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Jean Régis, Motohiro Hayashi, Denis Porcheron, Christine Delsanti, Xavier Muracciole, and Jean Claude Peragut

Object. The technical advances associated with the model C gamma knife include a robotized system enabling automatic positioning of the stereotactic coordinates. The purpose of this study was to analyze the clinical impact of this technical modification.

Methods. The authors studied a sample of patients with vestibular schwannoma (VS). This sample included three groups treated using gamma knife radiosurgery. Group I comprised 21 patients with VS treated just before the installation of the Automatic Positioning System (APS). Group II included patients in Group I with new dose plans created using the APS (in other words, simulated dose plans). Group III consisted of a control group of 20 patients matched for tumor grade with the previous group and treated recently with the APS. Treatment times were calculated after correcting the time for each shot according to the age of the sources after reloading. The treatment times, including total time, irradiation time, and duration of the neurosurgical procedure, were analyzed. In addition, dose planning including number of isocenters, number of different collimators, malfunctions, and the conformity and selectivity indices were recorded.

The trend was to reduce the mean number of collimator runs from 7.9 to 1.2 and to increase the mean number of shots from 7.9 to 15.6, mostly by using the 4-mm collimator exclusively. The APS-related conformity and selectivity were improved from 95 to 97% and from 78 to 84%, respectively. The total treatment time was reduced by 53%, and time required to interact with the patient in the room was considerably reduced (75%), giving the neurosurgeon greater freedom to perform other tasks during the treatment period. The reduction of the time spent by the neurosurgeon at work in the room was 84%. The total radiation time was increased by 54%.

Conclusions. The preliminary results of this study indicate that the robotization of the gamma knife is likely a major advance in radiosurgery.

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Douglas Kondziolka

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Shoji Yomo, Yasser Arkha, Anne Donnet, and Jean Régis

Gamma Knife surgery (GKS) is widely recognized as an effective, minimally invasive treatment for intractable trigeminal neuralgia, but the role of GKS in glossopharyngeal neuralgia (GPN) remains unclear. This study involved 2 patients with medically intractable GPN who were treated using GKS. One patient required 2 treatments because of a recurrence of symptoms (at maximum doses of 60 and 70 Gy), and the other patient had a single intervention (at a maximum dose of 75 Gy). The GKS target was the distal part of the glossopharyngeal nerve. Patients were investigated prospectively, treated, and then assessed periodically with respect to pain relief and neurological function. Complete pain relief was achieved initially after all 3 interventions. The first patient was pain free without medication for 2 months after the first treatment (60 Gy) and for 4 months after the second treatment (70 Gy). The second patient (treated with 75 Gy) was still pain free without medication at the last follow-up (12 months). Neither patient had any neurological complications. The initial response of GPN to low-dose GKS was favorable, but symptoms may recur. No adverse neurological effects were observed in any of the lower cranial nerves. It will be necessary to investigate the optimal radiation dose and target of GKS for achieving long-term pain relief in GPN.

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Jean Régis, Christine Delsanti, and Pierre-Hugues Roche

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J. Kenneth Burkus, Kevin Foley, Regis Haid, and Jean-Charles LeHuec

The authors present their radiographic criteria for assessing fusion of the lumbar spine after anterior interbody fusion with intradiscal implants. These criteria include the assessment of plain radiographs, dynamic motion radiographs, and thin-cut computerized tomography scans. Fusion within the instrumented spinal motion segment can be determined using radiographic evaluation to assess spinal alignment on sequential examinations, angular and translational changes on dynamic motion studies, and device–host interface, and to identify new bone formation and bone remodeling. Finally, to aid the clinician in assessing fusion, the authors describe the five zones of fusion within the intervertebral disc space.

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Shoji Yomo, Romain Carron, Jean-Marc Thomassin, Pierre-Hugues Roche, and Jean Régis


The aim of this study was to perform an accurate analysis of changes in hearing in patients with vestibular schwannoma (VS) who have undergone Gamma Knife surgery (GKS) and distinguish the impact of radiosurgery from the natural course of hearing deterioration due to the tumor itself.


This study was a retrospective review of prospectively collected patient data. A group of 154 patients with unilateral nonsurgically treated VS was conservatively monitored for more than 6 months and then treated with GKS between July 1997 and September 2005. They were followed up with serial clinical examination, MRI, and audiometry. The annual hearing decrease rate (AHDR) was measured before and after radiosurgery, and the possible prognostic factors for hearing preservation were investigated.


