How i do it: Robot-assisted transcerebellar stereotactic approach for brainstem lesion.

BACKGROUND: Stereotactic approaches to diffuse intrinsic pontine gliomas (DIPGs) remain essential due to advances in molecular biology and management, necessitating tissue sampling. Here we present an effective technique with a biopsy by robot-assisted transcerebellar approach. METHOD: Our procedure was performed using the ROSA robotic system and the OARM CT scan, which provided stereotactic conditions for this transcerebellar approach to brainstem lesions. CONCLUSION: The robot-assisted transcerebellar stereotactic approach remains essential to provide complications for biopsy of brainstem lesions.

Pediatric Brainstem Tumor Biopsy: Surgical Planning and Execution for Maximal Safety and Tissue Yield.

Brainstem tumors account for 10-20% of pediatric brain tumors with a peak age of diagnosis between 7 and 9 years old and are often fatal. Historically, diagnosis of brainstem tumors has been largely based on imaging; however, recent studies have demonstrated the incongruities between preoperative MRI diagnosis and postoperative pathological findings highlighting the importance of brainstem biopsy for diagnostic accuracy. Stereotactic brainstem biopsy for pediatric brainstem tumors has been proven to be safe with a high diagnostic yield (96.1-97.4%) and relatively low morbidity and mortality. Successful pediatric brainstem tumor biopsy demands intricate knowledge of brainstem anatomy, cranial nerves and vasculature, and common pediatric brainstem tumors by the performing surgeon. Additionally, understanding of the surgical indications and techniques (e.g., frame-based versus frameless, robotic assistance, surgical approach, and targets selection) helps to ensure maximal safety and tissue yield. Pediatric brainstem biopsy permits histological conformation of brainstem lesions leading to accurate diagnosis and the potential for personalized treatment and future therapeutic research.

Development and Validation of a Supplementary Grading Scale for Outcomes of Brainstem Cavernous Malformations.

BACKGROUND: Surgical risk assessment is intriguing for clinical decision-making of brainstem cavernous malformation (BSCM) treatment. While the BSCM grading scale, encompassing size, developmental venous anomaly, crossing axial midpoint, age, and timing of intervention, is increasingly utilized, the clinical relevance of neurological fluctuation and recurrent hemorrhage has not been incorporated. This study aimed to propose a supplementary grading scale with enhanced predictive efficacy. METHODS: Using a retrospective nationwide registry of consecutive patients with BSCMs undergoing surgery in China from March 2011 to May 2023, a new supplementary BSCM grading scale was developed from a derivative cohort of 260 patients and validated in an independent concurrent cohort of 67 patients. The primary outcome was unfavorable neurological function (modified Rankin Scale score >2) at the latest follow-up. The performance of the supplementary grading system was evaluated for discrimination, calibration, and clinical utility and further compared with its original counterpart. RESULTS: Over a follow-up of at least 6 months after surgery, the unfavorable outcomes were 31% in the overall cohort (101/327 patients). A preoperative motor deficit (odds ratio, 3.13; P=0.001), recurrent hemorrhage (odds ratio, 3.05; P<0.001), timing of intervention (odds ratio, 7.08; P<0.001), and crossing the axial midpoint (odds ratio, 2.57; P=0.006) were associated with the unfavorable outcomes and composed the initial Huashan grading variables. A supplementary BSCM grading system was subsequently developed by incorporating the Huashan grading variables into the original BSCM grading scale. The predictive capability of the supplementary scale was consistently superior to the original counterpart in either the derivative cohort (area under the receiver operating characteristic curve, 0.74 [95% CI, 0.68-0.80] for the supplementary versus 0.68 [95% CI, 0.61-0.74] for the original) or the validation cohort (0.75 [95% CI, 0.62-0.87] versus 0.64 [95% CI, 0.48-0.81]). CONCLUSIONS: This study highlights the neurological relevance of BSCM hemorrhage in surgical risk assessment. Via compositing preoperative motor function and recurrent hemorrhages, a supplementary grading scale may improve a dynamic risk assessment for clinical decisions in the management of BSCMs.

Anatomical Study of the Supratentorial Extension for the Retrolabyrinthine Presigmoid Approaches.

