Marc Sindou

Clinical manifestations of insular lobe seizures: a stereo-electroencephalographic study.

Summary:  Purpose: In this study, we report the clinical features of insular lobe seizures based on data from video and stereo‐electroencephalographic (SEEG) ictal recordings and direct electric insular stimulation of the insular cortex performed in patients referred for presurgical evaluation of temporal lobe epilepsy (TLE).

The role of the insular cortex in temporal lobe epilepsy

The role of the insular cortex in the genesis of temporal lobe epileptic (TLE) seizures has been investigated in 21 patients with drug‐refractory TLE using chronic depth stereotactic recordings of the insular cortex activity and video recordings of ictal symptoms during 81 spontaneous electroclinical seizures. All of the recorded seizures were found to invade the insula, most often after a relay in the ipsilateral hippocampus (19/21 patients). However, 2 patients had seizures that originated in the insular cortex itself. Ictal symptoms associated with the insular discharges were similar to those usually attributed to mesial temporal lobe seizures, so that scalp video‐electroencephalographic monitoring does not permit making any difference between ictal symptoms of temporo‐mesial and insular discharges. A favorable outcome was obtained after a temporal cortectomy sparing the insular cortex in 15 of 17 operated patients. Seizures propagating to the insular cortex were found to be fully controlled by surgery, whereas those originating in the insular cortex persisted after temporal cortectomy. The fact that seizures originating in the insular cortex are not influenced by temporal lobectomy is likely to explain some of the failures of this surgical procedure in TLE. Ann Neurol 2000;48:614–623

Electrical stimulation of precentral cortical area in the treatment of central pain: electrophysiological and PET study

&NA; The clinical, electrophysiological and haemodynamic effects of precentral gyrus stimulation (PGS) as a treatment of refractory post‐stroke pain were studied in 2 patients. The first patient had a right hemibody pain secondary to a left parietal infarct sparing the thalamus, while the second patient had left lower limb pain developed after a right mesencephalic infarct. In both cases, spontaneous pain was associated with hyperpathia, allodynia and hypoaesthesia in the painful territory involving both lemniscal and extra‐lemniscal sensory modalities in patient 1, extra‐lemniscal sensory modality only in patient 2. Both patients were treated with electrical PGS by means of a 4‐pole electrode, the central sulcus being per‐operatively located using the phase‐reversal of the N20 wave of somatosensory evoked potentials. No sensory side effect, abnormal movement or epileptic seizure were observed during PGS. The analgesic effects were somatotopically distributed according to the localization of electrode on motor cortex. A satisfactory long‐lasting pain control (60–70% on visual analog scale) as well as attenuation of nociceptive reflexes were obtained during PGS in the first patient. Pain relief was less marked and only transient (2 months) in patient 2, in spite of a similar operative procedure. In this patient, in whom PGS eventually evoked painful dysesthesiae, no attenuation of nociceptive RIII reflex could be evidenced during PGS. Cerebral blood flow (CBF) was studied using positron emission tomography (PET) with 15O‐labeled water. The sites of CBF increase during PGS were the same in both patients, namely the thalamus ipsilateral to PGS, cingulate gyrus, orbito‐frontal cortex and brainstem. CBF increase in brainstem structures was greater and lasted longer in patient 1 while patient 2 showed a greater CBF increase in orbito‐frontal and cingular regions. Our results suggest that PGS‐induced analgesia is somatotopically mediated and does not require the integrity of somatosensory cortex and lemniscal system. PGS analgesic efficacy may be mainly related to increased synaptic activity in the thalamus and brainstem while changes in cingulate gyrus and orbito‐frontal cortex may be rather related to attentional and/or emotional processes. The inhibitory control on pain would involve thalamic and/or brainstem relays on descending pathways down to the spinal cord segments, leading to a depression of nociceptive reflexes. Painful dysesthesiae during stimulation have to be distinguished from other innocuous sensory side effects, since they may compromise PGS efficacy.

Anatomical observations during microvascular decompression for idiopathic trigeminal neuralgia (with correlations between topography of pain and site of the neurovascular conflict). Prospective study in a series of 579 patients.

