Outcome of surgery in children with focal cortical dysplasia younger than 5 years explored by stereo-electroencephalography.

PURPOSE: Focal cortical dysplasia (FCD) is the most frequent etiology for drug-resistant epilepsy in young children. Complete removal of the lesion is mandatory to cure the epilepsy. Stereo-EEG (SEEG) is an excellent method to delimitate the zone to be resected in older children and adults. We studied its feasibility in younger children. METHODS: We retrospectively studied 19 children under 5 years of age who underwent SEEG between January 2009 and December 2012 and were subsequently operated on. FCD was diagnosed in all. We reviewed magnetic resonance imaging (MRI), electrophysiological and clinical data, as well as postoperative seizure outcome. We also included fluoro-deoxyglucose positron emission tomography (FDG-PET) studies, which had been systematically performed before invasive recording in 16 of the 19 children. RESULTS: The mean patient's age at the time of SEEG was 38.6 months, and the mean age at seizure onset was 8 months. Three patients had normal MRI. No SEEG-associated complications occurred. We were able to delineate the epileptogenic zone in all children, and electrode stimulation localized the motor area when necessary (12 patients). Hypometabolic areas on FDG-PET included the epileptogenic zone in 13 of the 16 children, with a lobar concordance in 9 (56 %) and the same anatomical extent in 6 (38 %). Twelve children subsequently underwent focal or sublobar resection, six had multilobar resection, and one had hemispherotomy. The etiology was FCD type 2 in 15 and FCD type 1 or type 3 in three children. Eighty-four percent of our population have remained seizure-free at a mean follow-up of 29 months (12-48 months). CONCLUSION: Although children with FCD can successfully undergo resective surgery without invasive EEG, poor seizure semiology at this age inclines to perform SEEG when the dysplastic lesion is ill-defined and/or the electroclinical correlation is unclear. In cases with normal imaging as well as with suspected huge malformations, as was the case in 52 % of our patients, we consider it to be indispensable.

Heterotopia associated with hippocampal sclerosis: an under-recognized cause of early onset epilepsy in children operated on for temporal lobe epilepsy.

PURPOSE: The aim of this study is to report on 52 children operated on for pharmacoresistant temporal lobe epilepsy, with special emphasis on histopathology and correlation with clinical features. METHODS: Charts were retrospectively analyzed. All children underwent comprehensive clinical, electrophysiological and radiological investigations before surgery. Surgical procedures were tailored according to scalp, foramen ovale and eventually depth electrode recordings. Histopathology was compared with clinical variables (χ (2) and Fisher's exact tests). Outcome was evaluated using the Engel scale. RESULTS: Developmental tumor was found in 14 cases, malformation of cortical development (MCD) in 26, isolated hippocampal sclerosis (HS) in 5 and gliosis in 7. Dual pathology (DP) affected 18 patients and the main extrahippocampal lesion consisted of microscopic sub-cortical heterotopias (HS-HT) for 15 patients who shared a particular clinical pattern: a history of febrile seizures (FS) and/or brain injury, early onset of epilepsy without latent period from FS to the first temporal seizure, and a particularly good outcome following surgery. CONCLUSION: In our pediatric temporal lobe surgery series, the prevalence for MCD and for DP was higher than in adult series. Age at seizure onset depends on pathology, and is earlier when involving the neocortex rather than only the hippocampus. We identify the association HS-HT (the most frequent DP in this series), with particular clinical features.

[CT and MR brain imaging following hemispherotomy]. / Imagerie scanner et IRM de l'encéphale après hémisphérotomie.

PURPOSE: The aim of the study was to define the usual and pathological modifications arising in the brain following hemispherotomy for intractable epilepsy in children. METHODS: Preoperative MRI and postoperative imaging scans (CT in the first week, MRI at 3 months and 1 year after surgery) were reviewed in a series of 52 patients, average age 8 years and 7 months, with intractable epilepsy due to dysplasia, Rasmussen's encephalitis, ischemic lesions and/or Sturge-Weber disease. The posterior fossa, brain parenchyma, ventricles and subdural space were also analyzed. RESULTS: Hemispheric scarring was a typical finding on CT and MRI as a consequence of the surgical procedure. Also frequently seen were small subdural effusions, bleeding along the surgical scar on early CT, and chronic subdural effusions with no mass effect on mid-term and late MRI scans. Other features - such as large subdural effusions that required external shunts and hydrocephalus - were rare, but severe, and considered to be postoperative complications. In contrast to the complications associated with other surgical techniques such as hemispherectomy, infection, extensive edema or hemosiderosis were never found in our series. CONCLUSION: Hemispherotomy is a surgical technique performed to treat intractable epilepsy. Our findings will help to identify the typical morphology of postsurgical scars, and to differentiate the usual features and complications seen in the postoperative period on CT and MRI brain scans.

