Convergent structural network and gene signatures for MRgFUS thalamotomy in patients with Parkinson's disease

Disrupted topological properties of structural brain networks present a glutamatergic neuropathophysiology in people with narcolepsy

STUDY OBJECTIVES

Growing evidences have documented various abnormalities of the white matter bundles in people with narcolepsy. We sought to evaluate topological properties of brain structural networks, and their association with symptoms and neuropathophysiological features in people with narcolepsy.

METHODS

Diffusion tensor imaging was conducted for people with narcolepsy (n = 30) and matched healthy controls as well as symptoms assessment. Structural connectivity for each participant was generated to analyze global and regional topological properties and their correlations with narcoleptic features. Further human brain transcriptome was extracted and spatially registered for connectivity vulnerability. Genetic functional enrichment analysis was performed and further clarified using in vivo emission computed tomography data.

RESULTS

A wide and dramatic decrease in structural connectivities was observed in people with narcolepsy, with descending network degree and global efficiency. These metrics were not only correlated with sleep latency and awakening features, but also reflected alterations of sleep macrostructure in people with narcolepsy. Network-based statistics identified a small hyperenhanced subnetwork of cingulate gyrus that was closely related to rapid eye movement sleep behavior disorder (RBD) in narcolepsy. Further imaging genetics analysis suggested glutamatergic signatures were responsible for the preferential vulnerability of connectivity alterations in people with narcolepsy, while additional PET/SPECT data verified that structural alteration was significantly correlated with metabotropic glutamate receptor 5 (mGlutR5) and N-methyl-D-aspartate receptor (NMDA).

CONCLUSIONS

People with narcolepsy endured a remarkable decrease in the structural architecture, which was not only closely related to narcolepsy symptoms but also glutamatergic signatures.

Profiling functional networks identify activation of corticostriatal connectivity in ET patients after MRgFUS thalamotomy

BACKGROUND

MR-guided focused ultrasound (MRgFUS) thalamotomy is a novel and effective treatment for medication-refractory tremor in essential tremor (ET), but how the brain responds to this deliberate lesion is not clear.

OBJECTIVE

The current study aimed to evaluate the immediate and longitudinal alterations of functional networks after MRgFUS thalamotomy.

METHODS

We retrospectively obtained preoperative and postoperative 30-day, 90-day, and 180-day data of 31 ET patients subjected with MRgFUS thalamotomy from 2018 to 2020. Their archived resting-state functional MRI data were used for functional network comparison as well as graph-theory metrics analysis. Both partial least squares (PLS) regression and linear regression were conducted to associate functional features to tremor symptoms.

RESULTS

MRgFUS thalamotomy dramatically abolished tremors, while global functional network only sustained immediate fluctuation within one week after the surgery. Network-based statistics have identified a long-term enhanced corticostriatal subnetwork by comparison between 180-day and preoperative data (P = 0.019). Within this subnetwork, network degree, global efficiency and transitivity were significantly recovered in ET patients right after MRgFUS thalamotomy compared to the pre-operative timepoint (P < 0.05), as well as hemisphere lateralization (P < 0.001). The PLS main component significantly accounted for 33.68 % and 34.16 % of the total variances of hand tremor score and clinical rating scale for tremor (CRST)-total score (P = 0.037 and 0.027). Network transitivity of this subnetwork could serve as a reliable biomarker for hand tremor score control prediction at 180-day after the surgery (β = 2.94, P = 0.03).

CONCLUSION

MRgFUS thalamotomy promoted corticostriatal connectivity activation correlated with tremor improvement in ET patient after MRgFUS thalamotomy.

Alteration of White Matter Connectivity for MR-Guided Focused Ultrasound in the Treatment of Essential Tremor

BACKGROUND

Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy has been implemented as a therapeutic alternative for the treatment of drug-refractory essential tremor (ET). However, its impact on the brain structural network is still unclear.

PURPOSE

To investigate both global and local alterations of the white matter (WM) connectivity network in ET after MRgFUS thalamotomy.

STUDY TYPE

Retrospective.

SUBJECTS

Twenty-seven ET patients (61 ± 11 years, 19 males) with MRgFUS thalamotomy and 28 healthy controls (HC) (61 ± 11 years, 20 males) were recruited for comparison.

FIELD STRENGTH/SEQUENCE

A 3 T/single shell diffusion tensor imaging by using spin-echo-based echo-planar imaging, three-dimensional T1 weighted imaging by using gradient-echo-based sequence.

ASSESSMENT

Patients were undergoing MRgFUS thalamotomy and their clinical data were collected from pre-operation to 6-month post-operation. Network topological metrics, including rich-club organization, small-world, and efficiency properties were calculated. Correlation between the topological metrics and tremor scores in ET groups was also calculated to assess the role of neural remodeling in the brain.

STATISTICAL TESTS

Two-sample independent t-tests, chi-squared test, ANOVA, Bonferroni test, and Spearman's correlation. Statistical significance was set at P < 0.05.