Summary Background. The Micro-Vascular Decompression (MVD) procedure – developed for conservative treatment of idiopathic Trigeminal Neuralgia (TN) is based on the NeuroVascular Conflict (NVC) theory. Although MVD has become very popular over the last twenty years, its principles and value remain controversial. Detailed anatomical observations during posterior fossa exploration in patients with idiopathic TN may help to understand better the role of NVCs. Method. In this article, the authors report the anatomical observations made under the operating microscope in a consecutive series of 579 patients suffering from idiopathic TN who were treated by MVD. Findings. In 19 cases (3.3%) no neuro-vascular conflict was found. In the remaining 560 (96.7%) one or several offending vessel(s) were identified. A superior cerebellar artery alone or in association with other “conflicting” vessel(s) was found in 88% of the patients, an anterior-inferior cerebellar artery (alone or in association) in 25.1%, a vein embedded in the nerve (alone or in association) in 27.6%, the basilar artery (alone or in association) in 3.5%. Of prime importance, several “conflicting” vessels were found in association in 37.8% of the patients. Location of the NVC was in the trigeminal root entry zone in 52.3% of the patients, in the midthird of the nerve in 54.3% and at the exit of the nerve from Meckel cave in 9.8%. The relation of the predominant conflict with the surface of the nerve was supero-medial in 53.9%, supero-lateral in 31.6% and inferior in 14.5%. The degree of severity of the main conflict was a simple contact with the nerve in 17.6%, a distorsion of the nerve in 49.2% and a marked indentation in 33.2%. Alteration of the whole trigeminal nerve was frequently observed. In 42% of patients, the nerve had a significant degree of global atrophy. In 18.2%, there was a local thickening of arachnoid membranes, adherent to the nerve. In 12.6%, the root had a marked angulation on crossing over the petrous ridge. Finally in 3.9%, the nerve was compressed between pons and petrous bone, due to the small size of the posterior fossa. Interpretation. It is concluded that NVC in this series played an important role as a causative factor of the neuralgia, as classical; but other – possibly responsible – anatomical factors were found, especially a global atrophy of the root, a focal arachnoid thickening, a ribbon-shaped and angulated root on crossing over the petrous ridge . . .

Motor cortex stimulation for refractory neuropathic pain: four year outcome and predictors of efficacy.

&NA; Thirty‐one patients with medically refractory neuropathic pain were included in a prospective evaluation of motor cortex stimulation. The long‐term outcome was evaluated using five variables: (a) rate (percentage) of pain relief, (b) pain scores as assessed on VAS, (c) postoperative decrease in VAS scores, (d) reduction in analgesic drug intake, (e) a dichotomic (yes/no) response to the question whether the patient would accept, under similar circumstances, to be operated on again. Pain relief was rated as excellent (>70 % pain relief) in 10 % of cases, good (40‐69 %) in 42 %, poor (10‐39 %) in 35 % and negligible (0‐9 %) in 13 %. Intake of analgesic drugs was decreased in 52 % of patients and unchanged in 45 % (unavailable data in 3 %), with complete withdrawal of analgesic drugs in 36 % of patients. Twenty‐one patients (70 %) declared themselves favourable to re‐intervention if the same beneficial outcome could be guaranteed. Neither preoperative motor status, pain characteristics, type or localisation of lesions, quantitative sensory testing, Somatosensory Evoked Potentials, nor the interval between pain and surgery were found to predict the efficacy of MCS. The level of pain relief, as evaluated in the first month following implantation was a strong predictor of long‐term relief (regression analysis, R=0.744; p<0.0001). These results confirm that MCS can be a satisfactory and durable alternative to medical treatments in patients with refractory pain, and suggest that the efficacy of MCS may be predicted in the first month of therapy.

Various surgical modalities for trigeminal neuralgia: literature study of respective long-term outcomes.

