Trigeminal nerve

Randomized controlled trial of trigeminal nerve stimulation for drug-resistant epilepsy..

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To explore the safety and efficacy of external trigeminal nerve stimulation (eTNS) in patients with drug-resistant epilepsy (DRE) using a double-blind randomized controlled trial design, and to test the suitability of treatment and control parameters in preparation for a phase III multicenter clinical trial.

METHODS: This is a double-blind randomized active-control trial in DRE. Fifty subjects with 2 or more partial onset seizures per month (complex partial or tonic-clonic) entered a 6-week baseline period, and then were evaluated at 6, 12, and 18 weeks during the acute treatment period. Subjects were randomized to treatment (eTNS 120 Hz) or control (eTNS 2 Hz) parameters.
RESULTS: At entry, subjects were highly drug-resistant, averaging 8.7 seizures per month (treatment group) and 4.8 seizures per month (active controls). On average, subjects failed 3.35 antiepileptic drugs prior to enrollment, with an average duration of epilepsy of 21.5 years (treatment group) and 23.7 years (active control group), respectively. eTNS was well-tolerated. Side effects included anxiety (4%), headache (4%), and skin irritation (14%). The responder rate, defined as >50% reduction in seizure frequency, was 30.2% for the treatment group vs 21.1% for the active control group for the 18-week treatment period (not significant, p = 0.31, generalized estimating equation [GEE] model). The treatment group experienced a significant within-group improvement in responder rate over the 18-week treatment period (from 17.8% at 6 weeks to 40.5% at 18 weeks, p = 0.01, GEE). Subjects in the treatment group were more likely to respond than patients randomized to control (odds ratio 1.73, confidence interval 0.59-0.51). eTNS was associated with reductions in seizure frequency as measured by the response ratio (p = 0.04, analysis of variance [ANOVA]), and improvements in mood on the Beck Depression Inventory (p = 0.02, ANOVA).
CONCLUSIONS: This study provides preliminary evidence that eTNS is safe and may be effective in subjects with DRE. Side effects were primarily limited to anxiety, headache, and skin irritation. These results will serve as a basis to inform and power a larger multicenter phase III clinical trial. CLASSIFICATION OF EVIDENCE: This phase II study provides Class II evidence that trigeminal nerve stimulation may be safe and effective in reducing seizures in people with DRE.

Source: Neurology

Foramen ovale puncture, lesioning accuracy, and avoiding complications: microsurgical anatomy study with clinical implications.

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Abstract

OBJECT

Foramen ovale (FO) puncture allows for trigeminal neuralgia treatment, FO electrode placement, and selected biopsy studies. The goals of this study were to demonstrate the anatomical basis of complications related to FO puncture, and provide anatomical landmarks for improvement of safety, selective lesioning of the trigeminal nerve (TN), and optimal placement of electrodes.

METHODS

Both sides of 50 dry skulls were studied to obtain the distances from the FO to relevant cranial base references. A total of 36 sides from 18 formalin-fixed specimens were dissected for Meckel cave and TN measurements. The best radiographic projection for FO visualization was assessed in 40 skulls, and the optimal trajectory angles, insertion depths, and topographies of the lesions were evaluated in 17 specimens. In addition, the differences in postoperative pain relief after the radiofrequency procedure among different branches of the TN were statistically assessed in 49 patients to determine if there was any TN branch less efficiently targeted.

RESULTS

Most severe complications during FO puncture are related to incorrect needle placement intracranially or extracranially. The needle should be inserted 25 mm lateral to the oral commissure, forming an approximately 45° angle with the hard palate in the lateral radiographic view, directed 20° medially in the anteroposterior view. Once the needle reaches the FO, it can be advanced by 20 mm, on average, up to the petrous ridge. If the needle/radiofrequency electrode tip remains more than 18 mm away from the midline, injury to the cavernous carotid artery is minimized. Anatomically there is less potential for complications when the needle/radiofrequency electrode is advanced no more than 2 mm away from the clival line in the lateral view, when the needle pierces the medial part of the FO toward the medial part of the trigeminal impression in the petrous ridge, and no more than 4 mm in the lateral part. The 40°/45° inferior transfacial–20° oblique radiographic projection visualized 96.2% of the FOs in dry skulls, and the remainder were not visualized in any other projection of the radiograph. Patients with V1 involvement experienced postoperative pain more frequently than did patients with V2 or V3 involvement. Anatomical targeting of V1 in specimens was more efficiently achieved by inserting the needle in the medial third of the FO; for V2 targeting, in the middle of the FO; and for V3 targeting, in the lateral third of the FO.

CONCLUSIONS

Knowledge of the extracranial and intracranial anatomical relationships of the FO is essential to understanding and avoiding complications during FO puncture. These data suggest that better radiographic visualization of the FO can improve lesioning accuracy depending on the part of the FO to be punctured. The angles and safety distances obtained may help the neurosurgeon minimize complications during FO puncture and TN lesioning.

