Serial ¹H-MRS of thalamus during deep brain stimulation of bilateral globus pallidus internus for primary generalized dystonia

Introduction: The physiological mechanisms of deep brain stimulation (DBS) are not completely clear. Our understanding of them may be facilitated with the use of proton magnetic resonance spectroscopy (¹H-MRS). Methods: Serial ¹H-MRS of both thalami was performed during the course of DBS of bilateral globus pallidus internus in a patient with primary generalized dystonia. Results: Two days after microelectrode implantation, a pulse frequency of 185 Hz was applied for stimulation. It resulted in relief of symptoms and a decrease of Burke-Fahn-Marsden dystonia rating scale (BFMDRS) scores, and was accompanied by a prominent increase of N-acetylaspartate (NAA)/choline- containing compounds (Cho) ratio, a mild increase of NAA/creatine (Cr) ratio, and a moderate decrease of Cho/Cr ratio. Two weeks later, for a search of the optimal stimulation mode, the pulse frequency was switched to 60 Hz, which resulted in clinical deterioration and significant increase of BFMDRS scores. At that time, all investigated ¹H-MRS-detected metabolic parameters had nearly returned to the pretreatment levels. Conclusion: Use of serial ¹H-MRS investigations of various brain structures during DBS in cases of movement disorders permits detailed evaluation of the treatment response, has a potential for its possible prediction, and may facilitate understanding of the physiological mechanisms of stimulation.