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.     

Association between neurovascular contact on MRI and response to gamma knife radiosurgery in trigeminal neuralgia

Treatment with gamma knife radiosurgery (GKRS) provides adequate short-term pain control in about 70% of the patients with intractable trigeminal neuralgia (TN). The purpose of our study was to evaluate whether the presence of neurovascular contact (NVC) at the root entry zone of the trigeminal nerve on pre-gamma knife MR imaging predicts an increased likelihood of an adequate response to GKRS.We studied 40 consecutive patients who underwent GKRS for treatment of intractable TN. Two neuroradiologists blinded to the side of symptoms analyzed pre-treatment constructive interference in steady state (CISS) images to determine the presence of NVC by consensus. An adequate response was defined as freedom from pain with or without reduced need for medical therapy. Adequate short-term response to GKRS was seen in 29 (72.5%) of 40 patients. NVC was seen in 30 of the 40 patients. Twenty-five (83.3%) of 30 patients with NVC had adequate short-term response to GKRS. Only four (40%) of the 10 patients without NVC had adequate response to GKRS (X²=7.06; P<0.01). Patients with NVC were seven times more likely to have an adequate response to GKRS than those without NVC (odds ratio =7.5).The presence of NVC on pre-treatment MR imaging predicts an increased likelihood of an adequate response to GKRS.     

γ刀照射三叉神经的剂量-效应关系研究

目的 探讨伽玛刀不同剂量照射大鼠三叉神经(感觉根)后对照射范围内三叉神经组织的损伤以及对周围临近脑干组织和脑桥的影响,为优化伽玛刀照射剂量提供理论依据。方法 选用成年雄性SD大鼠65只,分别以不同照射剂量(20、40、80、160 Gy)照射三叉神经,观察照射后1周、2周、4周大鼠行为学变化,取全脑组织进行HE、Nissl、MAPLC3B、53BP1、XRCC1染色观察细胞形态学和自噬以及DNA损伤和修复等变化。结果 所有剂量组照射大鼠均存活。20和40 Gy组均无行为学和病理学改变;80和160 Gy组均出现了照射部位毛发脱落;HE、Nissle、LC3B、53BP1及XRCC1染色发现,受照部位组织在80和160 Gy照射后,可见神经元细胞固缩、膨胀,神经元细胞发生自噬以及DNA损伤明显,160 Gy组DNA损伤明显加重。40 Gy照射后,神经元发生DNA损伤修复的程度较其他剂量增高。结论 伽玛刀照射三叉神经根对神经元有明显的剂量-效应关系。     

Arterial compression of the fifth cranial nerve causing trigeminal neuralgia: angiographic findings

A common cause of trigeminal neuralgia (TN) is compression of the root of the fifth cranial nerve by a tortuous basilar artery or one of its branches. Microvascular decompression surgery has proved valuable in relieving the symptoms of these patients with nerve compression. We performed vertebral angiography on 22 patients with TN. The angiographic appearances were compared with the findings obtained from an anatomic study in which the positions of 20 trigeminal nerves in the skull were determined radiographically in 12 cadavers. By using this information, we were able to predict the presence of arterial-nerve compression in 20 of the 22 patients, and these positions were later confirmed at surgery. We describe the angiographic findings in patients with TN as well as the findings in a control group of 159 individuals with no history of TN. From these preliminary results, angiography appears to be valuable in the preoperative evaluation of patients with TN.     

Stereotaxic angiography in gamma knife radiosurgery of intracranial arteriovenous malformations.

Gamma knife radiosurgery is an effective alternative to embolization or microsurgical removal of small arteriovenous malformations, particularly in eloquent areas of brain tissue. Stereotaxic angiography is a useful diagnostic and targeting adjunct to gamma knife radiosurgery, and the authors present their experience (1,100 patients) with methods and technique, and show how the nidus of the arteriovenous malformation can be defined angiographically. Dose planning employing digitization of the subtraction image enables determination of the spatial coordinates of the lesion by means of an interactive computer program.     