RESULTS

For ET patients, the strength of rich-club connection and clustering coefficient significantly increased vs. characteristic path length decreased at 6-month post-operation compared with pre-operation. The distribution pattern of rich-club regions was different in ET groups. Specifically, the order of the rich-club regions was changed according to the network degree value after MRgFUS thalamotomy. Moreover, the altered nodal efficiency in the right temporal pole of the superior temporal gyrus (R = 0.434-0.596) and right putamen (R = 0.413-0.436) was positively correlated with different tremor improvement.

DATA CONCLUSION

These findings might improve understanding of treatment-induced modulation from a network perspective and may work as an objective marker in the assessment of ET tremor control with MRgFUS thalamotomy.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 4.

Magnetic Resonance-Guided Focused Ultrasound Thalamotomy Rebalances Atypical Functional Hierarchy in Patients with Essential Tremor

Magnetic resonance-guided focused ultrasound (MRgFUS) has brought thalamotomy back to the frontline for essential tremor (ET). As functional organization of human brain strictly follows hierarchical principles which are frequently deficient in neurological diseases, whether additional damage from MRgFUS thalamotomy induces further disruptions of ET functional scaffolds are still controversial. This study was to examine the alteration features of brain functional frameworks following MRgFUS thalamotomy in patients with ET. We retrospectively obtained preoperative (ETpre) and postoperative 6-month (ET6m) data of 30 ET patients underwent MRgFUS thalamotomy from 2018 to 2020. Their archived functional MR images were used to functional gradient comparison. Both supervised pattern learning and stepwise linear regression were conducted to associate gradient features to tremor symptoms with additional neuropathophysiological analysis. MRgFUS thalamotomy relieved 78.19% of hand tremor symptoms and induced vast global framework alteration (ET6m vs. ETpre: Cohen d = - 0.80, P < 0.001). Multiple robust alterations were identified especially in posterior cingulate cortex ([Formula: see text] ET6m vs. [Formula: see text] ETpre: Cohen d = 0.87, P = 0.048). Compared with matched health controls (HCs), its gradient distances to primary communities were significantly increased in [Formula: see text] ETpre patients with anomalous stepwise connectivity (P < 0.05 in ETpre vs. HCs), which were restored after MRgFUS thalamotomy. Both global and regional gradient features could be used for tremor symptom prediction and were linked to neuropathophysiological features of Parkinson disease and oxidative phosphorylation. MRgFUS thalamotomy not only suppress tremor symptoms but also rebalances atypical functional hierarchical architecture of ET patients.

Current applications for magnetic resonance-guided focused ultrasound in the treatment of Parkinson's disease

ABSTRACT

Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel and minimally invasive technology. Since the US Food and Drug Administration approved unilateral ventral intermediate nucleus-MRgFUS for medication-refractory essential tremor in 2016, studies on new indications, such as Parkinson's disease (PD), psychiatric diseases, and brain tumors, have been on the rise, and MRgFUS has become a promising method to treat such neurological diseases. Currently, as the second most common degenerative disease, PD is a research hotspot in the field of MRgFUS. The actions of MRgFUS on the brain range from thermoablation, blood-brain barrier (BBB) opening, to neuromodulation. Intensity is a key determinant of ultrasound actions. Generally, high intensity can be used to precisely thermoablate brain targets, whereas low intensity can be used as molecular therapies to modulate neuronal activity and open the BBB in conjunction with injected microbubbles. Here, we aimed to summarize advances in the application of MRgFUS for the treatment of PD, with a focus on thermal ablation, BBB opening, and neuromodulation, in the hope of informing clinicians of current applications.

Assessing the impact of MR-guided focused ultrasound thalamotomy on brain activity and connectivity in patients with essential tremor

OBJECTIVE

Although magnetic resonance-guided focused ultrasound (MRgFUS) at the ventral intermediate (VIM) thalamic nucleus is a novel and effective treatment for medication-refractory essential tremor (ET), it is unclear how the ablation lesion affects functional activity. The current study sought to evaluate the functional impact of MRgFUS thalamotomy in patients with ET, as well as to investigate the relationship between neuronal activity changes and tremor control.

METHODS

This study included 30 patients with ET who underwent MRgFUS thalamotomy with a 6-month follow-up involving MRI and clinical tremor rating. Additional sex- and age-matched healthy people were recruited for the healthy control group. The fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity were used to identify functional alteration regions of interest (ROIs). To investigate changes after treatment, ROI- and seed-based functional connectivity (FC) analyses were performed.

