| 1. |
- Awad, Amar, 1988-
(författare)
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Functional brain imaging of sensorimotor dysfunction and restoration : investigations of discomplete spinal cord injury and deep brain stimulation for essential tremor
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The nervous system exists to generate adaptive behaviour by processing sensory input from the body and the environment in order to produce appropriate motor output, and vice versa. Consequently, sensorimotor dysfunction is the basis of disability in most neurological pathologies. In the current thesis, I explore two conditions with different types and degrees of sensorimotor dysfunction by means of functional magnetic resonance imaging (fMRI). In part 1, I assess residual sensory connections to the brain in clinically complete spinal cord injury (SCI) with seemingly complete loss of sensorimotor function below the injury level. In part 2, fMRI is combined with deep brain stimulation (DBS) to investigate interventional mechanisms of restoring dysfunctional sensorimotor control in essential tremor (ET).Part 1: SCI disrupts the communication between the brain and below-injury body parts, but rarely results in complete anatomical transection of the spinal cord. In studies I and II, we demonstrate somatosensory cortex activation due to somatosensory (tactile and nociceptive) stimulation on below-level insensate body parts in clinically complete SCI. The results from studies I and II indicate preserved somatosensory conduction across the spinal lesion in some cases of clinically complete SCI, as classified according to international standards. This subgroup is referred to as sensory discomplete SCI, which represents a distinct injury phenotype with an intermediate degree of injury severity between clinically complete and incomplete SCI.Part 2: ET is effectively treated with DBS in the caudal zona incerta, but the neural mechanisms underlying the treatment effect are poorly understood. By exploring DBS mechanisms with fMRI, DBS was shown to cause modulation in the activity of the sensorimotor cerebello-cerebral regions during motor tasks (study III), but did not modulate the functional connectivity during resting-state (study IV).fMRI is a valuable tool to investigate sensorimotor dysfunction and restoration in SCI and DBS-treated ET. There is evidence for sensory discomplete SCI in about half of the patients with clinically complete SCI. DBS modulates DBS modulation of the activity in the sensorimotor cerebello-cerebral circuit during motor tasks, but not during resting-state, is action-dependent.
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| 2. |
- Philipson, Johanna, 1975-
(författare)
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Cognitive effects of deep brain stimulation : focus on caudal zona incerta for essential tremor and Parkinson´s disease, and on bed nucleus of stria terminalis for obsessive compulsive disorder
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Preserved cognition is an important determinant for perceived Quality of Life (QoL) and has been found to be essential in order to translate improvements in primary symptoms following Deep Brain Stimulation (DBS) into activities of daily living that drive QoL. Therefore, it is important to evaluate not only the clinical improvement, but also the cognitive impact of DBS.The aim of this thesis was to evaluate the cognitive effects of DBS in a new target, the caudal Zona incerta (cZi), which has shown promising results in patients with both Parkinson’s Disease (PD) and Essential Tremor (ET). Given that this is a novel target, the effects on cognition were lacking in the literature. In the same manner, the cognitive effects in patients with Obsessive-Compulsive Disorder (OCD) receiving DBS in the Bed Nucleus of Stria Terminalis (BNST) lacked long-term follow-up.The main findings from the studies included in this thesis, suggest that DBS in the cZi in patients with PD and ET, and in the BNST in patients with OCD, does not generate any major cognitive effects and can be considered safe from a cognitive perspective.However, subtle effects involving aspects of executive function may be present following cZi DBS in patients with PD. Significant results concerned primarily a decrease in selective attention and aspects of inhibition. cZi DBS in patients with ET generated fewer cognitive effects, including a decrease in semantic verbal fluency 12 months after DBS in the cZi. fMRI results evaluating the effects of cZi DBS on brain activity during a working memory task, did not show any significant changes when DBS was ON or OFF. This study also revealed a significant Task-x-DBS interaction, with faster response times during DBS ON relative to DBS OFF for the more cognitively demanding “manipulation” task. In OCD patients with BNST DBS, improved results on the Color-Word Inhibition/switching subtest were found, indicating a possible improvement in cognitive flexibility. However, there was a decrease of performance in visuo-spatial learning at 12 months after surgery.The studies in patients with PD and ET were the first to report comprehensive neuropsychological data regarding cZi DBS. The fMRI study was the first in patients with ET treated with cZi DBS, focusing on cognitive effects during a working memory task in on/off DBS conditions. The OCD study was the first to report long-term data on cognitive effects after BNST DBS. By showing that DBS in these targets does not produce any major cognitive side effects, valuable knowledge in terms of safety has been added. This will hopefully contribute to increased treatment options in DBS.
