Compression In Trigeminal Neuralgia Research Articles

Letter to the Editor Regarding “Outcomes After Microvascular Decompression for Sole Arterial versus Venous Compression in Trigeminal Neuralgia”

Letter to the Editor Regarding “Outcomes After Microvascular Decompression for Sole Arterial versus Venous Compression in Trigeminal Neuralgia”

Different MRI-based methods for the diagnosis of neurovascular compression in trigeminal neuralgia or hemifacial spasm: A network meta-analysis

BackgroundAccurate preoperative diagnosis of neurovascular compression (NVC) is crucial in the treatment of trigeminal neuralgia (TN) or hemifacial spasm (HFS). At present, there are many magnetic resonance imaging (MRI)-based methods for diagnosing NVC in clinical practice. This network meta-analysis (NMA) aimed to evaluate the diagnostic performance of different MRI-based imaging methods for NVC in patients with TN and HFS. Materials and methodsRelated studies based on a search of PubMed, Embase, Web of Science and the Cochrane Library were retrieved. A two-way analysis of variance model was constructed for the Bayesian NMA to compare the performance of different diagnostic imaging methods. ResultsOur search identified 595 articles, of which 26 studies (including 2085 patients) related to 4 diagnostic imaging methods (3D time-of-flight magnetic resonance angiography (3D TOF MRA), high resolution T2-weighted imaging (HR T2WI), 3D TOF MRA combined with HR T2WI, and 3D multimodal image fusion (MIF) based on 3D TOF MRA combined with HR T2WI) were included in this NMA. The results showed that 3D MIF based on 3D TOF MRA combined with HR T2WI had the highest related sensitivity, the highest superiority index and the largest area under the receiver operating characteristic curve among all the methods. Conclusions3D MIF based on 3D TOF MRA combined with HR T2WI had better diagnostic performance for detecting NVC in patients with TN or HSF than other MRI-based imaging methods. This method can be used as an effective tool for preoperative evaluation of MVD.

Multivariate models to predict pain recurrence and sensitive complications after percutaneous balloon compression in trigeminal neuralgia.

Percutaneous balloon compression (PBC) is a popular treatment option for trigeminal neuralgia. However, the efficacy of PBC is widely considered to be associated with the occurrence of sensitive complications, although neither this correlation nor the underlying mechanisms have been established. The objectives of the present study were to identify factors predicting time to pain recurrence after PBC and identify factors predicting a severe sensitive complication. The authors conducted a retrospective study on patients who underwent PBC for the first time between 1985 and 2019 in two French hospitals. Data were retrieved from patients' medical records. Potential clinical and radiological predictors for time to pain recurrence and severe sensitive complication were evaluated using a Cox model and a logistic regression, respectively. A total of 131 patients were included in the study, with a median follow-up of 3.0 years. Pain recurrence occurred in 77 patients, and the median time to pain recurrence was 2.0 years. In the multivariate analysis, six independent factors predicting pain recurrence were identified: 1) longer duration of presurgical symptoms; 2) localization of the pain along the mandibular branch of the trigeminal nerve (V3); 3) atypical pain; 4) diagnosis of multiple sclerosis; 5) use of a medical device not specifically adapted for trigeminal neuralgia surgery; and 6) duration of balloon compression > 60 seconds. Regarding the secondary objective, 26 patients presented a severe sensitive complication after PBC, which the authors defined as the development of a new sensitivity disorder of the cornea, deafferentation pain known as anesthesia dolorosa, and/or long-lasting hypoesthesia augmentation characterized by the new appearance or increase in size or intensity of an area of hypoesthesia in the face for at least 3 months. The only predictor associated with a severe sensitive complication in the multivariate analysis was compression duration > 60 seconds. These results show that the risk of postoperative complications can be assessed at the patient level, the most important modifiable parameter being the time of compression by the balloon. Although this study shows the relevance of a personalized medicine approach, its clinical application remains to be validated.

