Thalamic deep brain stimulation in the treatment of essential tremor: a long-term follow-up.

Deep brain stimulation (DBS) of the nucleus ventralis intermedius thalami (Vim) in the treatment of essential tremor (ET) is well documented concerning the acute effects. Reports of the long-term effects are, however, few and the aim of the present study was to analyse the long-term efficacy of this treatment. Nineteen patients operated with unilateral Vim-DBS were evaluated with the Essential Tremor Rating Scale (ETRS) before surgery, and after a mean time of 1 and 7 years after surgery. The ETRS score for tremor of the contralateral hand was reduced from 6.8 at baseline to 1.2 and 2.7, respectively, on stimulation at follow-up. For hand function (item 11 - 14) the score was reduced from 12.7 to 4.1 and 8.2, respectively. Vim-DBS is an efficient treatment for ET, also after many years of treatment. There is, however, a decreasing effect over time, most noticeable concerning tremor of action.

The subthalamic region is activated during valence-related emotional processing in patients with Parkinson's disease.

Visual stimuli are judged for their emotional significance based on two fundamental dimensions, valence and arousal, and may lead to changes in neural and body functions like attention, affect, memory and heart rate. Alterations in behaviour and mood have been encountered in patients with Parkinson's disease (PD) undergoing functional neurosurgery, suggesting that electrical high-frequency stimulation of the subthalamic nucleus (STN) may interfere with emotional information processing. Here, we use the opportunity to directly record neuronal activity from the STN macroelectrodes in patients with PD during presentation of emotionally laden and neutral pictures taken from the International Affective Picture System (IAPS) to further elucidate the role of the STN in emotional processing. We found a significant event-related desynchronization of STN alpha activity with pleasant stimuli that correlated with the individual valence rating of the pictures. Our findings suggest involvement of the human STN in valence-related emotional information processing that can potentially be altered during high-frequency stimulation of the STN in PD leading to behavioural complications.

Bilateral subthalamic nucleus stimulation in a parkinsonian patient with preoperative deficits in speech and cognition: persistent improvement in mobility but increased dependency: a case study.

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.

Tolerance and tremor rebound following long-term chronic thalamic stimulation for Parkinsonian and essential tremor.

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.

Assessment of ability/disability in patients treated with chronic thalamic stimulation for tremor.

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.

Comparison between stereotactic CT and MRI coordinates of pallidal and thalamic targets using the Laitinen noninvasive stereoadapter.

The coordinates of one and the same target were compared between stereotactic CT and MRI studies, using the original Laitinen noninvasive Stereoadapter, and a slightly modified stereoadapter in 34 patients scheduled for pallidotomy or thalamotomy. The differences between CT and MRI coordinates were significant for the anteroposterior y (p < 0.001) and the vertical z (p < 0.01) coordinates. When the targets were analyzed separately for the coordinates in the right and left hemispheres, only those of the left-sided targets were significantly different between CT and MRI measurements. In patients where a vertex support was added to the Stereoadapter, there were no differences between CT and MRI target coordinates, regardless of the side of the target. However, in all patient groups, the three-dimensional vectorial difference between CT and MRI coordinates showed that the MRI-defined targets lay anterior and dorsal, that is, rostral, to the CT-defined targets, with a 95% confidence interval of the differences ranging from 1.8 to 2.4 mm. This rostral shift in target coordinates on MRI versus CT happens to coincide with the usual approach of the probe towards the target during surgery. It is concluded that the differences in target coordinates in our study are due partly to MRI distortion and partly to repositioning error of the Stereoadapter on the head. The relatively low magnitude of these differences does not preclude the use of the Stereoadapter for MRI-guided functional stereotactic surgery, provided careful impedance monitoring and macrostimulation of the target area prior to lesioning.

The side-effects and complications of posteroventral pallidotomy.

