Functional Stereotactic Surgery Research Articles

The Pioneering and Unknown Stereotactic Approach of Roeder and Orthner from Göttingen. Part I. Surgical Technique for Tailoring Individualized Stereotactic Lesions

During the 1950s through the 1970s, Hans Orthner and Fritz Roeder, two German neurologists from Göttingen, developed a sophisticated technique to perform functional stereotactic surgery with outstanding accuracy. They introduced direct air ventriculography performed in the same surgical session as the ablative stereotactic procedure. For individualized surgical targeting, Orthner prepared a stereotactic atlas (>60 brains) with an ingenious brain-slicing device, the Göttinger macrotome. Brains were grouped based on similarity of six different head and ventricle measurements. A brain cluster representing the best match for a patient was selected for stereotactic targeting. Stereotactic lesions were tailored in an individual manner and shaped by stringing together multiple small coagulations following intraoperative test stimulation. This was achieved from a single probe trajectory by using well-engineered string electrodes with calibrated curving and involved laborious calculations. Only high-frequency thermocoagulation was regarded as appropriate for lesioning. With this meticulous technique, the most advanced stereotactic procedures were performed, including bilateral pallidotomy that ultimately could be restricted to the ansa lenticularis and ventromedial hypothalamotomy, the most delicate stereotactic operation performed to date. Outside Göttingen, this technique has only been used by Prof. Dieter Müller in Hamburg, Germany. This elaborate stereotactic approach is widely unknown and deserves to be discussed in a historical context.

Brain Tissue Oxygen Pressure Monitoring in Awake Patients during Functional Neurosurgery: The Assessment of Normal Values

Local brain tissue oxygen (ptiO2) monitoring is frequently applied in patients at risk for cerebral ischemia. To identify ischemic thresholds, the normal range of local brain tissue oxygen pressure (ptiO2) values needs to be established. Ideally, such normal values are determined in healthy and awake subjects, so as to eliminate the possible influences of anesthetics on cerebral physiology or ptiO2. Thus far, however, such measurements have not been conducted, and to fill this void, we determined the ptiO2 values in normal white matter of awake patients undergoing functional stereotactic brain surgery. In 25 otherwise healthy patients, who underwent functional neurosurgery for treatment of a refractory movement disorder under local anesthesia, the ptiO2 of white matter was recorded continuously using a polarographic Clark type electrode monitoring system. Preoperative screening ruled out cognitive dysfunction or structural cerebral lesions. Reliable intraoperative ptiO2 values were obtained in 22 patients. After an adaptation period of 118+/-35 min (range, 47-171 min), we found an average normal ptiO2 of 22.6+/-7.2 mm Hg in the frontal white matter. In 11 patients, ptiO2 measurements were continued postoperatively for 24 h. During this period, a similar normal ptiO2 value of 23.1+/-6.6 mm Hg was found. No iatrogenic complications occurred. In conclusion, the normal ptiO2 of cerebral white matter is most likely lower than previously assumed. Further, the long adaptation time renders this widely applied monitoring instrument unreliable in detecting ischemia early after insertion and limits its usefulness for intraoperative monitoring.

