Jan Gybels

Electrical stimulation in anterior limbs of internal capsules in patients with obsessive-compulsive disorder

Chronic electrical stimulation instead of bilateral capsulotomy was done in four selected patients with long-standing treatment-resistant obsessive-compulsive disorder. In three of them beneficial effects were observed.

LONG‐TERM ELECTRICAL CAPSULAR STIMULATION IN PATIENTS WITH OBSESSIVE‐COMPULSIVE DISORDER

OBJECTIVEBecause of the irreversibility of lesioning procedures and their possible side effects, we studied the efficacy of replacing bilateral anterior capsulotomy with chronic electrical capsular stimulation in patients with severe, long-standing, treatment-resistant obsessive-compulsive disorder. METHODSWe stereotactically implanted quadripolar electrodes in both anterior limbs of the internal capsules into six patients with severe obsessive-compulsive disorder. Psychiatrists and psychologists performed a double-blind clinical assessment. A blinded random crossover design was used to assess four of those patients, who underwent continuous stimulation thereafter. RESULTSThe psychiatrist-rated Yale-Brown Obsessive Compulsive Scale score was lower in the stimulation-on condition (mean, 19.8 ± 8.0) than in the postoperative stimulator-off condition (mean, 32.3 ± 3.9), and this stimulation-induced effect was maintained for at least 21 months after surgery. The Clinical Global Severity score decreased from 5 (severe; standard deviation, 0) in the stimulation-off condition to 3.3 (moderate to moderate-severe; standard deviation, 0.96) in the stimulation-on condition. The Clinical Global Improvement scores were unchanged in one patient and much improved in the other three during stimulation. During the stimulation-off period, symptom severity approached baseline levels in the four patients. Bilateral stimulation led to increased signal on functional magnetic resonance imaging studies, especially in the pons. Digital subtraction analysis of preoperative [18F]2-fluoro-2-deoxy-d-glucose positron emission tomographic scans and positron emission tomographic scans obtained after 3 months of stimulation showed decreased frontal metabolism during stimulation. CONCLUSIONThese observations indicate that capsular stimulation reduces core symptoms 21 months after surgery in patients with severe, long-standing, treatment-refractory obsessive-compulsive disorder. The stimulation elicited changes in regional brain activity as measured by functional magnetic resonance imaging and positron emission tomography.

Deep brain stimulation for treatment-refractory obsessive-compulsive disorder: psychopathological and neuropsychological outcome in three cases

Objective:  Investigation of deep brain stimulation (DBS) as a last‐resort treatment alternative to capsulotomy in treatment‐refractory obsessive‐compulsive disorder (OCD).

Morphine differentially affects the sensory and affective pain ratings in neurogenic and idiopathic forms of pain

&NA; In a double‐blind, placebo controlled crossover study, the effect of morphine on the affective and sensory pain ratings in different forms of chronic pain was investigated. Six patients suffering from central neurogenic pain, 8 from peripheral neurogenic pain and 6 from idiopathic pain participated in the study. Morphine (0.3 mg/kg bodyweight) and placebo (saline) were administered intravenously. Both the affective and sensory dimensions of pain sensation were assessed by means of the 101‐point rating scale. From our results it appeared that morphine reduced the affective but not the sensory dimension of pain sensation in both groups of neurogenic pain patients. In the idiopathic pain group, neither the affective nor the sensory dimension of pain sensation were affected. The observed differences in opioid responsiveness were neither the result of differences in opioid consumption nor of differences in baseline pain levels.

C nociceptor activity in human nerve during painful and non painful skin stimulation.

Percutaneous recordings from more than one hundred single C fibres have been performed in the radial nerve of conscious human subjects. All these fibres belong to the poly-modal C nociceptor group, being excited by mechanical and thermal and also by chemical stimulation. Conduction velocities showed a monophasic distribution with a mean value of 0.86 m/s (SD: 0.17). The mechanical threshold, measured with von Frey hairs, varied between 2.3 and 13.1 g. The receptive field was circular or elliptical; for 33 units the mean axes were 6 mm and 7 mm. Mechanically evoked C fibre discharge even up to more than 10 spikes/s was not necessarily accompanied by pain sensation. Nettle sting evoked an irregular C fibre discharge (maximum 10 spikes/s) accompanied by a pricking and burning sensation; the sensation of itch which was sometimes reported, was not correlated with the discharge frequency. C fibre activation by a chemical irritant (paint remover) also evoked an irregular discharge (maximum 3 to 6 spikes/s), accompanied by pricking and burning pain sensation. The C threshold for radiant heat usually lay below the subjects pain threshold. Increasing skin temperature produced increasing neural firing rate. The mean spike frequency rarely exceeded two spikes/s even with stimuli evoking strong heat pain. The occurrence of subjective heat pain response could be as well predicted from th C fibre spike frequency as from the skin temperature. It is concluded that nociceptive C input provoked by thermal or chemical stimuli correlates well with pain sensation. However, similar C input provided by mechanical stimulation which activates also A beta mechanoreceptors, did not necessarily produce pain sensation.