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| 3. |
- Asplund, Pär, 1974-
(författare)
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Percutaneous Balloon Compression for the Treatment of Trigeminal Neuralgia
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background. Trigeminal neuralgia (TN) is a paroxysmal unilateral facial pain condition. That it is rather rare is of little comfort to those who are affected, as TN is often described as one of the worst pains known to mankind. Advanced age and multiple sclerosis (MS) are risk factors for developing TN. The first line of treatment is medical, primarily with carbamazepine. When medical treatment fails, as it does in many patients, there are several surgical options. One of the minimally invasive options, suitable for patients with comorbidity, is percutaneous balloon compression (PBC). Despite its introduction in the early 1980s, PBC is arguably the least well studied of the minimally invasive procedures for the treatment of TN.Aims. The aim of this thesis was to evaluate the efficacy of PBC, both overall and in MS-TN patients specifically. Further, it intended to identify and evaluate pre- and intraoperative parameters associated with the efficacy of PBC. It also investigated changes in sensory function after PBC, and identified side effects and complications associated with PBC. Finally, it sought to evaluate how efficacy, side effects and complications differed between PBC and another minimally invasive technique; percutaneous retrogasserian glycerol rhizotomy (PRGR).Methods. Cohorts of patients treated with PBC in Umeå and Stockholm, and with PRGR in Umeå, were followed retrospectively. Data from an existing database was combined with data from medical records, radiographs and telephone interviews.Results. After PBC, 90 % of the patients were completely pain free without medication for TN. The median time to recurrence of pain was 28 months. In patients with concurrent MS, the initial success rate was 67 % and the median time to recurrence was 8 months. In patients without MS, who had not previously been treated surgically, the initial success rate was 91 % and the median time to recurrence was 48 months. The procedure could, however, be repeated with good results. A good compression, indicated by a pear-shaped balloon as seen on intraoperative lateral radiograph, was crucial to achieve good pain relief. Postoperative hypoesthesia was present in the majority of patients, but after 3-6 months, sensibility was partly or fully normalized in most patients. Severe complications were rare, but included transient cardiac arrest, meningitis and dysesthesia. The side effects profile was favorable to that of percutaneous retrogasserian glycerol rhizotomy, in that the latter produced more cases of dysesthesia and decreased corneal sensibility. The efficacy of the two treatments were, however, not significantly different.Conclusions. PBC is an effective and relatively safe treatment option for patients with TN refractory to medical treatment. It deserves its place among the standard treatments for TN, and could be considered for those patients eligible for surgery for which open surgery is a less suitable option.