SummaryBackground. The literature contains many varying, often conflicting surgical results. However, there is no study comparing long-term effectiveness of all surgical procedures for trigeminal neuralgia (TN). The aim of the present analysis is to report the long-term outcomes of surgical options of TN since the development of electronic databases, to evaluate them with the same clinical and statistical criteria and determine the most appropriate treatment.Method. All studies that had a minimum 5 years or more (≥5 years) mean duration of follow-up were included in the review. The identified studies were evaluated independently by two authors for quality using a modified inclusion criteria. The evaluated outcome measures of this study were, the initial acute pain relief (APR), follow-up pain free period and recurrence rates as well as complications. In comparisons of the data, the Student’s t-test, Chi-square followed by Pearson’s risk analysis tests were used. Kaplan–Meier actuarial analysis of pain free-survival curves were constructed for each surgical option that had enough data.Findings. Twenty-eight studies, mostly including microvascular decompression (MVD) and radiofrequency thermorhizotomy (RF-TR), that met the inclusion criteria were included in the review. The efficacy of MVD and percutaneous balloon microcompression (PBC) were similar (Odds ratio = 0.15, P > 0.05), and their effects were superior to those of the other modalities (P < 0.001). Although RF-TR provided a high initial pain relief, its average pain free rate was 50.4% for a mean follow-up of 5 years. The recurrence rate was high after RF-TR (46%), while the lowest recurrence rate (18.3%) was after MVD (P < 0.001). Within the long-term follow-up period recurrence of pain affects at least 19% of patients who undergo any surgical treatment for TN.Conclusions. The study suggests that each surgical technique for treatment of trigeminal neuralgia has merits and limitations. However, MVD provides the highest rate of long-term patient’ satisfaction with the lowest rate of pain recurrence.

Neurophysiological Monitoring for Epilepsy Surgery: The Talairach SEEG Method

Object of the Study: In some candidates for epilepsy surgery in whom the decision to operate is difficult to make, invasive presurgical investigations, namely depth electrode recordings, may be needed. The SEEG (StereoElectroEncephaloGraphy) method consists of stereotactic orthogonal implantation of depth electrodes (5 to 15, 11 on average). The object of this study is to clarify the indications for SEEG, to expose its complications, and to display its usefulness in terms of surgical strategy and results. Patients and Methods: 100 patients, suffering from drug-resistant epilepsy and selected as candidates for surgical resection, underwent SEEG between 1996 and 2000. A total of 1,118 electrodes were implanted. For each single case, the sites of implantation of the electrodes were chosen in order to determine either the side of the onset of seizures, or the uni- or multilobar feature of them, or a possible operculo-insular propagation from a temporal onset, and also, using direct electrode stimulation, the proximity of speech or motor area. Results: Complications occurred in 5 patients (2 superficial infections, 2 breakages of electrodes, and 1 intracerebral hematoma responsible for death). SEEG was helpful in most (84%) of the 100 patients to confirm or annul surgical indication, and to adjust the extent of the resection. In some cases (14%), SEEG allowed to propose a resection that might have been disputable based solely on noninvasive investigation data. For frontal epilepsy, SEEG was crucial in all cases to delineate the extent of resection. Conclusion: SEEG proved to be a relatively safe and a very useful method in ‘difficult’ candidates for epilepsy surgery. In addition, in some cases the implanted electrodes can be used to perform therapeutic RF thermocoagulation of epileptic foci or networks.

Micro-vascular decompression for primary Trigeminal Neuralgia (typical or atypical). Long-term effectiveness on pain; prospective study with survival analysis in a consecutive series of 362 patients.

