Professor Daniel Jeanmonod faced a packed meeting room at the Philadelphia convention Center on May 3 when he presented his much-anticipated results treating 12 patients in Zürich using transcranial MR-guided focused ultrasound (TcFUS). Many neurosurgeons in the audience at the Stereotactic and Functional Neurosurgery Session of the 2010 annual meeting of the American Association of Neurological Surgeons were there mainly for his presentation.
He reported on 18 ablative lesions performed in 12 patients using transcranial central lateral thalamotomy with the Exablate 4000 (Insightec Ltd, Haifa). All patients suffered from chronic therapy-resistant neuropathic pain, including some who had failed prior radiofrequency lesioning. Real-time MR image monitoring (thermometry) was performed in awake patients, allowing for on-line control of targeting parameters, precision and safety.
His work confirmed the high level of precision in lesion placement (< 1.0 mm) that had been previously reported (Martin E. et al., Annals of Neurology 66(6):858-861, 2009). Skull heating was minimal.
Peri-lesional edema appeared on MRI within 48 hours, but was resolved at the time of the 1-month MRI.
Subjective descriptions of pain parameters and body sensation (stimulation effects, deficits or improvements) as well as neurological examinations were regularly collected during the whole treatment phase. Ultrasound stimulation effects prior to thermal ablation included vestibular (vertigo and nausea, 8 patients), uncomfortable sensations (dysesthesias, 10 patients) and a sense of vibration (tingling paresthesias, 4 patients).
Professor Jeanmonod discussed the one adverse event in the patient series, a small hemorrhage in the target zone in the twelfth patient associated with symptoms in contralateral movement (dysmetria) and speech articulation, significantly improved at 48 hours after treatment. He also covered corrective actions (thermal lesioning limitations) being implemented to continue the trial safely.
At three months follow up, 48% of treatments (completed CL thalamotomies) were associated with ongoing pain relief. Mean improvement in the Visual Analog Scale (VAS) at that time was 54%. Immediate and stable improvement in somatosensory function occurred in 6 of 12 patients.
Functional neurosurgeons and neurologists worldwide are interested in TcMRgFUS as a noninvasive technique for treating a host of disorders including essential tremor, Parkinson’s disease, neuropathic pain and dystonia. The potential for safe neurophysiological assessment of the target prior to lesioning (neuromodulation), completely non-invasive nature, and lack of ionizing radiation make it a very appealing alternative to current treatments.