PROTON SPECTROSCOPY IN THE NARCOLEPTIC SYNDROME - IS THERE EVIDENCE OF A BRAIN-STEM LESION

There is controversy regarding the relationship of structural or bioch emical brainstem lesions to ''idiopathic'' narcolepsy. Most cases of t he narcoleptic syndrome are considered to be idiopathic because no str uctural lesion is detectable, although some cases of secondary narcole psy are known to be associated with no structural brainstem lesions. U sing proton spectroscopy, we determined levels of ventral pontine meta bolite pools in 12 normal subjects and 12 subjects with idiopathic nar colepsy. REM sleep is generated in ventral pontine areas. Proton spect roscopy was used to study levels of N-acetyl aspartate (NAA) as a mark er of cell mass, creatine and phosphocreatine (Cr + PCr), and choline (Cho). The intensity of the peaks, as determined by the area under the peak (AUP), was measured. The AUP correlates with the quantity of che mical present. In this study, the ratios of NAA to Cr + PCr were simil ar in normal subjects and in narcoleptic subjects with idiopathic narc olepsy. No differences in measured metabolic ratio were observed in su bjects who slept during the scan procedure compared with those who rem ained awake. Subjects with ''symptomatic'' narcolepsy accompanied by a n obvious structural brain lesion were not studied. Proton spectroscop y of the brain initiates a new kind of neurochemistry, allowing the no ninvasive study of metabolic pools in the living human brain without t he use of any kind of tracer or radioactive molecule. In this study, t here was no evidence of cell loss in the ventral pontine areas of subj ects with the narcoleptic syndrome.