Radiosurgical Pallidotomy for Parkinson's Disease.

Deep brain stimulation (DBS) has been widely accepted as a tool for treating many symptoms of Parkinson's disease (PD); pallidotomy has been nearly abandoned. Concerns about both the safety and efficacy of pallidotomy are based on small series, isolated case reports, and techniques that would now be considered obsolete. The senior author recently reviewed long-term follow-up of a series of patients who had gamma knife pallidotomy (GKP) for advanced PD. GKP leads to durable, clinically significant benefit. Bilateral GKP adds incremental improvement. The complication rate was 4% when calculated on a per lesion basis. GKP is not quite as effective as DBS for tremor and bradykinesia; the results of GKP and DBS are equivalent for dyskinesia. GKP should be considered in patients who are not candidates for DBS. GKP is not as invasive as radiofrequency pallidotomy and avoids the problems and expenses associated with DBS. Patients on anticoagulants, with cognitive deficits or with other contraindications to DBS can be offered GKP to alleviate many of the motor symptoms of PD.

Dosimetry of a novel rotating gamma system for stereotactic radiosurgery.

This is the first report of the basic dosimetric properties of a new rotating gamma system: the RGS Vertex360™. Dosimetric properties were compared to those measured with traditional rotating gamma systems and with the Leksell Gamma Knife. The RGS Vertex360 is similar to the original rotating gamma system developed by OUR New Medical Technology Development Co., Ltd. (Shenzen, China), however, there are a few notable differences including the angular arrangement of the sources. Basic dosimetric properties of the RGS Vertex360 were measured including: absorbed dose rate, output factors, mechanical and radiation center accuracy and dose profiles. A significant discrepancy was observed for the 4 mm output measured from the RGS Vertex360 compared to those obtained from previous rotating gamma units: the 4 mm output from the RGS Vertex360 (0.807) was 32-38% higher than those measured from previous units. This is somewhat surprising considering the excellent agreement in 4 mm outputs from the RGS Vertex360, the corresponding outputs specified by the manufacturer of the original OUR unit and those measured for the Leksell Gamma Knife. The mechanical accuracy was similar to previous rotating gamma systems while the 50-90% penumbra was narrower. Dose profiles compared favorably with the Leksell Gamma Knife: in many instances the measured penumbra was narrower for the RGS Vertex360. Notwithstanding the 4 mm output factor, the dosimetric properties of the RGS Vertex360 compared favorably with those of previous rotating gamma systems. The 4 mm output discrepancy was attributed to suboptimal alignment of the primary and secondary collimators in previous studies. The dosimetric properties of the RGS Vertex360 and the Leksell Gamma Knife were similar and, taken together, the results suggest that the new rotating gamma system is well suited for stereotactic radiosurgery procedures.

Gamma Knife thalamotomy for treatment of essential tremor: long-term results.

OBJECT: The goal of this report was to describe the safety and effectiveness of nucleus ventralis intermedius (VIM) thalamotomy performed with the Leksell Gamma Knife (GK) for the treatment of essential tremor (ET). METHODS: One hundred seventy-two patients underwent a total of 214 VIM thalamotomy procedures with the Leksell GK between February 1994 and March 2007 for treatment of disabling ET. Eleven patients were lost to follow-up less than 1 year after the procedures, so that in this report the authors describe the results in 161 patients who underwent a total of 203 thalamotomies (119 unilateral and 42 bilateral). RESULTS: There were statistically significant decreases (p < 0.0001) in tremor scores for both writing and drawing. The mean postoperative follow-up duration for all patients was 44 +/- 33 months. Fifty-four patients have been followed for more than 60 months posttreatment. There were 14 patients who suffered neurological side effects that were temporary (6) or permanent (8), which accounted for 6.9% of the 203 treatments. All complications were related to lesions that grew larger than expected. CONCLUSIONS: A VIM thalamotomy with the Leksell GK offers a safe and effective alternative for surgical treatment of ET. It is particularly applicable to patients who are not ideal candidates for deep brain stimulation but can be offered to all patients who are considering surgical intervention for ET.

Deep brain stimulation for the treatment of various chronic pain syndromes.

OBJECT: Electrical intracerebral stimulation (also referred to as deep brain stimulation [DBS]) is a tool for the treatment of chronic pain states that do not respond to less invasive or conservative treatment options. Careful patient selection, accurate target localization, and identification with intraoperative neurophysiological techniques and blinded test evaluation are the key requirements for success and good long-term results. The authors present their experience with DBS for the treatment of various chronic pain syndromes. METHODS: In this study 56 patients with different forms of neuropathic and mixed nociceptive/neuropathic pain syndromes were treated with DBS according to a rigorous protocol. The postoperative follow-up duration ranged from 1 to 8 years, with a mean of 3.5 years. Electrodes were implanted in the somatosensory thalamus and the periventricular gray region. Before implantation of the stimulation device, a double-blinded evaluation was carefully performed to test the effect of each electrode on its own as well as combined stimulation with different parameter settings. The best long-term results were attained in patients with chronic low-back and leg pain, for example, in so-called failed-back surgery syndrome. Patients with neuropathic pain of peripheral origin (such as complex regional pain syndrome Type II) also responded well to DBS. Disappointing results were documented in patients with central pain syndromes, such as pain due to spinal cord injury and poststroke pain. Possible reasons for the therapeutic failures are discussed; these include central reorganization and neuroplastic changes of the pain-transmitting pathways and pain modulation centers after brain and spinal cord lesions. CONCLUSIONS: The authors found that, in carefully selected patients with chronic pain syndromes, DBS can be helpful and can add to the quality of life.

Contrast medium causes the apparent increase in beta-endorphin levels in human cerebrospinal fluid following brain stimulation.

Levels of beta-endorphin immunoreactivity in cerebrospinal fluid were measured in 12 chronic pain patients undergoing the surgical implantation of an electrode into the periventricular gray matter. Cerebrospinal fluid fractions were collected following placement of a cannula into the third ventricle, following injection of metrizamide contrast medium into the ventricles, following implantation of the electrode, and following electrical stimulation. A second set of samples was collected on a non-surgical day before and after stimulation. Levels of beta-endorphin immunoreactivity increased significantly from baseline levels to post-electrode implantation in one group of patients, but no significant change was seen following the onset of stimulation. Immunoreactivity increased significantly following metrizamide injection in a second group and was still elevated, in comparison to baseline, following electrode placement, but no increase was seen following the onset of stimulation. Levels of immunoreactive beta-endorphin did not increase in either group after stimulation on a post-surgical day, despite consistent reports of pain relief. Addition of metrizamide or a related contrast medium, iothalamate meglumine (Conray) to the beta-endorphin radioimmunoassay revealed that both compounds interfered with antigen-antibody binding and also quenched the gamma radiation emitted by iodinated peptide ligands. Due to these combined effects, the contrast media alone produced results similar to those of the beta-endorphin standard. Moreover, similar observations were made when contrast media were incorporated into radioimmunoassays for met-enkephalin, dynorphin and cholecystokinin octapeptide. These findings indicate that increased levels of beta-endorphin in cerebrospinal fluid are not directly associated with patient report of pain relief following periventricular gray stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)