SummaryBackground. Few publications on primary Trigeminal Neuralgia treated by Micro-Vascular Decompression (MVD) report large series, with long-term follow-up, using Kaplan-Meier (K-M) analysis. None was specifically directed to the comparative study of MVD effectiveness on Trigeminal Neuralgia with typical (i.e., with paroxysmal pain only) and atypical features (i.e., with association of a permanent background of pain). Method. The authors report a series of 362 patients having clearcut vascular compression and treated with pure MVD – i.e., without any additional cut or coagulation of the adjacent root fibers. Follow-up was 1 to 18 y (8 y on average, with a median of 7.2 y). Results were considered overall, then separately for patients with typical (237 (65.5%)) and atypical (125 (34.5%)) clinical presentation. Findings. One year after operation, (294 (81.2%) of patients were totally-free – of paroxysmal pain, and also of permanent background pain – and not needing any medication) 13 (3.6%) still had a background of pain but without the need for medication which 55 patients (15.2%), treatment had failed. At latest review (8 y on average) the corresponding rates were 80, 4.9 and 15.1%, respectively. Kaplan-Meier analysis estimated the probability of total cure at 15 y to be 73.4%.There was no difference in the cure rate between patients with typical and atypical features at one year: 81 and 81.16%, respectively. The probability of cure at 15 y was identical for the two clinical presentations. Conclusions. Pure MVD offers patients affected by Trigeminal Neuralgia due to vascular compression a long-lasting cure in three-fourths of the cases. Both typical and atypical presentations respond well to MVD, view in contrast to the classical view that an atypical presentation has an adverse effect on outcome after surgery.

Microvascular decompression for primary hemifacial spasm. Importance of intraoperative neurophysiological monitoring

SummaryThere is considerable evidence that primary Hemi-Facial Spasm (HFS) is in almost all cases related to a vascular compression of the facial nerve at its Root Exit Zone (REZ) from brainstem, and that Micro-Vascular Decompression (MVD) constitutes its curative treatment. Clinical as well as electrophysiological features plead for mechanisms of the disease in structural lesions at the neural fibers (putatively: focal demyelination at origin of ephapses) and functional changes in the nuclear cells (hyperactivity of the facial nucleus).Lateral Spread Responses (LSRs) elicited by stimulation of the facial nerve branches testify of these electrophysiological perturbations. Monitoring LSRs during surgery is feasible; however the practical value of their intraoperative disappearance as control-test of an effective decompression remains controversial.MVD allows cure of the disease in most cases. Because the VIIIth nerve is at risk during surgery, intraoperative monitoring of Brainstem Auditory Evoked Potentials (BEAPs) is of value to reduce occurrence of hearing loss. Increase in latency of Peak V and decrease in amplitude of Peak I are warning-signals of an excessive stretching of the the cochlear nerve and impairment of the cochlear vascular supply, respectively.

Microsurgical DREZotomy for pain due to spinal cord and/or cauda equina injuries : long-term results in a series of 44 patients

&NA; According to the literature estimations, 10–25% of patients with spinal cord and cauda equina injuries eventually develop refractory pain. Due to the fact that most classical neurosurgical methods are considered of little or no efficacy in controlling this type of pain, the authors had recourse to microsurgery in the dorsal root entry zone (DREZ). This article reports on the long‐term results of the microsurgical approach to the dorsal root entry zone (DREZotomy) in a series of 44 patients suffering from unbearable neuropathic pain secondary to spine injury. The follow‐up ranged from 1 to 20 years (6 years on average). The series includes 25 cases with conus medullaris, 12 with thoracic cord, four with cauda equina and three with cervical cord injuries. Surgery was performed in 37 cases at the pathological spinal cord levels that corresponded to the territory of the so‐called ‘segmental pain’, and in seven cases, on the spinal cord levels below the lesion for ‘infralesional pain’ syndromes. The post‐operative analgesic effect was considered to be ‘good’ when a patients estimation of pain relief exceeded 75%, ‘fair’ if pain was reduced by 25–75%, and ‘poor’ when the residual pain was more than 75% of preoperative estimations. Immediate pain relief was obtained in 70% of patients and was long‐lasting in 60% of the total series. The results varied essentially according to the distribution of pain. Good long‐term results were obtained in 68% of the patients who had a segmental pain distribution, compared with 0% in patients with predominant infralesional pain. Regarding pain characteristics, a good result was obtained in 88% of the cases with predominantly paroxysmal pain, compared with 26% with continuous pain. There were no perioperative mortalities. Morbidity included cerebrospinal fluid leak (three patients), wound infection (two patients), subcutaneous hematoma (one patient) and bacteremia (in one patient). The above data justify the inclusion of DREZ‐lesioning surgery in the neurosurgical armamentarium for treating ‘segmental’ pain due to spinal cord injuries.