RESULTS

Patients with ET had significantly increased fALFF in the right postcentral gyrus (PoCG; ROI 1), regional homogeneity in the left PoCG (ROI 2), and regional homogeneity in the right PoCG (ROI 3, cluster-level p value family-wise error [pFWE] < 0.05), which were recovered and normalized at 6 months after MRgFUS thalamotomy. FCs between ROI 2 and the right supramarginal gyrus, ROI 2 and the right superior parietal gyrus, and ROI 3 and the left precentral gyrus were also found to be increased after treatment (cluster-level pFWE < 0.05). Furthermore, changes in fALFF, regional homogeneity, and FC values were significantly correlated with tremor relief (p < 0.05). Preoperative FC strengths were found to be inversely related to the postoperative tremor control ratio (p < 0.05).

CONCLUSIONS

In patients with ET, the VIM lesion of MRgFUS thalamotomy resulted in symptom-related regional functional recovery associated with sensorimotor and attention networks. Preoperative FC strengths may reflect the postoperative tremor control ratio, implying that this metric could be a useful neuroimaging biomarker for predicting symptom relief in patients with ET following thalamotomy.

Treatment-Specific Network Modulation of MRI-Guided Focused Ultrasound Thalamotomy in Essential Tremor : Modulation of ET-Related Network by MRgFUS Thalamotomy

MRI-guided focused ultrasound (MRgFUS) thalamotomy is a novel, effective, and non-invasive treatment for essential tremor (ET). However, the network mediating MRgFUS in treating ET is not precisely known. This study aimed to identify the disease-specific network associated with the therapeutic effects of MRgFUS thalamotomy on ET and investigate its regional characteristics and genetic signatures to gain insights into the neurobiological mechanism of ET and MRgFUS thalamotomy. Twenty-four ET patients treated with MRgFUS thalamotomy underwent resting-state functional MRI at baseline and postoperative 6 months to measure the fractional amplitude of low-frequency fluctuation (fALFF). Ordinal trends canonical variates analysis (OrT/CVA) was performed on the within-subject fALFF data to identify the ET-related network. Genetic functional enrichment analysis was conducted to study the genetic signatures of this ET-related network using brain-wide gene expression data. OrT/CVA analysis revealed a significant ET-related network for which subject expression showed consistent increases after surgery. The treatment-induced increases in subject expression were significantly correlated with concurrent tremor improvement. This network was characterized by increased activity in the sensorimotor cortex and decreased activity in the posterior cingulate cortex. It was correlated with an expression map of a weighted combination genes enriched for mitochondria relevant ontology terms. This study demonstrates that the therapeutic effects of MRgFUS thalamotomy on ET are associated with modulating a distinct ET-related network which may be driven by mitochondria relevant neurobiological mechanism. Quantification of treatment-induced modulation on the ET-related network can provide an objective marker for evaluating the efficacy of MRgFUS thalamotomy.

Comparison of Motor Scores between OFF and ON States in Tremor-Dominant Parkinson's Disease after MRgFUS Treatment

Objective: To compare the motor function improvements in ON and OFF states in tremor-dominant Parkinson’s disease (TDPD) patients within one year of follow-up after ablation of the unilateral ventral intermediate nucleus of the thalamus (Vim) by magnetic resonance imaging-guided focused ultrasound surgery (MRgFUS). Methods: A total of nine consecutive patients confirmed with TDPD who underwent unilateral Vim ablation by MRgFUS between April 2019 and September 2019 were included. The Movement Disorder Society Unified Parkinson’s Disease Rating Scale part III (MDS-UPDRSIII) and Clinical Rating Scale for Tremor (CRST) were performed in the ON and OFF stages to distinguish the surgical effects from drug therapy effects. The adverse events and adjustment of drug doses were also recorded. Results: The preoperative MDS-UPDRSIII score in OFF and ON states was 55.0 (48.0, 65.5) and 26.0 (17.0, 27.0), while the CRST score was 46.0 (39.5, 53.5) and 20.0 (13.0, 23.5), respectively; the Levodopa equivalent dose was 600 (456, 600) mg/d. At 1 year after operation, the total MDS-UPDRSIII score and CRST score were 40.0 (30.0, 60.5) and 16.0 (10.0, 29.5) in the OFF state, and 21.0 (17.5, 27.0) and 2.0 (1.5, 7.0) in the ON state, respectively. Compared with the preoperative levels, follow-up at the two-time points (three months and one year after operation) showed the total MDS-UPDRSIII score, as well as MDS-UPDRSIII tremor, bradykinesia, and rigidity scores of contralateral limbs all significantly improved in OFF state. However, in the ON state, only the total MDS-UPDRSIII score and tremor score of contralateral limbs significantly improved. The total CRST score and the CRST (A + B) score of contralateral limbs significantly improved at three months and one year after the operation compared with before the operation in both ON and OFF states. The Levodopa equivalent dose at one and three months were not significantly different from the preoperative dose (p > 0.05). No serious adverse responses were observed. Conclusion: Treating TDPD with unilateral Vim ablation by MRgFUS could improve the symptoms of limb tremor and the other core symptoms, such as bradykinesia and rigidity, as well as some non-motor symptoms and the symptoms of ipsilateral limbs.