BACKGROUND: Supratentorial craniotomy represents the upper part of the combined trans-tentorial or the supra-infratentorial presigmoid approach. In this study, we provide qualitative and quantitative analyses for the supratentorial extension of the presigmoid retrolabyrinthine suprameatal approach (PRSA). METHODS: The infratentorial PRSA followed by the supratentorial extension craniotomy with dividing and removal of the tentorial strip were performed on both sides of 5 injected human cadaver heads (n = 10 sides). Quantitative analysis was performed for the surface area gained (surgical accessibility) by adding the supratentorial craniotomy. Qualitative analysis was performed for the parts of the brainstem, cranial nerves, and vascular structures that became accessible by adding the supratentorial craniotomy. The anatomical obstacles encountered in the added operative corridor were analyzed. RESULTS: The supratentorial extension of PRSA provides an increase in surgical accessibility of 102.65% as compared to the PRSA standalone. The mean surface area of the exposed brainstem is 197.98 (standard deviation: 76.222) and 401.209 (standard deviation: 123.96) for the infratentorial and the combined supra-infratentorial presigmoid approach, respectively. Exposure for parts of III, IV, and V cranial nerves is added after the extension, and the surface area of the outer craniotomy defect has increased by 60.32%. Parts of the basilar, anterior inferior cerebellar, and superior cerebellar arteries are accessible after the supratentorial extension. CONCLUSIONS: The supratentorial extension of PRSA allows access to the supra-trigeminal area of the pons and the lower part of the midbrain. Considering this surgical accessibility and exposure significantly assists in planning such complex approaches while targeting central skull base lesions.

Fully endoscopic approach for resection of brainstem cavernous malformations: a systematic review of the literature.

BACKGROUND: Brainstem cavernous malformations (BCMs) are benign lesions that typically have an acute onset and are associated with a high rate of morbidity. The selection of the optimal surgical approach is crucial for obtaining favorable outcomes, considering the different anatomical locations of various brainstem lesions. Endoscopic surgery is increasingly utilized in treating of BCMs, owing to its depth illumination and panoramic view capabilities. For intra-axial ventral BCMs, the best surgical options are endoscopic endonasal approaches, following the "two-point method. For cavernous hemangiomas on the dorsal side of the brainstem, endoscopy proves valuable by providing enhanced visualization of the operative field and minimizing the need for brain retraction. METHODS: In this review, we gathered data on the fully endoscopic approach for the resection of BCMs, and outlined technical notes and tips. Total of 15 articles were included in this review. The endoscopic endonasal approach was utilized in 19 patients, and the endoscopic transcranial approach was performed in 3 patients. RESULTS: The overall resection rate was 81.8% (18/22). Among the 19 cases of endoscopic endonasal surgery, postoperative cerebrospinal fluid (CSF) leakage occurred in 5 cases, with lesions exceeding 2 cm in diameter in 3 patients with postoperative CSF rhinorrhea. Among the 20 patients with follow-up data, 2 showed no significant improvement after surgery, whereas the remaining 18 patients showed significant improvement compared to their admission symptoms. CONCLUSIONS: This systematic literature review demonstrates that a fully endoscopic approach is a safe and effective option for the resection of BCMs. Further, it can be considered an alternative to conventional craniotomy, particularly when managed by a neurosurgical team with extensive experience in endoscopic surgery, addressing these challenging lesions.

Association of hemorrhage-to-treatment time with outcomes in patients with brainstem cavernous malformations: a nationwide cohort study.