Whither lesional surgery for movement disorders

Stereotactic surgery gained relevance in neurosurgery mainly as a surgical procedure to ameliorate symptoms of Parkinson's disease (PD) and other movement disorders. However stereotactic surgery for movement disorders has experienced fluctuating fortunes with a fall in the 1970s and resurgence in the 1990s. Lesional surgery for PD and other movement disorders gained momentum after the publication of the landmark article on pallidotomy by Laitinen et al in 1992.[1] This led to renewed interest in functional stereotactic surgery particularly pallidotomy in patients with PD. The interest in pallidotomy and thalamotomy, however, has died down in recent years due to emergence of deep brain stimulation (DBS). DBS is touted as being superior to lesional surgery such as thalamotomy and pallidotomy, as it does not destroy brain tissue and therefore, adverse effects, if any, of the stimulation are reversible unlike lesional surgery where the adverse effects of destruction of the target site are likely to be permanent. However, there have been very few articles discussing all the pros and cons of lesional surgery and DBS. In recent years DBS has almost completely replaced thalamotomy and pallidotomy in most developed countries. The question being raised in this editorial is whether lesional surgery is still relevant and whether it should be promoted amongst neurologists, neurosurgeons and patients as a safe and effective surgery for selected patients with PD and other movement disorders. The author is not exploring the relative merits and drawbacks of the two procedures (lesional surgery and DBS) to arrive at a conclusion regarding the superiority of one of the procedures. The purpose of this editorial is only to evaluate the evidence on the safety, efficacy and durability of lesional surgery for movement disorders.

Stereotactic Surgery: The Early Years

ALTHOUGH STEREOTACTIC SURGERY was conceived at the turn of the 20th century, human applications did not gain momentum until the 1950s. Modern stereotactic surgery, as currently practiced, has rapidly developed in the past decade with computer assistance obviating the need for invasive localization techniques and ultimately leading to the development of frameless instruments. Applications of these techniques have also greatly expanded the use of stereotactic methods beyond functional neurosurgery. This article describes the author's involvement in the early development of stereotactic surgery, beginning in the late 1950s. With the recognition that physiological confirmation of targets is important in improving the safety and accuracy of functional stereotactic surgery, a number of approaches were developed that are still in use today.

Modeling of the sedative and airway obstruction effects of propofol in patients with Parkinson disease undergoing stereotactic surgery.

Functional stereotactic surgery requires careful titration of sedation since patients with Parkinson disease need to be rapidly awakened for testing. This study reports a population pharmacodynamic model of propofol sedation and airway obstruction in the Parkinson disease population. Twenty-one patients with advanced Parkinson disease undergoing functional stereotactic surgery were included in the study and received propofol target-controlled infusion to achieve an initial steady state concentration of 1 microg/ml. Sedation was measured using the Ramsay Sedation Scale. Airway obstruction was measured using a four-category score. Blood samples were drawn for propofol measurement. Individual pharmacokinetic profiles were constructed nonparametrically using linear interpolation. Time course of sedation and respiratory effects were described with population pharmacodynamic models using NONMEM. The probability (P) of a given level of sedation or airway obstruction was related to the estimated effect-site concentration of propofol (Ce) using a logistic regression model. The concentrations predicted by the target-controlled infusion system generally exceeded the measured concentrations. The estimates of C(50) for Ramsay scores 3, 4, and 5 were 0.1, 1.02, and 2.28 microg/ml, respectively. For airway obstruction scores 2 and 3, the estimates of C(50) were 0.32 and 2.98 microg/ml, respectively. Estimates of k(e0) were 0.24 and 0.5 1/min for the sedation and respiratory effects, respectively. The pharmacokinetic behavior of propofol in patients with Parkinson disease differs with respect to the population from which the model used by the target-controlled infusion device was developed. Based on the results from the final models, a typical steady state plasma propofol concentration of 0.35 microg/ml eliciting a sedation score of 3 with only minimal, if any, airway obstruction has been defined as the therapeutic target.

Head injury and posttraumatic movement disorders.

WE REVIEW THE phenomenology, pathophysiology, pathological anatomy, and therapy of posttraumatic movement disorders with special emphasis on neurosurgical treatment options. We also explore possible links between craniocerebral trauma and parkinsonism. The cause-effect relationship between head injury and subsequent movement disorder is not fully appreciated. This may be related partially to the delayed appearance of the movement disorder. Movement disorders after severe head injury have been reported in 13 to 66% of patients. Although movement disorders after mild or moderate head injury are frequently transient and, in general, do not result in additional disability, kinetic tremors and dystonia may be a source of marked disability in survivors of severe head injury. Functional stereotactic surgery provides long-term symptomatic and functional benefits in the majority of patients. Thalamic radiofrequency lesioning, although beneficial in some patients, frequently is associated with side effects such as increased dysarthria or gait disturbance, particularly in patients with kinetic tremor secondary to diffuse axonal injury. Deep brain stimulation is used increasingly as an option in such patients. It remains unclear whether pallidal or thalamic targets are more beneficial for treatment of posttraumatic dystonia. Trauma to the central nervous system is an important causative factor in a variety of movement disorders. The mediation of the effects of trauma and the pathophysiology of the development of posttraumatic movement disorders require further study. Functional stereotactic surgery should be considered in patients with disabling movement disorders refractory to medical treatment.