Purely venous compression in trigeminal neuralgia—can we predict the outcome of surgery

PurposeControversies regarding venous compression and trigeminal neuralgia (TN) still exist. The study demonstrates our experience for microvascular decompression (MVD) in TN caused by purely venous compression. The goal was to identify prognostic anatomical or surgical factors that may influence the outcome.MethodsBetween 2004 and 2020, 49 patients were operated with purely venous compression. Average age was 58.4 years. Mean history of TN was 7.8 years. Microsurgical procedures included transposition or separation of the vein, coagulation, and division. Several features have been analyzed with respect to BNI scores.ResultsEvaluation on discharge revealed a complete pain relief in 39 (80%), partial improvement in 7 (14%), and no benefit in 3 (6%) patients. Facial hypesthesia was reported by 14 (28.6%) patients. Mean follow-up (FU) was 42.1 months. BNI pain intensity score on FU revealed 71.4% excellent to very good scores (score 1: 32 (65.3%); 2: 3 (6.1%)). BNI facial numbness score 2 could be detected in 13 patients (26.5%) during FU. There was no statistical relationship between immediate pain improvement or BNI pain intensity score on FU with respect to surgical procedure, size of trigeminal cistern, type of venous compression, venous caliber, trigeminal nerve indentation, or neurovascular adherence. BNI facial numbness score was dependent on type of venous compression (p < 0.05).ConclusionWe did not find typical anatomical features that could either predict or influence the outcome regarding pain improvement or resolution in any form. Neither classic microvascular decompression (interposition/transposition) nor sacrificing the offending vein made any difference in outcome.

Efficacy of microvascular decompression in patients with trigeminal neuralgia with negative neurovascular relationship shown by magnetic resonance tomography

ObjectiveTo explore the surgical efficacy of microvascular decompression(MVD) when the recent magnetic resonance tomography angiography(MRA) is unable to determine the relationship between blood vessels and nerves in patients with trigeminal neuralgia(TN). Materials and methodsThe MRI images of 146 patients with TN who underwent MVD from January 2016 to December 2019 were analyzed retrospectively. The relationship between nerves and vessels was categorized as no contact, suspicious contact, and clear contact. Suspicious contact and clear contact were both defined as positive neurovascular relationship, whereas no contact was defined as negative neurovascular relationship. The efficacy of MVD in positive and negative groups was compared. Results1. A total of 146 TN patients underwent MVD. Intraoperative examination revealed that out of 146, 143 patients exhibited contacts, including 110 cases with arterial contact, 22 cases with combined arterial and venous contact, and 11 cases with venous contact. Considering the surgical result as a gold standard, the sensitivity of three-dimensional time leap angiography (3D-TOF-MRA) in assessing vascular compression in TN was 74.0 %; and the sensitivity of three-dimensional steady-state precession rapid imaging sequence (3D-FIESTA) in determining vascular compression was 82.2 %. Out of a total of 17 cases demonstrating negative neurovascular relationship by 3D-TOF-MRA together with 3D-FIESTA, 14 cases were found to have vascular contact during the surgery, and the sensitivity was determined to be 88.4 %. 2.Among the 38 patients with a negative neurovascular relationship demonstrated by 3D-TOF, postoperative efficacy was noted as a cure: 30 cases, improved: 5 cases, no effect: 3 cases. 3D-FIESTA showed 26 cases of negative neurovascular relationship, among them, cured: 20 cases, improved: 3 cases, no effect: 3 cases. A total of 17 patients with negative neurovascular relationships were established by 3D-TOF-MRA together with 3D-FIESTA, and the postoperative effects were found to be cure: 13 cases, improvement: 2 cases, and no effect: 2 cases. There was no statistically significant difference between the negative group and the positive group (x2 test; p > 0.05). ConclusionTo conclude, 3D-TOF-MRA, together with 3D-FIESTA, can illustrate the large blood vessels surrounding the trigeminal nerve efficiently, and determine whether it is the offending blood vessel. The interpretation would help reproduce the local anatomical spatial structure of the site before surgery, yet it is impossible to assess the peripheral anatomical relationship of the trigeminal nerve cistern comprehensively and accurately. This hints that a perfect prediction of the surgical effect of MVD is not possible at present. Thus, typical symptoms of TN are the most critical indicators for MVD surgery.

Sensitivity of magnetic resonance tomographic angiography for detecting the degree of neurovascular compression in trigeminal neuralgia

PurposeNeurovascular compression (NVC) is hypothesized to be the main pathogenic factor of trigeminal neuralgia (TN). Microvascular decompression (MVD) has become a popular surgery for TN, and the success rate depends on the degree of NVC. As the routine examination before MVD, magnetic resonance tomographic angiography (MRTA) shows high sensitivity for detecting NVC. However, there are no reports on the sensitivity of MRTA for assessing the degree of NVC.MethodsThis study aimed to evaluate the sensitivity of MRTA for determining the degree of NVC by comparing preoperative MRTA and intraoperative endoscopy findings. A total of 480 patients who suffered from TN and underwent MVD were included. Their preoperative MRTA and intraoperative endoscopy findings were reviewed. The kappa test was used to identify similarities between the MRTA and endoscopy findings.ResultsThe degree of NVC on preoperative MRTA was similar to that on endoscopy (kappa = 0.770). The number of offending vessels according to preoperative MRTA was coincident with that according to endoscopy (kappa = 0.722).ConclusionMRTA had high sensitivity for detecting not only the presence of NVC but also the degree of NVC.

