Cerebellothalamic Tract Research Articles

MR-guided focused ultrasound technique in functional neurosurgery: targeting accuracy.

BackgroundThe purpose of this study was to describe targeting accuracy in functional neurosurgery using incisionless transcranial magnetic resonance (MR)-guided focused ultrasound technology.MethodsMR examinations were performed before and 2 days after the ultrasound functional neurosurgical treatment to visualize the targets on T2-weighted images and determine their coordinates. Thirty consecutive targets were reconstructed: 18 were in the central lateral nucleus of the medial thalamus (central lateral thalamotomies against neurogenic pain), 1 in the centrum medianum thalamic nucleus (centrum medianum thalamotomy against essential tremor), 10 on the pallido-thalamic tract (pallido-thalamic tractotomies against Parkinson's disease), and 1 on the cerebello-thalamic tract (cerebello-thalamic tractotomy against essential tremor). We describe a method for reconstruction of the lesion coordinates on post-treatment MR images, which were compared with the desired atlas target coordinates. We also calculated the accuracy of the intra-operative target placement, thus allowing to determine the global, planning, and device accuracies. We also estimated the target lesion volume.ResultsWe found mean absolute global targeting accuracies of 0.44 mm for the medio-lateral dimension (standard deviation 0.35 mm), 0.38 mm for the antero-posterior dimension (standard deviation 0.33 mm), and 0.66 mm for the dorso-ventral dimension (standard deviation 0.37 mm). Out of the 90 measured coordinates, 83 (92.2%) were inside the millimeter domain. The mean three-dimensional (3D) global accuracy was 0.99 mm (standard deviation 0.39 mm). The mean target volumes, reconstructed from surface measurements on 3D T1 series, were 68.5 mm3 (standard deviation 39.7 mm3), and 68.9 mm3 (standard deviation 40 mm3) using an ellipsoidal approximation.ConclusionThis study demonstrates a high accuracy of the MR-guided focused ultrasound technique. This high accuracy is due not only to the device qualities but also to the possibility for the operator to perform on-going real-time monitoring of the lesioning process. A precise method for determination of targeting accuracy is an essential component and basic requirement of the functional neurosurgical activity, allowing an on-going control of the performed therapeutic work indispensable for any target efficiency analysis and the maintenance of a low risk profile.

Parkinson’s disease: news on tremor, subthalamic stimulation and impulse control disorders

This month’s Journal Club will focus on three recently published articles which deepen our knowledge in three fields of Parkinson’s disease (PD). The first article deals with the understanding of rest and postural tremors in PD. The authors found evidence that the excitability of the cerebellothalamocortical pathway is decreased in PD and seems to be involved in the generation or transmission of postural tremor. This article is accompanied by quite a critical editorial, which points out that there is still room for further discoveries. The second article deals with the effects of subthalamic stimulation on speech in consecutive patients with PD. It shows that, depending on the localisation of the electrodes, subthalamic stimulation can cause a significant deterioration of speech or improve loudness of speech. As in the study mentioned above on tremor, the cerebellothalamic tract seems also to be involved in speech deterioration. The third article shows that amantadine use is associated with impulse control disorders in PD, mainly due to its pro-dopaminergic activity, whereas its antiglutaminergic properties may even have a beneficial effect when amantadine is introduced in patients already suffering from impulse control disorders.

Truncal Contrapulsion in Pretectal Syndrome

Truncal contrapulsion in association with pretectal syndrome has not been described previously. We report a patient with vertical-gaze palsy and severe truncal contrapulsion due to an infarction in the mesodiencephalic junction. Truncal contrapulsion in this patient may have resulted from the disruption of the ascending fibers in the crossed cerebellothalamic tract.