[Parasagittal vertical hemispherotomy: surgical procedure]. / Hémisphérotomie verticale parasagittale: technique opératoire.

After the occurrence of long-term complications of hemispherectomy, various methods have been used to reduce them. The aim was to reduce the large dead space left inside the skull. We have developed an original hemispheric disconnection technique that can achieve the same results as anatomic hemispherectomy in epilepsy, with excellent short- and long term-reliability. The detailed technique is described.

[Surgical disconnection of hypothalamic hamartomas]. / Déconnexion chirurgicale des hamartomes hypothalamiques.

BACKGROUND AND PURPOSE: Surgical resection of hypothalamic hamartomas (HHs) associated with drug-resistant gelastic epilepsy carries a considerable risk of neurological and endocrine morbidity. Alternative surgical routes and techniques have therefore been proposed, especially for broadly attached lesions and for those with a third ventricular location. METHODS: We present an updated series of 43 patients (aged nine months to 34 years), operated on from 1998 through 2005 at our institution. The hamartoma was disconnected using a microsurgical pterional approach of those lesions extending from the hypothalamic floor downward into the interpeduncular cistern. When the HH presented as a paramedian mass, partly or exclusively bulging into the third ventricle, with a rather vertical plane of attachment, we chose a frameless stereotactic endoscopic technique to disconnect the lesion. In several of our patients, both methods were applied subsequently. RESULTS: Surgery-related morbidity was lower with the ventricular endoscopic technique. Twenty-one patients (50%) are seizure-free and two patients (5%) almost seizure-free, while in 17 patients (40%), there was a significant seizure reduction. Two patients (5%) had no postoperative improvement. According to the different topographic features of the HHs, for which we have recently proposed a classification into four subtypes, the intraventricularly located hamartoma had the best prognosis following endoscopic disconnection. Ten of the 12 patients (83%) with this HH location became seizure-free. CONCLUSIONS: Resection of epilepsy-related HHs can be replaced by disconnective procedures. Our results confirm their feasibility and acceptable morbidity, with particularly good seizure outcome in patients with intraventricularly located HHs.

[Long-term outcome after hemispheric disconnection]. / Evaluation à long terme des déconnexions hémisphériques.

Hemispheric disconnection has been largely proposed for patients with severe epilepsy associated with a congenital or acquired hemispheric cerebral pathology. The classical procedure of anatomical hemispherectomy was progressively abandoned by neurosurgeons in order to avoid postoperative complications since then hemispherotomy techniques have been developed. Globally, with hemispheric disconnection, the rate of patients becoming seizure-free has been between 50 and 80%. The factors affecting seizure control have not been completely elucidated, but several authors suggested that differences in etiology as well as the hemispheric disconnection technique used may partially explain this variability. The percentage of seizure-free patients is higher with hemispherotomy techniques and in the group of patients with Rasmussen encephalitis, Sturge-Weber syndrome, and vascular insults. Depending on overall long-term progression, there is an improvement compared to preoperative status even if children exhibit heterogenous abilities. The lowest scores are observed for motor skills but communication and socialization are relatively well-preserved and strongly related to the duration of epilepsy: the longer the duration, the lower the scores were. Neuropsychological outcome following hemispheric disconnection makes it possible to study the development of hemispheric specialization during infancy and to provide information on cognitive recovery. Cerebral reorganization has been proved to exist in motor and language recovery. Ipsilateral corticospinal pathways seem to be involved in the movement of hemiplegic limbs. Everyday language can be supported by both hemispheres, but there is an early hemispheric specialization of the left hemisphere according to metaphonologic abilities.

[Epilepsy surgery during infancy and early childhood in France]. / Chirurgie de l'épilepsie de l'enfant et du nourrisson en France.

