Venous anomalies and abnormalities of the posterior fossa

Summary The authors report a series of 16 patients with venous anomalies or abnormalities of the posterior fossa studied by angiography, CT and/or MRI. We believe that so-called venous angiomas are extreme anatomic variants that drain normal territories, and we prefer to call them developmental venous anomalies (DVAs). Posterior fossa DVAs, like the supratentorial ones are classified according to their drainage into deep and superficial types. They are exclusively located in the cerebellum or tectum. In 4 cases DNA was an incidental finding; in 3 an associated cerebral venous malformation (CVM) was found and felt to be the cause of the symptoms; and only in one (with trigeminal pain) was a link between both suspected. Cavernous venous malformations (CVMs) were found in frequent association with DVA (27%). Four cases were single and 2 multiple. Five CVMs were located in the brain stem and 3 in the cerebellum. The clinical and radiological files were reviewed and a direct relationship between symptoms and localization was found in all patients with CVM. In 2 cases venous dysplasia was found: 1 Sturge-Weber and 1 first branchial arch syndrome. Both posterior fossa venous abnormalities were incidental findings.     

Spontaneous thrombosis of developmental venous anomaly (DVA) with venous infarct and acute cerebellar ataxia

Developmental venous anomaly (DVA), formally known as venous angioma, is a congenital anatomic variant of the venous drainage of the brain. Although they typically have a benign clinical course and a low symptomatic rate, thrombosis of a drainage vein may occur, leading to potentially debilitating complications. We report a unique case of spontaneous thrombosis of a posterior fossa developmental venous anomaly with cerebellar infarct in a 61-year-old man who presented with acute onset cerebellar ataxia. DVA thrombosis was well-depicted on CT and MR studies. Patient was put on anticoagulant therapy and complete recanalization was seen on follow-up imaging.     

Posterior fossa venous angiomas with drainage through the brain stem.

PURPOSETo describe 11 cases of posterior fossa venous angiomas with drainage through the brain stem.METHODSEleven cases of posterior fossa venous angioma with drainage through the brain stem were evaluated using MR. Correlation with known routes of venous drainage for the cerebellum and brain stem is made.RESULTSSix of the 11 venous angiomas were found in the cerebellum, four in the brain stem; one involved both the cerebellum and brain stem. The cerebellar venous angiomas drained to subependymal veins about the fourth ventricle and dorsal pons. These then connected with an enlarged transmesencephalic or transpontine vein, to drain anteriorly to the anterior pontine veins. The brain stem angiomas had variable drainage depending on location. Evidence of hemorrhage was seen in five cases.CONCLUSIONCerebellar and brain stem venous angiomas have several potential routes of drainage, including an enlarged vein traversing the pons, midbrain, or medulla. A knowledge of the normal venous anatomy of this region helps to understand the occurrence of these uncommon routes of venous drainage.     

Venous angioma adjacent to the root entry zone of the trigeminal nerve: implications for management of trigeminal neuralgia

Detection of a venous angioma at the root entry zone is important for surgical planning, so that the neurosurgeon will be aware that both veins and arteries may require microvascular decompression. In selected cases, alternative treatment may be indicated to avoid the potential surgical complication of a venous infarct. Trigeminal neuralgia typically occurs in the middle-aged to elderly population, usually the result of compression of the trigeminal nerve at its root entry zone by an ectatic, aging artery or, less commonly, a regional vein [1, 2, 3]. When associated with a venous angioma at the root entry zone, trigeminal neuralgia usually presents at a younger age [4, 5, 6]. We review the imaging examinations and clinical data of five patients with trigeminal neuralgia who had a venous angioma adjacent to the root entry zone of the trigeminal nerve, and discuss how the imaging findings affected their management.     

