Brainstem Cavernoma Surgery: The State of the Art

Olivary body exposure through far lateral and lower retrosigmoid approaches. Comparative analysis of the exposed surface and angle of attack

OBJECTIVES

Throughout neurosurgical history, the treatment of intrinsic lesions located in the brainstem has been subject of much controversy. The brainstem is the anatomical structure of the central nervous system (CNS) that presents the highest concentration of nuclei and fibers, and its simple manipulation can lead to significant morbidity and mortality. Once one of the safe entry points at the medulla oblongata has been established, we wanted to evaluate the safest approach to the olivary body (the most used safe entry zone on the anterolateral surface of the medulla oblongata). The proposed objective was to evaluate the working channel from the surface of each of the far lateral and retrosigmoid approaches to the olivary body: distances, angles of attack and channel content.

MATERIAL AND METHODS

To complete this work, a total of 10 heads injected with red/blue silicone were used. A total of 40 approaches were made in the 10 heads used (20 retrosigmoid and 20 far lateral). After completing the anatomical study and obtaining the data referring to all the approaches performed, it was decided to expand the sample of this research study by using 30 high-definition magnetic resonance imaging of anonymous patients without cranial or cerebral pathology. The reference points used were the same ones defined in the anatomical study. After defining the working channels in each of the approaches, the working distances, angle of attack, exposed surface, and the number of neurovascular structures present in the central trajectory were analyzed.

RESULTS

The distances to the cranial and medial region of the olivary body were 52.71 mm (SD 3.59) from the retrosigmoid approach and 27.94 mm (SD 3.99) from the far lateral; to the most basal region of the olivary body, the distances were 49.93 (SD 3.72) from the retrosigmoid approach and 18.1 mm (SD 2.5) from the far lateral. The angle of attack to the caudal region was 19.44° (SD 1.3) for the retrosigmoid approach and 50.97° (SD 8.01) for the far lateral approach; the angle of attack to the cranial region was 20.3° (SD 1.22) for the retrosigmoid and 39.9° (SD 5.12) for the far lateral. Regarding neurovascular structures, the probability of finding an arterial structure is higher for the lateral far, whereas a neural structure will be more likely from a retrosigmoid approach.

CONCLUSIONS

As conclusions of this work, we can say that far lateral approach presents more favorable conditions for the microsurgical treatment of intrinsic bulbar and bulbomedullary lesions approached through the caudal half of the olivary body. In those cases of bulbar and pontine-bulbar lesions approached through the cranial half of the olivary body, the retrosigmoid approach can be considered for selected cases.

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.

The benefit and outcome prediction of acute surgery for hemorrhagic brainstem cavernous malformation with impending respiratory failure

OBJECTIVES

Impending respiratory failure is catastrophic neurological deterioration caused by repeated c of a brainstem cavernous malformation (BSCM). The benefit and outcome prediction of acute surgery for this fatal condition is rarely reported. In this study, the authors reported a case series of acute surgical treatment (≤3 weeks after the last hemorrhagic episode) for the BSCM with impending respiratory failure and reviewed literature over the past 20 years.

MATERIALS AND METHODS

Clinical and outcome data from 6 consecutive acute surgically-treated BSCM patients were analyzed. Intracerebral hemorrhage (ICH) scores, primary pontine hemorrhage (PPH) scores, and Lawton's BSCM grading were applied for surgical outcome prediction. Ten related articles were included for the literature review.

RESULTS

There were three men and three women, with a mean age of 32.2 ± 9.3 years (range 15-45 years). The BSCMs were located at the pons in 5 cases and the medulla in 1 case. The ICH score was 1-2 in all cases, while the PPH score was 0 in all pontine BSCMs. For Lawton's BSCM grading, 3 cases were grade 2, 2 cases were grade 3, and 1 case was grade 1. All patients achieved spontaneous respiratory dysfunction relief postoperatively and significantly improved at follow-up (mean 4.47 ± 0.24 years;range4.0-5.6 years).

CONCLUSIONS

Repeated hemorrhagic BSCM with impending respiratory failure can benefit from acute surgical treatment. The ICH score, PPH score, and Lawton's BSCM grading are promisingly useful tools for fast and efficient surgical outcome prediction.

Utility of a Quantitative Approach Using Diffusion Tensor Imaging for Prognostication Regarding Motor and Functional Outcomes in Patients With Surgically Resected Deep Intracranial Cavernous Malformations

BACKGROUND

Resection of deep intracranial cavernous malformations (CMs) is associated with a higher risk of neurological deterioration and uncertainty regarding clinical outcomes.

OBJECTIVE

To examine diffusion tractography imaging (DTI) data evaluating the corticospinal tract (CST) in relation to motor and functional outcomes in patients with surgically resected deep CMs.

METHODS

Perilesional CST was characterized as disrupted, displaced, or normal. Mean fractional anisotropy (FA) values were obtained for whole ipsilateral CST and in 3 regions: subcortical (proximal), perilesional, and distally. Mean FA values in anatomically equivalent regions in the contralateral CST were obtained. Clinical and radiological data were collected independently. Multivariable regression analysis was used for statistical analysis.

