Treatment Of Brainstem Cavernous Malformations Research Articles

One-Point Technique in Brainstem Cavernous Malformation Surgery: Evaluation of Approaches and Outcomes From a Different Perspective.

Brainstem cavernous malformations (BCMs) are a distinct clinical entity that carry a high risk of patient morbidity because of location and risk of hemorrhage. Surgical management of these lesions requires intimate knowledge of surgical anatomy and skull base approaches. This article is intended to highlight a modern approach for the treatment of BCMs, with an emphasis on the use of the one-point technique to guide resection. We describe a case series of BCMs treated through a variety of skull base approaches, describing our decision-making strategy. We review the concept of the one-point technique focusing on the safest access to the malformation through 2 representative cases and also perform a retrospective review of 32 consecutive patients who underwent BCM resection to present outcomes and the comparison of two-point vs one-point techniques. Consecutive series of 32 patients in whom the one-point technique was used is presented. In 8 patients (25%), the traditional two-point technique would suggest a different trajectory than the one-point technique. Postoperative MRI confirmed complete resection in 30 patients (95%), and 29 patients (91%) had modified Rankin Scale (0-2) at follow-up. All patients in whom the one-point technique guided a different trajectory had gross total removal of the cavernous malformation, with one patient having long-term new neurological impairment from the surgery. There were no mortalities. Despite surgical advances in recent decades and more widespread understanding of surgical anatomy and safe entry zones, surgical resection of BCMs remains a formidable challenge. While not necessarily the shortest access, the one-point technique offers a safe approach considering all the different modalities in our armamentarium and can be used as part of a strategy to determine the optimal approach to resect BCMs.

Safety and efficacy of the endoscopic transsphenoidal transclival approach performed using direct cortical stimulation for pontine cavernous malformations.

Surgical treatment of brainstem cavernous malformations (CMs) is challenging. Surgery using the endoscopic transsphenoidal transclival approach (eTSTCA) is reported as a useful alternative for ventral brainstem CMs. However, CMs located in the ventral midline of the brainstem are rare, and only a small number of case reports on these CMs treated with the eTSTCA exist. The efficacy and safety of the eTSTCA have not yet been fully examined. A retrospective analysis was performed for 5 consecutive patients who underwent surgery via the eTSTCA for treating ventral pontine CMs. The average maximum CM diameter was 26.0 mm (18-38 mm). All patients underwent MR-diffusion tensor imaging, which confirmed that the corticospinal tract (CST) deviated posteriorly or laterally to the CM. Direct brainstem cortical stimulation was performed to localize the CST before making the cortical incision. After the excision of the CM, the cavity was filled with artificial CSF to make an aqueous surgical field (wet-field technique) for observing the tumor cavity and confirming complete hemostasis and resection. Total removal was achieved in all patients. The preoperative modified Rankin Scale score was 3 in 3 patients and 4 in 2 patients, whereas it was 1 in 2 patients and 0 in 3 patients 3 months after surgery. Postoperative CSF leakage was observed in 1 patient, and transient abducens nerve palsy was observed in 1 patient. No other intra- or postoperative complications were observed. MR-diffusion tensor imaging and direct brainstem cortical stimulation were useful to ascertain the proximity of the CST to the CM. The endoscope provides a clear view even underwater, and it was safe and effective to observe the entire CM cavity and confirm complete hemostasis without additional retraction of the brainstem parenchyma, including the CST. The eTSTCA provides a direct access point to the lesion and may be a safer alternative treatment for patients whose CST deviates laterally or posteriorly to the CM.

Surgical treatment of brainstem cavernous malformations: an international Delphi consensus.

Indication for surgery in brainstem cavernous malformations (BSCMs) is based on many case series, few comparative studies, and no randomized controlled trials. The objective of this study was to seek consensus about surgical management aspects of BSCM. A total of 29 experts were invited to participate in a multistep Delphi consensus process on the surgical treatment of BSCM. Twenty-two (76%) of 29 experts participated in the consensus. Qualitative analysis (content analysis) of an initial open-ended question survey resulted in 99 statements regarding surgical treatment of BSCM. By using a multistep survey with 100% participation in each round, consensus was reached on 52 (53%) of 99 statements. These were grouped into 4 categories: 1) definitions and reporting standards (7/14, 50%); 2) general and patient-related aspects (11/16, 69%); 3) anatomical-, timing of surgery-, and BSCM-related aspects (22/37, 59%); and 4) clinical situation-based decision-making (12/32, 38%). Among other things, a consensus was reached for surgical timing, handling of associated developmental venous anomalies, handling of postoperative BSCM remnants, assessment of specific anatomical BSCM localizations, and treatment decisions in typical clinical BSCM scenarios. A summary of typical clinical scenarios and a catalog of various BSCM- and patient-related aspects that influence the surgical treatment decision have been defined, rated, and interpreted.