Coincidence of developmental venous anomalies and other brain lesions: a clinical study

In a retrospective study of 72 patients with developmental venous anomalies (DVA) diagnosed by MRI and/or angiography, 33 associated lesions were found in 32 patients (44%). Study of the clinical files allowed classification of the patient population into three groups. In group 1 (11 patients: 34%) the symptoms were attributed with certainty to the associated lesions (1 brain infarction, 2 multiple sclerosis patients, 1 case of meningitis, and 7 patients with tumors). In group 2 (9 patients: 28%) the symptoms were probably caused by the associated lesion and not by the associated DVA (1 contusion, 1 Sturge-Weber angiomatosis, and 7 hemorrhagic DVA). In group 3 (12 patients: 38%) the symptoms were nonspecific (10 cavernous angiomas, 1 varix with sinus pericranii, and 1 ectasia of the middle cerebral artery. These findings sustain the theory that DVA is a congenital anomaly of the venous drainage of the brain, without pathological significance, and must be considered as an incidental finding. Correspondence to: G. Wilms     

An adult case of congenital external carotid-jugular arteriovenous fistula with reversible circulatory insufficiency in the cerebellum and lower brain stem

A 27-year-old man with congenital external carotid-jugular arteriovenous fistula presented with a diminished level of consciousness and an ataxic gait. Axial fluid-attenuated inversion-recovery (FLAIR) MR imaging revealed venous congestion, a dilated right jugular vein, and an area of high signal intensity in the brain stem and cerebellum. Angiography showed a dilated right external carotid artery and jugular vein and the presence of a fistula. After coil embolization of the fistula, axial MR FLAIR images showed only a few areas of high signal intensity in the brain stem and cerebellum. The causal factor was venous congestion in the inferior petrosal sinus and basilar plexus due to high blood pressure in the jugular vein. This case is presented for its unusual clinical and radiologic findings.     

Developmental venous anomaly in the newborn brain

Introduction

Cerebral developmental venous anomaly (DVA) is considered a benign anatomical variant of parenchymal venous drainage; it is the most common vascular malformation seen in the adult brain. Despite its assumed congenital origin, little is known about DVA in the neonatal brain. We report here the first cohort study of 14 neonates with DVA.

Methods

Fourteen infants (seven preterm) with DVA diagnosed neonatally using cranial ultrasound (cUS) and magnetic resonance imaging (MRI) from three tertiary neonatal units over 14 years are reviewed.

Results

DVA was first detected on cUS in 6 and on MRI in 8 of the 14 infants. The cUS appearances of DVA showed a focal fairly uniform area of increased echogenicity, often (86 %) adjacent to the lateral ventricle and located in the frontal lobe (58 %). Blood flow in the dilated collector vein detected by Doppler ultrasound (US) varied between cases (venous flow pattern in ten and arterialized in four). The appearance on conventional MRI was similar to findings in adults. Serial imaging showed a fairly constant appearance to the DVAs in some cases while others varied considerably regarding anatomical extent and flow velocity.

Conclusions

This case series underlines that a neonatal diagnosis of DVA is possible with carefully performed cUS and MRI and that DVA tends to be an incidental finding with a diverse spectrum of imaging appearances. Serial imaging suggests that some DVAs undergo dynamic changes during the neonatal period and early infancy; this may contribute to why diagnosis is rare at this age.     

Parenchymal abnormalities associated with developmental venous anomalies

Introduction To report a retrospective series of 84 cerebral developmental venous anomalies (DVAs), focusing on associated parenchymal abnormalities within the drainage territory of the DVA. Methods DVAs were identified during routine diagnostic radiological work-up based on magnetic resonance imaging (MRI) (60 cases), computed tomography (CT) (62 cases) or both (36 cases). Regional parenchymal modifications within the drainage territory of the DVA, such as cortical or subcortical atrophy, white matter density or signal alterations, dystrophic calcifications, presence of haemorrhage or a cavernous-like vascular malformation (CVM), were noted. A stenosis of the collecting vein of the DVA was also sought for. Results Brain abnormalities within the drainage territory of a DVA were encountered in 65.4% of the cases. Locoregional brain atrophy occurred in 29.7% of the cases, followed by white matter lesions in 28.3% of MRI investigations and 19.3% of CT investigations, CVMs in 13.3% of MRI investigations and dystrophic calcification in 9.6% of CT investigations. An intracranial haemorrhage possibly related to a DVA occurred in 2.4% cases, and a stenosis on the collecting vein was documented in 13.1% of cases. Parenchymal abnormalities were identified for all DVA sizes. Conclusion Brain parenchymal abnormalities were associated with DVAs in close to two thirds of the cases evaluated. These abnormalities are thought to occur secondarily, likely during post-natal life, as a result of chronic venous hypertension. Outflow obstruction, progressive thickening of the walls of the DVA and their morphological organization into a venous convergence zone are thought to contribute to the development of venous hypertension in DVA. Presented at the 44th Annual Meeting of the American Society of Neuroradiology, San Diego, Calif., USA, May 1–5, 2006.     

