>>Permanently altering brain function, outside the skull (CK)
March 19, 2009
A surgical team from Italy have just reported that they've altered human brain function through neurosurgery conducted from outside the skull, by using beams of radiation.
The technique is known as radiosurgery and, in itself, isn't novel. The team used the Cyberknife system, specifically designed to do this sort of operation.
However, the technique is typically used to treat brain tumours, and what is new is that the team have adapted this method to permanently knock out targeted areas to alter overall brain function.
They were inspired by deep brain stimulation and functional brain surgery. These aim to do a similar thing and are most commonly used to treat tremors and movement problems in Parkinson's disease by altering the movement circuits in the brain.
This new operation aimed to do something similar, but with radiosurgery.
Their report appears in the journal Medical Physics, where they describe the treatment of two patients with, until then, untreatable disorders. One with chronic pain, stemming from nerve damage, and other with dystonia, a neurological disorder that causes certain muscles to painfully contract.
One of the challenges with this sort of operation is hitting exactly the right spot, and to achieve the necessary accuracy the team built a 3D computer model of the key areas from the brain scans which they then used to electronically direct the radiosurgery equipment.
The patient with dystonia had a pallidotomy, where part of his basal ganglia was ablated (destroyed), whereas the patient with chronic pain had a thalamotomy, taking out a section of his medial thalamus.
Both patients recovered well, significantly improved and showed no major side-effects at 15 months.
The image on the left shows where the radiation beams entered the head during the operation on the patient with chronic pain.
Link to research report
Link to PubMed entry for same
Politecnico di Milano, Bioengineering Department and NEARlab, Milano 20133, Italy. email@example.com
Functional disorders of the brain, such as dystonia and neuropathic pain, may respond poorly to medical therapy. Deep brain stimulation (DBS) of the globus pallidus pars interna (GPi) and the centromedian nucleus of the thalamus (CMN) may alleviate dystonia and neuropathic pain, respectively. A noninvasive alternative to DBS is radiosurgical ablation [internal pallidotomy (IP) and medial thalamotomy (MT)]. The main technical limitation of radiosurgery is that targets are selected only on the basis of MRI anatomy, without electrophysiological confirmation. This means that, to be feasible, image-based targeting must be highly accurate and reproducible. Here, we report on the feasibility of an atlas-based approach to targeting for functional radiosurgery. In this method, masks of the GPi, CMN, and medio-dorsal nucleus were nonrigidly registered to patients' T1-weighted MRI (T1w-MRI) and superimposed on patients' T2-weighted MRI (T2w-MRI). Radiosurgical targets were identified on the T2w-MRI registered to the planning CT by an expert functional neurosurgeon. To assess its feasibility, two patients were treated with the CyberKnife using this method of targeting; a patient with dystonia received an IP (120 Gy prescribed to the 65% isodose) and a patient with neuropathic pain received a MT (120 Gy to the 77% isodose). Six months after treatment, T2w-MRIs and contrast-enhanced T1w-MRIs showed edematous regions around the lesions; target placements were reevaluated by DW-MRIs. At 12 months post-treatment steroids for radiation-induced edema and medications for dystonia and neuropathic pain were suppressed. Both patients experienced significant relief from pain and dystonia-related problems. Fifteen months after treatment edema had disappeared. Thus, this work shows promising feasibility of atlas-based functional radiosurgery to improve patient condition. Further investigations are indicated for optimizing treatment dose.