BACKGROUND: Brainstem cavernous malformations (BSCMs) often present with haemorrhage, but the optimal timing for microsurgical intervention remains unclear. This study aims to explore how intervention timing relates to neurological outcomes in haemorrhagic BSCM patients undergoing microsurgery, offering insights for clinical decisions. METHODS: A total of 293 consecutive patients diagnosed with BSCMs, who underwent microsurgery were identified between March 2011 and January 2023 at two comprehensive centres in China, with a postoperative follow-up duration exceeding 6 months. Utilizing logistic regression models with restricted cubic splines, distinct time groups were identified. Subsequently, matching weight analysis compared these groups in terms of outcomes, new haemorrhage rates, cranial nerve deficits, and perioperative complications. The primary outcome was an unfavourable outcome, which was defined as a mRS score greater than 2 at the latest follow-up. RESULTS: Among the 293 patients, 48.5% were female, median age was (39.9±14.3) years, and median haemorrhage-to-treatment time was 42 days. Patients were categorized into acute (≤21 days), subacute (22-42 days), and delay (>42 days) intervention groups. After matching, 186 patients were analyzed. Adjusted analysis showed lower unfavourable outcome rates for acute [adjusted odds ratio (OR), 0.73; 95% CI, 0.65-0.82; P<0.001] and subacute (adjusted OR, 0.83; 95% CI, 0.72-0.95; P=0.007) groups compared to the delay group. Subacute intervention led to fewer cranial nerve deficits (adjusted OR, 0.76; 95% CI, 0.66-0.88, P<0.001). New haemorrhage incidence didn't significantly differ among groups. CONCLUSIONS: For haemorrhagic BSCMs patients, delayed microsurgical intervention that exceeded 42 days after a prior haemorrhage were associated with an increased risk of unfavourable neurological outcomes.

[Microanatomical Investigation of the Subtemporal Transtentorial Approach]. / é¢žä¸‹ç»å°è„‘å¹•å ¥è·¯çš„æ˜¾å¾®è§£å‰–å­¦ç ”ç©¶.

Objective: To study the microanatomic structure of the subtemporal transtentorial approach to the lateral side of the brainstem, and to provide anatomical information that will assist clinicians to perform surgeries on the lateral, circumferential, and petroclival regions of the brainstem. Methods: Anatomical investigations were conducted on 8 cadaveric head specimens (16 sides) using the infratemporal transtentorial approach. The heads were tilted to one side, with the zygomatic arch at its highest point. Then, a horseshoe incision was made above the auricle. The incision extended from the midpoint of the zygomatic arch to one third of the mesolateral length of the transverse sinus, with the flap turned towards the temporal part. After removing the bone, the arachnoid and the soft meninges were carefully stripped under the microscope. The exposure range of the surgical approach was observed and the positional relationships of relevant nerves and blood vessels in the approach were clarified. Important structures were photographed and the relevant parameters were measured. Results: The upper edge of the zygomatic arch root could be used to accurately locate the base of the middle cranial fossa. The average distances of the star point to the apex of mastoid, the star point to the superior ridge of external auditory canal, the anterior angle of parietomastoid suture to the superior ridge of external auditory canal, and the anterior angle of parietomastoid suture to the star point of the 10 adult skull specimens were 47.23 mm, 45.27 mm, 26.16 mm, and 23.08 mm, respectively. The subtemporal approach could fully expose the area from as high as the posterior clinoid process to as low as the petrous ridge and the arcuate protuberance after cutting through the cerebellar tentorium. The approach makes it possible to handle lesions on the ventral or lateral sides of the middle clivus, the cistern ambiens, the midbrain, midbrain, and pons. In addition, the approach can significantly expand the exposure area of the upper part of the tentorium cerebelli through cheekbone excision and expand the exposure range of the lower part of the tentorium cerebelli through rock bone grinding technology. The total length of the trochlear nerve, distance of the trochlear nerve to the tentorial edge of cerebellum, length of its shape in the tentorial mezzanine, and its lower part of entering into the tentorium cerebelli to the petrosal ridge were (16.95±4.74) mm, (1.27±0.73) mm, (5.72±1.37) mm, and (4.51±0.39) mm, respectively. The cerebellar tentorium could be safely opened through the posterior clinoid process or arcuate protrusion for localization. The oculomotor nerve could serve as an anatomical landmark to locate the posterior cerebral artery and superior cerebellar artery. Conclusion: Through microanatomic investigation, the exposure range and intraoperative difficulties of the infratemporal transtentorial approach can be clarified, which facilitates clinicians to accurately and safely plan surgical methods and reduce surgical complications.

Brainstem cavernous hemangioma with improvement of Holmes tremor on excision.