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.

Thalamic relay site for cold perception in humans.

The neural pathways subserving the sensation of temperature are virtually unknown. However, recent findings in the monkey suggest that the sensation of cold may be mediated by an ascending pathway relaying in the posterior part of the thalamic ventromedial nucleus (VMpo). To test this hypothesis we examined the responses of neurons to thermal stimulation of the skin and determined the perceptual effects of microstimulation in the VMpo region in awake patients undergoing functional stereotactic surgery. In 16 patients, microstimulation in the VMpo region evoked cold sensations in a circumscribed body part. Furthermore, at some of these sites thalamic neurons were found that responded to innocuous cooling of the skin area corresponding to the stimulation-evoked cold sensations. These data provide the first direct demonstration of a pathway mediating cold sensation and its location in the human thalamus.

Bilateral dorsolateral subthalamotomy for advanced Parkinson's disease

Functional surgery for Parkinson's disease has undergone a resurgence since the motor complications of chronic levodopa use have become apparent. Laitinen et al showed a beneficial effect on dyskinesia, bradykinesia, and rigidity with unilateral pallidotomy. Limousin and co-workers 2 Limousin P Pollak P Benazzouz A et al. Effect on parkinsonian signs and symptoms of bilateral subthalamic nucleus stimulation. Lancet. 1995; 345: 91-95 Summary PubMed Google Scholar have presented evidence that bilateral implantation of deep brain stimulators into the central portion of the subthalamic nuclei (STN) can be undertaken safely and will improve all features of parkinsonism. The caudomedial aspect of STN is thought to be the origin of excitatory tracts to the globus pallidus interna (GPi) and the substantia nigra reticulata (SNR) via the subthalamic fasciculus. 3 Carpenter MB Batton RB Carleton SC Keller JT Interconnections and organisation of pallidal and subthalamic nucleus neurons in the monkey. J Comparative Neurol. 1981; 197: 579-603 Crossref PubMed Scopus (136) Google Scholar A discrete lesion in this area should have an effect equivalent to STN stimulation. Lesions of STN carry a risk of hemiballismus. Surgical targets for treating hemiballism are the zona incerta and the ventral intermediate nucleus (VIM). 4 Krauss KJ Mundinger F Functional stereotactic surgery for hemiballism. J Neurosurg. 1996; 85: 278-285 Crossref PubMed Scopus (50) Google Scholar These structures lie immediately above the dorsolateral STN. If a lesion in the dorsolateral STN were to produce hemiballism, then extending the lesion 2–3 mm ventrally should suppress it. Stimulators are bulky and costly, require regular adjustment, and patients may develop tolerance. They preclude further magnetic resonance imaging (MRI) scans and the stimulator units need to be replaced every 3–5 years. Lesions do not have these problems, but unlike stimulators side-effects may not be reversible. Unilateral STN lesions are reported in 5 patients by Obeso et al. 5 Obeso JA Alvarez LM Macias RJ et al. Lesion of the subthalamic nucleus in Parkinson's disease. Neurology. 1997; 48: A138 Google Scholar We report two cases of safe and so far effective bilateral STN lesions.

Patterns of neuronal firing in the human lateral thalamus during sleep and wakefulness.

