hyperintense lesion in the left paramedian area, next to the aqueduct of Sylvius [Figure 1]. Narcolepsy is a chronic lifelong sleep disorder, with a severe effect on the patients’ quality of life. It is a sporadic disorder with genetic susceptibility. Moreover, the strong association with human leukocyte antigen (HLA) DQ beta 1 (DQB1)*06:02 strongly suggests an autoimmune basis for the disease.[1] It is often misdiagnosed, or the diagnosis may be delayed, in part, because of the wide spectrum of clinical phenotypes. Age at onset is usually in the second or third decade, with a small peak in the fourth decade. Narcolepsy has been associated with deficiency of the hypothalamic neuropeptide hypocretin,[2] causing the classic tetrad of excessive daytime sleepiness, and sleep paralysis. Secondary etiologies due to hypothalamus or pons lesions have been described.[3] Our case, related to a midbrain ischemic lesion, extends the spectrum of structural lesions in narcolepsy.

Figure 1

Sagittal (A) and axial (2) T2-weighted MRI showing a hyperintense lesion localized in the left midbrain paramedian area (arrows), next to the aqueduct of Sylvius, corresponding to the median column of the midbrain reticular formation. The lesion, extending for 12 mm in the rostrocaudal plan, does not show contrast enhancement and is likely due to an ischemic damage

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