title: Low thalamic NAA-concentration corresponds to strong neural activation in working memory in Kleine-Levin syndrome.
abstract: BACKGROUND
  Kleine Levin Syndrome (KLS) is a rare disorder of periodic hypersomnia and behavioural disturbances in young individuals. It has previously been shown to be associated with disturbances of working memory (WM), which, in turn, was associated with higher activation of the thalamus with increasing WM load, demonstrated with functional magnetic resonance imaging (fMRI). In this study we aimed to further elucidate how these findings are related to the metabolism of the thalamus.
  
  
  METHODS
  fMRI and magnetic resonance spectroscopy were applied while performing a WM task. Standard metabolites were examined: n-acetylaspartate (NAA), myo-inositol, choline, creatine and glutamate-glutamine. Fourteen KLS-patients and 15 healthy controls participated in the study. The patients with active disease were examined in asymptomatic periods.
  
  
  RESULTS
  There was a statistically significant negative correlation between thalamic fMRI-activation and thalamic NAA, i.e., high fMRI-activation corresponded to low NAA-levels. This correlation was not seen in healthy controls. Thalamic levels of NAA in patients and controls showed no significant differences between the groups. None of the other metabolites showed any co-variation with fMRI-activation.
  
  
  CONCLUSIONS
  This study shows negative correlation between NAA-levels and fMRI-activity in the left thalamus of KLS-patients while performing a WM task. This correlation could not be found in healthy control subjects, primarily interpreted as an effect of increased effort in the patient group upon performing the task. It might indicate a disturbance in the neuronal networks responsible for WM in KLS patients, resulting in higher effort at lower WM load, compared with healthy subjects. The general relationship between NAA and BOLD-signal is also discussed in the article.
authors: Department of Clinical and Experimental Medicine IKE/Neuroscience, Linköping University, Linköping, Sweden.
authors: Patrick
authors: P
authors: Vigren
authors: Anders
authors: A
authors: Tisell
authors: Maria
authors: M
authors: Engström
authors: Thomas
authors: T
authors: Karlsson
authors: Olof
authors: O
authors: Leinhard Dahlqvist
authors: Peter
authors: P
authors: Lundberg
authors: Anne-Marie
authors: AM
authors: Landtblom
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D017593:Kleine-Levin Syndrome / Q000378:metabolism* / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D013788:Thalamus / Q000378:metabolism* / Q000473:pathology; D055815:Young Adult