Fiber tractography of the axonal pathways linking the basal ganglia and cerebellum in Parkinson disease: implications for targeting in deep brain stimulation

Abstract

Object Stimulation of white matter pathways near targeted structures may contribute to therapeutic effects of deep brain stimulation (DBS) for patients with Parkinson disease (PD). Two tracts linking the basal ganglia and cerebellum have been described in primates: the subthalamopontocerebellar tract (SPCT) and the dentatothalamic tract (DTT). The authors used fiber tractography to evaluate white matter tracts that connect the cerebellum to the region of the basal ganglia in patients with PD who were candidates for DBS. Methods Fourteen patients with advanced PD underwent 3-T MRI, including 30-directional diffusion-weighted imaging sequences. Diffusion tensor tractography was performed using 2 regions of interest: ipsilateral subthalamic and red nuclei, and contralateral cerebellar hemisphere. Nine patients underwent subthalamic DBS, and the course of each tract was observed relative to the location of the most effective stimulation contact and the volume of tissue activated. Results In all patients 2 distinct tracts were identified that corresponded closely to the described anatomical features of the SPCT and DTT, respectively. The mean overall distance from the active contact to the DTT was 2.18 ± 0.35 mm, and the mean proportional distance relative to the volume of tissue activated was 1.35 ± 0.48. There was a nonsignificant trend toward better postoperative tremor control in patients with electrodes closer to the DTT. Conclusions The SPCT and the DTT may be related to the expression of symptoms in PD, and this may have implications for DBS targeting. The use of tractography to identify the DTT might assist with DBS targeting in the future.

Letters to the Editor: Value-based neurosurgery and microvascular decompression

“…1). 8 In fact, as outlined by the authors, the occurrence of small silent thromboembolic events is usual after aneurysm coiling, however no cases of delayed IPH have been reported. 6 PVP is known to compose the outer coat of many devices, but the relation between the presence of PVP in the small vessels of the hemorrhagic area and the occurrence of delayed IPH is not clear.…”

“…8 This underscores the value of surgical evacuation of the hematoma in this specific situation even in patients receiving dual antiplatelet therapy.…”

“…8 As suggested by the authors, it is difficult to consider delayed IPH as hemorrhagic transformation of a thromboembolic ischemic lesion in the absence of large territories of acute stroke on pathological examination of the brain tissue. We recently reported similar findings in 2 cases of delayed IPH in which postflow-diverter treatment MRI studies (a few hours or days before IPH) showing no ischemic lesion in the area where the IPH occurred (Fig.…”

“…Although the use of flow diverters in these subgroups of aneurysms has demonstrated encouraging results, cases of delayed IPH after flow-diverter placement have been described with potential serious clinical worsening. 1,3,8 In this context, Hu et al performed 3 post mortem histopathological analyses of brain sections from 3 patients who suffered fatal delayed IPH.…”

“…Rule and regulation changes are perhaps most important, as they will limit the number of head impacts in football. 6,8 When incidental head impacts do occur, having the best head protection available will further reduce risk. Going back to the automobile safety analogy, this is similar to requiring seatbelt use and mandating airbags in all vehicles, in addition to optimizing vehicle structure.…”