Proton MR spectroscopic features of the cisternal segment of the trigeminal nerve in patients with trigeminal neuralgia: A pilot study

PurposeTo investigate normal quantitative proton magnetic resonance spectroscopy (MRS) features of the cisternal segment of the trigeminal nerve and evaluate possible metabolite concentration differences in the affected and unaffected nerves of trigeminal neuralgia patients.Material and methodsA total of 33 consecutive patients who underwent a MR study of the internal auditory canal/posterior fossa and dedicated trigeminal nerve multivoxel MRS were enrolled. Measurements of N-acetyl aspartate (NAA), creatine (Cr), choline (Cho), myoinositol (mI), glutamate-glutamine (Glx) concentrations, and ratios of NAA-to-Cr, Cho-to-Cr, and Cho-to-NAA were automatically calculated by the dedicated software. Vascular conflicts were also recorded.ResultsThe mean Cr concentration was significantly higher on the affected sides in all parts of the nerve (p < 0.05), while the mean NAA concentration was significantly higher in only the distal portion (p = 0.04). Mean mI concentration was significantly higher in the middle and distal parts (p < 0.05). NAA-to-Cr ratio was significantly higher in the proximal and middle parts (p < 0.05), while Cho-to-Cr ratio was significantly higher only in the middle portion (p = 0.028). Finally, the Cho-to-NAA ratio was significantly higher only in the distal portion (p = 0.04). Vascular conflicts were observed in 24 patients (72.7%), and in 20 of them (60.6%) the conflict was on the same side as the neuralgia symptoms.ConclusionAlthough the detected statistical relationships were variable in the spectroscopic measurements, metabolite concentrations and ratios were successfully exhibited in all patients. Features of a normal trigeminal nerve were able to determine by MRS. All calculated metabolite concentrations were higher in the affected nerves; however, only some of them were statistically significant. No statistically significant relationships were found between the MRS measurements and nerves with and without vascular compression.     

Single-photon emission CT in the evaluation of recurrent brain tumor in patients treated with gamma knife radiosurgery or conventional radiation therapy.

PURPOSETo differentiate radiation necrosis from tumor recurrence using single-photon emission CT (SPECT).METHODSForty-two thallium-201 SPECT scans were obtained in 33 adult patients. All patients had previously been treated with either conventional external-beam radiation therapy (XRT) (26 patients) or gamma knife radiosurgery (16 patients) and had subsequent contrast-enhanced MR examinations before nuclear medicine imaging. Patients were injected intravenously with 4 mCi of thallous chloride Tl 201 with rapid acquisition of SPECT scans thereafter. Findings on thallium-201 SPECT scans were categorized as either positive or negative on the basis of an abnormal focus of increased activity in the area of the known lesion. Evaluation of the accuracy of the thallium-201 SPECT scan was made by correlation with subsequent histologic or cytologic analysis (28 cases) or, in cases in which biopsy was not performed, by subsequent clinical course or MR findings (14 cases).RESULTSFor all patients in this series, the sensitivity and specificity of thallium-201 SPECT scans in detecting tumor recurrence were 94% and 63%, respectively. The sensitivity and specificity for patients who had been treated with XRT were 95% and 60%, respectively. The sensitivity and specificity for patients who had been treated with gamma knife therapy were 92% and 67%, respectively. Tumor/scalp (T/S) ratios were calculated for all patients. High T/S ratios (> 2.0) had a positive predictive value for tumor recurrence of 92%. T/S ratios less than 0.5 had a negative predictive value for tumor recurrence of 83%.CONCLUSIONThallium-201 SPECT is a sensitive and accurate test to differentiate tumor recurrence from radiation necrosis in a population of patients with abnormal MR findings. This technique was equally efficacious in patients who had undergone gamma knife radiosurgery and in those who had received XRT.     