Role of Fused Three-Dimensional Time-of-Flight Magnetic Resonance Angiography and 3-Dimensional T2-Weighted Imaging Sequences in Neurovascular Compression

To evaluate role of fused 3-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) and 3-dimensional constructive interference in steady state (3D-CISS) in neurovascular compression in trigeminal neuralgia (TN) and hemifacial spasm (HFS). A prospective study was conducted on 30 patients (mean age 47.20 ± 11.69 years), 17(56.7%) male and 13 (43.3%) female, with TN and HFS. 3D-TOF-MRA and 3D-CISS sequences of the cerebellopontine angle were performed, as well as postprocessing with fusion of the images. Two independent readers assessed the degree of neurovascular conflict. The images were evaluated for site, signal, and degree of nerve compression and the offending vessel. The kappa test for interobserver agreement was done. The interobserver agreement of both readers was excellent for degree of compression (k= 0.70, 95% confidence interval [CI] 0.49-0.92, r= 0.856, P= 0.001), excellent for the side affected (k= 1.0, 95% CI= 1.0-1.0, r= 1.000, P= 0.001), excellent for the offending vessel (k= 0.85, 95% CI= 0.66-1.0, P= < 0.001), and excellent for the position of the offending vessel (k= 0.685, 95% CI= 0.489-0.882, r= 0.863, P ≤ 0.001). There was no significant correlation between the degree of compression and signal intensity. Fused 3D-TOF-MRA and 3D-CISS images are a reliable, noninvasive tool for the evaluation of offending vessel and degree of affection in patients with neurovascular compression. MRA-CISS can be used for evaluation and treatment planning of neurovascular compression in TN and HFS.

Computational Fluid Dynamics Analysis of the Offending Artery at Sites of Neurovascular Compression in Trigeminal Neuralgia Using Preoperative MRI Data.

This study aimed to analyze the hemodynamic features of the offending artery at sites of neurovascular compression (NVC) using computational fluid dynamics (CFD). A total of 23 patients who underwent microvascular decompression (MVD) for primary trigeminal neuralgia (TN) between January 2015 and December 2016 were enrolled in this study. The compressing vessel at the NVC site was identified microsurgically in all cases, and patients were divided into two groups based on the intraoperative findings: (1) the arterial NVC group and (2) the non-arterial NVC control group. A 3D surface model of the structures surrounding the NVC was created using preoperative magnetic resonance imaging (MRI), and CFD analysis was performed for the target artery. In addition to standard parameters, such as the wall shear stress (WSS), flow velocity, and pressure, we calculated the WSS ratio (WSSR) by dividing the WSS at the NVC by the mean WSS of the target. Arterial compression was observed intraoperatively in 13 patients. The mean WSSR of the arterial NVC group was significantly higher than that of the control group (2.36 ± 1.00 vs. 1.18 ± 0.73, P <0.05). There were no significant intergroup differences in the other calculated parameters. High WSSR, which indicates elevated WSS at the sites of NVC, was identified as a unique parameter of arterial compression that may contribute to TN. CFD could be a useful clinical tool in determining the target of MVD under preoperative conditions.

Contrast-Enhanced CISS Imaging for Evaluation of Neurovascular Compression in Trigeminal Neuralgia: Improved Correlation with Symptoms and Prediction of Surgical Outcomes.