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| 4. |
- Naesström, Matilda, 1987-
(författare)
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Deep brain stimulation in obsessive-compulsive disorder
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deep brain stimulation (DBS) is under investigation for severe obsessive-compulsive disorder (OCD) resistant to other therapies. As a crucial part of the anxiety circuit in the brain, the bed nucleus of stria terminalis (BNST) has been proposed as a target for DBS in OCD. However, the mechanism of action of BNST DBS in OCD is not yet fully understood. In our studies, the aim was to evaluate the effect and side effects of DBS in the BNST in severe OCD, to investigate which anatomical areas are being affected by the stimulation and what could be the potential mechanism of action of DBS in this target. We also explored the knowledge and concerns regarding DBS in OCD among psychiatrists, psychotherapists and patients suffering from the disorder. We investigate clinical outcomes and safety of DBS in the BNST in a series of 11 participants with severe therapy-refractory OCD. The primary outcome was a change in the Yale-Brown Obsessive-Compulsive Scale (YBOCS) scores one year after surgery. Using image and stimulation parameter data from the study above, we investigate through participant-specific simulation of the electric field, which anatomical areas are affected by the electric field, and if this can be related to the clinical results. Six of the participants were evaluated with symptom provocation fMRI pre-operatively and in DBS ON and OFF conditions. A web-based study surveyed psychiatrists, patients, and cognitive-behavioural therapists regarding previous knowledge of DBS, source of knowledge, attitudes, and concerns towards the therapy.At baseline, the mean±SD YBOCS score was 33±3.0. One year after DBS, mean±SD YBOCS score was 20±4.8 (38% improvement (range 10- 60%) p <0.01). Of the 11 participants, six were considered responders (decrease in YBOCS ≥35%) and four partial responders (decrease in YBOCS 25-34%). Surgical adverse events included one case of skin infection leading to reimplantation. The most common transient stimulation-related side-effects were anxiety and insomnia. The individual electric stimulation fields by stimulation in the BNST were similar at the 12 and 24-months follow up, involving mainly the anterior limb of the internal capsule (ALIC), genu of the internal capsule, BNST, fornix, anteromedial globus pallidus externa (GPe) and the anterior commissure. A statistically significant correlation (p < 0.05) between clinical effect measured by the YBOCS and simulation was found at the 12-month follow-up in the ventral ALIC and anteromedial GPe. A significant decrease in anxiety-related brain activity in the pre-supplementary motor area (pre-SMA) and the anterior insula was seen in 3/6 participants, with a comparable reduction (below significance level) in the other three participants. Results from the survey found that the primary source of information was from scientific sources among psychiatrists and psychotherapists. The patients' primary source of information was the media. Common concerns among the groups included complications from surgery, anaesthesia, stimulation side effects, and the novelty of the treatment. Specific concerns for the groups included; personality changes mentioned by patients and psychotherapists and ethical concerns among psychiatrists.BNST DBS is a promising therapy in severe therapy-refractory OCD. Our results are in line with previous publications regarding effect and safety profiles. We hypothesise that possible mechanisms of BNST DBS in OCD could be modulation of anxiety-related activity in the pre-SMA and anterior insula, two regions that play an important role in the pathophysiology of OCD. Many of the targets under investigation for OCD are in anatomical proximity, and as seen in our study, offtarget effects overlap. Therefore, DBS in the region of ALIC, NA, and BNST may perhaps be considered to be stimulation of the same target. DBS challenges in obsessive-compulsive disorder consist of source and quality of information, potential long-term adverse effects and eligibility. A broad research agenda is needed for studies as we advance in this field.
