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Deep brain stimulation (DBS) of the subthalamic nucleus (STN) can be a highly effective treatment for Parkinson's disease (PD). However, therapeutic efficacy is limited by difficulties in consistently and correctly targeting this nucleus. Increasing evidence suggests that there is abnormal synchronization of beta frequency band activity (approximately 20 Hz) in the STN of PD patients, as reflected in the oscillatory nature of the local field potential (LFP). We hypothesized that an increase in the power of the LFP beta activity may provide intra-operative confirmation of STN targeting in patients undergoing STN implantation for the treatment of advanced PD. Accordingly, we recorded LFPs from the four contacts of DBS electrodes as the latter were advanced in 2 mm steps from a point 4-6 mm above the intended surgical target point in the STN, to a point 4 mm below this. Contacts were configured to give three bipolar recordings of LFPs. These were analyzed on 16 sides in 9 patients. The power in the 13-35 Hz band recorded at the lowest contact pair underwent a steep but focal increase during electrode descent. The depth of the peak beta activity showed excellent agreement with the level of the intra-operative clinical stun effect (k coefficient = 0.792). The depth of peak beta activity also showed 100% specificity and 100% sensitivity for placement within STN in comparison to pre- and Post-operative stereotactic MRI. Functional physiological localization of STN by the on-line spectral analysis of LFPs is quick to perform and may provide information directly relevant to the position of the electrode contact actually used for DBS.

We evaluated the impact of pallidotomy and thalamic deep brain stimulation (DBS) on disability of patients with advanced Parkinson's disease and investigated whether the activities of daily living (ADL) section of the Unified Parkinson's Disease Rating Scale (UPDRS) measures disability in everyday life. Nineteen patients who had pallidotomy and 14 patients who had thalamic DBS were followed for a mean of 11 months. Evaluation tools included the UPDRS as well as a generic ADL scale, called ADL taxonomy. The 13 items belonging to the ADL part of the UPDRS were classified into two categories according to whether the items described a disability or impairment. The total scores of the UPDRS Part II (ADL) were ameliorated in both the pallidotomy and the thalamic DBS groups. When analysing separately the scores from the two categories of the ADL part of the UPDRS, i.e., disability and impairment, only patients who underwent pallidotomy showed improvement in disability-related items. These findings were confirmed when evaluating the patients with the ADL taxonomy. The ADL part of the UPDRS contains a mixture of impairment- and disability-related items. This mixture may confound results when evaluating the impact of surgery on ADL., (Copyright 2002 Movement Disorder Society)

For deep brain stimulation (DBS) of the subthalamic nucleus (STN), it would be an advantage if the STN could be visualized with fast acquisition of MR images, allowing direct and individual targeting. We present a protocol for T2-weighted, nonvolumetric fast-acquisition MRI, implemented at 8 centers in 6 countries. Acquisition time varied between 3 min 5 s and 7 min 48 s according to the center, and imaging often provided visualization of the STN on axial and coronal scans. Postoperatively, the same imaging protocol permitted visualization of the target area and DBS electrodes with minimum artifacts. This imaging technique may contribute to a decrease in the number of electrode passes at surgery., (Copyright 2003 S. Karger AG, Basel)

Currently, DBS is a commonly performed surgery for treatment of movement disorders, especially Parkinson's disease. Although nonablative and minimally invasive, this procedure may give rise to many complications and side effects, some of which are neither reversible nor adaptable. This study reviews the potential complications of DBS along the entire path of this procedure, from patient selection through the postoperative period. Although intraoperative complications such as paralysis and hematoma are rare, other serious complications due to the hardware, such as lead fracture, dislocation, and infection, are not uncommon. Complications or side effects as a result of chronic stimulation itself may be the most common. It is concluded that every member of the surgical team, including the referring neurologist, has an important role in the avoidance of such complications. Proper and careful patient selection, matching each patient to the specific DBS procedure appropriate for his/her symptom profile and suitable for his/her social and cognitive condition, along with experienced and careful intraoperative surgical routine, may be the best way to prevent the complications of DBS procedures., (Copyright 2002 Movement Disorder Society)

We report a patient with advanced Parkinson's disease, including severe and frequent off periods with freezing of gait, moderate dysphonia, and some cognitive impairment, who underwent bilateral subthalamic nucleus (STN) stimulation. The patient was followed for 1 year after surgery, showing persistent good mobility without off periods and without freezing, which reverted completely when stopping the stimulation. There was deterioration of cognition as well as increased aphonia and drooling, all of which remained when the stimulation was turned off. The striking improvement in motor symptoms following STN stimulation was not paralleled by improvement in disability, probably as a result of a cognitive decline, suggesting a diagnosis of Parkinson's disease with dementia. We conclude that chronic STN stimulation is efficient in alleviating akinetic motor symptoms including gait freezing; this surgery should be offered before patients start to exhibit speech or cognitive disturbances.

Fifty-eight patients, 36 with essential tremor (ET) and 22 with Parkinson's disease (PD), received deep brain stimulation (DBS) in the thalamic ventral intermediate (Vim) nucleus. The mean follow-up was 17 months for ET and 21 months for PD patients. Stimulation parameters were adjusted as needed, at various intervals after surgery. Results were assessed using routine clinical evaluation and established outcome scales. All patients needed incremental increase in stimulation parameters at various intervals during the first 6-12 months after surgery. The mean voltage 1 week postoperatively was 1. 45 V in PD patients, and 1.37 V in ET patients. Twelve months later, the figures were 2.14 V in PD and 2.25 V in ET patients. At 1 year, the Essential Tremor Rating Scale (ETRS) improved from 54 to 28 (p < 0.0001). The motor part of the Unified Parkinson's Disease Rating Scale (UPDRS) improved from 37 to 26 (p < 0.01). Tremor items of the UPDRS improved more markedly (p < 0.0001). One week postoperatively 90% of PD, and 89% of ET patients were tremor free. One year later, 70% of PD and 60% of ET patients remained mostly tremor free. Upon switching off stimulation, there was a clear tendency for tremor rebound (p = 0.07) in the PD group, requiring continuous 24-hour stimulation in some patients. Permanent non-adjustable ataxia was induced by stimulation in 2 PD patients., (Copyright 2000 S. Karger AG, Basel)

Chronic thalamic stimulation (CTS) has a documented good effect on tremor in patients with Parkinson's disease (PD) and essential tremor (ET). This study evaluates whether the alleviation of impairment, i.e., tremor, translates into improvement of the patient's ability in performing instrumental activities of daily living (IADL). Thirteen patients were assessed with an occupational therapy tool called Assessment of Motor and Process Skills (AMPS). This observation-based scale rates the patient's motor and process skills needed to perform a given task. The evaluations were done at a mean of 13 months after surgery in the patient's home, and included assessments of IADL with the CTS activated and switched off, respectively. The results showed that most patients improved to variable degrees in their IADL ability when the thalamic stimulation was on. The improvement was more marked in patients operated on for tremor of their dominant hand. The improvement concerned mainly the skill items related to the patients' abilities of coordination, calibration, endurance, and accommodation during IADL task performance. The authors concluded that for some patients with tremor, CTS can improve independence in domestic activities of daily living.