The firing patterns of thalamic neurons in mammals undergo a dramatic change as the animal's state changes between sleep and wakefulness. During sleep the normal tonic firing of thalamic neurons changes into a slower bursting mode characterized by repetitive activation of a low-threshold calcium (Ca2+) current. The present report describes the patterns of thalamic neuronal firing during sleep and wakefulness in one human patient. Extracellular single neuron activity was recorded during functional stereotactic surgery in the thalamus of a patient with chronic pain, who was observed to fall asleep during the recording. Evolutive power spectra of the thalamic slow wave were used in place of cortical encephalography to confirm the patient's states of sleep and wakefulness. Twenty-nine sites were observed in motor and somatosensory thalamus (Vop, Vim, and Vc) that were characterized by the presence of neurons with bursting activity when the patient was asleep. Such bursting was not observed in the patient when she was awakened. At 14 of these sites we were able to discriminate the bursting activity of single units. In each case the cell stopped firing or its bursting was replaced by a tonic firing pattern when the patient was awakened. In three cases the patient began to lapse back into sleep and the neuron resumed firing in a bursting pattern once again. None of these units had a peripheral receptive field (RF), while several other units recorded in nearby regions that did not fire in a bursting pattern during sleep had kinesthetic or cutaneous RFs. Analysis of the intraburst firing pattern revealed increasing interspike intervals (ISI) for successive action potentials in a burst and that the duration of the first ISI in the burst decreased as the number of ISIs increased. This pattern is similar to that reported to occur as a result of a calcium spike. These data have confirmed for the first time that state-dependent changes in thalamic firing exist in the human and that the physiological substrates at the thalamic level that are involved in human sleep are similar to those observed in animals.

Functional stereotactic surgery for hemiballism.

The symptomatic and functional outcomes of a series of 14 patients with disabling and medically refractory hemiballism who were treated with functional stereotactic surgery are reported. Seven (50%) of the 14 patients had concomitant hemichorea. To relieve the hyperkinesia, the 14 patients underwent a total of 15 stereotactic operations (one patient had a second stereotactic procedure). Combined lesions in the contralateral zona incerta and the base of the ventrolateral (oroventral) thalamus were applied in 13 instances. The zona incerta was reached by means of a movable chord electrode to obviate the need for repeated puncture. In two instances the medial pallidum was used as the stereotactic target. Hemiballism was abolished or considerably improved in 13 (93%) of 14 patients in the immediate postoperative phase. Residual dyskinesia was evaluated using the hemiballism/hemichorea outcome rating scale. Long-term follow-up review was available for 13 of the 14 patients (mean follow-up period 11 years). Persistent improvement in the hemiballism was found in 12 of these 13 patients: seven patients (54%) were free of any hyperkinesia and five patients (39%) had minor residual and predominantly hemichoreic hyperkinesia. One of the 13 patients presented with a probable psychogenic movement disorder at long-term follow-up examination. Persistent morbidity, most likely related to the operative intervention, was detected in three of the 13 patients; this included mild hemiparesis and dystonia. Functional disability was assessed using the Huntington's Disease Activities of Daily Living scale. The patients' preoperative mean value of 83% of maximum disability was reduced to a mean of 30% observed at long-term follow-up review (p < 0.001). The residual disability exhibited in most older patients was associated with cardiovascular disease. The authors compare their findings with the results of 44 cases reported previously. The authors contend that functional stereotactic surgery should be considered in patients with persistent, medically refractory hemiballism.

Evaluation of the effect of treatment on movement disorders in astrocytomas of the basal ganglia and the thalamus.