An 8-year-old boy presenting with left-angle paralysis, tremor in upper and lower extremities, and diplopia was diagnosed with hemorrhage from a mesencephalic cavernous hemangioma. He underwent hemangiomectomy through the occipital transtentorial approach 4 weeks post-hemorrhage, after which Holmes tremor (HT) markedly reduced. A year later, hemangioma has not recurred; he is now independent in his daily activities. Early intervention in the subacute stage allows for the complete removal of brainstem cavernomas (BSCs), with minimal risk of complications or sequelae. Proper timing and surgical approach for BSCs can prevent re-bleeding and improve HT after an initial hemorrhage, without any lasting negative consequences.

Resection of the quadrangular lobule of the cerebellum to increase exposure of the cerebellomesencephalic fissure: an anatomical study with clinical correlation.

OBJECTIVE: The lateral aspect of the cerebellomesencephalic fissure frequently harbors vascular pathology and is a common surgical corridor used to access the pons tegmentum, as well as the cerebellum and its superior and middle peduncles. The quadrangular lobule of the cerebellum (QLC) represents an obstacle to reach these structures. The authors sought to analyze and compare exposure of the cerebellar interpeduncular region (CIPR) before and after QLC resection and provide a case series to evaluate its clinical applicability. METHODS: Forty-two sides of human brainstems were prepared with Klingler's method and dissected. The exposure area before and after resection of the QLC was measured and statistically studied. A case series of 59 patients who underwent QLC resection for the treatment of CIPR lesions was presented and clinical outcomes were evaluated at 1-year follow-up. RESULTS: The anteroposterior surgical corridor of the CIPR increased by 10.3 mm after resection of the QLC. The mean exposure areas were 42 mm2 before resection of the QLC and 159.6 mm2 after resection. In this series, ataxia, extrapyramidal syndrome, and akinetic mutism were found after surgery. However, all these cases resolved within 1 year of follow-up. Modified Rankin Scale score improved by 1 grade, on average. CONCLUSIONS: QLC resection significantly increased the exposure area, mainly in the anteroposterior axis. This surgical strategy appears to be safe and may help the neurosurgeon when operating on the lateral aspect of the cerebellomesencephalic fissure.

A novel method of neurophysiological brainstem mapping in neurosurgery.

BACKGROUND: Brainstem mapping with electrical stimulation allows functional identification of neural structures during resection of deep lesions. Single pulses or train of pulses are delivered to map cranial nerves and corticospinal tracts, respectively. NEW METHOD: We introduce a hybrid stimulation technique for mapping the brainstem. The stimulus consists of an electrical single pulse followed by a short train of 3-5 pulses at 500 Hz, at an interval of 60-75 ms. The responses to this stimulation pattern are recorded from appropriate cranial and limb muscles. RESULTS: Both the single pulse and the short train elicit electromyographic responses when motor fibers or motor nuclei of the cranial nerves are stimulated. Responses to the train but not to the preceding single pulse indicate activation of the descending motor tracts, in the mesencephalon and the pons. Conversely, in the medulla, limb responses to stimulation of the corticospinal tracts are elicited by a single pulse. Identification of the extra and intra-axial courses of the trigeminal motor and sensory fibers is possible by recording responses from the masseter and the tongue muscles. COMPARISON WITH EXISTING METHOD(S): To date, either a pulse or a train is delivered during brainstem mapping, switching from one to the other modality according to the expected target structure. This procedure can be time-consuming and may even lead to false negative responses to the stimulation, eventually leading to inaccurate neurosurgical procedures. CONCLUSIONS: The novel hybrid pulse-train technique enhances the advantage of brainstem mapping procedure, minimizing pitfalls and improving patient safety.

Microsurgical Resection of Brainstem Cavernous Malformations in Older Adults: A Multicenter, 30-Year Experience.

