Destructive stereotactic surgery for treatment of dystonia

Surgical Neurology 64 (2005) S2:89 – S2:95 www.surgicalneurology-online.com

Destructive stereotactic surgery for treatment of dystoniaB ¨ zeren Bekir, MDb, Karadereler Selhan, MDc, YapVcV Zuhal, MDd, I˙mer Murat, MDa, O Omay Bqlent, MDa,T, Hanag˘asV HaYmet, MDd, Eraksoy Mefkure, MDc Departments of aNeurosurgery, bState Hospital, Kars, Turkey, cIstanbul Haydarpasa State Hospital, and dNeurology, Istanbul Faculty of Medicine, University of Istanbul, C¸apa-Istanbul 34390, Turkey

Abstract

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. D 2005 Elsevier Inc. All rights reserved.

Keywords:

Stereotactic surgery; Dystonia; Destructive; Drug resistance

1. Introduction

Abbreviations: CP, cerebral palsy; FMDS, Fahn-Marsden Dystonia Scale; HSD, Hallervorden-Spatz disease; ITD, idiopathic torsion dystonia; MS, multiple sclerosis; NWUDS, Northwestern University Deficiency Scale; VIM, ventralis intermedius; VOP, ventralis oralis posterior. B We confirm that all human studies have been approved by the appropriate ethics committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. All persons gave their informed consent before their inclusion in the study. Details that might disclose the identity of the subjects under study were omitted. T Corresponding author. Tel.: +90 533 371 2292; fax: +90 212 661 5865. E-mail address: [email protected] (O. Bqlent). 0090-3019/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2005.07.036

Dystonia is a movement disorder that can be described as the uncontrolled and continuous contraction of the muscle groups. Dystonia can be of genetic origin or can develop secondary to certain central nervous system diseases [4,11,12,22,35]. In treating dystonia, the first choice should be medical therapy, but the side effects or ineffectiveness can render medical therapy useless. In such cases, surgical therapy can be an alternative [2,3,6,7,13,15,16,20,34,41]. This retrospective study was designed to evaluate the effectiveness of stereotactic destructive surgery in patients with drug-resistant dystonia and also to compare and analyze the results of lesions produced in different targets. The medical records of 58 patients who were diagnosed as having either idiopathic or secondary dystonia, and who

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Table 1 Distribution of dystonic cases according to etiology Primary ITD Spasmodic torticollis Secondary CP Perinatal hypoxia Hyperbilirubinemia (in newborn) Convulsions (in newborn) Meningitis/encephalitis Posttraumatic HSD Pyramidocerebellar degenerative disease MS Poststroke Intracerebral hemorrhage Total

n

%

12 11 1 46 34 11 3 2 13 5 3 1 1 1 1 58

20.7 19 1.7 79.3 58.6 18.9 5.17 3.4 24 8.6 5.2 1.4 1.4 1.4 1.4 100

were surgically treated between 1991 and 1999 in Department of Neurosurgery, Istanbul Faculty of Medicine, Istanbul University, were retrospectively analyzed. 2. Methods 2.1. Patients The study group consisted of patients who were diagnosed as having dystonia and who could not benefit from medical treatment either because of side effects or because of inadequate/insufficient efficacy. 2.2. Procedures The stereotactic procedures were performed by computed tomography guidance with local anesthesia in adults and with general anesthesia in children and in patients with severe muscle contractions. Leksell stereotactic apparatus (Elekta AB, Stockholm, Sweden) was used in the interventions. The posterior and anterior commissures were defined, and the coordinates of the midcommissural point were calculated under computed tomography guidance. After the preparation of the precoronal burr hole, the dura mater was opened. The electrode was advanced to the target. The correct localization was confirmed by macrostimulation. A destructive lesion was produced by controlling the intensity of current. The maximum diameter of the lesions was 0.5 cm. In case of uncertainty about the target localization or any sign of problem during stimulation (hemiparesis, paresthesias), the procedure was cancelled. The terminology of Hassler [18] was used in this study [7]. 2.3. Evaluation of the cases The patients were video-recorded preoperatively and were followed-up in the postoperative first week, sixth month, and first year, and yearly thereafter. Patients were evaluated by using FMDS and NWUDS, and after each