The mean dose prescribed to the tumor margins was 12.1 Gy. The mean radiological follow-up period after GKS was 60 months (range 7–123 months). The tumor control rate was 94.8%, and 8 patients underwent subsequent intervention due to tumor progression. The mean audiological follow-up times before and after GKS were 22 and 52 months, respectively. The mean AHDRs before and after GKS were 5.39 dB/year (95% CI 3.31–7.47 dB/year) and 3.77 dB/year (95% CI 3.13–4.40 dB/year), respectively (p > 0.05). The mean pre- and post-GKS AHDRs in patients who initially had Gardner-Robertson (GR) Class I hearing were −0.57 dB/year (95% CI −2.95 to 1.81 dB/year) and 3.59 dB/year (95% CI 2.52–4.65 dB/year), respectively (p = 0.007). The mean pre- and post-GKS AHDRs in patients who initially had GR Class II hearing were 5.09 dB/year (95% CI 1.36–8.82 dB/year) and 4.98 dB/year (95% CI 3.86–6.10 dB/year), respectively (p > 0.05). A subgroup of 80 patients had both early and late post-intervention AHDR assessment (with early referring to the period from GKS to the assessment closest to the 2-year follow-up point and late referring to the period from that assessment to the most recent one); in these patients, the mean early post-GKS AHDR was 5.86 dB/year (95% CI 4.25–7.50 dB/year) and the mean late post-GKS AHDR was 1.86 dB/year (95% CI 0.77–2.96 dB/year) (p < 0.001). A maximum cochlear dose of less than 4 Gy was found to be the sole prognostic factor for hearing preservation.


The present study demonstrated the absence of an increase in AHDR after radiosurgery as compared with the preoperative AHDR. There was even a trend indicating a reduction in the annual hearing loss after radiosurgery over the long term. To fully elucidate a possible protective effect of radiosurgery, longer-term follow-up with a larger group of patients will be required.

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Jean Régis, Fabrice Bartolomei, M. Rey, Motohiro Hayashi, Patrick Chauvel, and Jean-Claude Peragut

Object. Gamma knife radiosurgery (GKS) allows precise and complete destruction of chosen target structures containing healthy and/or pathological cells, without causing significant radiation damage to adjacent tissues. Almost all the well-documented cases of radiosurgery for epilepsy are for epilepsies associated with space-occupying lesions. These results prompted the authors to investigate the use of radiosurgery as a new way of treating epilepsy not associated with space-occupying lesions.

Methods. To evaluate this new method, 25 patients who presented with drug-resistant mesial temporal lobe epilepsy (MTLE) were selected. A follow up of more than 24 months is now available for 16 patients. The preoperative evaluation was performed as it usually is in patients selected for microsurgery for MTLE. In lieu of microsurgery, the treatment of amygdalohippocampal structures was performed using GKS.

Thirteen (81%) of these 16 patients are seizure free, and two are improved. The median latent interval from GKS to seizure cessation was 10.5 months (range 6–21 months). Two patients were immediately seizure free. The median latency in aura cessation was 15.5 months (range 9–22 months). Morphological changes on magnetic resonance imaging were visible at 11 months (median) after GKS (range 7–22 months). During the onset period of these radiological changes, three patients experienced headache associated, in two cases, with nausea and vomiting. In these three patients the signs resolved immediately after prescription of low doses of steroids. No cases of permanent neurological deficit (except three cases of nonsymptomatic visual field deficit), or morbidity, or mortality were observed.

Conclusions. This initial experience indicates that there is short- to middle-term efficiency and safety when using GKS to treat MTLE. Further long-term follow up is required. It seems that the introduction of GKS into epilepsy treatment can reduce the invasiveness and morbidity.

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Jean Régis, William Pellet, Christine Delsanti, Henry Dufour, Pierre Hughes Roche, Jean Marc Thomassin, Michel Zanaret, and Jean Claude Peragut

Object. Microsurgical excision is an established treatment for vestibular schwannoma (VS). In 1992 the authors used a patient questionnaire to evaluate the functional outcome and quality of life in a series of 224 consecutive patients. In addition, starting with gamma knife surgery (GKS) in 1992, the authors decided to use the same methodology to evaluate prospectively the results of this modality to compare the two alternatives.

Methods. Among the 500 patients who were included prospectively, the authors only evaluated patients in whom GKS was the primary treatment for unilateral VS. Four years of follow up was available for the first 104 consecutive patients. Statistical analysis of the GKS and microsurgery populations has shown that only a comparison of Stage II and III (according to the Koos classification) was meaningful in terms of group size and preoperative risk factor distribution. Objective results and questionnaire answers from the first 97 consecutive patients were compared with the 110 patients in the microsurgery group who fulfilled the inclusion criteria.

Questionnaire answers indicated that 100% of patients who underwent GKS compared with 63% of patients who underwent microsurgery had no new facial motor disturbance. Forty-nine percent of patients who underwent GKS (17% in the microsurgery study) had no ocular symptoms, and 91% of patients treated with GKS (61% in the microsurgery study) had no functional deterioration after treatment. The mean hospitalization stay was 3 days after GKS and 23 days after microsurgery. All the patients who underwent GKS who had been employed, except one, had kept the same professional activity (56% in the microsurgery study). The mean time away from work was 7 days for GKS (130 days in the microsurgery study). Among patients whose preoperative hearing level was Class 1 according to the Gardner and Robertson scale, 70% preserved functional hearing after GKS (Class 1 or 2) compared with only 37.5% in the microsurgery group.

Conclusions. Functional side effects happen during the first 2 years after radiosurgery. Findings after 4 years of follow up indicated that GKS provided better functional outcomes than microsurgery in this patient series.