Transcondylar Approach for Resection of Medullary Cavernous Malformation: 2-Dimensional Operative Video.

Cavernous malformations located within the brainstem present with a high rate of neurological symptoms and carry a more aggressive course in both pediatric and adult populations.1,2 Cavernomas within the medulla are the rarest form, representing only 5% of all brainstem lesions.3 Repeated hemorrhage of brainstem cavernomas is associated with significant and cumulative neurological deficits and thus requires treatment.4 Microsurgical resection has become the optimal mode of treatment with the aim of resecting the live malformation and not merely the multiaged, organized hematoma.4 This is best achieved by approaching the cavernoma at the location where it projects to the surface and entering the lesion through a safe brainstem anatomic zone. For ventrally located lesions in the medulla, a transcondylar skull base approach provides a direct trajectory to the entry zone through a short surgical distance without the need to manipulate or retract neurovascular structures.5-8 Neuronavigation and intraoperative neurophysiological monitoring of somatosensory evoked potential, motor, and lower cranial nerves are adjuncts to increase patient safety. Radiosurgery for the treatment of brainstem cavernous malformations has been proposed; however, it demonstrates high risk and variable and often poor response rates.9 We present a surgical video demonstrating the transcondylar approach and resection of a medullary cavernoma in a 54-yr-old woman who has had multiple known prior hemorrhages and presented with a new onset of facial numbness and weakness, ataxia, and left body sensory loss. The patient consented to surgery and to photograph publication. Images at 1:28, 1:43 (left), 2:02 from Al-Mefty O, Operative Atlas of Meningiomas, © LWW, 1997,5 with permission. Images at 1:43 (right) from Arnautovic et al,8 with permission from JNSPG.

Transcallosal Anterior Interforniceal Approach for Removal of Superior Midbrain Cavernous Malformations in Children: A Retrospective Series of 10 Cases in a Single Center

Surgical treatment of brainstem cavernous malformations (CMs) remains a great challenge for neurosurgeons. Several cases published in the literature have addressed surgical approaches. However, no surgical approach has been reported to provide better exposure for CMs located in the superior midbrain. We presented 10 cases of superior midbrain CMs in children treated in Beijing Tiantan Hospital from 2002 to 2016. The most common presenting signs and symptoms were hydrocephalus and cranial nerve deficit. We used the transcallosal anterior interforniceal approach in all patients to remove the CM lesion. Total resection was achieved in all patients. During the follow-up period, temporary short-term memory impairment was present in 5 patients, unilateral ptosis occurred in 1 patient, and upward gaze dysfunction occurred in 2 patients. There was complete neurologic functional improvement for cranial nerves. Exacerbation of hydrocephalus occurred in 4 patients requiring additional ventriculoperitoneal shunt postoperatively. The transcallosal anterior interforniceal approach can provide good exposure and direct visualization to superior midbrain CMs. Complications are short-term and reversible.

Cranial Cavernous Malformations: Natural History and Treatment.

Cavernous malformations (CMs), also known as cavernous angiomas or cavernomas, are low-flow vascular malformations of the brain and spinal cord that consist of clusters of dilated sinusoidal channels lined with endothelial cells that do not exhibit intervening tight junctions. The involved blood vessels lack muscular and elastic layers, and blood at various stages of thrombosis and organization often fills the thin-walled vascular caverns. CMs are grossly distinct from adjacent brain and have a lobulated appearance sometimes likened to a mulberry, with a characteristic dark red or purple color. Hemosiderin and gliosis often surround CMs of the brain and spinal cord; no neural tissue is present inside the lesion. Except for developmental venous anomalies (DVAs) present in ≈33% of CMs,1 no abnormal vascularity is typically seen on digital subtraction angiography, leading CMs to be termed cryptic or occult vascular malformations (Figure 1). Multiple small hemorrhage events lead to a pathognomonic popcorn appearance on magnetic resonance (MR) imaging because of hemosiderin staining from blood products of various ages. Calcifications may be present on computed tomographic imaging (Figure 2). Figure 1. A 48-year-old woman presented with headaches. A , Magnetic resonance imaging of the brain with T2-weighted imaging demonstrated a 1.1-cm lesion in the cerebellar vermis with mixed signal intensity. B – D , Susceptibility-weighted imaging demonstrated hemosiderin within the lesion’s core and a developmental venous anomaly associated with the cavernous malformation (arrowheads). Figure 2. A 28-year-old woman presented with partial seizures without secondary generalization. A , Noncontrast computed tomography of the head demonstrated a 1.4-cm right posterior cingulate hyperdensity, with evidence of mild hemorrhage and calcification. Magnetic resonance imaging of the brain demonstrated the cavernous malformation to have a core of mixed signal intensity, heterogeneous enhancement, and a rim of hemosiderin consistent with a cavernous malformation, as evidenced on ( B ) susceptibility-weighted imaging, ( C ) T2-weighted …