血管压迫性三叉神经痛责任血管的3.0T MRI研究

目的 采用3.0 T MRI显示三叉神经及周围血管的解剖关系,分析产生原发性三叉神经痛(TN)的血管压迫特点.方法 选择50例TN患者(50支TN患侧和50支TN对侧三叉神经;其中23例行微血管解压术)和50名没有面部疼痛的志愿者(100支非TN三叉神经),在3.0TMR采用三维快速稳态梯度回波序列(3D TRU-FISP)及3D 三维时间飞跃(TOF-MRA)扫描.若判断TN患者为静脉病变,并行增强3D快速小角度反转序列(3DFLASH)扫描.以上图像融合重建成虚拟脑池图,评价神经血管压迫程度分级(1级无压迫,2级静脉性压迫,3级神经与动脉接触,4级有动脉压痕,5级动脉压迫导致神经明显移位),以及血管接触神经的方位(三叉神经的上侧或其他侧)、血管神经接触点的位置(近:位于三叉神经脑池段近脑干1/3长度区域,远:位于三叉神经脑池段远脑干2/3长度区域).3D TRU-FISP序列重建的冠、矢状面图像用于测量神经长度、神经横截面及脑池面积.采用卡方检验观察2组的三叉神经:血管压迫神经引起神经切迹或移位(4级和5级)、血管神经压迫点和神经出脑干处距离、血管压迫神经的位置位于神经上侧方的发生率.采用t检验观察测量数值的统计学意义,并用Logisac回归分析三叉神经痛的发病因素.结果 两序列及融合图像可以清晰显示神经血管的关系,与23例微血管解压术中所见吻合度高,术后症状消失或明显减轻21例.血管压迫或接触三叉神经的发生率在志愿者组(1级79支,2级5支,3级8支,4级8支)、TN对侧(1级27支,2级6支,3级9支,4级8支)及TN患侧(1级4支,2级t2支,3级12支,4级7支,5级15支)分别为21.0％(21/100)、46.0％ (23/50)、92.0％ (46/50).TN患侧三叉神经较志愿者三叉神经血管受压迫程度4、5级者差异有统计学意义(x2=27.0,P ＜0.01);血管接触点的位置在TN患侧近32支、远14支,在志愿者近4支、远17支(x2=14.8,p＜0.01);压迫血管位置中,TN患侧位于神经上侧36支、其他侧10支,志愿者中位于神经上侧5支、其他侧16支(x2=18.0,P＜0.01);所在层面脑桥池面积,TN患侧为(183.9+52.5) mm2、对侧为(217.8±58.8)mm2(t=-3.04,P＜0.01);脑池段神经中点截面积,TN患侧为(6.3±1.3)mm2、对侧为(7.7±1.6) mm2(t=-4.8,P＜0.01);脑池段神经长度,TN患侧为(8.0±1.9)mm、对侧为(9.0±2.0)mm(t=-2.64,P＜0.05),差异均有统计学意义.结论 MR可以清楚显示TN患者血管与三叉神经的关系,受压迫神经位置更靠神经近端及头侧、神经所在层面脑桥池面积较小者,均是较强的手术指征.     

Dose distributions at extreme irradiation depths of gamma knife radiosurgery: EGS4 Monte Carlo calculations.

The accuracy of the dose planning system (Leksell GammaPlan), used in Gamma Knife (type B) radiosurgery at extreme irradiation depths, was verified using the Monte Carlo technique. EGS4 Monte Carlo calculations were employed to calculate the dose distribution along the x, y and z axes for an irradiation relatively shallow in a spherical bony cavity water phantom. Two different sizes of the collimator helmets, 8 and 18 mm, of the Leksell Gamma Knife Unit were studied. The results of GammaPlan showed good consistency with the Monte Carlo results. Furthermore, small dose enhancements were observed in the skull bone where accurate dose measurements are difficult due to the presence of the air-phantom interface. Therefore, the results of this project can promote confidence to all Gamma Knife centres in the world when using the Leksell GammaPlan.     

Microstructural abnormalities in the trigeminal nerves of patients with trigeminal neuralgia revealed by multiple diffusion metrics

Objective

To investigate microstructural tissue changes of trigeminal nerve (TGN) in patients with unilateral trigeminal neuralgia (TN) by multiple diffusion metrics, and correlate the diffusion indexes with the clinical variables.

Methods

16 patients with TN and 6 healthy controls (HC) were recruited into our study. All participants were imaged with a 3.0 T system with three-dimension time-of-flight (TOF) magnetic resonance angiography and fluid attenuated inversion recovery (FLAIR) DTI-sequence. We placed regions of interest over the root entry zone of the TGN and measured fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). The mean values of FA, MD, AD and RD were compared between the affected and unaffected sides in the same patient, and to HC values. The correlation between the side-to-side diffusion metric difference and clinical variables (disease duration and visual analogy scale, VAS) was further explored.

Results

Compared with the unaffected side and HC, the affected side showed significantly decreased FA and increased RD; however, no significant changes of AD were found. A trend toward significantly increased MD was identified on the affected side comparing with the unaffected side. We also found the significant correlation between the FA reduction and VAS of pain (r = −0.55, p = 0.03).

Conclusion

DTI can quantitatively assess the microstructural abnormalities of the affected TGN in patients with TN. Our results suggest demyelination without significant axonal injury is the essential pathological basis of the affected TGN by multiple diffusion metrics. The correlation between FA reduction and VAS suggests FA as a potential objective MRI biomarker to correlate with clinical severity.     

Stereotactic radiosurgical pallidotomy and thalamotomy with the gamma knife: MR imaging findings with clinical correlation--preliminary experience.