Trigeminal neuralgia caused by Dandy-walker malformation: A case report and systematic review of the literature

Trigeminal neuralgia is a pain condition that affects the face along the distribution of the trigeminal nerve and can be recurrent and chronic. Dandy-Walker syndrome is a complex congenital brain anomaly that occurs during embryonic development of the cerebellum and the fourth ventricle. It is characterized by inferior cerebellar vermis hypoplasia and incomplete formation of the fourth ventricle. Dandy-Walker Syndrome is associated with comorbid genetic conditions. It can include congenital heart defects, eye abnormalities, intellectual disability, congenital tumors, and other brain defects such as agenesis of the corpus callosum. However, associations of trigeminal neuralgia and Dandy Walker syndrome have been an infrequent entity. Herein, we report a case of a 23-year-old female patient that presented with complaints of severe left orofacial pain over two years. MRI evaluation was consistent with Dandy-Walker malformation findings that we suspect caused the compression in the trigeminal root entry zone that ultimately gave rise to the patient''s symptoms.     

Endovascular treatment for dural arteriovenous fistula of the anterior condylar vein with unusual venous drainage: report of two cases

We report 2 patients with dural arteriovenous fistula of the anterior condylar vein in which the patients presented with rare clinical symptoms related to unusual venous drainage patterns. The first patient had progressive myelopathy and showed venous drainage into the anterior spinal vein. The second had ocular signs and showed retrograde drainage into the superior ophthalmic vein. Complete cure was attained by transarterial glue injection in the first patient and transvenous coil embolization in the latter.     

MR imaging of posterior fossa infarctions: vascular territories and clinical correlates.

Ischemic infarctions in certain vascular territories of the cerebellum and brain stem can produce some characteristic radiologic and clinical patterns. The cerebellum serves as a coordination center for the maintenance of equilibrium and muscle tone and refines the movements of the somatic muscles. The anatomy of the brain stem is extremely complex, and small infarcts can potentially be disastrous. MR imaging depicts the anatomy of the posterior fossa and infarcts in this region with greater accuracy than was previously possible. Familiarity with the vascular territories and patterns of infarction of the posterior fossa depicted with MR imaging and familiarity with the associated clinical symptoms of stroke in this region can help the radiologist recognize these infarcts and correlate clinical and radiologic findings. When patients are referred for MR imaging of the brain because of clinical findings suggestive of infarction, it may be useful to obtain coronal or sagittal views in addition to axial images to better depict the vascular distribution of a suspected ischemic lesion.     

经口明视下神经干注射阿霉素治疗三叉神经痛的临床观察简

目的：探讨经口明视下神经干注射阿霉素治疗三叉神经痛的临床疗效。方法将符合标准的97例三叉神经痛患者的临床资料随机分成观察组（53例）与对照组（44例）,观察组患者给予经口明视下神经干注射阿霉素治疗,对照组患者给予周围支撕脱术治疗。结果观察组的近期有效率和两年内有效率分别为100.0%和92.5%,显著高于对照组的86.4%和56.8%（P＜0.05）。结论采用经口明视下神经干注射阿霉素治疗三叉神经痛安全有效,简单易行,易被患者接受。     

Brain parenchymal signal abnormalities associated with developmental venous anomalies: detailed MR imaging assessment

BACKGROUND AND PURPOSE: The occurrence of brain parenchymal signal-intensity changes within the drainage territory of developmental venous anomalies (DVAs) in the absence of cavernous malformations (CMs) has been incompletely assessed. This study was performed to evaluate the prevalence of brain parenchymal signal-intensity abnormalities subjacent to DVA, correlating with DVA morphology and location.MATERIALS AND METHODS: One hundred sixty-four patients with brain MR imaging with contrast studies performed from July 2005 through June 2006 formed the study group. The examinations were reviewed and data were collected regarding the following: location, depth, size of draining vein, associated increased signal intensity on fluid-attenuated inversion recovery and T2-weighted images, associated CMs, and associated signal intensity on gradient recalled-echo sequences.RESULTS: Of the 175 DVAs identified, 28 had associated signal-intensity abnormalities in the drainage territory. Seven of 28 DVAs with signal-intensity abnormalities were excluded because of significant adjacent white matter signal-intensity changes related to other pathology overlapping the drainage territory. Of the remaining DVAs imaged in this study, 21/168 (12.5%) had subjacent signal-intensity abnormalities. An adjusted prevalence rate of 9/115 (7.8%) was obtained by excluding patients with white matter disease more than minimal in degree. Periventricular location and older age were associated with DVA signal-intensity abnormality.CONCLUSION: Signal-intensity abnormalities detectable by standard clinical MR images were identified in association with 12.5% of consecutively identified DVAs. Excluding patients with significant underlying white matter disease, we adjusted the prevalence to 7.8%. The etiology of the signal-intensity changes is unclear but may be related to edema, gliosis, or leukoaraiosis secondary to altered hemodynamics in the drainage area.