Surgical Treatment of Brainstem Cavernous Malformations with Three Basic Skull Base Approaches and Minimally Invasive Techniques: Observations in 20 Patients

Objective Brainstem cavernous malformation (BSCM) is extremely challenging for neurosurgeons in terms of surgical approach choices. In this article, we summarized our experience in skull base approaches of BSCM, and elucidated the advance of surgical treatments of brain stem cavernous malformation through reviewing recent relevant articles. Methods We retrospectively reviewed 20 consecutive patients who underwent resection between May 1, 2014 and April 30, 2016. Only midline suboccipital, subtemporal approach and retrosigmoid approach were used in this series. The diagnoses of all patients were confirmed by radiological and histological examination. Results All 20 patients were completely extirpated without surgical-related mortality. The mean follow-up period was 9.5 months (range, 2-20 months). Of the 20 patients, 80% symptomatic patients underwent surgery after first bleeding episode within 3 months, 20% after two or more bleeding episodes by magnetic resonance imaging. After resection and during follow-up, 75% of patients had an improvement in their modified Rankin scale (mRS) scores, whereas 10% were worse compared with their preoperative presentation; 15% were unchanged. Conclusion Appropriate basic surgical approach and minimally invasive techniques are necessary in preventing impairment of neurologic function. The three common basic skull base approaches, combined with minimally invasive techniques can handle most of BSCMs with good surgical results.

Surgical treatment of brainstem cavernous malformations with three basic skull base approaches and minimally invasive techniques:Observations in 20 patients

Objective Brainstem cavernous malformation (BSCM) is extremely challenging for neurosurgeons in terms of surgical approach choices.In this article, we summarized our experience in skull base approaches of BSCM, and elucidated the advance of surgical treatments of brain stem cavernous malformation through reviewing recent relevant articles. Methods We retrospectively reviewed 20 consecutive patients who underwent resection between May 1, 2014 and April 30, 2016.Only midline suboccipital, subtemporal approach and retrosigmoid approach were used in this series.The diagnoses of all patients were confirmed by radiological and histological examination. Results All 20 patients were completely extirpated without surgical-related mortality.The mean follow-up period was 9.5 months (range, 2-20 months).Of the 20 patients, 80% symptomatic patients underwent surgery after first bleeding episode within 3 months, 20% after two or more bleeding episodes by magnetic resonance imaging.After resection and during follow-up, 75% of patients had an improvement in their modified Rankin scale (mRS) scores, whereas 10% were worse compared with their preoperative presentation; 15% were unchanged. Conclusion Appropriate basic surgical approach and minimally invasive techniques are necessary in preventing impairment of neurologic function.The three common basic skull base approaches, combined with minimally invasive techniques can handle most of BSCMs with good surgical results.

Gamma knife radiosurgery for brainstem cavernous malformations

ObjectiveThe goal of this retrospective study was to evaluate the efficacy and safety of gamma knife radiosurgery (GKS) for the treatment of brainstem cavernous malformations (CMs). MethodsBetween January of 2009 and December of 2014, 43 patients (20 males and 23 females) with brainstem CMs were treated at the West China Hospital, Sichuan University, Gamma Knife Center. The mean age of these patients was 41.7 years. All of the patients experienced 1 or more episodes of symptomatic bleeding (range 1–4) before undergoing GKS. The mean volume of the malformations at the time of GKS was 442.1mm3, and the mean prescribed marginal radiation dose was 11.9Gy. The mean follow-up period after radiosurgery was 36 months (range 12–120 months). ResultsBefore GKS, 50 hemorrhages (1.2 per patient) were observed (25.0% annual hemorrhage rate). Three hemorrhages following GKS were observed within the first 2 years (3.92% annual hemorrhage rate), and 1 hemorrhage was observed in the period after the first 2 years (1.85% annual hemorrhage rate). In this study of 43 patients, new neurological deficits developed in only 1 patient (2.32%; permanent paresthesia on the left side of the face and the right lower limb of the patient). There were no deaths in this study. ConclusionGKS is a favorable alternative treatment for brainstem CMs. Using a low marginal dose treatment might reduce the rate of hemorrhage and radiation-induced complications.