BACKGROUND AND PURPOSE: We present the epilepsy surgery activity in infants and children at the Fondation Rothschild Hospital, the main center dedicated to this activity in France. METHOD: A prospective study was conducted from 2003 to 2007 based on three populations: (1) children selected as candidates for surgery, (2) children undergoing presurgical evaluation and (3) children undergoing surgical procedures for epilepsy. RESULTS: Children selected as candidates for surgery: 304 children were referred and discussed by our multidisciplinary staff. They came from Paris and its suburbs (40%), the provinces (43%) or from other countries (14%). Sixty-one percent of them were included in our surgery program and 24% were excluded. Sixty-one percent of them were under 10 years of age. Children undergoing presurgical evaluation: 296 children were recorded: 140 EEG (47%), 46 with foramen ovale electrodes (16%) and 110 with invasive recording techniques (37%). Seventy percent of these children were under 10 years of age. Children undergoing surgical procedures: 316 children underwent surgery; 68% of them were under 10 years of age. The surgical procedures were focal resection (136 children), vertical parasagittal hemispherotomy (77 children), resection and or disconnection for hypothalamic hamartoma (69 children) and 34 had palliative surgery (callosotomy or vagal nerve stimulation). CONCLUSION: Eighty to 100 children undergo surgery each year in our department for drug-resistant partial epilepsy; 70% of them are less than 10 years of age. This activity is part of a network of pediatric neurologists who are deeply involved in treatment of severe epilepsy in children.

[Electrophysiological investigations in childhood epilepsy surgery]. / Explorations électroencéphalographiques préchirurgicales de l'enfant.

Epilepsy surgery in children is a functional surgery: its goal is to perform the resection of the epileptic brain tissue while sparing the eloquent cortex. Prolonged scalp video-EEGs allow recording of all types of seizures and play a crucial role in localizing the epileptogenic zone. Furthermore, EEG data correlation with clinical and radiological findings provides a guide for the surgical strategy: either resection without further investigations or an invasive recording procedure. In prehemispherotomy evaluation, EEG recordings confirm that limited resections are not indicated and demonstrate that the opposite hemisphere is not involved. If invasive recordings are needed, they consist in foramen ovale electrode insertion, which provides valuable information in mesial temporal lobe epilepsy, stereoelectroencephalography for children older than two years, and subdural grids associated with depth electrodes in infants or when the eloquent areas need to be carefully investigated. Such investigations allow tailoring surgery to each child.

Long term response to steroid therapy in Rasmussen encephalitis.

Rasmussen encephalitis (RE) is a severe and progressive focal epilepsy of unknown origin that leads to deterioration of motor and cognitive function. In a previous study, we described positive effect of high doses of steroids during the first year after the onset of RE. The objective of this study was to evaluate this therapy at long term. We reviewed 11 patients (7 girls and 4 boys) with RE of the right hemisphere (7) and the left (4) at a follow-up of 9+/-2 years. Age at onset of RE ranged from 2 to 14 years. Six patients had no benefit from steroid therapy and underwent hemispherotomy. Five had significant reduction of seizure frequency with disappearance of epilepsia partialis continua, and improved motor function. Of these, two died of unexpected sudden death 5 and 7 years after seizure control. Two others with initial response experienced progressive recurrence of seizures 1 to 4 years after the end of steroid therapy and required hemispherotomy. Finally, only one patient exhibited total cessation of seizures with steroids for 3 years, but seizures progressively recurred although the frequency was moderate. Our data confirm that although steroid treatment can be useful when given early in the course of RE, long term relapse can occur among the good responders requiring delayed hemispheric disconnection.

6E11, a highly selective inhibitor of Receptor-Interacting Protein Kinase 1, protects cells against cold hypoxia-reoxygenation injury.