Developmental venous anomalies (DVAs) are encountered frequently on postcontrast MR imaging of the brain and are usually regarded as normal variants of venous development. The association between DVAs and cavernous malformations (CMs) has been well described.^1–3 Intracranial hemorrhage in the absence of CM has been rarely reported as a complication of DVA.⁴ There have also been a few case reports of nonhemorrhagic presumed venous infarction in the drainage territory of the DVA.^5–8 Signal-intensity abnormality on T2-weighted or fluid-attenuated inversion recovery (FLAIR) sequences has been infrequently reported in the drainage territory of DVAs and has not been thoroughly investigated. Although some of the early literature described signal-intensity abnormalities in the adjacent parenchyma, these were in small case series and appeared, in some instances, to be related to prior hemorrhage.^9,10 A more recent investigation reported parenchymal alterations in up to 65% of DVAs by MR imaging and CT evaluation in a retrospectively identified patient population.¹¹ We chose to specifically evaluate the frequency of signal-intensity abnormalities in association with DVAs in a more detailed fashion by evaluating a series of consecutive DVAs identified on MR imaging examinations during a defined time interval and correlating the presence of associated signal intensity with DVA morphology, location, size, and drainage pattern. We also attempted to assess the relationship of other white matter signal-intensity alterations not in the DVA territory to presumed DVA-associated signal-intensity changes.     

Brain Metabolic Abnormalities Associated with Developmental Venous Anomalies

BACKGROUND AND PURPOSE:Developmental venous anomalies are the most common intracranial vascular malformation and are typically regarded as inconsequential, especially when small. While there are data regarding the prevalence of MR imaging findings associated with developmental venous anomalies, FDG-PET findings have not been well-characterized.MATERIALS AND METHODS:Clinical information systems were used to retrospectively identify patients with developmental venous anomalies depicted on MR imaging examinations who had also undergone FDG-PET. Both the MR imaging and FDG-PET scans were analyzed to characterize the developmental venous anomalies and associated findings on the structural and functional scans. Qualitative and quantitative assessments were performed, including evaluation of the size of the developmental venous anomaly, associated MR imaging findings, and characterization of the FDG uptake in the region of the developmental venous anomaly.RESULTS:Twenty-five developmental venous anomalies in 22 patients were identified that had been characterized with both MR imaging and FDG-PET, of which 76% (19/25) were associated with significant metabolic abnormality in the adjacent brain parenchyma, most commonly hypometabolism. Patients with moderate and severe hypometabolism were significantly older (moderate: mean age, 65 ± 7.4 years, P = .001; severe: mean age, 61 ± 8.9 years, P = .008) than patients with developmental venous aberrancies that did not have abnormal metabolic activity (none: mean age, 29 ± 14 years).CONCLUSIONS:Most (more than three-quarters) developmental venous anomalies in our series of 25 cases were associated with metabolic abnormality in the adjacent brain parenchyma, often in the absence of any other structural abnormality. Consequently, we suggest that developmental venous anomalies may be better regarded as developmental venous aberrancies.