Brainstem cavernous malformations: Natural history versus surgical management

While brainstem cavernous malformations were once considered inoperable, improvements in patient selection, surgical exposures, intraoperative MRI-guidance, MR tractography, and neurophysiologic monitoring have resulted in good outcomes in the majority of operated patients. In a consecutive series of 104 patients with brainstem cavernous malformations, only 14% of patients experienced cranial nerve or motor dysfunction that was worse at late follow-up, relative to their preoperative condition. Outcomes were predicted by several factors, including larger lesion size, lesions that crossed the midline, the presence of a developmental venous anomaly, older age, and greater time interval from lesion hemorrhage to surgery. The 14% of patients who experienced a persistent neurological deficit as a result of surgery, while substantial from any perspective, compares favorably with the risks of observation based on a recent meta-analysis. Curative resection is a safe and effective treatment for brainstem cavernous malformations that will prevent re-hemorrhage in symptomatic patients.

Surgical treatment of hemorrhagic brainstem cavernous malformations.

Microsurgery is considered to be the optimal treatment for brainstem cavernous malformations (BCMs); however, the high surgery-related morbidity requires further assessment of therapeutic protocols. The surgical experience and the optimal surgical strategy for the management of brainstem cavernous malformations is discussed. From September 2007 to August 2014, a total of 120 patients with BCMs underwent surgical treatment in our hospital. The clinical features and neurological outcome of these patients were retrospectively analysed, and our institutional surgical strategy was discussed. The preoperative annual hemorrhage and rehemorrhage rates were 4.2% and 42.9%, respectively. Gross total resection was achieved in 116 patients (96.7%) and subtotal resection in 4 (3.3%). After a mean follow-up of 50.7 ± 26.5 months (range: 18-90 months), the neurological status showed improvement in 71 patients (67.0%) and remained stable in 24 (22.6%). The postoperative new-onset or worsened symptoms occurred in 53 cases. During the follow-up period, 58.5% of these symptoms improved and 32.1% remained stable. The mean modified Rankin score (mRS) score was 2.51 ± 0.90 preoperatively, 2.73 ± 0.83 postoperatively, and 1.71 ± 0.98 at the recent follow-up. The surgery-related mortality was 1.7% (n = 2), and two patients suffered from recurrence during the follow-up period. The preoperative mRS was considered to be an independent predictive factor of the neurological outcome (P = 0.003). Safe resection and a favourable outcome can be achieved via a standardized surgical strategy based on appropriate surgical indications, optimal selection of safe trajectories, and application of advanced supplementary techniques in the surgical treatment of BCMs.

Stereotactic radiosurgery of brainstem cavernous malformations: a systematic review and meta-analysis

Over the last two decades, stereotactic radiosurgery (SRS) has arisen as a promising approach in the management of brainstem cavernous malformations (CMs). In the present study, the authors report a systematic review and meta-analysis of the available published data regarding the radiosurgical management of brainstem CMs. To identify eligible studies, systematic searches for brainstem CMs treated with SRS were conducted in major scientific publication databases. The search yielded 5 studies, which were included in the meta-analysis. Data from 178 patients with brainstem CMs were extracted. Hemorrhage rates before and after SRS were calculated, a meta-analysis was performed, and the risk ratio (RR) was determined. Four studies showed a statically significant reduction in the annual hemorrhage rate after SRS. The overall RR was 0.161 (95% CI 0.052-0.493; p = 0.001), and 21 patients (11.8%) had transient or permanent neurological deficits. The present meta-analysis for the radiosurgical management of brainstem CMs shows that SRS can decrease the rate of repeat hemorrhage and has a low rate of adverse effects compared with surgery. The authors suggest that SRS may be considered as an alternative treatment for brainstem CMs that are inoperable or have a high operative risk.

