Neurosurgical neuromodulation therapy for psychiatric disorders

Psychiatric disorders are among the leading contributors to global disease burden and disability. A significant portion of patients with psychiatric disorders remain treatment-refractory to best available therapy. With insights from the neurocircuitry of psychiatric disorders and extensive experience of neuromodulation with deep brain stimulation (DBS) in movement disorders, DBS is increasingly being considered to modulate the neural network in psychiatric disorders. Currently, obsessive-compulsive disorder (OCD) is the only U.S. FDA (United States Food and Drug Administration) approved DBS indication for psychiatric disorders. Medically refractory depression, addiction, and other psychiatric disorders are being explored for DBS neuromodulation. Studies evaluating DBS for psychiatric disorders are promising but lack larger, controlled studies. This paper presents a brief review and the current state of DBS and other neurosurgical neuromodulation therapies for OCD and other psychiatric disorders. We also present a brief review of MR-guided Focused Ultrasound (MRgFUS), a novel form of neurosurgical neuromodulation, which can target deep subcortical structures similar to DBS, but in a noninvasive fashion. Early experiences of neurosurgical neuromodulation therapies, including MRgFUS neuromodulation are encouraging in psychiatric disorders; however, they remain investigational. Currently, DBS and VNS are the only FDA approved neurosurgical neuromodulation options in properly selected cases of OCD and depression, respectively.

MR-guided focused ultrasound thalamotomy for lithium-induced tremor: a case report and literature review

Drug-induced tremor is a common side effect of lithium with an occurrence of approximately 25% of patients. Cessation of the offending drug can be difficult, and many medical treatments for drug-induced tremor are ineffective. Deep brain stimulation (DBS) has been shown in a limited number of case reports to effectively reduce drug-induced tremor, however, which remains an invasive therapeutic option. MR-guided focused ultrasound (MRgFUS) thalamotomy is an FDA-approved non-invasive treatment for essential tremor (ET). To the best of our knowledge, MRgFUS thalamotomy has never been reported to treat drug-induced tremor. Here, we present a case of a left-handed 55-year-old man with a progressive, medically refractory lithium-induced tremor of the bilateral upper extremities. The patient underwent MRgFUS thalamotomy targeting the right ventral intermediate nucleus (VIM) of the thalamus to treat the left hand. There was almost complete resolution of his left-hand tremor immediately following MRgFUS. There were no side effects. The patient continues to show excellent tremor control at 90-day follow-up and remains free from side effects. This case demonstrates MRgFUS thalamotomy as a possible novel treatment option to treat drug-induced tremor.

Stepwise Dual-Target Magnetic Resonance-Guided Focused Ultrasound in Tremor-Dominant Parkinson Disease: A Feasibility Study

BACKGROUND

Magnetic resonance-guided focused ultrasound (MRgFUS) has been applied successfully in treating refractory tremors in Parkinson disease (PD). It generates a precise thermal ablation in a specific nucleus or tract, such as ventral intermediate nucleus (VIM) or pallidothalamic tract (PTT). Despite a single lesion improving parts of the PD symptoms, the feasibility and efficacy of a stepwise dual-lesion in VIM and PTT are yet to be explored.

METHODS

Three patients with tremor-dominant PD (aged 60.7 ± 6.0 years) received dual-target MRgFUS treatment with a series of primary and secondary outcome measures. The VIM and PTT were navigated based on individual magnetic resonance imaging planning of the brain. The primary outcome measures were the off-status Clinical Rating Scale for Tremor and Unified Parkinson's Disease Rating Scale part III (UPDRS-III). The secondary outcome measures included UPDRS I, II, IV, Hohen and Yahr score, Neuropsychiatry Inventory, Quality of life in PD Rating Scale, Non-Motor Symptoms Scale, and Clinical Global Impression. The baseline data were compared with those acquired 1 day and 1 month following the treatment.

RESULTS

The severity of tremor and motor deficits represented by Clinical Rating Scale for Tremor-part B and UPDRS III were significantly improved (P < 0.05 by nonparametric Mann-Whitney U tests) after dual-target ablations. The nonmotor symptoms investigated by UPDRS II and Non-Motor Symptoms Scale also showed significant improvement at the 1-day and 1-month follow-up. There was no adverse effect except temporary procedure-related headache and dizziness during the treatment.

CONCLUSIONS

Stepwise dual-lesion targeting VIM and PTT is a safe and effective MRgFUS therapeutic strategy for patients with PD.

Open-source, small-animal magnetic resonance-guided focused ultrasound system

BACKGROUND

MR-guided focused ultrasound or high-intensity focused ultrasound (MRgFUS/MRgHIFU) is a non-invasive therapeutic modality with many potential applications in areas such as cancer therapy, drug delivery, and blood-brain barrier opening. However, the large financial costs involved in developing preclinical MRgFUS systems represent a barrier to research groups interested in developing new techniques and applications. We aim to mitigate these challenges by detailing a validated, open-source preclinical MRgFUS system capable of delivering thermal and mechanical FUS in a quantifiable and repeatable manner under real-time MRI guidance.

METHODS

A hardware and software package was developed that includes closed-loop feedback controlled thermometry code and CAD drawings for a therapy table designed for a preclinical MRI scanner. For thermal treatments, the modular software uses a proportional integral derivative controller to maintain a precise focal temperature rise in the target given input from MR phase images obtained concurrently. The software computes the required voltage output and transmits it to a FUS transducer that is embedded in the delivery table within the magnet bore. The delivery table holds the FUS transducer, a small animal and its monitoring equipment, and a transmit/receive RF coil. The transducer is coupled to the animal via a water bath and is translatable in two dimensions from outside the magnet. The transducer is driven by a waveform generator and amplifier controlled by real-time software in Matlab. MR acoustic radiation force imaging is also implemented to confirm the position of the focus for mechanical and thermal treatments.

RESULTS

The system was validated in tissue-mimicking phantoms and in vivo during murine tumor hyperthermia treatments. Sonications were successfully controlled over a range of temperatures and thermal doses for up to 20 min with minimal temperature overshoot. MR thermometry was validated with an optical temperature probe, and focus visualization was achieved with acoustic radiation force imaging.

CONCLUSIONS

We developed an MRgFUS platform for small-animal treatments that robustly delivers accurate, precise, and controllable sonications over extended time periods. This system is an open source and could increase the availability of low-cost small-animal systems to interdisciplinary researchers seeking to develop new MRgFUS applications and technology.