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| 5. |
- Sandström, Linda, 1973-
(författare)
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Impact of deep brain stimulation in the caudal zona incerta on voice tremor and speech in persons with essential tremor
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Objectives: Deep brain stimulation (DBS) is a symptomatic treatment for people with essential tremor (ET) who have unsatisfactory tremor relief with pharmacological treatment alone. A common symptom of ET is voice tremor, but only about 50% of patients with voice tremor get a satisfactory result with DBS. Moreover, stimulation-induced adverse effects on speech are often reported, especially with bilateral stimulation. In recent years, the caudal zona incerta (cZi) has been highlighted as a particularly efficient DBS-target for tremor; however, less is known about the effects of cZi-DBS on voice and speech. The aims of this thesis were to (i) describe how voice tremor and speech production are affected by habitual cZi-DBS optimized to treat the motor symptoms of ET, (ii) investigate how voice tremor and speech production are affected by unilateral cZi-stimulation at increasing amplitudes, with a particular focus on high-amplitude stimulation, and (iii) explore the extent to which patient characteristics and DBS related factors, such as electrode location and stimulation settings, influence the outcome.Methods: This thesis comprises two different study protocols. Study I was a retrospective study of 19 patients with ET and voice tremor, and DBS effects on voice tremor were evaluated from clinical assessments made at baseline and 1, 3, and 5 years after surgery, respectively. Studies II-V included 37 persons with ET, and DBS effects on voice tremor and speech production were evaluated off- and on habitual stimulation, as well as in an experimental protocol with unilateral stimulation at increasing amplitudes (up to a maximum of 4.5V). Voice tremor (study II, III) was assessed by two listeners using the Visual Sort and Rate (VISOR) method. Speech intelligibility (study IV) was estimated from orthographic transcriptions of nonsense sentences made by two speech-language pathology students. Speech function, including articulation and voice quality (study V) were analysed in 14 participants and assessed by two speech-language pathologists using VISOR. Voice and speech outcomes following the experimental stimulation condition were evaluated in relation to the location of the active electrode contacts.Results: Habitual cZi-DBS reduced voice tremor at all examinations and did not affect speech production on the group-level. By contrast, during unilateral high-amplitude stimulation, more negative effects on speech were noted, and the proportion of individuals with affected speech more than doubled at maximal amplitude stimulation compared with habitual cZi-DBS (40% compared to 17%). While most of these adverse effects were mild in general, a few participants exhibited more severe impairments of high-amplitude stimulation, especially on speech intelligibility and articulation. There were also cases in which high-amplitude stimulation worsened voice tremor or even induced the symptom. As for the contribution of electrode location, a deeper and more posterior stimulation origin were found to yield the most efficient voice tremor reduction, more medially located electrodes were associated with affected articulation, whereas deteriorated speech intelligibility was related to stimulation originating from a more superior location.Conclusions: cZi-DBS is relatively safe in the sense that adverse effects on speech production are rarely seen during stimulation with the clinical settings. Furthermore, voice tremor can be expected to improve, both short- and long- term, although not always to such an extent that the symptom is alleviated completely. However, by increasing the stimulation amplitude beyond the clinical setting, one increases the risk of inducing unwanted speech-related effects and worsen voice tremor. Thus, it appears as though the challenge in the postoperative management of the DBS treatment lies in maintaining the therapeutic effect while still keeping the stimulation amplitude at a low level. The combined results of this thesis indicate that the best outcome for voice and speech might be achieved by stimulating from the posterior-inferior-lateral part of the cZi.
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| 6. |
- Stenmark Persson, Rasmus, 1990-
(författare)
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Deep brain stimulation targeting the caudal zona incerta as a treatment for parkinsonian and essential tremor
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Deep brain stimulation (DBS) is used as a treatment for Parkinson’s disease (PD) and Essential tremor (ET) when medications are insufficient. The most common DBS-targets for PD and ET, the subthalamic nucleus (STN) and the ventral intermediate nucleus of the thalamus (Vim) respectively, have certain side effects and limitations. In the early 2000s, the posterior subthalamic area (PSA) was introduced as an alternative DBS-target with good results on PD and ET in non-blinded, non-randomised, short-term studies. Different structures in the PSA, such as the caudal zona incerta (cZi), have been used as targets but an optimal target within this area has not been established. Furthermore, there has been an increased interest in asleep DBS surgery but with a paucity of results of asleep surgery for ET, as the Vim is not visible on conventional MRI.Aims: To evaluate DBS targeting the cZi for PD in a blinded, randomised manner. To spatially map the effects of DBS within the PSA. To evaluate the long-term effects of cZi-DBS on PD tremor and ET. To analyse the outcome of awake and asleep cZi-DBS surgery for ET. Method: The thesis is based on five studies. Bilateral cZi-DBS was compared to Best Medical Treatment for PD in a randomised blinded trial. The long-term effects of unilateral cZi-DBS on PD tremor were evaluated retrospectively. Prospectively collected data on cZi-DBS for ET were used to evaluate long-term effects and compare awake and asleep surgery. The effects of cZi-DBS were spatially mapped within the PSA using electric field simulations and contact location in relation to the STN.Results: Bilateral cZi-DBS improved motor symptoms and quality of life in patients with PD in both blinded and non-blinded evaluations with a pronounced effect on tremor (90%) and a modest on bradykinesia (25-40%). The effects of unilateral cZi-DBS on PD tremor remained undiminished at a mean of five years after surgery. cZi-DBS significantly improved ET 10 years after surgery with a slight deterioration over time. Asleep surgery had similar effects and side effects as awake surgery for patients with ET. Electric field simulations did not reveal an optimal target but together with contact location analyses consistently found that the stimulation was concentrated within the PSA, overlapping the cZi and the cerebellothalamic tract. Conclusion: DBS targeting the cZi reliably achieved a pronounced effect on PD tremor and ET up to at least five and ten years after surgery respectively. In addition, cZi-DBS had a modest effect on bradykinesia and improved quality of life in patients with PD. Finally, targeting the cZi enabled asleep surgery with seemingly similar efficacy as awake surgery for ET.
