In Vivo Dentate Nucleus Gamma-aminobutyric Acid Concentration in Essential Tremor vs. Controls

Elan D. Louis, Nora Hernandez, Jonathan P. Dyke, Ruoyun E. Ma, Ulrike Dydak
2017 Cerebellum  
Background-Despite its high prevalence, essential tremor (ET) is among the most poorly understood neurological diseases. The presence and extent of Purkinje cell (PC) loss in ET is the subject of controversy. PCs are a major storehouse of central nervous system gamma-aminobutyric acid (GABA), releasing GABA at the level of the dentate nucleus. It is therefore conceivable that cerebellar dentate GABA concentration could be an in vivo marker of PC number. Objectives-We used in-vivo 1H magnetic
more » ... onance spectroscopy (MRS) to quantify GABA concentrations in two cerebellar volumes of interest, left and right, which included the dentate nucleus, comparing 45 ET cases to 35 age-matched controls. Methods-1H MRS was performed using a 3.0 Tesla Siemens Tim Trio scanner. The MEGA-PRESS J-editing sequence was used for GABA detection in two cerebellar volumes of interest (left and right) that included the dentate nucleus. Results-The two groups did not differ with respect to our primary outcome of GABA concentration (given in institutional units). For right dentate: [GABA] in ET cases = 2.01 ± 0.45 and [GABA] in controls = 1.86 ± 0.53, p = 0.17. For left dentate: [GABA] in ET cases = 1.68 ± 0.49 and [GABA] controls = 1.80 ± 0.53, p = 0.33. The controls had similar dentate [GABA] in the right vs. left dentate (p = 0.52); however, in ET cases, the value on the right was considerably higher than on the left (p = 0.001). Conclusions-We did not detect a reduction in dentate GABA concentration in ET cases vs. controls. One interpretation of the finding is that it does not support the existence of PC loss in ET; however, an alternative interpretation is the observed pattern could be due to the effects of terminal sprouting in ET (i.e., collateral sprouting from surviving PCs making up for the loss of GABAergic terminals from PC degeneration). Further research is needed.
doi:10.1007/s12311-017-0891-4 pmid:29039117 fatcat:ltxhehilkrgs7kmvmkyguilyma