Symptomatic cavernous malformations of the brainstem: functional outcome after microsurgical resection

Brainstem cavernous malformations are associated with a considerable risk of hemorrhage and subsequent morbidity. This study provides a detailed work-up of clinical and radiological outcome as well as identification of prognostic factors in patients who had suffered from symptomatic hemorrhages. Patients who had undergone surgery of symptomatic BSCMs were evaluated pre- and postoperatively both neurologically and neuroradiologically supplemented by telephone interviews. Additionally, patients were scored according to the Scandinavian Stroke Scale. Multiple uni- and multivariate analyses of possible clinical and radiological prognostic factors were conducted. The study population comprised 35 patients. Mean age at operation was 39.3±13.0years with microsurgical resection of a total of 37 different BSCMs between 2002 and 2011. Median clinical follow-up was 44.0months (range 8-116months). Postoperative MRI showed eventually complete resection of all BSCMs. Postoperative overall outcome revealed complete resolution of neurological symptoms for 5/35 patients, 14/35 improved and 9/35 remained unchanged. 7/35 suffered from a postoperative new and permanent neurological deficit, mostly affecting the facial nerve or hemipareses with mild impairment. Pre- and postoperative Scandinavian Stroke Scale scores were 11.0±2.4 and 11.4±2.2 (p=0.55). None of the analyzed factors were found to significantly correlate with patients' clinical outcome. Complete resection of brainstem cavernous malformations can be achieved with an acceptable risk for long-term morbidity and surgery-related new deficits (~20%). Neurological outcome is mainly determined within the first 6months after surgery. Surgical treatment of brainstem cavernous malformations is recommended in symptomatic patients, in whom the lesion is accessible for surgery.

Brainstem cavernous malformations: the role of Gamma Knife surgery

The authors retrospectively reviewed the efficacy and safety of Gamma Knife surgery (GKS) in patients with brainstem cavernous malformations (CMs). The CMs had bled repeatedly and placed the patients at high risk with respect to surgical intervention. Between 1993 and 2010, 49 patients with symptomatic CMs were treated by GKS. The mean age in these patients was 37.8 years, and the predominant sex was female (59.2%). All 49 patients experienced at least 2 instances of repeated bleeding before GKS; these hemorrhages caused neurological deficits including cranial nerve deficits, hemiparesis, hemisensory deficits, spasticity, chorea or athetosis, and consciousness disturbance. The mean size of the CMs at the time of GKS was 3.2 cm(3) (range 0.1-14.6 cm(3)). The mean radiation dose directed to the lesion was 11 Gy with an isodose level at 60.0%. The mean clinical and imaging follow-up time was 40.6 months (range 1.0-150.7 months). Forty-five patients participated in regularly scheduled follow-up. Twenty-nine patients (59.2%) were followed up for > 2 years, and 16 (32.7%) were followed up for < 2 years. The pre-GKS annual hemorrhage rate was 31.3% (69 symptomatic hemorrhages during a total of 220.3 patient-years). After GKS, 3 episodes of symptomatic hemorrhage were observed within the first 2 years of follow-up (4.29% [corrected] annual hemorrhage rate), and 3 episodes of symptomatic hemorrhage were observed after the first 2 years of follow-up (3.64% [corrected] annual hemorrhage rate). In this study of 49 patients, symptomatic radiation-induced complications developed in only 2 patients (4.1%; cyst formation in 1 patient and perifocal edema with neurological deficits in the other patient). There were no deaths in this group. Gamma Knife surgery is effective in reducing the rate of recurrent hemorrhage. In the authors' experience, it was possible to control bleeding using a low-dose treatment. In addition, there were few symptomatic radiation-induced complications. As a result, the authors believe that GKS is a good alternative treatment for brainstem CMs.

A new strategic neurosurgical planning tool for brainstem cavernous malformations using interactive computer graphics with multimodal fusion images

In this study, the authors used preoperative simulation employing 3D computer graphics (interactive computer graphics) to fuse all imaging data for brainstem cavernous malformations. The authors evaluated whether interactive computer graphics or 2D imaging correlated better with the actual operative field, particularly in identifying a developmental venous anomaly (DVA). The study population consisted of 10 patients scheduled for surgical treatment of brainstem cavernous malformations. Data from preoperative imaging (MRI, CT, and 3D rotational angiography) were automatically fused using a normalized mutual information method, and then reconstructed by a hybrid method combining surface rendering and volume rendering methods. With surface rendering, multimodality and multithreshold techniques for 1 tissue were applied. The completed interactive computer graphics were used for simulation of surgical approaches and assumed surgical fields. Preoperative diagnostic rates for a DVA associated with brainstem cavernous malformation were compared between conventional 2D imaging and interactive computer graphics employing receiver operating characteristic (ROC) analysis. The time required for reconstruction of 3D images was 3-6 hours for interactive computer graphics. Observation in interactive mode required approximately 15 minutes. Detailed anatomical information for operative procedures, from the craniotomy to microsurgical operations, could be visualized and simulated three-dimensionally as 1 computer graphic using interactive computer graphics. Virtual surgical views were consistent with actual operative views. This technique was very useful for examining various surgical approaches. Mean (±SEM) area under the ROC curve for rate of DVA diagnosis was significantly better for interactive computer graphics (1.000±0.000) than for 2D imaging (0.766±0.091; p<0.001, Mann-Whitney U-test). The authors report a new method for automatic registration of preoperative imaging data from CT, MRI, and 3D rotational angiography for reconstruction into 1 computer graphic. The diagnostic rate of DVA associated with brainstem cavernous malformation was significantly better using interactive computer graphics than with 2D images. Interactive computer graphics was also useful in helping to plan the surgical access corridor.