Necroptosis is a programmed cell death pathway that has been shown to be of central pathophysiological relevance in multiple disorders (hepatitis, brain and cardiac ischemia, pancreatitis, viral infection and inflammatory diseases). Necroptosis is driven by two serine threonine kinases, RIPK1 (Receptor Interacting Protein Kinase 1) and RIPK3, and a pseudo-kinase MLKL (Mixed Lineage Kinase domain-Like) associated in a multi-protein complex called necrosome. In order to find new inhibitors for use in human therapy, a chemical library containing highly diverse chemical structures was screened using a cell-based assay. The compound 6E11, a natural product derivative, was characterized as a positive hit. Interestingly, this flavanone compound: inhibits necroptosis induced by death receptors ligands TNF-α (Tumor Necrosis Factor) or TRAIL (TNF-Related Apoptosis-Inducing Ligand); is an extremely selective inhibitor, among kinases, of human RIPK1 enzymatic activity with a nM Kd; has a non-ATP competitive mode of action and a novel putative binding site; is weakly cytotoxic towards human primary blood leukocytes or retinal pigment epithelial cells at effective concentrations; protects human aortic endothelial cells (HAEC) from cold hypoxia/reoxygenation injury more effectively than necrostatin-1 (Nec-1) and Nec-1s. Altogether, these data demonstrate that 6E11 is a novel potent small molecular inhibitor of RIPK1-driven necroptosis.

[Recent advances in pathogenic concepts and therapeutic strategies in Rasmussen's encephalitis]. / Avancées actuelles sur les concepts pathogéniques et thérapeutiques de l'encéphalite de Rasmussen.

Rasmussen's encephalitis (RE) is a rare inflammatory brain disease mainly affecting children and characterised by intractable epilepsy involving a single hemisphere that undergoes progressive atrophy. RE is characterized by refractory focal seizures, often associated with epilepsia partialis continua, progressive unilateral motor defect, slow EEG activity over the entire contralateral hemisphere, with focal white matter hyperintensity and insular cortical atrophy on neuroimaging. Surgical exclusion of the affected hemisphere is the only treatment that interrupts progression of the disease. Pathogenic concepts have considered viruses, autoimmune antibodies and autoimmune cytotoxic T lymphocytes that might contribute to the initiating or perpetuating events in the central nervous system. Based on these concepts, different therapeutic strategies have been pursued, such as antiviral agents, plasmapheresis, immuno-adsorption, immunosuppression or immunomodulation with intravenous immunoglobulins. However, due to the lack of large studies, to date there is no established therapeutic strategy for this devastating condition. In this review, we give an overview of the current state of immunopathogenic concepts for Rasmussen's encephalitis and discuss the different therapeutic options for future perspectives.

Transsphenoidal surgery for pituitary adenomas in children.

The authors have reviewed the results of transsphenoidal surgery for pituitary adenomas done on 66 children (younger than 16 yr of age) between 1966 and 1992. Ninety-four percent (62 of 66) showed clinical evidence of pituitary hormonal hypersecretion. The most common type was the adrenocorticotropic hormone-secreting adenoma (n = 36), followed by the prolactinoma (n = 18) and the growth hormone-secreting types (n = 8). There were four cases of nonfunctioning adenomas. Adrenocorticotropic hormone-secreting tumors in children had presentations and surgical results similar to those seen in adults. Twenty-three of 33 patients with Cushing's disease had simple adenomectomy or subtotal hypophysectomy without symptomatic recurrence. Four of 10 initial treatment failures had subsequent successful surgical intervention, resulting in an overall cure rate of 78%. Postoperative hypocortisolism was suggestive of surgical success but was not absolute. Of three patients with Nelson syndrome, none were successfully treated with surgery alone and two developed invasive disease. Prolactin-secreting and growth hormone-secreting tumors in children occurred more commonly with suprasellar expansion than did their adult counterparts. Transsphenoidal surgery was capable of controlling disease in only 12% (1 of 8) of growth hormone-secreting tumors, and 67% (12 of 18) of prolactin-secreting tumors required postoperative medical therapy or radiotherapy for persistently elevated prolactin levels. Special difficulty was noted in boys with prolactinomas and in girls with primary amenorrhea. As in adults, preoperative prolactin levels correlated with ultimate surgical success rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Chiari I malformation associated with syringomyelia and scoliosis.

