Improvement in essential tremor after pure sensory stroke due to thalamic infarction

Clinical Heterogeneity of Essential Tremor: Understanding Neural Substrates of Action Tremor Subtypes

Essential tremor (ET) is a common movement disorder affecting millions of people. Studies of ET patients and perturbations in animal models have provided a foundation for the neural networks involved in its pathophysiology. However, ET encompasses a wide variability of phenotypic expression, and this may be the consequence of dysfunction in distinct subcircuits in the brain. The cerebello-thalamo-cortical circuit is a common substrate for the multiple subtypes of action tremor. Within the cerebellum, three sets of cerebellar cortex-deep cerebellar nuclei connections are important for tremor. The lateral hemispheres and dentate nuclei may be involved in intention, postural and isometric tremor. The intermediate zone and interposed nuclei could be involved in intention tremor. The vermis and fastigial nuclei could be involved in head and proximal upper extremity tremor. Studying distinct cerebellar circuitry will provide important framework for understanding the clinical heterogeneity of ET.

Advanced MRI techniques for transcranial high intensity focused ultrasound targeting

Magnetic resonance guided high intensity focused ultrasound is a novel, non-invasive, image-guided procedure that is able to ablate intracranial tissue with submillimetre precision. It is currently FDA approved for essential tremor and tremor dominant Parkinson’s disease. The aim of this update is to review the limitations of current landmark-based targeting techniques of the ventral intermediate nucleus and demonstrate the role of emerging imaging techniques that are relevant for both magnetic resonance guided high intensity focused ultrasound and deep brain stimulation. A significant limitation of standard MRI sequences is that the ventral intermediate nucleus, dentatorubrothalamic tract, and other deep brain nuclei cannot be clearly identified. This paper provides original, annotated images demarcating the ventral intermediate nucleus, dentatorubrothalamic tract, and other deep brain nuclei on advanced MRI sequences such as fast grey matter acquisition T1 inversion recovery, quantitative susceptibility mapping, susceptibility weighted imaging, and diffusion tensor imaging tractography. Additionally, the paper reviews clinical efficacy of targeting with these novel MRI techniques when compared to current established landmark-based targeting techniques. The paper has widespread applicability to both deep brain stimulation and magnetic resonance guided high intensity focused ultrasound.

Post-Thalamic Stroke Movement Disorders: A Systematic Review

BACKGROUND

After a stroke, movement disorders are rare manifestations mainly affecting the deep structures of the brain like the basal ganglia (44%) and thalamus (37%), although there have been case studies of movement disorders in strokes affecting the cerebral cortex also.

SUMMARY

This review aims to delineate the various movement disorders seen in association with thalamic strokes and tries to identify the location of the nuclei affected in each of the described movement disorders. Cases were identified through a search of PubMed database using different search terms related to post-thalamic stroke movement disorders and a secondary search of references of identified articles. We reviewed 2,520 research articles and only 86 papers met the inclusion criteria. Cases were included if they met criteria for post-thalamic stroke movement disorders. Case-cohort studies were also reviewed and will be discussed further. Key Messages: The most common post-stroke abnormal movement disorder reported in our review was dystonia followed by hemiataxia. There was a higher association between ischaemic stroke and movement disorder. Acute onset movement disorders were more common than delayed. The posterolateral thalamus was most commonly involved in post-thalamic stroke movement disorders.

Proliferation of Bilateral Nerve Fibers Following Thalamic Infarction Contributes to Neurological Function Recovery: A Diffusion Tensor Imaging (DTI) Study

BACKGROUND The aim of this study was to investigate the reorganization in ipsilesional and contralesional thalamic radiation fibers after unilateral focal thalamic stroke in sensory disturbance patients. MATERIAL AND METHODS We recruited 12 patients with acute unilateral thalamic infarction and sensory disturbance and 12 healthy age- and sex-matched controls. All patients underwent diffusion tensor imaging (DTI) and were assessed with National Institutes of Health stroke scale (NIHSS), Barthel index (BI), and paragraph 8 of NIHSS (NIHSS8) at 1 week (W1), 4 weeks (W4), 3 months (M3), and 6 months (M6) after thalamic infraction. The relationship between FA changes and the clinical scores changes were then examined. RESULTS NIHSS and NIHSS8 scores decreased while BI scores increased gradually from W1 to M6 in patients, but not in controls. FA values of the patients gradually increased in ipsilesional and contralesional thalamic radiation fibers from W1 to M6. In addition, the FA values in patients were significantly higher at M3 and M6 compared to W1. No significant changes were observed in the controls. Regarding the relationship between FA changes and the clinical scores changes, the FA increases were negatively correlated with NIHSS and NIHSS8 decrease while FA increases were positively correlated with BI increases. CONCLUSIONS Our results indicate that reorganization occurred after unilateral focal thalamic infarct not only in ipsilesional, but also in contralesional thalamic radiation fibers in patients with sensory disturbance. In addition, the results suggested that the reorganization can support and promote stroke restoration.

Disappearance of essential tremor after stroke

Improvement of a patient's essential tremor (ET) after a stroke has rarely been reported. In such patients, cerebral imaging could help to identify structures involved in the maintenance of ET and improves the knowledge of its physiopathology. This article reports the disappearance of ET, after a stroke in 4 patients and reviews similar previously published cases. These cases suggest that the interruption of cerebellar loops during a stroke could be responsible for the disappearance of ET.

Disappearance of resting tremor after thalamic stroke involving the territory of the tuberothalamic artery

Disappearance of resting tremor was observed in a 76-year-old patient with Parkinson's disease after a contralateral thalamic infarct involving the territory of the tuberothalamic artery. Based on the analysis of surgical data of Parkinson's disease patients, this might be explained by the lesion of the ventral lateral nucleus, which is supplied by the inferolateral and tuberothalamic arteries. Thalamic infarction in the territory of the tuberothalamic artery as well as the inferolateral artery can produce amelioration of tremor.