The cross-hemispheric nigrostriatal pathway prevents the expression of levodopa-induced dyskinesias.

Parkinson's disease (PD) is a neurodegenerative movement disorder that is routinely treated with levodopa. Unfortunately, long-term dopamine replacement therapy using levodopa leads to levodopa-induced dyskinesias (LID), a significant and disabling side-effect. Clinical findings indicate that LID typically only occurs following the progression of PD motor symptoms from the unilateral (Hoehn and Yahr (HY) Stage I) to the bilateral stage (HY Stage II). This suggests the presence of some compensatory interhemispheric mechanisms that delay the occurrence of LID. We therefore investigated the role of interhemispheric connections of the nigrostriatal pathway on LID expression in a rat model of PD. The striatum of one hemisphere of rats was first injected with a retrograde tracer to label the ipsi- and cross-hemispheric nigrostriatal pathways. Rats were then split into groups and unilaterally lesioned in the striatum or medial forebrain bundle of the tracer-injected hemisphere to induce varying levels of hemiparkinsonism. Finally, rats were treated with levodopa and tested for the expression of LID. Distinct subsets emerged from rats that underwent the same lesioning paradigm based on LID. Strikingly, non-dyskinetic rats had significant sparing of their cross-hemispheric nigrostriatal pathway projecting from the unlesioned hemisphere. In contrast, dyskinetic rats only had a small proportion of this cross-hemispheric nigrostriatal pathway survive lesioning. Crucially, both non-dyskinetic and dyskinetic rats had nearly identical levels of ipsi-hemispheric nigrostriatal pathway survival and parkinsonian motor deficits. Our data suggest that the survival of the cross-hemispheric nigrostriatal pathway plays a crucial role in preventing the expression of LID and represents a potentially novel target to halt the progression of this devastating side-effect of a common anti-PD therapeutic.

Self-expanding covered stent placement to treat a pseudoaneurysm caused by iatrogenic vertebral artery injury.

Vertebral artery injuries account for approximately 19% of cerebral vascular injuries and are typically managed conservatively. However, some patients require operative intervention to gain control of an active hemorrhage, either via surgical ligation or endovascular intervention. We present a case of iatrogenic vertebral artery injury occurring during cervical spine surgery which was treated emergently with a self-expanding covered stent. A 58-year-old male presented for cervical traction, C5 and C6 corpectomy, and possible C4 to T2 posterior fusion following a motor vehicle accident. Intraoperatively, following drilling the C5 endplate, copious bleeding was observed from injury to the right vertebral artery resulting in pseudoaneurysm formation. The patient was loaded with ticagrelor and a self-expanding covered stent was placed via a transfemoral approach, resulting in obliteration of the pseudoaneurysm prior to completion of his cervical spine surgery. Emergent self-expanding covered stent placement for iatrogenic vertebral artery injury in the setting of an intraoperative injury is a safe and effective option. Ticagrelor is a viable alternative to traditional dual antiplatelet therapy for preventing thromboembolic complications in this urgent setting.

The comparative accuracy of the ROSA stereotactic robot across a wide range of clinical applications and registration techniques.

Robot-assisted stereotactic neurosurgery is an emerging technology with a growing range of applications. The ROSA system is a robotic stereotactic system that has been shown to be accurate in laboratory studies and large case series. The goal of this study was to examine the accuracy of the ROSA across different registration methods as well as different clinical applications. Sixteen patients with one hundred and seventeen stereotactic trajectories were examined. Accuracy was compared by measuring the distance between the trajectory target and the actual termination of the device as determined by imaging. Entry error and angular deviation were also measured. Variables included bone fiducials vs. laser facial scanning, the clinical indication for stereotactic surgery, and the effect of lead deflection on accuracy. Bone fiducials did not offer an accuracy benefit over laser facial scanning (mean target error 4.5-3.9 mm, p = 0.34) in these clinical scenarios. Laser interstitial thermal therapy, responsive neurostimulation, and stereo electroencephalography were equally accurate when placed by the ROSA (mean target error 4.4-4.3-4.0 mm, respectively, p = 0.69). Deflection did not affect lead accuracy (mean target error 4.4-3.9 mm, p = 0.11). Similar results are seen for entry error and angular deviation. ROSA is a highly accurate stereotactic system. Laser facial scanning provides the same accuracy as bone fiducials in these stereotactic applications. The ROSA is equally accurate across a wide spectrum of applications. The ROSA is effective at limiting lead deflection, and when it does occur, it does not impact target accuracy in a significant way.