Background and aim: Friedreich's ataxia (FRDA) and ataxia with oculomotor apraxia type 2 (AOA2) are the two most frequent forms of autosomal recessive cerebellar ataxias. However, brain metabolism in these disorders is poorly characterized and biomarkers of the disease progression are lacking. We aimed at assessing the neurochemical profile of the pons, the cerebellar hemisphere and the vermis in patients with FRDA and AOA2 to identify potential biomarkers of these diseases. Methods: Short-echo, single-voxel proton (1H) magnetic resonance spectroscopy data were acquired from 8 volunteers with FRDA, 9 volunteers with AOA2, and 38 control volunteers at 4T. Disease severity was assessed by the Friedreich's Ataxia Rating Scale (FARS). Results: Neuronal loss/dysfunction was indicated in the cerebellar vermis and hemispheres in both diseases by lower total N-acetylaspartate levels than controls. The putative gliosis marker myo-inositol was higher than controls in the vermis and pons in AOA2 and in the vermis in FRDA. Total creatine, another potential gliosis marker, was higher in the cerebellar hemispheres in FRDA relative to controls. Higher glutamine in FRDA and lower glutamate in AOA2 than controls were observed in the vermis, indicating different mechanisms possibly leading to altered glutamatergic neurotransmission. In AOA2, total N-acetylaspartate levels in the cerebellum strongly correlated with the FARS score (p < 0.01). Conclusion: Distinct neurochemical patterns were observed in the two patient populations, warranting further studies with larger patient populations to determine if the alterations in metabolite levels observed here may be utilized to monitor disease progression and treatment.
Bibliographical noteFunding Information:
This work was supported by the Kory and Scott Tabor Ataxia Research Fund and NINDS grant R21NS056172 (to GÖ). The 4T TEM coil was built with a grant ( 3761-9236-07 ) from the Minnesota Medical Foundation (to GÖ). The Center for MR Research is supported by National Center for Research Resources (NCRR) biotechnology research resource grant P41RR008079 and Neuroscience Center Core Blueprint Award P30NS057091 . The General Clinical Research Center is supported by NCRR grant M01RR00400 . The authors thank Drs. Susan Perlman (UCLA), Bernard Brais (CHUM), and David Lynch (UPenn) and their assistants for supporting this work by referring their patients to our institution. We also thank the patients and their families for participating in this study.