Twenty patients with movement disorders associated with astrocytomas (grade I-IV according to the WHO tumour classification) of the basal ganglia and the thalamus were evaluated for the effects of treatment. Five patients had more than one movement disorder when the histological diagnosis was verified by stereotactic biopsy. Twelve had tremors, eight hemidystonia, three hemichorea, and one hemichorea/ballismus, and myoclonus respectively. Ten patients died during the follow up period, and for the surviving patients follow up periods ranged from 6-21 years. The movement disorders changed over long periods of time related to therapeutic interventions. CSF shunt operations and percutaneous radiotherapy had no definite effect on the movement disorders. There was a moderate response to medical treatment in a few patients. Stereotactic aspiration of tumour cysts had a marked influence on the movement disorder in two patients, and functional stereotactic surgery abolished tumour induced tremor in one. Interstitial radiotherapy was performed in fifteen patients for treatment of the underlying neoplasm and resulted in different and variable alterations of the movement disorders. These differences may be explained by complex interactions involving structures affected primarily by the tumour, as well as by secondary functional lesions of adjacent structures.

Rapid determination of thalamic CT-stereotactic coordinates: A method

The anterior and posterior commissures (AC; PC) are the most frequently used reference points for target determination in functional stereotactic surgery. Computerized tomography (CT) has been slow in replacing ventriculography for identification of these points, primarily because in most methods described to date, the AC/PC plane had to be identified by reformatted CT images or cumbersome mapping procedures. The authors describe their methodology for determination of functional CT-stereotactic coordinates using the Brown-Robert-Wells (BRW) stereotactic system, axial CT imaging, and a proportional method to rapidly scale standard stereotactic map coordinates to the diencephalic size of any individual patient. 1. CT gantry angulation coinciding with Twining's line allows rapid identification of the AC/PC plane on axial CT. 2. Determination of the AC/PC distance with the "measure distance" function of the scanner enables the surgeon to rapidly find the proportional coordinates for either V.O.P., V.im., or V.C. 3. This localization method takes little more time than a routine stereotactic biopsy. Its application is easy, demanding only a few minutes of CT-console time, employing the standard computer software available in every current CT scanner. The method was been successfully employed in 25 functional thalamic procedures.

Configuration of a Robot Dedicated to Stereotactic Surgery

The design of a robot for functional stereotactic surgery which is under construction in our laboratory is described. The main features include operation inside the computed tomographic (CT) scanner, the possibility of intraoperative CT scanning and complete handling of the stereotactic probes by the robot.

New trends in computer graphics and computer vision to assist functional neurosurgery.

Computer vision (CV), a computerized method to analyze digital images (e.g., CT scans), and computer graphics (CG), a set of computer programs for displaying two, three- or four-dimensional data, are recent computer techniques which are appropriate to assist functional stereotactic surgery. CV and CG are useful for the evaluation of spatial relations between anatomical structures and the sites of spontaneous neuronal noise or of electrophysiological stimulation data gathered during stereotactic interventions for movement disorders. CV and CG can be employed for stereotactic operation planning, during the operation for target point evaluation and for further postoperative data analysis.

Microelectrode techniques in localization of stereotactic targets.

Although physiological corroboration of the target is essential in functional stereotactic surgery, the collected data can also be used for the offline study of normal and abnormal brain function. Such studies have the advantage of being made in actual clinical states with the unique opportunity of communicating with the patient. Correlations were made between microelectrode recordings and microstimulation at the same thalamic site with the same microelectrode in 'normal' patients, in those with tremor and in those with central and deafferentation pain. Human somatosensory organization is similar to that of subhuman primates. Five types of tremor cells have been identified-unresponsive nonsynchronous, unresponsive synchronous, kinaesthetic, voluntary, and voluntary with receptive field. While the last two qualify in latency and connectivity as tremor pacemakers, system analysis suggests an important element of long loop feedback as well. In the pain patients, five features were identified-somatotopic reorganization, altered firing in reorganized cells, bursting cells induction of burning widespread in thalamus and reproduction of the patient's pain by microstimulation-possibly a 'central allodynia' found in deafferented somatosensory thalamus particularly in patients with allodynia or hyperpathia. All but the latter effects may be merely the consequence of deafferentation and were seen in a 'control' stroke patient with dystonia, sensory loss but no pain.