surgical procedure, early and long-term improvement ratios were determined. Six groups were formed on the basis of the percentage ratios. These groups were designated as A (improvement of very high degree, N40%), B (improvement of high degree, 20%-40%), C (improvement of medium degree, 10%-20%), D (improvement of low degree, 10%-20%), E (no improvement), and F (deterioration). The cases in the first 3 groups (A, B, C) were considered successful. After the production of each lesion, the relationship between the quantity of improvement and the localization of the lesion was analyzed. The mean follow-up time for these cases was 102.2 months (range, 6-154 months). 2.4. Statistical analysis v 2 Test was used to compare the 2 different groups. P values of less than .05 were accepted as significant.

3. Results In this study, 28 of 58 patients were female (48.2%) and 30 were male (51.7%). The mean age was 17.3 F 9.1 years with a range of 5 to 47 years. The mean duration of the disease before the operation was found to be 10.8 F 7 years with a range of 2 to 34 years. 3.1. Distribution of the patients regarding the anatomic localization and etiology Clinical presentations of the patients were classified as follows: 41 patients (70.1%) had generalized dystonia, 11 patients (19%) had hemidystonia, 5 patients (8.6%) had focal dystonia, and 1 patient (1.7%) had segmental dystonia (Table 1). 3.2. Lesions In this series, 103 destructive lesions were produced in 86 separate surgical sessions. The sessions consisted of thalamotomy (n = 63), pallidotomy (n = 32), subthalamotomy (n = 1), and lesions formed in the Forel region (n = 7). Thirty-eight patients had a single operation, and 28 of these had a single lesion (21 thalamotomies and 7 pallidotomies). Nine patients (2 cases who underwent thalamotomy and who also had destructive lesions produced in the Forel region, and 7 cases who underwent thalamotomy and pallidotomy) had unilateral multiple lesions, and 1 patient had bilateral and multiple destructive lesions (thalamotomies and pallidotomy). The remaining 20 patients had ablative lesions created in several numbers of sessions. Five of these patients had unilateral lesions, whereas 15 had bilateral lesions. 3.3. The degree of improvement regarding the lesions Each surgical session was analyzed separately for individual patients. The degrees of the improvement that were obtained are shown in Table 2.

˙I. Murat et al. / Surgical Neurology 64 (2005) S2:89 – S2:95 Table 2 Target localizations and the success rates of 103 ablative lesions Pallidotomy

Forel

Target localization A 12 (3 + 9) B 9 (4 + 5) C 12 (3 + 9) D 12 (3 + 9) E 16 (4 + 12) F 2 (0 + 2) Total 63 (17 + 46)

Thalamotomy

5 2 8 7 9 1 32

1 (0 + 1 (1 + – 3 (1 + 2 (1 + – 7 (3 +

Success rate General Primary Secondary

47 83 38

(%) 52 59 50

(1 (0 (4 (0 (1 (0 (6

+ + + + + + +

4) 2) 4) 7) 8) 1) 26)

Subthalamotomy 1) 0) 2) 1) 4)

29 33 25

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common etiologic diagnosis was CP (24%), followed by ITD (6%) (Table 3). 3.5. Cases with bilateral lesions

– – 1 (0 + 1) – – – 1 (0 + 1)

The number of patients who were operated to produce bilateral destructive lesions was 16. The most common etiologic diagnosis was CP (n = 9), followed by ITD (n = 6) and HSD (n = 1). In cases with ITD, the success rate was 83%. The success rates in patients with bilateral lesions in regard to the etiologic diagnosis and lesion localization are shown in Table 3.

– – 100%

3.6. Cases where the target lesion could not be exactly localized

The first values in parentheses refer to primary dystonias, whereas the second values refer to secondary dystonias. Overall success was indicated separately.

