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.

A new robotic assistance system for percutaneous CT-guided punctures: Initial experience.

PURPOSE: To evaluate the feasibility of CT-guided bone biopsies using a novel robotic needle guide. MATERIAL AND METHODS: The robotic needle guide iSYS 1.3 (iSYS Medzintechnik, GmbH, Kitzbuehel, Austria) mounted on the standard table of a CT scanner was used for all studies. For preclinical testing, eight vertebral bodies of dead swine were biopsied, trying to place the needle in the center of the vertebral body via a transpedicular access. For clinical evaluation, bone biopsies were taken in three different patients with ambiguous bone lesions. All biopsies were performed under general anesthesia, using a 12G bone biopsy needle. RESULTS: The animal studies demonstrated that the biopsy needle could be placed accurately in the center of the vertebral body in all cases. No readjustment was necessary, the CT scans demonstrated an intrapedicular trajectory avoiding the spinal canal or the neural foramina. Subsequently, following the animal studies, all biopsies could be performed successfully. Needle placement was accurate without any need for readjustment. No complications occurred during the procedure. CONCLUSION: Using the iSYS 1.3 allows for accurate and simple stereotactic biopsies of bone lesions, avoiding the need for needle readjustment. The systems may offer even less experienced teams to take biopsies in regions which are difficult to access.

Radiographic evaluation of ventral instability in lumbar spondylolisthesis: do we need extension radiographs in routine exams?

PURPOSE: To determine the usefulness of acquiring extension radiographs for the evaluation of the degree of spondylolisthesis. METHODS: Routine radiographs of the lumbar spine were retrospectively evaluated in 87 patients (mean-age 63, range 32-86) by two independent radiologists. All patients received radiographs in standing neutral, flexion and extension position. Vertebral body depth, sagittal translational displacement and lordosis angle were measured and slip percentage (SP) was calculated on standing neutral, flexion and extension radiographs. Statistical analysis was performed with a two-sided t test. Inter- and intraobserver reliability was assessed using the kappa-coefficient. RESULTS: There was no statistically significant SP-difference between neutral standing and extension images. Ventral instability was diagnosed in 25-34 % (cut-off >8 % SP-difference) for neutral versus flexion comparison. The detection rate of flexion-extension radiographs representing the extremes of motion was lower with 15-22 %. Inter- and intraobserver reliability was good to excellent. CONCLUSION: Slip percentage in routine standing extension radiography ultimately does not differ from that obtained in a static neutral standing view. Extension radiography may therefore be omitted in a routine work-up of ventral instability in lumbar spondylolisthesis.

Thermometry during coblation and radiofrequency ablation of vertebral metastases: a cadaver study.

PURPOSE: To evaluate safety of coblation of simulated lytic metastases in human cadaveric vertebral bodies by measuring heat distribution during thermal tissue ablation and comparing it to radiofrequency ablation (RFA). MATERIALS AND METHODS: Three devices were compared: a 10 mm single-needle RFA electrode, a 20 mm array RFA electrode and the coblation device. To simulate bone metastases, a spinal tumor model was used stuffing a created lytic cavity with muscle tissue. Measuring of heat distribution was performed during thermal therapy within the vertebral body, in the epidural space and at the ipsilateral neural foramen. Eight vertebral bodies were used for each device. RESULTS: Temperatures at heat-sensitive neural structures during coblation were significantly lower than using RFA. Maximum temperatures measured at the end of the procedure at the neural foramen: 46.4 °C (± 2.51; RFA 10 mm), 52.2 °C (± 5.62; RFA 20 mm) and 42.5 °C (± 2.88; coblation). Maximum temperatures in the epidural space: 46.8 °C (± 4.7; RFA 10 mm), 49.5 °C (± 6.48; RFA 20 mm) and 42.1 °C (± 2.5; coblation). Maximum temperatures measured within the vertebral body: 50.6 °C (± 10.48; RFA 10 mm), 61.9 °C (± 15.39; RFA 20 mm) and 54.4 °C (± 15.77; coblation). CONCLUSION: In addition to RFA, the application of coblation is a safe method to ablate vertebral lesions with regards to heat distribution at heat-sensitive neural spots. The measured temperatures did not harbor danger of thermal damage to the spinal cord or the spinal nerves.