Microvascular decompression in trigeminal neuralgia: predictors of pain relief, complication avoidance, and lessons learned.

OBJECTIVE: To analyze characteristics associated with long-term pain relief after microvascular decompression (MVD) for trigeminal neuralgia (TGN). Description of associated morbidity and complication avoidance. METHODS: One hundred sixty-five patients with TGN underwent 171 MVD surgeries at the authors' institution. Patient characteristics and magnetic resonance imaging (MRI) datasets were obtained through the hospital's archiving system. Patients provided information about pre- and post-operative pain characteristics and neurologic outcome. Favorable outcome was defined as a Barrow Neurological Institute (BNI) pain intensity score of I to III with post-operative improvement of I grade. RESULTS: Type of TGN pain with purely paroxysmal pain (p = 0.0202*) and TGN classification with classical TGN (p = 0.0372*) were the only significant predictors for long-term pain relief. Immediate pain relief occurred in 90.6% of patients with a recurrence rate of 39.4% after 3.5 ± 4.6 years. MRI reporting of a neurovascular conflict had a low negative predictive value of 39.6%. Mortality was 0% with major complications observed in 8.2% of patients. Older age was associated with lower complication rates (p = 0.0009***). Re-MVD surgeries showed improved long-term pain relief in four out of five cases. CONCLUSIONS: MVD is a safe and effective procedure even in the elderly. It has the unique potential to cure TGN if performed on a regular basis, and if key surgical steps are respected. Early MVD should be offered in case of medical treatment failure and paroxysmal pain symptoms. The presence of a neurovascular conflict on MRI is not mandatory. In case of recurrence, re-MVD is a good treatment option that should be discussed with patients. HIGHLIGHTS: • Long-term analysis of pain relief after MVD. • Positive predictors for outcome: classical TGN and purely paroxysmal pain. • Presence of neurovascular conflict in MRI is not mandatory for MVD surgery. • Analysis of complications and surgical nuances for avoidance. • MVD is a safe procedure also in the elderly.

Novel Software-Derived Workflow in Extracranial-Intracranial Bypass Surgery Validated by Transdural Indocyanine Green Videoangiography.

BACKGROUND: The introduction of image-guided methods to bypass surgery has resulted in optimized preoperative identification of the recipients and excellent patency rates. However, the recently presented methods have also been resource-consuming. In the present study, we have reported a cost-efficient planning workflow for extracranial-intracranial (EC-IC) revascularization combined with transdural indocyanine green videoangiography (tICG-VA). METHODS: We performed a retrospective review at a single tertiary referral center from 2011 to 2018. A novel software-derived workflow was applied for 25 of 92 bypass procedures during the study period. The precision and accuracy were assessed using tICG-VA identification of the cortical recipients and a comparison of the virtual and actual data. The data from a control group of 25 traditionally planned procedures were also matched. RESULTS: The intraoperative transfer time of the calculated coordinates averaged 0.8 minute (range, 0.4-1.9 minutes). The definitive recipients matched the targeted branches in 80%, and a neighboring branch was used in 16%. Our workflow led to a significant craniotomy size reduction in the study group compared with that in the control group (P = 0.005). tICG-VA was successfully applied in 19 cases. An average of 2 potential recipient arteries were identified transdurally, resulting in tailored durotomy and 3 craniotomy adjustments. Follow-up patency results were available for 49 bypass surgeries, comprising 54 grafts. The overall patency rate was 91% at a median follow-up period of 26 months. No significant difference was found in the patency rate between the study and control groups (P = 0.317). CONCLUSIONS: Our clinical results have validated the presented planning and surgical workflow and support the routine implementation of tICG-VA for recipient identification before durotomy.

An experimental animal model for percutaneous procedures used in trigeminal neuralgia.

OBJECT: This study describes an experimental rabbit model that allows the reproduction of percutaneous operations that are used in patients with trigeminal neuralgia (TN). Attention was given to an exact anatomical description of the rabbit's middle cranial fossa as well as the establishment of conditions for a successful procedure. METHODS: Morphometric measurements were taken from 20 rabbit skulls and CT scans. The anatomy of the trigeminal nerve, as well as its surrounding structures, was assessed by bilateral dissection of 13 New Zealand white rabbits (NWR). An ideal approach of placing a needle through the foramen ovale to reach the TG was sought. Validation of correct placement was realized by fluoroscopy and confirmed by dissection. RESULTS: Precise instructions for successful reproduction of percutaneous procedures in NWR were described. According to morphological measurements, for balloon compression of the trigeminal ganglion (TG) the maximal diameter of an introducing cannula is 1.85 mm. The diameter of an empty balloon catheter should not exceed 1.19 mm, and the length of the inflatable part of the balloon can range up to 4 mm. For thermocoagulation the needle electrodes must not exceed an external diameter of 1.39, mm and the length of the non-insolated tip can range up to 4 mm. Glycerol rhizolysis can be achieved because the trigeminal cistern in the NWR is a closed space that allows a long dwelling time (>10 min) of the contrast agent. CONCLUSIONS: An experimental NWR model intended for the reproduction of percutaneous procedures on the TG has been meticulously described. This provides a tool that enables further standardized animal research in the field of surgical treatment of TN.