3.4. Cases with unilateral lesions A total of 42 patients was operated to produce unilateral ablative lesions. Their diagnosis included segmental dystonia, focal dystonia, and hemidystonia, whereas a few patients had generalized dystonia. The most

Two patients were found to have increased severity of dystonia, and the reason for this result was considered an error in designating the optimum lesion localization. The medical and surgical therapies were planned for these patients. 3.7. Cases that worsened during the follow-up period The condition of well-being obtained in a group of patients after surgery was found to have deteriorated over

Table 3 The distribution of success rates in regard to etiology Unilateral lesions

Bilateral lesions n

Primary dystonias ITDs Thalamotomy Pallidotomy Thalamotomy + Forel

Spasmodic torticollis Thalamotomy Secondary dystonias CP Thalamotomy Pallidotomy Thalamotomy + pallidotomy Thalamotomy + Forel

Posttraumatic dystonias Pallidotomy Thalamotomy + pallidotomy Thalamotomy + Forel HSD Thalamotomy Thalamotomy + pallidotomy Pyramidocerebellar degenerative disease Pallidotomy Post–intracerebral hemorrhage Thalamotomy + Pallidotomy Stroke Thalamotomy MS Thalamotomy

Success (%)

6 5 3 1 1

33 20 33 0 0

1 1 36 25 15 2 6 2

100 100 50 56 60 50 50 50

5 3 1 1 2 1 1 1 1 1 1 1 1 1 1

40 33 100 0 0 0 0 0 0 0 0 100 100 100 100

n

Success (%)

Primary dystonias ITDs Thalamotomy + thalamotomy Pallidotomy + pallidotomy Thalamotomy + pallidotomy Bilateral thalamotomy + unilateral Forel Bilateral (thalamotomy + pallidotomy)

6 2 1 1 1 1

83 100 100 100 0 100

Secondary dystonias CP Thalamotomy + thalamotomy Thalamotomy + pallidotomy Bilateral (thalamotomy + pallidotomy) Bilateral thalamotomy + unilateral pallidotomy Bilateral pallidotomy + unilateral thalamotomy Bilateral thalamotomy + Forel Pallidotomy + subthalamotomy

2 9 1 1 1 2 1 1

50 56 0 100 100 50 100 100

1 1

100 100

HSD Bilateral thalamotomy

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time. This situation was observed for 2 years in a patient with ITD, for a range of 1 month to 2 years in 7 patients with CP, and for 1 year in 3 patients diagnosed with MS (n = 1), with intracerebral hemorrhage (n = 1), and with HSD (n = 1).

4. Discussion Thalamus, with its important role in the control and organization of movement and with its close connections with the basal ganglia, has been an important target in stereotactic destructive surgery in the treatment of dystonia [25,30,39,40]. In older studies, a certain target within thalamus was not specified and the procedure performed was named as thalamotomy or thalamosubthalamotomy [15,17,20]. Later studies are more concentrated on nuclei that are effective as surgical targets: ventralis oralis anterior, VOP, and VIM [9,22,35]. In these studies, it is accepted that permanent and improved results are obtained in the treatment of dystonia when selective lesions in the VIM and VOP nuclei are produced. Among patients in whom lesions were specifically produced with VOP thalamotomy, the results were not successful only in 2 cases. Although the number of patients is not adequate to draw a conclusion, the authors agree that the target nucleus for ablative lesions in the thalamus should be in the ventrolateral nuclei (specifically VIM). There are some series of studies regarding the usage of thalamotomy procedures in cervical dystonia (spasmodic torticollis) [37]. Although ventralis oralis internus thalamotomy was used in the earlier studies, it was found to be ineffective and highly prone to cause complications. Bertrand et al [3], to overcome these problems, used combined ablation (ventralis oralis internus thalamotomy with pallidotomy) with surgical peripheral denervation. Cooper [10] preferred the ventrolateral, ventroposteromedian, and centromedian nuclei thalamotomy. Andrew et al [1] preferred VIM, ventrocaudalis externus, and internus thalamotomy and induced lesions several times both in it and in different localizations (92 lesions in 22 patients). In our study, the main target was the VIM nucleus, and the results obtained were close to the results in literature. This is the reason why the VIM thalamotomy is the better choice in cases of cervical dystonia. Bilateral thalamic lesions have been limited to treating spasmodic torticollis for some time because important complications such as dysarthria have been observed. This study supports the view that new and more appropriate localizations can be safely used. Pallidum has gained popularity in the treatment of dystonia in the last decade. The most important reason for this is that pallidotomy has been found to be relatively more effective especially in treating axial and truncal symptoms [19,23,28,29]. There are many studies concerning the treatment dystonia with CP lesions. Speelman and van Manen [31] had 6 patients with CP who were treated with