Thin-section MR imaging through the posterior fossa is frequently used for trigeminal neuralgia. Typical heavily T2-weighted imaging methods yield high anatomic detail and contrast between CSF and neurovascular structures, but poor contrast between vessels and nerves. We hypothesized that the addition of gadolinium-based contrast material to 3D-constructive interference in steady-state imaging would improve the characterization of trigeminal compression. Retrospective review of high-resolution MRIs was performed in patients without prior microvascular decompression. 3D-CISS imaging without contrast and with contrast for 81 patients with trigeminal neuralgia and 15 controls was intermixed and independently reviewed in a blinded fashion. Cisternal segments of both trigeminal nerves were assessed for the grade of neurovascular conflict, cross-sectional area, and degree of flattening. Data were correlated with symptom side and pain relief after microvascular decompression using the Fisher exact test, receiver operating curve analysis, and a paired t test. Contrast-enhanced CISS more than doubled the prevalence of the highest grade of neurovascular conflict (14.8% versus 33.3%, P = .001) and yielded significantly lower cross-sectional area (P = 8.6 × 10-6) and greater degree of flattening (P = .02) for advanced-grade neurovascular conflict on the symptoms side compared with non-contrast-enhanced CISS. Patients with complete pain relief after microvascular decompression had significantly lower cross-sectional area on contrast-enhanced CISS compared with non-contrast-enhanced CISS on preoperative imaging (P = 2.0 × 10-7). Performance based on receiver operating curve analysis was significantly improved for contrast-enhanced CISS compared with non-contrast-enhanced CISS. The addition of contrast material to 3D-CISS imaging improves the performance of identifying unilateral neurovascular compression for symptomatic trigeminal neuralgia and predicting outcomes after microvascular decompression.

The role of neurovascular compression in trigeminal neuralgia

The role of neurovascular compression in trigeminal neuralgia

177 Microstructural Neural Changes Due to Neurovascular Compression in Trigeminal Neuralgia Detcted by Diffusion Tensor Imaging (DTI

177 Microstructural Neural Changes Due to Neurovascular Compression in Trigeminal Neuralgia Detcted by Diffusion Tensor Imaging (DTI

The Anatomy of Vascular Compression in Trigeminal Neuralgia (P07.051)

The Anatomy of Vascular Compression in Trigeminal Neuralgia (P07.051)

The anatomy of vascular compression in trigeminal neuralgia

The etiological basis of trigeminal neuralgia (TN) is unknown but vascular (arterial and venous) compression of the trigeminal nerve roots has emerged as the likely cause in most cases. Here we examine the evidence for the "brain sagging/arterial elongation hypothesis" with reference to the cerebral arteries and veins believed to cause the compression. Most often implicated are the superior cerebellar artery, the anterior and posterior inferior cerebellar arteries, and the superior petrosal vein including several of its tributaries. The reviewed data suggest that the theoretical support for a vascular compressive etiology of TN is weak, albeit the surgical outcome data are relatively convincing.

Preoperative demonstration of neurovascular compression in trigeminal neuralgia with contrast - enhanced 3D - SPGR sequence

Objective To assess the value of contrast - enhanced three - dimensional spoiled gradient recalled (3D - SPGR ) sequence in the preoperative visualization of neurovascular compression (NVC) in patients with trigeminal neuralgia(TN) and to evaluate the relationship between clinical symptoms of neuralgia related to trigeminal branches and the sites of trigeminal nerve compression.Method Thirty -seven patients(21 males,16 females; the age ranged from 26 to 81 years with a mean age of 55.3 years) with unilateral typical TN underwent preoperative contrast - enhanced 3D - SPGR sequence.The vascular contact with the trigeminal nerve at the root entry zone (REZ) was reviewed by an experienced neuroradiologist,who was blinded to the clinical details.The imaging results were compared with the operative findings and clinical symptoms related to trigeminal branches in patients.Results In 37 patients with TN,contrast - enhanced 3D - SPGR sequence identified surgically verified neurovascular contact in 35 of 36 symptomatic nerves.Based on surgical findings,the sensitivity of MR imaging was 97.2％ and the specificity 100％.Agreement between the position ( medial,lateral,cranial,and caudal) of the compressing vessel relative to the trigeminal nerve defined by MR imaging and findings at surgery was good( K =0.81 ;95％ confidence interval,0.56 ～ 1.00).Twelve(85.7％ ) of 14 patients with symptoms related to the maxillary division had their NVC at the medial site of the REZ.Thirteen(81.3％ ) of 16 patients with symptoms related to the mandibular division had their NVC at the lateral site of the REZ.A statistically significant difference was observed between the NVC site and the clinically manifested symptoms in the branches of the trigeminal nerve( P ＜ 0.001 ).Conclusions Contrast - enhanced 3D - SPGR sequence is useful in detection of NVC in patients with TN.Anatomic relationships defined by this method may be useful in predicting surgical findings. Key words: Magnetic resonance imaging; Microvascular decompression; Neurovascular compression; Trigeminal neuralgia; Comparative studies