BACKGROUND AND OBJECTIVES: Microsurgical resection is the only curative intervention for symptomatic brainstem cavernous malformations (BSCMs), but the management of these lesions in older adults (≥65 years) is not well described. This study sought to address this gap by examining the safety and efficacy of BSCM resection in a cohort of older adults. METHODS: Records of patients who underwent BSCM resection over a 30-year period were reviewed retrospectively. Baseline characteristics and outcomes were compared between older (≥65 years) and younger (<65 years) patients. RESULTS: Of 550 patients with BSCM who met inclusion criteria, 41 (7.5%) were older than 65 years. Midbrain (43.9% vs 26.1%) and medullary lesions (19.5% vs 13.6%) were more common in the older cohort than in the younger cohort ( P = .01). Components of the Lawton BSCM grading system (ie, lesion size, crossing axial midpoint, developmental venous anomaly, and timing of hemorrhage) were not significantly different between cohorts ( P ≥ .11). Mean (SD) Elixhauser comorbidity score was significantly higher in older patients (1.86 [1.06]) than in younger patients (0.66 [0.95]; P < .001). Older patients were significantly more likely than younger patients to have poor outcomes at final follow-up (28.9% vs 13.8%, P = .01; mean follow-up duration, 28.7 [39.1] months). However, regarding relative neurological outcome (preoperative modified Rankin Scale to final modified Rankin Scale), rate of worsening was not significantly different between older and younger patients (23.7% vs 14.9%, P = .15). CONCLUSION: BSCMs can be safely resected in older patients, and when each patient's unique health status and life expectancy are taken into account, these patients can have outcomes similar to younger patients.

Stereotactic frame-based biopsy of infratentorial lesions via the suboccipital-transcerebellar approach with the Zamorano-Duchovny stereotactic system-a retrospective analysis of 79 consecutive cases.

OBJECTIVE: Lesions of the posterior fossa (brainstem and cerebellum) are challenging in diagnosis and treatment due to the fact that they are often located eloquently and total resection is rarely possible. Therefore, frame-based stereotactic biopsies are commonly used to asservate tissue for neuropathological diagnosis and further treatment determination. The aim of our study was to assess the safety and diagnostic success rate of frame-based stereotactic biopsies for lesions in the posterior fossa via the suboccipital-transcerebellar approach. METHODS: We performed a retrospective database analysis of all frame-based stereotactic biopsy cases at our institution since 2007. The aim was to identify all surgical cases for infratentorial lesion biopsies via the suboccipital-transcerebellar approach. We collected clinical data regarding outcomes, complications, diagnostic success, radiological appearances, and stereotactic trajectories. RESULTS: A total of n = 79 cases of stereotactic biopsies for posterior fossa lesions via the suboccipital-transcerebellar approach (41 female and 38 male) utilizing the Zamorano-Duchovny stereotactic system were identified. The mean age at the time of surgery was 42.5 years (± 23.3; range, 1-87 years). All patients were operated with intraoperative stereotactic imaging (n = 62 MRI, n = 17 CT). The absolute diagnostic success rate was 87.3%. The most common diagnoses were glioma, lymphoma, and inflammatory disease. The overall complication rate was 8.7% (seven cases). All patients with complications showed new neurological deficits; of those, three were permanent. Hemorrhage was detected in five of the cases having complications. The 30-day mortality rate was 7.6%, and 1-year survival rate was 70%. CONCLUSIONS: Our data suggests that frame-based stereotactic biopsies with the Zamorano-Duchovny stereotactic system via the suboccipital-transcerebellar approach are safe and reliable for infratentorial lesions bearing a high diagnostic yield and an acceptable complication rate. Further research should focus on the planning of safe trajectories and a careful case selection with the goal of minimizing complications and maximizing diagnostic success.

Neglected tracts of the brainstem: transverse peduncular tract of Gudden and taenia pontis.