pallidotomy with a follow-up period of 21 years. Their success rate was 44% to 90%, but it was not clear whether these cases were dystonias. Studies of success with bilateral CP lesions have been reported [26]. Justesen et al [21] reported that a patient with HSD had improved dystonia after the production of a CP lesion. We have had 26 cases with pallidotomy. The number of pallidotomy cases reported in literature is 38. The mean follow-up time for the pallidotomy cases in our study was 97.2 months, but when all of our pallidotomy cases were evaluated, the number of cases was found to be too small to make a significant comparison with the thalamotomy cases. Subthalamotomy was first mentioned with Parkinson disease in the 1960s, but because of the possibility of initiation of hemiballismus, this method was not used for some time [32]. No study exists about the use of subthalamotomy in dystonia, but Gros et al [17] have reported that 6 patients with dystonia secondary to CP have shown temporary improvement not longer than 1 year after the thalamosubthalamotomy. Our study is the first one where subthalamotomy is reported in the case of dystonia, and the procedure has been of benefit at a satisfactory level (C: improvement of medium degree, 10%-20%) for the patient that has been followed for 101 months. Producing lesions in the Forel region (tracts from pallidum to thalamus) has been replaced by more efficient methods of thalamotomy and pallidotomy. In cases with unsatisfactory results after initial lesions, although a detailed study about the treatment of dystonia by producing lesions in the Forel region does not exist in the current literature, Forel region lesions can be combined with thalamic, subthalamic, or pallidal lesions [15]. In earlier studies, the degrees of improvement were usually based on scales described by those authors and classified under 4 categories such as good, medium, fair, and no change. Comparisons based on these subjective categorizations provided many difficulties. When dystonia evaluation scales started to be widely used, preoperative and postoperative follow-up evaluation and comparisons between different series became easier [8,14,38]. In our study, the cases were evaluated according to NWUDS and FMDS [14,38]. When the dystonia in the nondominant hand was evaluated, the increase in the quality of life was relatively smaller; that is why NWUDS, which evaluates bfunctionalQ recovery, rather than FMDS, which evaluates banatomicQ recovery, was used in our study. Our cases were found to be more successful when they were evaluated with FMDS. Although the results of destructive therapy in secondary dystonias are found to be longlasting, the results for the potentially progressive primary dystonias are reported to be temporary in the current literature (9,23). However, we believe it is better to classify secondary dystonias as those caused by progressive diseases such as MS, HSD, and those that are not such as CP. The regression of the optimistic results obtained in our patients with MS and HSD support this view.