Surgical approaches to brainstem cavernous malformations

Brainstem cavernous malformations (CMs) are low-flow vascular lesions in eloquent locations. Their presentation is often marked with symptomatic hemorrhages that appear to occur more frequently than hemorrhage from supratentorial cavernomas. Brainstem CMs can be removed using 1 of the 5 standard skull-base approaches: retrosigmoid, suboccipital (with or without telovelar approach), supracerebellar infratentorial, orbitozygomatic, and far lateral. Patients being referred to a tertiary institution often have lesions that are aggressive with respect to bleeding rates. Nonetheless, the indications for surgery, in the authors' opinion, are the same for all lesions: those that are symptomatic, those that cause mass effect, or those that abut a pial surface. Patients often have relapsing and remitting courses of symptoms, with each hemorrhage causing a progressive and stepwise decline. Many patients experience new postoperative deficits, most of which are transient and resolve fully. Despite the risks associated with operating in this highly eloquent tissue, most patients have had favorable outcomes in the authors' experience. Surgical treatment of brainstem CMs protects patients from the potentially devastating effects of rehemorrhage, and the authors believe that the benefits of intervention outweigh the risks in patients with the appropriate indications.

Surgical treatment of brainstem cavernous malformations

Background The contemporary neurosurgeon is often confronted by cavernous malformations. Those located in the brainstem are particularly challenging Methods This article reviews published series on the natural history and surgical outcomes of these lesions and discusses the surgical approaches used at our institution for their resection. Results Despite their challenging location in the brainstem, appropriately selected lesions can be resected surgically with acceptable rates of morbidity and mortality. Conclusions Our institutional philosophy on the surgical treatment of brainstem cavernous malformations reflects the substantial surgical experience of the senior author.

Cavernous Malformations of the Brainstem: Three-Dimensional-Constructive Interference in Steady-State Magnetic Resonance Imaging for Improvement of Surgical Approach and Clinical Results

The indications for resection of cavernous malformations (CMs) of the brainstem include neurological deficits, (recurrent) hemorrhage, and surgically accessible location. In particular, knowledge of the thickness of the parenchymal layer and of the CM's spatial relation to nuclei, tracts, cranial nerves, and vessels is critical for planning the surgical approach. We reviewed the operative treatment of 13 patients with 14 brainstem CMs, with special regard to refined three-dimensional (3D)-constructive interference in steady-state (CISS) magnetic resonance imaging (MRI). Patients were evaluated neurologically and by conventional spin-echo/fast spin-echo and 3D-CISS MRI. Surgery was performed with the use of microsurgical techniques and neurophysiological monitoring. Eleven CMs were located in the pons/pontomedullary region; 10 of the 11 were operated on via the lateral suboccipital approach. Three CMs were located near the floor of the fourth ventricle and operated on via the median suboccipital approach, with total removal of all CMs. Results were excellent or good in 10 patients; one patient transiently required tracheostomy, and two patients developed new hemipareses/ataxia with subsequent improvement. Not only did 3D-CISS sequences allow improved judgment of the thickness of the parenchymal layer over the lesion compared with spin-echo/fast spin-echo MRI, but 3D-CISS imaging also proved particularly superior in demonstrating the spatial relation of the lesion to fairly "safe" entry zones (e.g., between the trigeminal nerve and the VIIth and VIIIth nerve groups) by displaying the cranial nerves and vessels within the cerebellopontine cistern more precisely. Surgical treatment of brainstem CMs is recommended in symptomatic patients. Especially in patients with lesions situated ventrolaterally, the 3D-CISS sequence seems to be a valuable method for identifying the CM's relation to safe entry zones, thereby facilitating the surgical approach.