Coherent Structural and Functional Network Changes after Thalamic Lesions in Essential Tremor.

BACKGROUND: Magnetic resonance-guided focused ultrasound of the ventral intermediate nucleus is a novel incisionless ablative treatment for essential tremor (ET). OBJECTIVE: The aim was to study the structural and functional network changes induced by unilateral sonication of the ventral intermediate nucleus in ET. METHODS: Fifteen essential tremor patients (66.2 ± 15.4 years) underwent probabilistic tractography and functional magnetic resonance imaging (MRI) during unilateral postural tremor-eliciting tasks using 3-T MRI before, 1 month (N = 15), and 6 months (N = 10) post unilateral sonication. RESULTS: Tractography identified tract-specific alterations within the dentato-thalamo-cortical tract (DTCT) affected by the unilateral lesion after sonication. Relative to the treated hand, task-evoked activation was significantly reduced in contralateral primary sensorimotor cortex and ipsilateral cerebellar lobules IV/V and VI, and vermis. Dynamic causal modeling revealed a significant decrease in excitatory drive from the cerebellum to the contralateral sensorimotor cortex. CONCLUSIONS: Thalamic lesions induced by sonication induce specific functional network changes within the DTCT, notably reducing excitatory input to ipsilateral sensorimotor cortex in ET. ©[2022] International Parkinson and Movement Disorder Society. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

MRI follow-up after magnetic resonance-guided focused ultrasound for non-invasive thalamotomy: the neuroradiologist's perspective.

PURPOSE: Magnetic resonance-guided focused ultrasound (MRgFUS) systems are increasingly used to non-invasively treat tremor; consensus on imaging follow-up is poor in these patients. This study aims to elucidate how MRgFUS lesions evolve for a radiological readership with regard to clinical outcome. METHODS: MRgFUS-induced lesions and oedema were retrospectively evaluated based on DWI, SWI, T2-weighted and T1-weighted 3-T MRI data acquired 30 min and 3, 30 and 180 days after MRgFUS (n = 9 essential tremor, n = 1 Parkinson's patients). Lesions were assessed volumetrically, visually and by ADC measurements and compared with clinical effects using non-parametric testing. RESULTS: Thirty minutes after treatment, all lesions could be identified on T2-weighted images. Immediate oedema was rare (n = 1). Lesion volume as well as oedema reached a maximum on day 3 with a mean lesion size of 0.4 ± 0.2 cm3 and an oedema volume 3.7 ± 1.2 times the lesion volume. On day 3, a distinct diffusion-restricted rim was noted that corresponded well with SWI. Lesion shrinkage after day 3 was observed in all sequences. Lesions were no longer detectable on DWI in n = 7/10, on T2-weighted images in n = 4/10 and on T1-weighted images in n = 4/10 on day 180. No infarcts or haemorrhage were observed. There was no correlation between lesion size and initial motor skill improvement (p = 0.99). Tremor reduction dynamics correlated strongly with lesion shrinkage between days 3 and 180 (p = 0.01, R = 0.76). CONCLUSION: In conclusion, cerebral MRgFUS lesions variably shrink over months. SWI is the sequence of choice to identify lesions after 6 months. Lesion volume is arguably associated with intermediate-term outcome.

Supramodal language comprehension: role of the left temporal lobe for listening and reading.

In this fMRI study, we aimed at identifying the cortical areas engaged in supramodal processing of language comprehension. BOLD changes were recorded in 19 healthy right-handed subjects reading or listening to a story. During the visual control tasks the volunteers attended to a series of continuous letterstrings or a fixation cross, while during the acoustic control tasks either a reversed text or white noise were presented. The conjunction of the visual and acoustic story processing yielded left-dominant activations which in comparison to language-like stimuli focused to the left middle temporal gyrus as well as to the supramarginal gyrus. We conclude that the core structure representing supramodal language comprehension is the left temporal lobe at both banks of the superior temporal sulcus.