Adevelopmental venous anomaly (DVA) is a transparenchymal vein of greater than usual size into which coalesces a network of smaller veins, a configuration described as a caput medusa. DVAs may drain into either the superficial or deep venous systems and may occur in the cerebrum, cerebellum, brain stem, and spinal cord. DVAs are the most common intracranial vascular malformation, with a reported incidence of 2.6%.^1,2 The mechanism of DVA formation is still controversial. The term “developmental venous anomaly” was first coined by Lasjaunias et al³ to emphasize their belief that these are embryologic variants of venous drainage rather than true vascular anomalies.Brain parenchymal lesions have been widely reported in association with DVAs, with abnormalities apparent on angiography,⁴ CT⁵ and MR structural imaging,^6–8 and functional imaging methods such as perfusion and diffusion-weighted imaging.^9–12 Several case reports further exemplify how DVAs can be associated with clinical pathologies such as hemorrhagic transformation, ischemic complications, and epileptogenic foci.^13–16 Recent studies also indicate the possible role of DVAs in the formation of cavernous malformations.⁹ These findings suggest that the clinical significance of abnormal brain anatomy and activity near a DVA is uncertain and has yet to be accurately evaluated. Furthermore, our clinical experience has revealed metabolic abnormality associated with DVAs, as determined by FDG-PET. These findings led us to the hypothesis that the metabolic activity in brain parenchyma in the region of a DVA is abnormal. In this study, we sought to better understand metabolic activity in the region of DVAs as assessed by FDG-PET.     

Magnetic resonance angiography of cerebral developmental venous anomalies: its role in differential diagnosis

Summary CT, MRI and contrast angiography of 20 patients with 21 developmental venous anomalies (DVAs), so-called venous angiomas, were compared with magnetic resonance angiography employing a two-dimensional time-of-flight technique (2D-MRA). MRA was diagnostic in 17 DVAs, when both the primary 2D slices and the maximum-intensity-projection images were read. Contrast angiography still provides the best visualization of both DVA components: dilated medullary veins and transcerebral draining vein; however, it is an invasive procedure and delivers no information about brain parenchyma. We regard MRI as necessary in cases with a suspected DVA because of the high rate of association with cavernomas: 33% in this study. Acute neurological symptoms were caused by haemorrhage from an associated cavernoma and not from the DVA in 4 such cases. Thus MRA combined with MRI obviates angiography in most cases and offers a noninvasive diagnostic strategy adequate for DVAs.     

Correlation between electromyographic reflex and MR imaging examinations of the trigeminal nerve.

BACKGROUND AND PURPOSE: Previous studies have shown that clinical localization of trigeminal nerve lesions is inaccurate as compared with MR imaging findings. The purpose of our study was to ascertain the added value of electromyographic (EMG) investigation of the trigeminal nerve reflexes for the improvement of lesion localization and for the preselection of patients for MR imaging. METHODS: We reviewed the EMG studies of the trigeminal reflexes and the MR imaging studies of 20 patients with unilateral symptoms and signs related to the trigeminal nerve (40 trigeminal nerves examined). The results of the two studies were compared to assess the value of EMG in predicting MR imaging outcome. Lesion localization as demonstrated by EMG was compared with localization at MR imaging. MR imaging was used as the standard of reference. RESULTS: Eight (40%) of 20 patients had MR imaging findings related to presenting trigeminal symptoms, including five brain stem lesions and three peripheral lesions. Fourteen (70%) of 20 patients had EMG abnormalities related to presenting symptoms and signs. For brain stem lesions, lesion localization as shown by EMG corresponded well with MR imaging findings. EMG yielded a sensitivity of 100%, a specificity of 81%, a positive predictive value of 57%, and a negative predictive value of 100% in predicting MR imaging results. Interobserver agreement was good for both the EMG reflex and MR imaging examinations. CONCLUSION: Our data suggest that EMG recordings of the trigeminal reflexes can be used to exclude structural lesions in patients with symptoms related to the trigeminal nerve. When a lesion is localized in the brain stem with EMG, a tailored MR imaging examination of this region may be sufficient.     

Arteriovenous fistulas at the cervicomedullary junction presenting with subarachnoid hemorrhage: six case reports with special reference to the angiographic pattern of venous drainage

BACKGROUND AND PURPOSE: Cases with spinal perimedullary arteriovenous fistulas (SPAVFs) or spinal dural arteriovenous fistulas (SDAVFs) at the cervicomedullary junction are rare. We performed a retrospective, angiographic study of 6 such patients to assess whether available angiographic data were predictive of the risk for hemorrhage. METHODS: We report 6 patients with arteriovenous fistulas at the cervicomedullary junction. All presented with subarachnoid hemorrhage (SAH). Angiography demonstrated that 4 of the 6 fistulas were SDAVFs fed by the meningeal branch of the vertebral artery; the other 2 were SPAVFs fed by the anterior spinal artery. Drainage was via the perimedullary vein of the cervicomedullary junction. RESULTS: An ascending venous route into the intracranial sinus was recognized in all 6 cases; in 3 the draining system contained varices. In 2 cases, the venous route was on the ventral side of the brain stem with drainage into the cavernous sinus. In 4 cases, the venous route was lateral at the brain stem with drainage into the inferior petrosal sinus. CONCLUSION: SPAVFs and SDAVFs at the cervicomedullary junction that manifest an ascending venous route into the intracranial sinus present an increased risk for SAH.     