Séquences IRM pour la détection des conflits vasculonerveux à l’origine de la névralgie trigéminale et leur valeur prédictive pour la caractérisation du conflit (en particulier le degré de la compression vasculaire)

Background and purpose A long-term study of the results on trigeminal neuralgia (TN) after microsurgical vascular decompression (Kaplan-Meier curves at 20 years) showed that cure was achieved in 88.1 % of the patients with a neurovascular compression (NVC) producing a large groove on the nerve (Grade III), 78.3 % of the patients with a NVC with nerve distortion or displacement (Grade II), and 58.3 % of the patients with a NVC with simple contact on the nerve (Grade I). Therefore, preoperative visualization of the NVC by MRI and determination of its grading are important for the therapeutic decision. In this study, we investigated the predictive value of MRI for detecting and assessing the degree of vascular compression in trigeminal neuralgia. Methods The study included 91 consecutive patients with a preoperative MRI (1.5 Testa) using 3D T2-weighted and angio–MR–TOF. NVC prediction and the degree of compression made by an independent observer were correlated with surgical data. Results Eighty of the 91 patients had a NVC on MRI, but 83 (91.2 %) patients showed a NVC at surgical exploration (eight patients had no NCV). Thus, the sensitivity of imaging in detecting a NVC on the symptomatic nerves was 96 % (80/83) and the specificity 100 % (8/8). In addition, imaging analysis predicted the responsible vessel in 88.7 % (71/80) of the cases and characterized the degree of NVC in 85 % (68/80). The Kappa-coefficient (KC) for prediction of the NVC degree was 0.795 for arterial and venous compressions together ( p < 0.01; 95 % confidence interval, 0.71–0.88). The CK was 0.758 ( p < 0.01, good agreement) for grade I, 0.787 ( p < 0.01, good agreement) for grade II and 0.824 ( p < 0.01, excellent agreement) for grade III. Conclusions High-resolution 3D T2-weighted imaging in combination with angio–MR–TOF is a reliable technique for detecting NVC and predicting the degree of the compression in NVC.

Preoperative visualization of neurovascular anatomy in trigeminal neuralgia

The authors report on a novel technique to identify neurovascular compression in trigeminal neuralgia (TN). Using 3D reconstructed high-resolution balanced fast-field echo (BFFE) images fused with 3D time-of-flight (TOF) magnetic resonance (MR) angiography and Gd-enhanced 3D spoiled gradient recalled sequence, it is possible to objectively visualize the trigeminal nerve and nearby arteries and veins. Magnetic resonance imaging was performed in 18 patients with unilateral TN using 3 sequences: BFFE, 3D TOF angiography, and 3D Gd-enhanced imaging. The images were imported into OsiriX imaging software; after their fusion, a 3D false-color reconstruction was produced using surface rendering. The reconstructed images objectively differentiate nerves and vessels and can be viewed from any angle, including the anticipated surgical approach. Fifteen patients were predicted to have neurovascular compression on the symptomatic side (9 arterial and 6 venous compressions). All patients had a vascular structure that was identical in location and configuration to that predicted on preoperative analysis. The 3 patients without predicted compression underwent surgical exploration because they manifested the classic symptoms. As expected, exploration in 2 of these patients revealed no offending vessel. The third patient had a small vein embedded in the trigeminal nerve that was beyond the resolution of the 3D Gd-enhanced study. Combining BFFE with MR angiography and Gd-enhanced MR images capitalizes on the advantages of both techniques, enabling MR angiography and contrast-enhanced MR imaging discrimination of vascular structures at BFFE resolution. This results in an unambiguous 3D image that can be used to identify the neurovascular compression and plan the surgical approach.

Demonstration of neurovascular compression in trigeminal neuralgia and hemifacial spasm with magnetic resonance imaging: Comparison with surgical findings in 60 consecutive cases

