Fractional anisotropy within zone of destruction, tremor evaluation and MRI manifestation follow up after focused ultrasound thalamotomy for patients with Parkinson’s disease

Abstract

Purpose. Assessment of MRI manifestation including fractional anisotropy within nucleus of destruction after focused ultrasound thalamotomy and estimation of its correlation with tremor severity.Material and methods. 7 patients with clinically approved Parkinson's disease were included. MRI examinations of the brain were performed before FUS-thalamotomy, within 3 hours, after 24 hours, after 3 and 6 months after the operation. The study protocol included routine MR sequences; fractional anisotropy maps were generated. Before surgery, after a day, 3 and 6 months, the severity of tremor was assessed by the CRST scale; CRST values correlation with the values of fractional anisotropy, as well as the correlation of the coordinates of the destruction focus with the residual therapeutic effect of the operation was estimated using a linear regression model.Results. The general patterns of the MRI manifestation were revealed: the appearance after the operation of the nucleus of destruction with the accumulation of paramagnetic substances in the structure and perifocal edema. The severity of the MRI-changes reached a maximum one day after the operation, regressed and were practically not visualized after 3 and 6 months. There was a high correlation between the volumes of the nucleus of destruction and perifocal edema, no correlation between the severity of tremor and the values of fractional anisotropy in the nucleus of destruction, a weak correlation between the localization of the nucleus of destruction and the value of the residual therapeutic effect of FUS-thalamotomy 6 months after surgery.Conclusions. The MRI manifestation during 6 months after FUS-thalamotomy had a similar character in all patients, reached a maximum severity one day after the operation and had gradual regression. Fractional anisotropy values did not correlate with tremor severity. For a prolonged therapeutic effect the contribution of the localization of the focus along the sagittal axis is possible.