The side-effects and complications of posteroventral pallidotomy are analysed in 138 consecutive patients who underwent 152 pallidotomies. Transient side-effects, lasting less than three months, appeared in 18% of the patients, that is, 16.5% of the surgical procedures. Long term complications, lasting more than 6 months, were noted in 10% of the patients, that is, 9.2% of the surgical procedures. Sixteen complications occurred alone or in various combinations in 14 patients and included fatigue and sleepiness (2), worsening of memory (4), depression (1), aphonia (1), dysarthria (3), scotoma (1), slight facial and leg paresis (2) and delayed stroke (2). Complications such as dysarthria and paresis could be attributed to MR- or CT-verified pallidal lesions lying too medially and encroaching on the internal capsule. Two of the patients with deterioration in memory had some memory impairment before surgery, and the aphonic patient had dysphonia preoperatively. The study suggests that stereotactic MRI and careful impedance monitoring and macro-stimulation of the posteroventral pallidum area should be sufficient for minimizing the risk of complications; the stereotactic lesion should be centered within the posterior ventral pallidum without involvement of internal capsule. It is concluded that pallidotomy is a safe procedure if performed on cognitively alert patients, and it seems that both the incidence and especially the severity of complications are lower for posteroventral pallidotomy than for thalamotomy.

Is there a relationship between size and site of the stereotactic lesion and symptomatic results of pallidotomy and thalamotomy?

Forty-six patients who had 50 stereotactic procedures (36 pallidotomies and 14 thalamotomies) were assessed clinically with regard to akinesia, tremor, dyskinesias and dystonias, and underwent a stereotactic imaging study 6 months after surgery. The surgical results were rated as excellent, good/fair or no change, respectively, for each symptom, and were correlated to the volume and location of the stereotactic lesion. The effect of pallidotomy on akinesia was moderate and correlated with a larger lesion volume. The positive effect of pallidotomy on dyskinesias, dystonia and tremor was more pronounced and unrelated to the size of the lesion. The effect of thalamotomy on tremor was also unrelated to the lesion volume. The location of the pallidal lesions correlated only with the effect on akinesia: the more posterior the lesion in the pallidum, the better the effect on this symptom. For thalamotomy, there was no relationship between lesion location and effect on tremor. It is concluded that improvement in akinesia following pallidotomy is more difficult to obtain than improvement of the other parkinsonian symptoms, and this improvement requires a larger lesion which is located very posterior in the ventral pallidum.

Thalamic stereotaxis for chronic pain: ablative lesion or stimulation?

Twenty-five patients underwent 33 stereotactic procedures on the thalamus for the treatment of persistent pain of benign or malignant origin. There were 19 ablative and 14 stimulation procedures. The thalamic targets were the centrum medianum (CM), the pulvinar, the nucleus ventralis posteromedialis and/or the nucleus ventralis posterolateralis. Ablative surgery was successful in 52.6% of the procedures, and chronic stimulation in 66%. Stimulation in the ventroposterior group of the thalamus was most effective for peripheral deafferentation pain while ablative stereotaxis on the CM may be more appropriate for patients with central pain or cancer pain. ¿¿

Air-ventriculography provokes an anterior displacement of the third ventricle during functional stereotactic procedures.

The width of the third ventricle, the length of the anterior commissure-posterior commissure line (AC-PC line), the spatial position of the midplane of the third ventricle, and the co-ordinates of the AC, the PC, and of 17 brain targets in the thalamus, hypothalamus and pallidum, were assessed on a pre-operative stereotactic computed-tomography (CT) study and compared to measurements on intra-operative air-ventriculography, using a non-invasive relocatable stereotactic frame. There were no significant differences in the length of the AC-PC line, in the position of the midsagittal plane of the third ventricle, or in the vertical or lateral co-ordinates of the AC, the PC and the cerebral targets, between measurements on CT and on air-ventriculography. However, the width of the third ventricle was significantly larger, and the spatial positions of both AC and PC were significantly more anterior on air-ventriculography than on the CT study. This anterior dislocation of the commissures was presumably due to the insufflation of air into the ventricles of patients being in the supine position during surgery.