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It has been reported that, in evaluating the anatomic distribution of dystonia in the body, the size and the number of lesions are more important than choosing the target nucleus [23]. Thus, in dystonia cases where a larger part of the body is affected, increasing the size of the lesion or adding new lesions in the related somatotopic regions can obtain successful results. For the patients in our study, especially in generalized dystonias, several bilateral lesions were produced when needed and the results were in concordance with the literature. Although bilateral lesions can be used as reported in literature, it should be kept in mind that bilateral lesions can cause an increase in complications [9,23,26]. There are not many studies of series on the practice of stereotactic destructive surgery in dystonias. The main reason for this is that a sufficiently high number of cases have not been reached yet in newer studies. There are only 3 studies in literature that report a higher number of cases than our study [9,24,33]. 4.1. Evaluation of the statistical analysis Although it has been concluded that the number of cases in certain subgroups in our study was not enough to infer statistical results, a discussion has been provided here. In all dystonia cases, when the results of the thalamotomy and pallidotomy procedures were compared, it was seen that pallidotomy procedures are more successful, but the number of pallidotomy cases was too small to reach a statistically significant conclusion (Table 2). Groups of subthalamotomy, Forel region lesions, and bilateral lesions were in small numbers, and no statistical analysis was performed. When our results were evaluated in regard to the etiology, it was seen that, in ITD cases, pallidotomy is more effective than thalamotomy. This result, although insignificant, was quite close to the critical value (Table 3). It was found that pallidotomy is more effective in CP cases. Because the pallidotomy cases were small in number, the pallidotomy-thalamotomy comparison did not reveal any significant difference (Table 3). In other etiologic subtypes, statistical evaluation was not performed because of the limited numbers of cases. The frequency of complications encountered in ablative surgical procedures ranges between 7% and 47% in literature [1,5,9,23]. Thalamotomy complications mainly consist of aphasia-dysphasia, sensorial, cognitive, and motor disorders [23,27]. Many studies report that most of these complications do not regress. When the literature on movement disorders is taken into account, homonymous hemianopsia, contralateral central scotoma, apraxia of the foot, facial paresis, seizures, temporary chorea, euphoria, hyperventilation, and bulbar paralysis are seen among the reported complications of pallidotomy. There exists no study in literature regarding the procedure of subthalamotomy on patients with dystonia, which explains why no information has been reported on the complications of

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subthalamotomy in dystonic patients. When we take into account the literature on movement disorders, we see that a few older studies on Parkinson disease exist reporting the use of subthalamotomy procedure and hemiballismus occurring after the procedure [32]. In this study, of the 58 patients reported, 3 had temporary complications (5%). These were chronic subdural hematoma in 1 case, paresis of the right upper extremity in 1 case, and left hemiparesis in 1 case. These complications were all temporary, and patients were found to recover completely in the follow-up evaluations. No permanent complications were encountered. In the literature regarding the use of thalamotomy in the treatment of dystonia, the mortality rates were within the range of 2% to 4.5%. No mortality was reported related to the pallidotomy procedure [9,23,27]. In some of these series, the authors do not express a mortality rate. The mortality rate in our series was 0%. In selected cases of dystonia resistant to medical treatment, stereotactic destructive surgery can be performed as a safe alternative method providing satisfactory results. An increase in the quality of life was achieved with destructive surgery in both CP and ITD cases. Because the risk for worsening due to stereotactic destructive surgery is small and worsening due to the underlying disease is continuous, ablation should definitely be tried for these cases as well. Generally, it is thought that pallidotomy gives better results than thalamotomy; however, this view needs to be supported with data obtained from patient series. In appropriate cases, bilateral lesions can be performed. The result of this study shows that although the benefits of stereotactic destructive surgical procedures may regress in the progressive phases of the underlying diseases, the condition of well-being obtained by these interventions offers significant benefits to these patients, making their rehabilitation easier. In addition, the results of this study support that the methods used in stereotactic destructive surgical procedures are safe and repeatable for additional targets in patients with drug-resistant dystonia. The trend in functional neurosurgery is generally toward stimulation of specific targets rather than destruction, which is increasingly performed in our department. Recently, deep brain stimulation of the globus pallidus has emerged as a significant alternative in the treatment of intractable primary dystonia [36]. We believe that stimulation techniques, even with the disadvantage of their high cost, will replace destructive procedures in the future. Still, the procedures described previously are effective, safe, and deserve attention.

Acknowledgments We thank Mustafa ErtaY, MD, for the statistical analysis and Cengiz Gqnay and Frat Yildiz for the text and the tables.

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Commentary The article describes a large collection of patients treated with various destructive procedures (thalamotomy, pallidotomy, campotomy, subthalamotomy) for the treatment of dystonias and dystonic syndromes from a variety of causes. The only conclusion one can draw from this article is that destructive surgery, in general, is safe. There was no mortality. There were only 2 instances of temporary hemiparesis leading to a complication rate of 2% (per procedure) or 3% (per patient).