STUDY DESIGN: A retrospective review of a series of 12 children who underwent suboccipital foraminotomy and duroplasty for Chiari I malformation. OBJECTIVE: To assess the effects of this surgery on associated syringomyelia and scoliosis. SUMMARY OF BACKGROUND DATA: Suboccipital foraminotomy for the treatment of syringomyelia associated with Chiari I malformation was greatly stimulated by Gardner's hydrodynamic theory, and its results proved to be encouraging. However, several authors reported improvement or stabilization of associated scoliosis after this surgery. METHODS: A retrospective review was conducted on 12 patients who underwent suboccipital foraminotomy for Chiari I malformation associated with syringomyelia. Neurologic Impairment, extent of syringomyelia, and severity of associated spinal deformity were assessed preoperatively and at a 4.5-year average follow-up (range, 2.1-12 years). Anomaly of superficial abdominal reflexes was found in all cases, and para or tetraparesis in three cases. Syringomyelia was of variable localization and extent. Scoliosis was present in 7 cases (greater than 40 degrees in 5 cases). RESULTS: Diminution or complete disappearance of syringomyelia was observed in 11 cases, 3 months to 1 year after surgery. Superficial abdominal reflexes anomaly improved in four cases. Minimal neurologic deficit persisted in one case. Scoliosis improved in one case, remained unchanged in one case, and progressed in the five cases with preoperative severe deformity, requiring instrumentation and fusion. CONCLUSIONS: Improvement of syringomyelia and neurologic deficit, observed with suboccipital foraminotomy, supports the theory that abnormal hydrodynamics of the cerebral spinal fluid is most likely to cause these deficits.

Apparently silent somatotroph adenomas.

We describe here 9 patients with somatotroph adenomas associated with mild features of acromegaly and basal plasma GH levels in the normal range. In 5 women and 4 men, 26 to 61 yrs old, the diagnosis of prolactinoma or non-secreting pituitary adenoma had been previously made on the basis of amenorrhea-galactorrhea or tumoral symptoms. However, they had discrete signs of coarsening of the facial features and moderate but evolutive changes of hand and foot sizes. Basal GH levels were in the normal range (0.4 to 4.5 micrograms/l, N less than 5 micrograms/l) but unaffected by oral glucose and insulin tolerance tests while IGF-I concentrations were elevated in all the cases (range 1.7 to 5.8 U/ml, N: 0.37-1.41 U/ml). Plasma PRL concentrations were elevated in 5 patients (range 16 to 80 micrograms/l, N less than 13 micrograms/l in men and N less than 19 micrograms/l in women). The 9 patients had a macroadenoma with an extrasellar extension in 8 of them and all were operated on by the transsphenoidal route. Immunocytochemical studies demonstrated IRGH-cells in all the adenomas and IRPRL-cells in 5 of them. Electron microscopic analysis of 3 tumors showed that the secretory granules were sparse and the Golgi apparatus poorly developed. Molecular biology of 7 tumors showed the presence of small amounts of GH mRNA. This result was in agreement with the morphological aspect, suggesting a low rate of GH synthesis. Thanks to these different approaches the diagnosis of silent somatotroph adenoma should sometimes be reconsidered.(ABSTRACT TRUNCATED AT 250 WORDS)

Docking study of cistanoside C to telomeric DNA fragment.

Experiments show that the natural products phenyl propanoid glycosides (PPGs) extracted from the plant Pedicularis spicata are capable of repairing DNA damaged by oxygen radicals. Based on kinetic measurements and experiments on tumor cells, a theoretical study of the interaction between PPG molecule Cistanoside C and telomeric DNA fragment has been carried out. The docking calculations performed using JUMNA software showed that the Cistanoside C could be docked into the minor groove of telomeric DNA and form complexes with the geometry suitable for an electron transfer between guanine radical and the ligand. Such complexes can be formed without major distortions of DNA structure and are further stabilized by the interaction with the saccharide side-groups.

[Surgery for intractable focal epilepsy in children]. / Chirurgie de l'épilepsie chez l'enfant.

Surgery of drug resistant epilepsy in children is a functional surgery which aims at the suppression of the epileptogenic focus. The surgical decision is adopted or rejected as a result of the clinical examination and complementary investigations following a multidisciplinary discussion in which the benefit-risk ratio is being carefully weighed. The objective of the presurgical investigations, dominated by scalp-recorded video-electroencephalography and magnetic resonance imaging, is the localization of the epileptogenic focus. The invasive surgical investigations with intracranial electrode placement are indicated when the limits of a planned resection have to be defined precisely or when the focus is located nearby a functionally eloquent region (sensori-motor and language region). Their identification is possible by means of electrical stimulation. Two methods of exploration are available: The combination of subdural and intracerebral electrode placement through craniotomy and the stereotactic placement of intracerebral depth electrodes (Stereo-EEG). The choice of either of these two methods depends on the child's age and on the topography of the epileptogenic focus. Surgery can be either palliative, with the purpose of reducing the intensity and/or the frequency of a certain seizure type (callosotomy, multiple subpial transsections) or curative, aiming at a suppression of the epileptogenic focus through a resective or a disconnective surgical procedure. We have operated on a population of 148 children and infants between 3 months and 10 years of age during the years 1993 to 2001: In the infant group, dysplastic lesions represented the predominant etiology. In the age group of 3 to 10 years, the underlying pathology was more distributed (dysplastic lesions, epileptogenic tumors, Rasmussen's encephalitis, hypothalamic hamartomas). Extratemporal focal resections required, in the majority of cases, an invasive preoperative exploration and hemispherotomy was frequent in this group (44 p. 100). Sixty-seven percent of the children were seizure-free, with an acceptable morbidity rate, primarily due to shunt placement following hemispherotomy in children with dysplastic lesions. Our preliminary results concerning quality of life and socialization are encouraging and favor surgical treatment at an early stage.