Retrogasserian glycerol rhizotomy and its selectivity in the treatment of trigeminal neuralgia.

In the treatment of trigeminal neuralgia, the possibility of obtaining a selective effect on different trigeminal branches by glycerol rhizotomy was studied. Transcutaneous electrical stimulation was used to quantify sensory impairment. An attempt was made to obtain a localized neurotoxic effect of the glycerol on the different trigeminal branches by keeping the patient's head in different positions during and for one hour after glycerol injection. The amount of glycerol injected varied according to the estimated size of the trigeminal cistern and/or to which branch that was involved. The study demonstrated a highly selective effect on the ophthalmic branch, less selective on the maxillary, and a low selective effect on the mandibular branch. However, the clinical results were equal regardless of the affected trigeminal division.

Clinical evaluation of computed tomography-guided versus ventriculography-guided thalamotomy for movement disorders.

38 patients with Parkinsonian or essential tremor who underwent thalamotomy based on ventriculographic coordinates were compared to 23 patients whose thalamotomy was performed on the basis of computed tomography (CT)-derived target coordinates. The comparison between the two groups concerned the age, sex, duration of disease, target side, intra-operative target correction, duration of postoperative stay in hospital, transient side-effects, permanent complication, and tremor alleviation. The study showed that the surgical results in terms of tremor control were the same in the two groups. However, the percentage of post-operative transient side-effects was higher and the duration of stay in hospital was longer for the ventriculographic patients than for the CT patients.

Selectivity of retrogasserian glycerol rhizotomy in the treatment of trigeminal neuralgia.

The possibility of obtaining a selective effect on different trigeminal branches by glycerol rhizotomy was studied in the treatment of trigeminal neuralgia. Transcutaneous electrical stimulation was used to quantify sensory impairment. An attempt was made to direct the neurotoxic effect by maintaining the patient's head in different positions during and after glycerol injection. The amount of glycerol injected varied according to the estimated size of the trigeminal cistern and/or to which branch that was involved. The study demonstrated a good selective effect on the ophthalmic branch, less selective on the maxillary, and a poorly selective effect on the mandibular branch. However, the clinical result following glycerol rhizotomy was equal regardless of the affected trigeminal branch.

Clinical study on the accuracy of the Laitinen CT-guidance system in functional stereotactic neurosurgery.

The accuracy, reproducibility and reliability of CT-guided functional stereotaxis using Laitinen's Stereoadapter were assessed in 19 patients who underwent 14 thalamotomies and 5 pallidotomies for the treatment of essential tremor or Parkinson's disease. The coordinates of the target were obtained from a CT study with the Stereoadapter. At surgery, the Stereoadapter was remounted to the patient's head and the CT coordinates were transferred to Laitinen's Stereoguide without ventriculography. 3-12 months after surgery, a postoperative CT study with Stereoadapter was done. The coordinates of the stereotactic lesion were compared to the preoperative target coordinates. A new similar target was simulated on the postoperative CT study and its coordinates were compared to those of the preoperative target. The coordinates of the lesion versus preoperative target showed a maximal difference of 3.5 mm for the lateral (x-) coordinate, 3.5 mm for the anteroposterior (y-) coordinate, and 3.75 mm for the height (z-) coordinate. The differences were statistically significantly only for the x-coordinate: The lesions lay 1.25 mm, on the average, medial to the preoperative target. This medial displacement of the lesions was presumably due to a 10% inborn magnification error of the CT picture for the lateral direction. The maximal differences between the coordinates of the 'new' simulated target on the postoperative CT and those of the preoperative target were 2.5 mm for the x-, 2.25 mm for the y- and 3.75 mm for the z-coordinates. The differences were not statistically significant.