OBJECTIVE: The anatomy and function of the brainstem have fascinated scientists for centuries; however, the brainstem remains one of the least studied regions of the human brain. As the authors delved into studying this structure, they observed a growing tendency to forget or neglect previously identified structures. The aim of this study was to describe two such structures: the transverse peduncular tract, also known as the Gudden tract, and the taenia pontis. The authors analyzed the potential effects of neglecting these structures during brainstem surgery and the implications for clinical practice. METHODS: After removal of the arachnoid and vascular structures, 20 human brainstem specimens were frozen and stored at -16°C for 2 weeks, according to the method described by Klingler. The specimens were then thawed and dissected with microsurgical techniques. The results of microsurgical fiber dissection at each step were photographed. RESULTS: This study revealed two previously neglected or forgotten structures within the brainstem. The first is the transverse peduncular tract of Gudden, which arises from the brachium of the superior colliculus. This tract follows an arcuate course along the lateral and ventral surfaces of the midbrain, perpendicular to the cerebral peduncle, and terminates in the nuclei of the transverse peduncular tract within the interpeduncular fossa. The second structure is the taenia pontis, which originates contralaterally in the interpeduncular fossa. It becomes visible at the level of the pontomesencephalic sulcus and extends to the base of the lateral mesencephalic sulcus, where it divides into several thin bundles. Along the interpeduncular sulcus, between the superior and middle cerebellar peduncles, it reaches the parabrachial recess and enters the cerebellum. CONCLUSIONS: Recently, with increasing understanding and expertise in brainstem research, surgical approaches to this area have become more common, emphasizing the importance of a detailed knowledge of the brainstem. The two structures mentioned in this paper are described in history books and were widely studied in the 19th century but have not been mentioned in modern literature. The authors propose that a deeper understanding of these structures may prove valuable in neurosurgical practice and help reduce patient comorbidity.

[Brain Stem and Para-Brain Stem Lesions].

Surgeries for brainstem lesions and adjacent areas needs meticulous manipulation in the profoundly deep surgical field. Moreover, it is associated with a high risk of complications pertinent to resection. The opportunity for a surgeon to amass extensive surgical experience in these lesions is limited. Additionally, the reduced tissue mobility in the brainstem, compared to other lesions, makes selecting the optimal surgical approach critical. Preoperative simulation is pivotal in surmounting these challenges. However, the limitations of preoperative simulations should be recognized in accurately depicting diminutive vessels and cranial nerves around the brainstem. Incorporating intraoperative anatomical observations and data from intraoperative monitoring into a surgical strategy is imperative. Here, we present three cases in which we believe preoperative simulation was effective; a cavernous hemangioma of the brainstem, trochlear schwannoma, and diffuse midline glioma in the pons.

Axial Sections of Brainstem Safe Entry Zones and Clinical Importance of Intrinsic Structures: A Review.

Brainstem surgery is more difficult and riskier than surgeries in other parts of the brain due to the high density of critical tracts and cranial nerves nuclei in this region. For this reason, some safe entry zones into the brainstem have been described. The main purpose of this article is to bring on the agenda the significance of the intrinsic structures of the safe entry zones to the brainstem. Having detailed information about anatomic localization of these sensitive structures is important to predict and avoid possible surgical complications. In order to better understand this complex anatomy, we schematically drew the axial sections of the brainstem showing the intrinsic structures at the level of 9 safe entry zones that we used, taking into account basic neuroanatomy books and atlases. Some illustrations are also supported with intraoperative pictures to provide better surgical orientation. The second purpose is to remind surgeons of clinical syndromes that may occur in case of surgical injury to these delicate structures. Advanced techniques such as tractography, neuronavigation, and neuromonitorization should be used in brainstem surgery, but detailed neuroanatomic knowledge about safe entry zones and a meticulous surgery are more important. The axial brainstem sections we have drawn can help young neurosurgeons better understand this complex anatomy.

Intraoperative Neurophysiologic Monitoring and Mapping in Children Undergoing Brainstem Surgery.

SUMMARY: Intraoperative neurophysiologic monitoring during surgery for brainstem lesions is a challenge for intraoperative neurophysiologists and surgeons. The brainstem is a small structure packed with vital neuroanatomic networks of long and short pathways passing through the brainstem or originating from it. Many central pattern generators exist within the brainstem for breathing, swallowing, chewing, cardiovascular regulation, and eye movement. During surgery around the brainstem, these generators need to be preserved to maintain their function postoperatively. This short review presents neurophysiologic and neurosurgical experiences of brainstem surgery in children.

Postoperative disappearance of leptomeningeal enhancement around the brainstem in glioblastoma.