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| 7. |
- Fytagoridis, Anders
(författare)
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Deep brain stimulation of the posterior subthalamic area in the treatment of movement disorders
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The posterior subthalamic area (PSA) is essentially composed of the caudal Zona incerta and the prelemniscal radiation. Subthalamotomy in the PSA was renowned for its effectiveness in alleviating movement disorders and particularly tremor. The modern literature on DBS of this area is limited, but promising results have been presented for Parkinson’s disease (PD), essential tremor (ET) and other movement disorders. Aim: To evaluate the safety of PSA DBS with emphasis on the panorama of side effects, the distribution of stimulation-induced side effects and the effects of PSA DBS on verbal fluency. To evaluate the therapeutic effect of PSA DBS on less common forms of tremor, tremor-dominant PD, and concerning the long-term results in ET. Method: 40 patients were evaluated regarding side effects of the procedure. 28 patients with ET were analyzed for stimulation-induced side effects in a standardized manner. The locations of the contacts that caused stimulation-induced side effects were plotted on atlas slides. A 3-D model of the area was created based on these slides. Verbal fluency was analyzed in 17 patients with ET before surgery, after 3 days and finally after 1 year. Five patients with less common forms of tremor and 18 with ET were evaluated according to the ETRS at baseline and one year or 3-5 years after surgery, respectively. 14 patients with mainly unilateral tremor-dominant PD were evaluated a mean of 18 months after surgery according to the motor part of UPDRS. Results: PSA DBS was associated with few serious side-effects, but a transient and mild postoperative dysphasia was found in 22.5% of the patients. There was a slight transient decline in the performance on verbal fluency tests immediately after surgery. Visualization of the contacts causing stimulation-induced side effects showed that identical responses can be elicited from various points in the PSA and its vicinity. The effect on the less common forms of tremor was excellent except for neuropathic tremor where the effect was moderate. A pronounced and sustained microlesional effect was seen for some of the patients. After a mean of 4 years with unilateral PSA DBS the total ETRS score was improved by 52.4%, tremor by 91.8% and hand function by 78.0% in the patients with ET. There was no increase in the stimulation strength over time. In PD, the scores improved 47.7% for contralateral UPDRS III. Contralateral tremor, rigidity, and bradykinesia improved by 82.2%, 34.3%, and 26.7%, respectively. Conclusions: PSA DBS generally seem to be a safe procedure, but it may be associated with transient declines of verbal fluency. There was no clear somatotopic pattern with regard to stimulation-induced side effects in the PSA. PSA DBS can alleviate tremor regardless of the etiology. The long-term effects in ET were favorable when compared to our previous results of Vim DBS. The effect on Parkinsonian tremor was satisfying, however, the reductions of rigidity and bradykinesia were less compared to previous studies of PSA DBS for PD.