PURPOSE: To evaluate the temporal evolution and appearance of a radiosurgical lesion at magnetic resonance (MR) imaging and the clinical response in patients undergoing stereotactic radiosurgical pallidotomy or thalamotomy with the gamma knife. MATERIALS AND METHODS: Seventeen patients with medically refractory movement disorders underwent stereotactic radiosurgical pallidotomy (n = 2) or thalamotomy (n = 15). A single dose of 120-140 Gy was administered to a target in the globus pallidus interna or ventralis intermedius thalamic nucleus. Postprocedure gadolinium-enhanced MR imaging and clinical assessment were performed at 1 month and 3 months. RESULTS: At 3 months, the radiosurgical lesion most commonly (n = 11) appeared as a ring-enhancing focus 5 mm or less in diameter surrounded by vasogenic edema that extended less than 7 mm in radius beyond the target. Five patients had ring-enhancing lesions 7 mm or more in diameter; four of these developed symptomatic perilesional edema at 3 (n = 2) or 8 (n = 2) months after the procedure. Onset of therapeutic effect began approximately 4 weeks after treatment. In the 15 patients with tremor, there was a mean decline of 2.1 on the Tremor Rating Scale. CONCLUSION: Findings in this pilot study suggest that radiosurgical thalamotomy is a promising treatment for medically refractory tremor. Three-month follow-up MR studies show a ring-enhancing lesion surrounded by a variable amount of vasogenic edema. Visualization of the radiosurgical lesion and the clinical response are delayed compared to that with radio-frequency procedures.     

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.     

Usefulness of semiquantitative FDG-PET in the prediction of brain tumor treatment response to gamma knife radiosurgery

PURPOSE: The aim of this study is to evaluate whether posttreatment FDG-PET can predict the treatment response to gamma knife radiosurgery (GKRS) for patients with gliomas. METHOD: Eighteen patients with histologically confirmed gliomas treated by GKRS and followed for more than 24 months were enrolled in this study. All patients underwent FDG-PET 6-8 months after GKRS. PET images and MR images were integrated and tumor-to-cortex (T/C) and tumor-to-white matter (T/WM) FDG uptake ratios were measured. By estimating the change of the maximum tumor diameter measured on the contrast-enhanced MRI (the last follow-up MRI vs. the pre-GKRS MRI), the tumor response was classified as complete remission, partial remission (PR), stable disease (SD), and progression of disease (PD). Group 1 includes four tumors with PR and 6 tumors with SD; group 2 includes 8 tumors with PD after GKRS. RESULTS: Both mean T/C ratio and mean T/WM ratio of group 1 patients are statistically less than those of group 2 patients. CONCLUSION: Our study suggests that, for patients with gliomas treated by GKRS, the posttreatment FDG-PET may be useful to predict the treatment response.     

Size of the internal carotid and middle cerebral arteries in patients with trigeminal neuralgia

Internal carotid angiography was performed in 38 patients with trigeminal neuralgia. The diameters of the middle cerebral and internal carotid arteries were measured and compared with the expected normal values obtained from a previously published study of a reference group of patients. The internal carotid artery was narrower than expected in the region close to the Gasserian ganglion and wider proximal and distal to this region. The differences were statistically significant. In 45 per cent of the patients, tortuosity and kinking of the internal carotid artery was found, indicating ectasia. Thus, in spite of signs of ectasia of the internal carotid artery, a significant reduction of the vessel size was seen close to the Gasserian ganglion, suggesting an etiologic relationship between the vascular changes and trigeminal neuralgia.     

Patterns of neurovascular compression in patients with classic trigeminal neuralgia: A high-resolution MRI-based study

Purpose

To describe the anatomical characteristics and patterns of neurovascular compression in patients suffering classic trigeminal neuralgia (CTN), using high-resolution magnetic resonance imaging (MRI).

Materials and methods

The analysis of the anatomy of the trigeminal nerve, brain stem and the vascular structures related to this nerve was made in 100 consecutive patients treated with a Gamma Knife radiosurgery for CTN between December 1999 and September 2004. MRI studies (T1, T1 enhanced and T2-SPIR) with axial, coronal and sagital simultaneous visualization were dynamically assessed using the software GammaPlan™. Three-dimensional reconstructions were also developed in some representative cases.

Results

In 93 patients (93%), there were one or several vascular structures in contact, either, with the trigeminal nerve, or close to its origin in the pons. The superior cerebellar artery was involved in 71 cases (76%). Other vessels identified were the antero-inferior cerebellar artery, the basilar artery, the vertebral artery, and some venous structures. Vascular compression was found anywhere along the trigeminal nerve. The mean distance between the nerve compression and the origin of the nerve in the brainstem was 3.76 ± 2.9 mm (range 0–9.8 mm). In 39 patients (42%), the vascular compression was located proximally and in 42 (45%) the compression was located distally. Nerve dislocation or distortion by the vessel was observed in 30 cases (32%).

Conclusions

The findings of this study are similar to those reported in surgical and autopsy series. This non-invasive MRI-based approach could be useful for diagnostic and therapeutic decisions in CTN, and it could help to understand its pathogenesis.     