Production of tumor necrosis factor in spinal cord following traumatic injury in rats

Production of tumor necrosis factor (TNF) in the spinal cord following traumatic injury has been studied. In these experiments, the level of TNF was examined in the homogenate of the spinal cord, cerebrospinal fluid (CSF) and serum (n = 56). TNF could be detected in the injured spinal cord but not in the normal spinal cord. The TNF level increased in the spinal cord after the injury. At the lesion site, a maximal TNF concentration was observed 1 h after the injury, and the TNF concentration remained at this level until 8 h after the injury. Thereafter, it decreased gradually. However, TNF still could be detected 72 h after the injury. No TNF could be detected in the CSF and serum, collected from rats both with and without spinal cord injury (SCI). This study thus suggests that TNF is produced locally in the spinal cord following traumatic injury, and this TNF production is caused by the injury. The present results also demonstrate that TNF production is an acute and rapid reaction in the spinal cord following traumatic injury.

Positron emission tomography study of a chronic pain patient successfully treated with somatosensory thalamic stimulation

&NA; Previous neuroimaging studies suggested that the neuronal network underlying the perception of chronic pain may differ from that underlying acute pain. To further map the neural network associated with chronic pain, we used positron emission tomography (PET) to determine significant regional cerebral blood flow (rCBF) changes in a patient with chronic facial pain. The patient is implanted with a chronic stimulation electrode in the left ventroposterior medial thalamic nucleus with which he can completely suppress his chronic pain. The patient was scanned in the following conditions: before thalamic stimulation (pain, no stimulation), during thalamic stimulation (no pain, stimulation) and after successful thalamic stimulation (no pain, no stimulation). Comparing baseline scans during pain with scans taken after stimulation, when the patient had become pain‐free, revealed significant rCBF increases in the prefrontal (Brodmann areas (BA) 9, 10, 11 and 47) and anterior insular cortices, hypothalamus and periaqueductal gray associated with the presence of chronic pain. No significant rCBF changes occurred in thalamus, primary and secondary somatosensory cortex and anterior cingulate cortex, BA 24′. Significant rCBF decreases were observed in the substantia nigra/nucleus ruber and in the anterior pulvinar nucleus. During thalamic stimulation, blood flow significantly increased in the amygdala and anterior insular cortex. These data further support that there are important differences in the cerebral processing of acute and chronic pain.

Neuromodulation of pain. A consensus statement prepared in Brussels 16-18 January 1998 by the following task force of the European Federation of IASP Chapters (EFIC).

J. Gybels, Belgium (Chair); S. Erdine, Turkey (Vice-chairman); J. Maeyaert, Belgium (Vice-chairman); B. Meyerson, Sweden (Vice-chairman); W. Winkelmuller, Germany (Vice-chairman); L. Augustinsson, Sweden; C. Bonezzi, Italy; L. Brasseur, France; M. DeJongste, The Netherlands; R. Kupers, Denmark; P. Marchettini, Italy; G. Muller-Schwefe, Germany; P. Nitescu, Sweden; L. Plaghki, Belgium; E. Reig, Spain; G. Spincemaille, The Netherlands; S. Thomson, UK; V. Tronnier, Germany; J.-P. Van Buyten, Belgium

On the problem of geometric distortion in magnetic resonance images for stereotactic neurosurgery

In this paper, we discuss the issue of geometric distortion in magnetic resonance (MR) images used to plan stereotactic neurosurgical interventions. We analyze the process for the case of Fourier transform imaging and demonstrate that spatial misregistrations are fundamentally due to two causes: deviations of the magnetic field from its ideal value and blood flow. This enables us to relate the causes of geometric distortion to the MR imaging system, the patient and the stereotactic localizer frame. Based on the general model, we propose model refinements and discuss methods for the quantification and correction of all causes. The results of our calculations and experiments indicate that, using the proposed corrections, MRI and MR angiography should be considered valuable and reliable acquisition modalities for the planning of stereotactic neurosurgical interventions.

Spinal cord stimulation in Belgium: a nation-wide survey on the incidence, indications and therapeutic efficacy by the health insurer.

&NA; The present report describes a nation‐wide survey on the incidence, the indications and the efficacy of spinal cord stimulation (SCS), as assessed by the Belgian health authorities. The direct motive for this survey was the rapidly growing expenditures resulting from the increasing use of SCS. Between 1983 and 1992, nearly 700 SCS devices were implanted for a population of less than 10 million inhabitants. The most common indication for SCS was failed back surgery (61.4%). Whereas SCS was initially only performed in university teaching hospitals, it is now also widely practised in general hospitals. In 3 studies, the efficacy of SCS was assessed. In a first study, success was defined in terms of resumption of professional activities. After a mean follow‐up of more than 1 year, less than 5% of the 147 patients treated with SCS had returned to work. A second study investigated the subjective evaluation of the therapy by the patient. Seventy patients with a mean follow‐up of 3.5 years were studied. In 52% of the patients, the effect of SCS was judged as good to very good. Men scored better than women. In addition, the results obtained in the teaching hospitals were significantly better than those obtained in general hospitals. In a third study, the impact of psychiatric screening on patient selection was evaluated. Of the 100 candidates, 36 were withheld from implantation with a SCS device because of psychiatric contra‐indications. Patients who had received a positive psychiatric advice showed a significantly better therapeutic outcome than patients for whom the psychiatrist had made reservations.