PURPOSE: Leptomeningeal enhancement (LME) suggests leptomeningeal dissemination (LMD) of tumor cells, which is a complication of end-stage glioblastoma, and is associated with a poor prognosis. However, magnetic resonance imaging (MRI) occasionally indicates the disappearance of peri-brainstem LME after surgical resection of glioblastoma. Since preoperative LMD may affect treatment indications, we aimed to analyze the clinical significance of preoperative LME of the brainstem in glioblastoma. METHODS: We retrospectively collected clinical and radiological data from consecutive patients with glioblastoma and preoperative LME of the brainstem, who were treated at our hospital between 2017 and 2020. RESULTS: Among 112 patients with glioblastoma, nine (8%) showed preoperative LME of the brainstem. In comparison with tumors without LME, tumor size was significantly associated with the preoperative LME of the brainstem (p = 0.016). In addition, there was a trend toward significance for a relationship between deep tumor location and preoperative LME of the brainstem (p = 0.058). Notably, among six patients who underwent surgical resection for glioblastoma with LME of the brainstem, four showed significant radiological disappearance of the LME on postoperative MRI. This suggests that the LME did not result from LMD in these cases. Moreover, these four patients lived longer than would be expected from the presence of LMD. However, this LME disappearance was not observed after biopsy or chemoradiotherapy. CONCLUSIONS: These findings suggest that preoperative LME does not necessarily indicate the presence of untreatable LMD; moreover, LME may disappear after surgical tumor resection. Thus, transient preoperative LME could be attributed to other mechanisms, including impaired venous flow due to intratumoral arteriovenous shunts, which can be resolved by reducing the tumor burden.

Keyhole Retrosigmoid Craniotomy for Lateral Pontine Cavernous Malformation.

With improvements in anesthesia, monitoring, and peroperative care, the surgical removal of intrinsic brainstem pathology has become a possibility.1 Although surgical removal of deep-seated lesions continues to have significant morbidity, at least temporarily, associated with it, removal of exophytic lesions can be accomplished with little disability for the patient. The key to a good outcome, when removing cerebral cavernous malformation, is preservation of adjacent neurovascular bundles, use of sharp dissection over blunt pulling, judicious use of cautery in and around the brainstem, and preservation of the developmental venous anomaly, when present. The authors present a case of a lateral pontine cerebral cavernous malformation that was exophytic at the lateral and peritrigeminal safe entry zones.2 Neuromonitoring was used an adjunct to ensure safety of the procedure. The lesion is accessed using a keyhole retrosigmoid craniotomy (Video 1). We do not routinely use lumbar drains for these procedures as careful arachnoid dissection can result in adequate cerebrospinal fluid release. The window of access to this area is between CN 5 and the CN 7/8 complex. The arachnoid over the nerves is preserved, but the layer between the nerves is exposed to gain access to the lateral pons. The lesion is sharply dissected from the lateral pons, taking care to save the developmental venous anomaly, from which this lesion arises.

Trans-radial artery microcatheter angiography-assisted juvenile ruptured brainstem arteriovenous malformation resection.

BACKGROUND: Due to their crucial functional location, surgical treatment of brainstem arteriovenous malformations (AVMs) has always been challenging. For unruptured AVMs, we can determine whether radiological therapy, interventional treatment, or surgical resection is feasible based on the AVM structure. However, for ruptured AVMs, microsurgical resection and interventional embolization are effective methods to prevent further rupture. In the microsurgical resection of AVMs, we usually use a hybrid operation to confirm the AVM structure and determine if the AVM is completely resected during the surgery. METHOD: We report a case of juvenile ruptured brainstem AVM resection. The right lateral position and left suboccipital retrosigmoid approach were used. We established an interventional approach via left radial artery and set a microcatheter in the feeding artery. Methylene blue injection via a microcatheter showed the AVM structure, and we totally resected the brainstem AVM under electrophysiological monitoring and navigation. Intraoperative angiography was performed to ensure complete resection without residual nidus. CONCLUSION: This case demonstrates that the trans-radial approach is convenient and safe for special positions in hybrid operations. Methylene blue injection via a microcatheter in the feeding artery provides clearer visualization of the AVM structure under the microscope.

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

OBJECTIVE: 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. METHODS: A retrospective analysis was performed for 5 consecutive patients who underwent surgery via the eTSTCA for treating ventral pontine CMs. RESULTS: 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. CONCLUSIONS: 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.