Direct percutaneous puncture approach versus surgical cutdown technique for intracranial neuroendovascular procedures: technical aspects.

OBJECTIVE: To present the authors' experience with a direct transcervical or transbrachial puncture approach in neuroendovascular procedures in which cranial access via the commonly used percutaneous transfemoral route was impossible because of tortuous upstream angioarchitecture. METHODS: During 1992-2007, 23 neuroendovascular procedures were performed in 21 patients via a direct puncture approach. In 12 patients, surgical cutdown (SCD) and cannulation of the targeted artery (carotid, n = 8; vertebral, n = 4) were done. A direct percutaneous puncture (PP) of either the carotid (n = 5) or the brachial (n = 4) artery was done in nine patients. Treated pathologies were as follows: 10 ruptured and 6 unruptured cerebral aneurysms including two stent-assisted coiling and one internal carotid artery (ICA) balloon occlusion, four brain arteriovenous malformations (AVMs) and one carotid cavernous fistula (CCF). RESULTS: Of 21 patients, 19 (90.5%) had a direct puncture introduction of the microcatheter and successful endovascular procedure. No complications related to the technique were encountered either in the PP or in the SCD group. CONCLUSIONS: Transcervical or transbrachial direct puncture accomplished with PP or by SCD is an effective and safe access route in patients in whom neuroendovascular interventions cannot be done transfemorally. In cases where extensive perioperative anticoagulation is mandatory, bleeding at the puncture site may be a serious problem and can be controlled more effectively through an open surgical approach than by percutaneous maneuvers.

A simple method for evaluating the quality of microvascular anastomoses performed in vitro.

OBJECTIVE: The aim of this paper is to describe a simple and effective method for evaluating the quality of microvascular anastomoses performed in vitro. METHODS: After the microvascular anastomosis has been performed in vitro, the vessel is cannulated at a distance of several millimeters from the anastomosis site with a catheter that is connected to a syringe filled with commercially available silicone glue. The silicone glue is slowly injected into the artery until the whole specimen is filled. Small leaks at the anastomosis site can be seen directly as the silicone glue will slowly extrude at the point of a leak. Then, the catheter is withdrawn and the specimen, filled with silicone, is left for several hours to solidify. Subsequently, the specimen is immersed in H(2)O(2) for several hours in order to dissolve the tissue from the silicone cast. In this manner, the cast of the silicone represents the virtual lumen of the blood vessel and the print of the lumen surface. RESULTS: Using this method, several important technical aspect of the anastomosis can be easily evaluated, such as diameter differences of the blood vessel, stricture, narrowing, irregularities of the vessel wall, leakage through the anastomotic site, and the alignment of the vessel walls. CONCLUSION: The silicone cast method as described in this study can be used to evaluate some technical aspect of a microvascular anastomosis performed in vitro. Moreover, it can be used to monitor the progress of the trainee and as an aid in improving and mastering vascular microsurgery.

Age-related increase of kynurenic acid in human cerebrospinal fluid - IgG and beta2-microglobulin changes.

Kynurenic acid (KYNA) is an endogenous metabolite in the kynurenine pathway of tryptophan degradation and is an antagonist at the glycine site of the N-methyl-D-aspartate as well as at the alpha 7 nicotinic cholinergic receptors. In the brain tissue KYNA is synthesised from L-kynurenine by kynurenine aminotransferases (KAT) I and II. A host of immune mediators influence tryptophan degradation. In the present study, the levels of KYNA in cerebrospinal fluid (CSF) and serum in a group of human subjects aged between 25 and 74 years were determined by using a high performance liquid chromatography method. In CSF and serum KAT I and II activities were investigated by radioenzymatic assay, and the levels of beta(2)-microglobulin, a marker for cellular immune activation, were determined by ELISA. The correlations between neurochemical and biological parameters were evaluated. Two subject groups with significantly different ages, i.e. <50 years and >50 years, p < 0.001, showed statistically significantly different CSF KYNA levels, i.e. 2.84 +/- 0.16 fmol/microl vs. 4.09 +/- 0.14 fmol/microl, p < 0.001, respectively; but this difference was not seen in serum samples. Interestingly, KYNA is synthesised in CSF principally by KAT I and not KAT II, however no relationship was found between enzyme activity and ageing. A positive relationship between CSF KYNA levels and age of subjects indicates a 95% probability of elevated CSF KYNA with ageing (R = 0.6639, p = 0.0001). KYNA levels significantly correlated with IgG and beta(2)-microglobulin levels (R = 0.5244, p = 0.0049; R = 0.4253, p = 0.043, respectively). No correlation was found between other biological parameters in CSF or serum. In summary, a positive relationship between the CSF KYNA level and ageing was found, and the data would suggest age-dependent increase of kynurenine metabolism in the CNS. An enhancement of CSF IgG and beta(2)-microglobulin levels would suggest an activation of the immune system during ageing. Increased KYNA metabolism may be involved in the hypofunction of the glutamatergic and/or nicotinic cholinergic neurotransmission in the ageing CNS.