Background Until recently, it has been impossible to demonstrate vascular compression at the root entry or exit zone (REZ) of the trigeminal nerve and facial nerve in patients with trigeminal neuralgia (TN) and hemifacial spasm (HFS) preoperatively, although surgical findings have revealed apparent neurovascular compression and its correction has resulted in a good outcome in most cases. Revealing the anatomic correlation between nerves and vessels at the REZ preoperatively would be useful to predict operative findings. Methods To assess whether the vascular contact of the nerve at the REZ could be demonstrated preoperatively, high-resolution magnetic resonance tomographic angiography (MRTA) was performed in 21 patients with TN and 39 with HFS. Neuroradiological findings were compared with the operative findings in all patients. Contralateral asymptomatic nerves were evaluated as a control. Results MRTA correctly identified offending vessels in 14 (67%) of the 21 TN and 34 (87%) of the 39 HFS patients. Failure to identify neurovascular contact was noted in the cases with compression by veins or small arteries, thickened arachnoid, or distal compression. Neurovascular contact was also observed in 15% of the asymptomatic nerves. The deformity of the nerve seemed to be a more important factor for determining operative indication. Conclusions MRTA could demonstrate offending vessels in TN and HFS at a high rate and was useful to predict operative findings. MRTA gave supportive evidence of surgical indications in patients with TN and HFS, although attention should be paid to the fact that MRTA did not necessarily detect all of the offending vessels.

How accurate is magnetic resonance angiography in predicting neurovascular compression in patients with trigeminal neuralgia? A prospective, single-blinded comparative study

Ninety-two patients with trigeminal neuralgia (TGN) were investigated prior to posterior fossa surgery with magnetic resonance imaging (MRI) and contrast-enhanced magnetic resonance angiography (MRA). The preoperative investigation was matched to one consultant neuroradiologist (co-author) who was blinded to the side of symptomotology. The imaging results were compared with the operative findings in all patients. In 76 patients MRA showed present neurovascular compression in accordance with surgical findings. Eight cases had no compression either on MRA or intraoperatively. Eight predictions of no compression were false and there was no false positive. Based on surgical findings, the sensitivity of MRA was 90.5% and the specificity 100%. In 19 cases MRA predicted bilateral compression of the trigeminal nerves. Only two cases had clinically bilateral TGN. We conclude that MRA with gadolinium enhancement is an extremely sensitive and specific method for demonstrating compression in TGN. As a result posterior fossa surgery can be recommended with confidence, and microvascular decompression remains the treatment of choice for TGN at the authors' centre.

Evaluation of vascular compression in trigeminal neuralgia by 3D time-of-flight MRA.

Our goal was to assess the usefulness of 3D images in the preoperative evaluation of 16 patients with surgically confirmed trigeminal neuralgia. The axial source images from 3D TOF MRA were evaluated for a total of 32 sides by two observers in a blinded manner, focusing on the presence of the neurovascular compression and the identification of compressing vessels. All 3D images including coronal orientation and gadolinium-enhanced images were reviewed retrospectively by another two observers together with the surgical findings. In the blinded study with axial 3D images, the sensitivity was 75 and 75% with a specificity of 75 and 69% for observers A and B, respectively. By reviewing the coronal images, the relationship between trigeminal nerve and vessels became clearer, especially in sandwich-type compression. With gadolinium-enhanced images, three vessels that were not shown in the nonenhanced images could be identified. On the asymptomatic side, vascular compression could not be excluded retrospectively in five cases. Nonenhanced axial images may not display small arteries or veins that are compressing the trigeminal nerve. Gadolinium enhancement will be necessary for those patients without demonstrable compression on nonenhanced examination. Coronal images are also helpful in the evaluation of vascular compression.

Neurovascular compression in trigeminal neuralgia: a clinical and anatomical study.

Neurovascular decompression is a widely practiced technique for the treatment of trigeminal neuralgia, and yet there is still debate as to whether the beneficial effect results from relieving the nerve of compression by an anatomically abnormal vessel or from the manipulation and trauma the nerve undergoes during the procedure. The development of this operation has been hampered by the lack of adequate anatomical studies in normal controls. The authors present a combined study of clinical and anatomical material employing standardized definitions of the neurovascular relationships in both groups. Detailed simulations of the operative procedure were carried out on fresh cadavers matched for age, sex, and side, and a technique of in situ blood vessel perfusion was developed that enabled the normal neurovascular arrangement to be observed post mortem at physiological pressures. Neurovascular compression, typified by a large vessel distorting and creating a groove in the fifth cranial nerve, was found in 37 of the 41 cases of trigeminal neuralgia; recurrence of pain did not relate to the site of compression. A follow-up study was carried out for a median of 53 months (range 12 to 103 months). No distortion was found in a total of 50 normal cadaveric dissections; however, on perfusion to physiological pressures, the percentage of nerves with vessels adjacent or in simple contact increased from 16% to 40%. This study using this new technique confirms that vascular compression of the fifth cranial nerve is an anatomical abnormality specific to trigeminal neuralgia.