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| 8. |
- Hirabayashi, Hidehiro, 1958-
(författare)
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Stereotactic imaging in functional neurosurgery
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The birth of stereotactic functional neurosurgery in 1947 was to a great extent dependent on the development of ventriculography. The last decades have witnessed a renaissance of functional stereotactic neurosurgery in the treatment of patients with movement disorders. Initially, these procedures were largely based on the same imaging technique that had been used since the birth of this technique, and that is still used in some centers. The introduction of new imaging modalities such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) provided new potentials, but also new challenges for accurate identification and visualisation of the targets in the basal ganglia and the thalamus with an urge to thoroughly evaluate and optimize the stereotactic targeting technique, as well as evaluate accurately in stereotactic space the location and extent of stereotactic Radiofrequency (RF) lesions and the position of deep brain stimulation (DBS) electrodes. Aims: To study the differences between CT and MRI regarding indirect atlas coordinates in thalamic and pallidal procedures and to evaluate and validate visualisation of the pallidum and the subthalamic nucleus in view of direct targeting irrespective of atlas-derived coordinates. Furthermore, to evaluate the contribution of RF parameters on the size of stereotactic lesions, as well as the impact of size and location on clinical outcome. Method: The coordinates in relation to the landmarks of the 3rd ventricle of the targets in the pallidum and ventrolateral thalamus were compared between CT and MRI in 34 patients. In another 48 patients direct visualization of the pallidum was evaluated and compared to indirect atlas based targeting. The possibility and versatility of visualizing the Subthalamic Nucleus (STN) on short acquisition MRI were evaluated in a multicentre study, and the use of alternative landmarks in identification of the STN was demonstrated in another study. In 46 patients CT and MRI were compared regarding the volume of the visible RF lesions. The volume was analysed with regard to coagulation parameters, and the location and size of the lesions were further evaluated concerning the clinical outcome. Results:Minor deviations were seen between MRI and CT coordinates of brain targets. The rostro-caudal direction of these deviations were such that they would be easily accounted for during surgery, why MRI can obviate the need for CT in these procedures. MRI using a proton density sequence provided detailed images of the pallidal structures, which demonstrated considerable inter-individual variations in relation to the landmarks of the 3rd ventricle. By using a direct visualization of the target, each patient will act as his or her own atlas, avoiding the uncertainties of atlas-based targeting. The STN could be visualized on various brands of MRI machines in 8 centers in 6 countries with good discrimination and with a short acquisition time, allowing direct visual targeting. The same scanning technique could be used for postoperative localization of the implanted electrodes. In cases where the lateral and inferior borders of the STN cannot be easily distinguished on MRI the Sukeroku sign and the dent internal-capsule-sign signs might be useful. The volume of a stereotactic RF lesion could be as accurately assessed by CT as by MRI. The lesion´s size was most strongly influenced by the temperature used for coagulation. The lesions´ volumes were however rather scattered and difficult to predict in the individual patient based solely on the coagulation parameters. For thalamotomy, the results on tremor was not related to the lesion´s volume. For pallidotomy, larger and more posterior-ventral lesions had better effect on akinesia while effects on tremor and dyskinesias were not related to size or location of the lesions. Conclusions: The minor deviations of MRI from CT coordinates can be accounted for during surgery, why MRI can obviate the need of CT in these procedures. Direct visualized targeting on MRI of the pallidum is superior to atlas based targeting. The targets in the pallidum and the STN, as well as the location of the electrodes, can be well visualized with short acquisition MRI. When borders of the STN are poorly defined on MRI the Sukeroku sign and the dent internal-capsule-sign signs proved to be useful. The volumes of RF lesions can be accurately assessed by both stereotactic thin slice CT and MRI. The size of these lesions is most strongly influenced by the temperature of coagulation, but difficult to predict in the individual patient based on the coagulation parameters. Within certain limits, there were no clear relationships between lesions´ volume and location and clinical effects of thalamotomies and pallidotomies.
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