3D-TOF磁共振血管成像诊断血管压迫性三叉神经痛的价值

目的　探讨增强薄层三维体积扫描时间飞跃法磁共振血管成像 ( 3D -TOFMRA)诊断血管压迫性三叉神经痛的价值。方法　回顾性分析 37例临床拟诊为血管压迫性三叉神经痛患者的常规颅脑MRI及增强薄层 3D -TOF磁共振血管成像资料。结果　增强薄层 3D -TOFMRA发现 37例中 2 4例共 2 7侧三叉神经存在血管压迫或接触 ,其中症状侧三叉神经有血管压迫或接触 2 4例 ,无症状侧三叉神经有血管压迫或接触 3例 ,本组病例统计学分析表明 ,三叉神经痛患者症状的出现与三叉神经存在血管压迫或接触有显著相关关系 (Ρ <0 .0 0 5 )。 13例为非血管压迫性三叉神经痛。压迫三叉神经的血管为小脑上动脉 (SCA) 14例 ,小脑前下动脉(AICA) 5例 ,起源不清的血管 3例 ,扭曲的椎动脉 1例 ,血管畸形 1例。结论　增强薄层 3D -TOFMRA可清楚显示三叉神经脑池段与毗邻血管的关系 ,明显优于常规颅脑MRI,是目前检测血管压迫性三叉神经痛最佳的影像学检查方法 ,对明确诊断和指导治疗三叉神经痛具有重大意义。     

3D-CISS序列MR成像在血管压迫性三叉神经痛中的应用

目的　探讨三叉神经痛患者的神经血管解剖关系。方法　应用 3D -CISS序列并结合 3D -TOF血管造影及MPR重建技术对 49例三叉神经痛患者进行MR检查并部分与手术结果对照。结果　 (1) 13例手术患者中 ,10例 3D -CISS和 3D -TOF序列均显示血管压迫的患者经手术证实为动脉压迫 ,另 3例仅在 3D -CISS序列显示的压迫血管 ,手术证实为静脉压迫。 (2 ) 2 0例伴有上颌神经症状的病人有 18例 (90 % )在三叉神经根部内侧有压迫点 ;19例伴有下颌神经症状的病人有 15例 (79% )在三叉神经外侧有压迫点 (经 χ2 检验 ,P <0 .0 0 1)。结论　 3D -CISS序列对显示三叉神经痛病人的神经血管关系、三叉神经的压迫部位与三叉神经痛区域相关性有重要作用。     

Role of enhanced MRI in the follow-up of patients with medically refractory trigeminal neuralgia undergoing stereotactic radiosurgery using the gamma knife: initial experience

PURPOSE: The purpose of this work was to evaluate the early posttreatment MR findings, and their clinical utility, in patients with trigeminal neuralgia undergoing stereotactic radiosurgery using the gamma knife. METHOD: Twenty-six patients with medically refractory trigeminal neuralgia underwent stereotactic radiosurgery. A single dose of 70-90 Gy was administered to the proximal root entry zone (n = 21) or the retrogasserian portion (n = 5) of the trigeminal nerve. Posttreatment enhanced MRI and clinical assessment were performed at 3-6 months. RESULTS: Five patients did not have radiologic follow-up. There were no changes identified in the treated trigeminal nerve or adjacent brainstem in 19 of 21 patients. Two patients with multiple sclerosis developed abnormal signal and enhancement in the brainstem and/or trigeminal nerve; neither had clinical complications. Onset of therapeutic effect ranged from 3 weeks to 3 months; 19 patients had a beneficial response. CONCLUSION: Results of enhanced MRI 3-6 months after stereotactic radiosurgical treatment of trigeminal neuralgia do not correlate with the clinical response. Because beneficial clinical responses or treatment failures are apparent by 3 months, routine posttreatment MRI in these patients is not warranted.