三叉神经痛MRI序列研究及诊断价值

目的 探讨MR序列对导致三叉神经痛病变的显示能力及诊断价值.方法 回顾性分析60例三叉神经痛患者临床及MRI资料,与临床手术对照,比较不同序列MRI显示病变能力.所有患者均行常规头部MR平扫,其中9例行增强扫描,49例行桥小脑角区高分辨3D-TOF和3D-快速SE(TSE)序列扫描.利用x2检验分析3D-TOF和3D-TSE两序列的敏感度、特异度和准确度.结果 MR常规平扫及增强扫描显示6例桥小脑区肿瘤、3例三叉神经根及其周围脑膜炎,以及脑干多发硬化斑块及梗死各1例.49例为神经血管压迫所致,与手术对照3D-TOF和3D-TSE序列显示血管压迫的敏感度、特异度、准确度分别为95.3％ (41/43)、66.7％ (4/6)、91.8％ (45/49)和95.6％ (43/45)、50.0％ (2/4)、91.8％ (45/49),两者差异无统计学意义(x2值分别为0.13、0.19、0.17,P值均＞0.5).结论MRI对显示和诊断三叉神经痛病因具有重要意义.MR全脑常规扫描可以显示或排除肿瘤、炎症等病变.桥小脑角区3D-TOF和3D-TSE扫描可以敏感和准确地显示和明确神经、血管的关系.     

Sensitivity and specificity of MRA in the diagnosis of neurovascular compression in patients with trigeminal neuralgia

The published rates of operatively confirmed neurovascular compression as the cause for trigeminal neuralgia range from 10 % to nearly 100 %. High-definition magnetic resonance angiography (MRA) was performed in 27 consecutive patients (in 6 cases with 3D reconstructions) to show neurovascular compression preoperatively. The MRA findings were compared with the relationship between the Vth nerve and the surrounding vessels at surgery. In 23 patients MRA showed present neurovascular compression in accordance with surgical findings (18/27 in complete accordance of type and side of vessel, site and direction of compression). One woman had no neurovascular compression either on MRA or intraoperatively. One MRA prediction of neurovascular compression was false, and two results were false negative. The sensitivity of MRA was therefore 88.5 % but the specificity only 50 %, if surgical findings are the reference. In one patient with right trigeminal neuralgia MRA revealed bilateral neurovascular compression of the Vth nerves. Therefore, the overall specificity of MRA might be below 50 %. In one patient with multiple sclerosis, the decision to operate was markedly influenced by the clear finding of neurovascular compression on MRA. The patient has been free from trigeminal pain for 149 weeks after microvascular decompression. In 6 patients, 3D reconstructions of the MRA data were performed. The images helped in 3D visualisation of the operation, but did not yield new information about the nature of the vessels revealed, or the site, direction or side of the neurovascular compression. Received: 15 May 1997 Accepted: 18 June 1997     

MRI对明确三叉神经痛患者神经血管关系的诊断意义

 目的 探讨磁共振对三叉神经痛(Trigeminal neuralgia,TN)患者神经血管关系的诊断价值及可靠性.方法 对25例正常对照及25例TN患者三叉神经行三维快速平衡稳态进动(3D-FIESTA)和三维时间飞跃-扰相梯度回波(3D TOF-SPGR)序列成像并多平面重建,分别记录各序列对神经血管关系的诊断结果,其中15例与手术结果对照.结果 正常对照组双侧及TN组患侧神经血管接触或压迫的阳性率分别为24%与87.5%,二者差异有统计学意义(P<0. 001).3D-FIESTA对15例TN患者诊断的敏感度、一致率分别为93%与67%,而3D TOF-SPGR分别为67%和60%.结论 MRI是显示TN神经血管关系的可靠方法;3D-FIESTA序列对神经血管关系诊断的敏感度及一致率高于3D TOF-SPGR,可作为TN患者的首选序列.     

原发性三叉神经痛患者射频热凝术后脑干听觉诱发电位的研究

目的探讨脑干听觉诱发电位（brainstem auditory evoked potentials,BAEP）V波在原发性三叉神经痛患者射频热凝术前后的变化意义。方法对29例原发性三叉神经痛患者行射频热凝术前后BAEP的V波值进行测定,并行统计学分析。结果射频治疗前后,患侧V波潜伏期、Ⅰ-Ⅴ波间期、双侧V波潜伏期差、双侧Ⅰ-Ⅴ波间期有统计学差异（P〈0.05）.结论BAEP的V波值在临床上可以作为原发性三叉神经痛射频治疗疗效评价的客观指标之一。