Revisiting Forel Field Surgery.

BACKGROUND: Lesioning the Forel field or the subthalamic region is considered a possible treatment for tremoric patients with Parkinson disease, essential tremor, and other diseases. This surgical treatment was performed in the 1960s to 1970s and was an alternative to thalamotomy. Recently, there has been increasing interest in the reappraisal of stimulating and/or lesioning these targets, partly as a result of innovations in imaging and noninvasive ablative technologies, such as magnetic resonance-guided focused ultrasonography. OBJECTIVE: We wanted to perform a thorough review of the subthalamic region, both from an anatomic and a surgical standpoint, to offer a comprehensive and updated analysis of the techniques and results reported for patients with tremor treated with different techniques. METHODS: We performed a systematic review of the literature, gathering articles that included patients who underwent ablative or stimulation surgical techniques, targeting the pallidothalamic pathways (pallidothalamic tractotomy), cerebellothalamic pathway (cerebellothalamic tractotomy), or subthalamic area. RESULTS: Pallidothalamic tractotomy consists of a reduced area that includes pallidofugal pathways. It may be considered an interesting target, given the benefit/risk ratio and the clinical effect, which, compared with pallidotomy, involves a lower risk of injury or involvement of vital structures such as the internal capsule or optic tract. Cerebellothalamic tractotomy and/or posterior subthalamic area are other alternative targets to thalamic stimulation or ablative surgery. CONCLUSIONS: Based on the significant breakthrough that magnetic resonance-guided focused ultrasonography has meant in the neurosurgical world, some classic targets such as the pallidothalamic tract, Forel field, and posterior subthalamic area may be reconsidered as surgical alternatives for patients with movement disorders.

Individualized current-shaping reduces DBS-induced dysarthria in patients with essential tremor.

OBJECTIVE: To investigate in patients with essential tremor (ET) treated with thalamic/subthalamic deep brain stimulation (DBS) whether stimulation-induced dysarthria (SID) can be diminished by individualized current-shaping with interleaving stimulation (cs-ILS) while maintaining tremor suppression (TS). METHODS: Of 26 patients screened, 10 reported SID and were invited for testing. TS was assessed by the Tremor Rating Scale and kinematic analysis of postural and action tremor. SID was assessed by phonetic and logopedic means. Additionally, patients rated their dysarthria on a visual analog scale. RESULTS: In 6 of the 10 patients with ET, DBS-ON (relative to DBS-OFF) led to SID while tremor was successfully reduced. When comparing individualized cs-ILS with a non-current-shaped interleaving stimulation (ILS) in these patients, there was no difference in TS while 4 of the 6 patients showed subjective improvement of speech during cs-ILS. Phonetic analysis (ILS vs cs-ILS) revealed that during cs-ILS there was a reduction of voicing during the production of voiceless stop consonants and also a trend toward an improvement in oral diadochokinetic rate, reflecting less dysarthria. Logopedic rating showed a trend toward deterioration in the diadochokinesis task when comparing ON with OFF but no difference between ILS and cs-ILS. CONCLUSION: This is a proof-of-principle evaluation of current-shaping in patients with ET treated with thalamic/subthalamic DBS and experiencing SID. Data suggest a benefit on SID from individual shaping of current spread while TS is preserved. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that in patients with ET treated with DBS with SID, individualized cs-ILS reduces dysarthria while maintaining tremor control.

Prospective randomized 1-year follow-up comparison of bilateral subthalamotomy versus bilateral subthalamic stimulation and the combination of both in Parkinson's disease patients: a pilot study.

It has been suggested that potential risk of hemiballismus after subthalamotomy makes DBS preferable to ablation for IPD treatment; however, cost and the need for regular electrode control have also been observed as disadvantages to stimulation. The objective was to compare efficacy and safety of different surgical approaches to STN, in a prospective randomized pilot study. Sixteen consecutive IPD patients randomized to receive either: bilateral STN-DBS, bilateral subthalamotomy or unilateral subthalamotomy plus contralateral STN-DBS implantation, and followed for 12 months after surgery. One patient died and was excluded from the analysis. Total and motor UPDRS scores, as well as drug-induced dyskinesias improved significantly at 1 year follow-up, regardless of the procedure administered and without statistically significant differences between treatment modalities. Discrete changes were observed on ACE and MMSE scores. Psychiatric examination of patients subjected to bilateral stimulation and lesion, revealed slight increment in apathy and irritability scores, coinciding with significant deterioration of mentation, behaviour and mood as measured using the UPDRS. One patient presented persistent hemiballismus and required ulterior posteroventral pallidotomy. In this small group of patients, overall motor performance significantly improved after all three procedures, without major differences in outcome. Adverse events were, nevertheless, observed after both ablation and stimulation. The role of bilateral subthalamotomy in patients unable to receive a DBS electrode-implant merits further exploration in a larger series of patients with longer follow-up.