[Treatment of abnormal movements by thalamic lesions]. / Traitement des mouvements anormaux par lésions thalamiques.

Thalamic targets in the treatment of involuntary movements include the lateral and usually the intermediary ventral nuclei. Destruction of their afferents in Forel's fields provides the same therapeutic result but the size of the lesion must then be very small due to the proximity of essential structures, particularly corpus Luysi. Efficacy of treatment depends partly on the aetiology of the involuntary movement (and thus from the indication for surgery) and also on the technical possibilities of electrophysiologic mapping. The true dystonic element of the involuntary movement is usually little improved whereas tremors of all types are improved or suppressed. Essential tremor, familial or not, of large amplitude and very disabling, is an ideal indication for stereotaxic surgery when it presents as intention tremor. In Parkinson's disease, the treatment is effective against tremor and rigidity but akinesia is unaltered and the progressive course of the disease uninterrupted. Indications for surgery have become rare since the availability of L-dopa, perhaps too rare for the slowly progressive forms with predominant tremor poorly relieved by dopa-therapy, surgery has a curative and probably preventive effect on the involuntary movements of limbs induced by this treatment. Suppression of post-traumatic tremor and that due to multiple sclerosis is dependent on various factors: electrophysiologic precise mapping of the target since "electrical silences or holes" exist that disturb or prevent collection of evoked potentials or spike activity; multiple neurologic lesions that may be worsened by an additional thalamic lesion; finally residual cerebellar disturbance unmasked by the suppression of tremor, a poor "functional" result despite a good operative result.(ABSTRACT TRUNCATED AT 250 WORDS)

[Problems related to neurosurgical treatment of epilepsy in children]. / Problèmes posés par la neurochirurgie de l'épilepsie de l'enfant.

Neurosurgery of epilepsy in children has undergone rapid development during the past decade. This was justified by the high incidence of intractable epilepsy and its consequences on cognitive development. Any decision in the area of surgery must take in account specific etiology and the rapid maturation of the infant's brain. As in adulthood, both the epileptogenic and the functional zones must be identified, but this is a challenge when the brain is not mature and the functions not yet developed. In addition, the ability to recover must be determined. At the present time no precise methodology can be advised for presurgical work-up and surgical indications.

[Surgery and epilepsy]. / Chirurgie et épilepsie.

Corpus callosotmy was introduced in 1940 as a palliative treatment for generalized epilepsies. The improvement of the surgical technique, and the simplification of the initial "total commissurotomy" made that procedure proposed in order to decrease the frequency and the severity of the seizures occurring in the secondary geralzed epilepsies. However the indication criteria remain unclear, due to the difficulty for analysing the results and the feterogenity of the series. A careful selection requiring a comprehensive epilepsy team remains mandatory despite the relative simplicity of the procedure.

[Stereotaxic treatment in Parkinson's disease]. / Le traitement stéréotaxique de la maladie de Parkinson.

For the stereotactic treatment of Parkinson's disease, the target is usually located in the thalamus; this point is related to nearby structures (third ventricle). Then the position is controlled by electrophysiological recordings. The lesion of the target results in permanent suppression of the contralateral tremor and/or rigidity but it changes neither the course of the disease nor the akinesia. Owing to the risk of dysarthria with bilateral procedures, the main indication for surgery is parkinsonism with unilateral tremor or rigidity. Particularly interesting for the future are the possibilities of stimulation through implanted chronic electrodes.