Source: JNS

 

Long-term outcome of high-dose Gamma Knife surgery in treatment of trigeminal neuralgia.

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Abstract

OBJECT

Despite the widespread use of Gamma Knife surgery (GKS) for trigeminal neuralgia (TN), controversy remains regarding the optimal treatment dose and target site. Among the published studies, only a few have focused on long-term outcomes (beyond 2 years) using 90 Gy, which is in the higher range of treatment doses used (70–90 Gy).

METHODS

The authors followed up on 315 consecutive patients treated with the Leksell Gamma Knife unit using a 4-mm isocenter without blocks. The isocenter was placed on the trigeminal nerve with the 20% isodose line tangential to the pontine surface (18 Gy). At follow-up, 33 patients were deceased; 282 were mailed an extensive questionnaire regarding their outcomes, but 32 could not be reached. The authors report their analysis of the remaining 250 cases. The patients’ mean age at the time of survey response and the mean duration of follow-up were 70.8 ± 13.1 years and 68.9 ± 41.8 months, respectively.

RESULTS

One hundred eighty-five patients (85.6%) had decreased pain intensity after GKS. Modified Marseille Scale (MMS) pain classifications after GKS at follow-up were: Class I (pain free without medication[s]) in 104 (43.7%), Class II (pain free with medication[s]) in 66 (27.7%), Class III (> 90% decrease in pain intensity) in 23 (9.7%), Class IV (50%–90% decrease in pain intensity) in 20 (8.4%), Class V (< 50% decrease in pain intensity) in 11 (4.6%), and Class VI (pain becoming worse) in 14 (5.9%). Therefore, 170 patients (71.4%) were pain free (Classes I and II) and 213 (89.5%) had at least 50% pain relief. All patients had pain that was refractory to medical management prior to GKS, but only 111 (44.4%) were being treated with medication at follow-up (p < 0.0001). Eighty patients (32.9%) developed numbness after GKS, and 74.5% of patients with numbness had complete pain relief. Quality of life and patient satisfaction on a 10-point scale were reported at mean values (± SD) of 7.8 ± 3.1 and 7.7 ± 3.4, respectively. Most of the patients (87.7%) would recommend GKS to another patient. Patients with prior surgical treatments had increased latency to pain relief and were more likely to continue medicines (p < 0.05). Moreover, presence of altered facial sensations prior to radiosurgery was associated with higher pain intensity, longer pain episodes, more frequent pain attacks, worse MMS pain classification, and more medication use after GKS (p < 0.05). Conversely, increase in numbness intensity after GKS was associated with a decrease in pain intensity and pain length (p < 0.05).

CONCLUSIONS

Gamma Knife surgery using a maximum dose of 90 Gy to the trigeminal nerve provides satisfactory long-term pain control, reduces the use of medication, and improves quality of life. Physicians must be aware that higher doses may be associated with an increase in bothersome sensory complications. The benefits and risks of higher dose selection must be carefully discussed with patients, since facial numbness, even if bothersome, may be an acceptable trade-off for patients with severe pain.

Source: JNS

 

Endoscopic approaches to the trigeminal nerve and clinical consideration for trigeminal schwannomas: a cadaveric study.

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The course of the trigeminal nerve straddles multiple fossae and is known to be very complex. Comprehensive anatomical knowledge and skull base techniques are required for surgical management of trigeminal schwannomas. The aims of this study were to become familiar with the endoscopic anatomy of the trigeminal nerve and to develop a minimally invasive surgical strategy for the treatment of trigeminal schwannomas.

Methods

Ten fresh cadavers were studied using 5 endoscopic approaches with the aid of 4-mm 0° and 30° endoscopes to identify surgical landmarks associated with the trigeminal nerve. The endoscopic approaches included 3 transcranial keyhole approaches (the extradural supraorbital, extradural subtemporal, and retrosigmoid approaches), and 2 endonasal approaches (the transpterygoid and the transmaxillary transpterygoid approaches).

Results

The trajectories of the extradural supraorbital, transpterygoid, and extradural subtemporal approaches corresponded with the course of the first, second, and third divisions of the trigeminal nerve, respectively. The 3 approaches demonstrated each division in intra- and extracranial spaces, as well as the Meckel cave in the middle cranial fossa. The interdural space at the lateral wall of the cavernous sinus was exposed by the extradural supraorbital and subtemporal approaches. The extradural subtemporal approach with anterior petrosectomy and the retrosigmoid approach visualized the trigeminal sensory root and its neighboring neurovascular structures in the posterior cranial fossa. The transmaxillary transpterygoid approach revealed the course of the third division in the infratemporal fossa.

Conclusions

The 5 endoscopic approaches effectively followed the course of the trigeminal nerve with minimal invasiveness. These approaches could provide alternative options for the management of trigeminal schwannoma.

Source: Journal of Neurosurgery.