The time course of the return of upper limb bradykinesia after cessation of subthalamic stimulation in Parkinson's disease.

To investigate the time span within which bradykinesia re-occurs, we registered movement parameters immediately after the termination of deep brain stimulation of the subthalamic nucleus (STN) in nine Parkinson patients with chronically implanted bilateral STN electrodes. Two repetitive movements were investigated: finger-tapping and forearm pronation-supination. When stimulation was switched off, the amplitude and velocity of the investigated movements significantly declined, but the frequency did not. The time course of this decline was modeled by an exponential function that yielded time constants between 15 and 30s. The effect of stimulation had completely disappeared within 1 min. These results suggest that it is necessary to wait at least for 1 min after the end of stimulation before performing further assessments.

Destructive stereotactic surgery for treatment of dystonia.

BACKGROUND: This study is a retrospective review of the results of stereotactic destructive surgery in selected cases of drug-resistant dystonia. METHODS: Fifty-eight patients with drug-resistant dystonia were treated with stereotactic surgery between 1991 and 1999 in our institution. These patients' charts were retrospectively analyzed. The timing of the conducted evaluations was as follows: preoperatively, postoperatively, in the postoperative 1st week, 6th month, 12th month, and also thereafter every year. RESULTS: Symptoms of dystonia occurred before the age of 10 years in 30 patients (51.8%) and after the age of 10 years in 28 patients (48.2%). Generalized dystonia was detected in 41 patients, whereas 11 patients had hemidystonia, 5 patients had focal dystonia, and 1 patient had segmental dystonia. The most common etiologic factor was CP (n = 34). A total of 103 ablative lesions were created in 86 surgical sessions. Thalamotomy, pallidotomy, subthalamotomy, and the region of Forel lesions were performed either separately or in combination. In this series, the mean follow-up time was 102.2 months. Except for 2 cases of temporary hemiparesis, no other complications were observed. Minor improvement was obtained in 17 patients (19.7%), improvement of a medium degree was obtained in 17 patients (19.7%), high-degree improvement was obtained in 11 (12.8%), and very high degree improvement was obtained in 16 (18.6%) patients. A final evaluation revealed permanent improvement in 32 patients (55.2%). CONCLUSION: Production of stereotactic destructive lesions in certain specified targets is a safe method that improves quality of life and aids ambulation in patients with dystonia resistant to medical therapy.

[Neurochemical treatment of Parkinson's disease and essential tremor]. / Tratamiento neuroquirúrgico en la enfermedad de Parkinson y el temblor esencial.

INTRODUCTION: Recent technological advances along with new neuroimaging techniques and progress in neuro-monitoring have provided us with new therapeutical options from the neurosurgical point of view in the management of movement disorders. Deep brain stimulators become more and more frequently used in the last few years since they have reversible effects, are easily implantable and have shown good initial results. However, only now we start knowing the clinical effects in the middle run. AIM: To review the main neurosurgical options in Parkinson's disease and tremor. DEVELOPMENT: We reviewed the articles considering ablative or stimulating neurosurgical treatments in these diseases, and we grouped the results according to the technique performed and the time of follow-up. CONCLUSION: Clinical results are often similar despite the use of different techniques. However, the side-effects are critical in deciding which technique should be used once medical therapy has been considered insufficient.

Electrophysiological confirmation of the zona incerta as a target for surgical treatment of disabling involuntary arm movements in multiple sclerosis: use of local field potentials.

Lesioning or chronic deep brain stimulation (DBS) of the nucleus ventralis intermedius results in abolition of tremor in the contralateral limbs in Parkinson's disease (PD) and also in essential tremor. Recently, chronic DBS of the subthalamic nucleus has also proved to be very effective in reducing contralateral limb tremor in PD. These targets have been less effective in controlling the complex limb tremor often seen in multiple sclerosis (MS). Consequently, other targets have been sought in cases of MS with tremor. We describe a patient with MS with disabling proximal and distal involuntary arm movements in whom we were able to obtain sustained control of contralateral arm tremor and achieve functional improvement of the affected arm by chronic DBS of the region of the zona incerta. We also highlight the important role played by local field potentials recorded from the brain, with simultaneous recording of corresponding EMGs, in target localisation.

Microelectrode recording and macrostimulation in thalamic and subthalamic MRI guided stereotactic surgery.

Stereotactic neurosurgery aims at placing therapeutic lesions or chronic stimulating electrodes at very precise locations within the brain. Microelectrode recording and macrostimulation are used in addition to anatomoradiological techniques to optimize targeting. Recently, the usefulness of electrophysiological procedures has been questioned. Based on more than 500 therapeutic stereotactic lesions in the last 10 years at the thalamic and subthalamic levels, we evaluate here retrospectively the utility of the two electrophysiological procedures. In two of the three stereotactic targets considered in this study, intraoperative electrophysiological confirmation is mandatory because of the target size with respect to interindividual anatomical variations and of the more or less close vicinity of eloquent structures.