Search

Essential tremor is the most common movement disorder in adults. In patients who are not responsive to medical treatment, functional neurosurgery and, more recently, transcranial MR‐guided focused ultrasound thalamotomy are considered effective therapeutic approaches. However, the structural brain changes following a thalamotomy that mediates the clinical improvement are still unclear. In here diffusion weighted images were acquired in a cohort of 24 essential tremor patients before and 3 months after unilateral transcranial MR‐guided focused ultrasound thalamotomy targeting at the posteroventral part of the VIM. Microstructural changes along the DRTT were quantified by means of probabilistic tractography, and later related to the clinical improvement of the patients at 3‐months and at 1‐year after the intervention. In addition the changes along two neighboring tracts, that is, the corticospinal tract and the medial lemniscus, were assessed, as well as the relation between these changes and the presence of side effects. Thalamic lesions produced local and distant alterations along the trajectory of the DRTT, and each correlated with clinical improvement. Regarding side effects, gait imbalance after thalamotomy was associated with greater impact on the DRTT, whereas the presence of paresthesias was significantly related to a higher overlap between the lesion and the medial lemniscus. This work represents the largest series describing the microstructural changes following transcranial MR‐guided focused ultrasound thalamotomy in essential tremor. These results suggest that clinical benefits are specific for the impact on the cerebello‐thalamo‐cortical pathway, thus reaffirming the potential of tractography to aid thalamotomy targeting. [ABSTRACT FROM AUTHOR]

Abstract: The pedunculopontine nucleus (PPN) has recently been introduced as a new therapeutic target for deep brain stimulation (DBS) in patients suffering from Parkinson''s disease (PD). In a recent case report it was demonstrated that alpha frequency oscillations appear in PPN after the administration of levodopa in PD, indicating a possible physiological role of these oscillations. Here we confirm this result and investigate the functional connectivity and reactivity of subcortical alpha activity by recording LFP activity from the PPN area and EEG in six patients with PD while at rest and in four of them while they performed ipsi- and contralateral self-paced joystick movements. Levodopa strongly promoted 7–11 Hz oscillatory synchronization in the region of PPN and coupling of this activity with similar activity in the cortical EEG. Such coupling was bidirectional. Moreover, the 7–11 Hz oscillatory synchronization in the PPN area increased about 3 s prior to self-paced movements, but only following levodopa treatment. These findings suggest that alpha oscillations in the PPN area may represent a physiological pattern of activity. The subcortical oscillations are coupled to cortical alpha activity and possibly allied to motor related attentional processes. [Copyright &y& Elsevier]