RESULTS

A total of 18 patients [brainstem (15) and thalamus/basal ganglia (3); median follow-up: 270 d] were identified over 2 yr. The CST was identified preoperatively as disrupted (6), displaced (8), and normal (4). Five of 6 patients with disruption had weakness. Higher preoperative mean FA values for distal ipsilateral CST segment were associated with better preoperative lower (P < .001), upper limb (P = .004), postoperative lower (P = .005), and upper limb (P < .001) motor examination. Preoperative mean FA values for distal ipsilateral CST segment (P = .001) and contralateral perilesional CST segment (P < .001) were negatively associated with postoperative modified Rankin scale scores.

CONCLUSION

Lower preoperative mean FA values for overall and defined CST segments corresponded to worse patient pre- and postoperative motor examination and/or functional status. FA value for the distal ipsilateral CST segment has prognostic potential with respect to clinical outcomes.

Endoscope-assisted resection of a brainstem cavernoma

Procedures on cavernous malformations of the brainstem are challenging due to their eloquent location. This accounts especially for recurrent cavernomas as surgical scars, adhesions, and functional shift might have occurred since primary surgery. We report on a 38-year-old female patient with a large recurrent brainstem cavernoma, who underwent previous successful surgery and experienced recurrent bleeding about 2 years later. She harbored a large associated developmental venous anomaly (DVA) traversing the cavernoma through the midline of the brainstem. In order to visualize complete resection and preservation of the DVA at the same time, endoscopic-assisted resection within the brainstem after decompression in the semisitting position was performed.

The video can be found here: https://youtu.be/K1p-Sx7jUpA.

Impact of Timing of Intervention Among 397 Consecutively Treated Brainstem Cavernous Malformations

BACKGROUND

Surgical resection of brainstem cavernous malformations (BSCMs) is challenging, and patient selection and timing of intervention remain controversial.

OBJECTIVE

To evaluate the impact of surgical timing and predictors of neurological outcome after surgical resection of BSCMs.

METHODS

Consecutive adult patients (≥18 years) with BSCMs undergoing surgical resection between 1985 and 2014 by the senior author (RFS) were retrospectively reviewed. Patient demographics, lesion characteristics, imaging results, surgical approach, and perioperative and long-term neurological morbidity were analyzed.

RESULTS

Data were analyzed for a total of 397 adult patients (160, 40% male). On univariate analysis, a greater proportion of patients treated within 6 weeks of hemorrhage had an improved Glasgow Outcome Scale score (P = .06). On logistic regression analysis, patients treated within 6 weeks of hemorrhage experienced improved clinical outcomes (odds ratio = 1.73; 95% confidence interval = 1.06-2.83; P = .03).

CONCLUSIONS

Although BSCM surgery is associated with significant perioperative morbidity and mortality, favorable long-term hemorrhage rates and symptom resolution can be achieved in a carefully selected group of patients. Overall, patients treated acutely, within 6 weeks, benefited the most from surgical intervention.

Endoscopic endonasal transclival approach to a pontine cavernous malformation: case report

Cavernous malformations of the brainstem are difficult to manage because of their location in eloquent tissue and their high propensity for symptomatic bleeding. Traditional neurosurgical approaches are often associated with significant morbidities. Here we present the case of a 15 year-old male patient with an acute onset of severe cephalalgia associated with neurological signs (right cranial nerve VI, VII and VIII palsies). MRI revealed a ventral pontine cavernous malformation with signs of recent bleeding. The lesion was removed by way of an endoscopic endonasal transclival approach. Post-operative neurological examination showed a dramatic improvement in cranial nerves function. The patient remains stable two years after surgery.

Anatomy and approaches along the cerebellar-brainstem fissures

OBJECT Fissure dissection is routinely used in the supratentorial region to access deeply situated pathology while minimizing division of neural tissue. Use of fissure dissection is also practical in the posterior fossa. In this study, the microsurgical anatomy of the 3 cerebellar-brainstem fissures (cerebellomesencephalic, cerebellopontine, and cerebellomedullary) and the various procedures exposing these fissures in brainstem surgery were examined. METHODS Seven cadaveric heads were examined with a microsurgical technique and 3 with fiber dissection to clarify the anatomy of the cerebellar-brainstem and adjacent cerebellar fissures, in which the major vessels and neural structures are located. Several approaches directed along the cerebellar surfaces and fissures, including the supracerebellar infratentorial, occipital transtentorial, retrosigmoid, and midline suboccipital approaches, were examined. The 3 heads examined using fiber dissection defined the anatomy of the cerebellar peduncles coursing in the depths of these fissures. RESULTS Dissections directed along the cerebellar-brainstem and cerebellar fissures provided access to the posterior and posterolateral midbrain and upper pons, lateral pons, floor and lateral wall of the fourth ventricle, and dorsal and lateral medulla. CONCLUSIONS Opening the cerebellar-brainstem and adjacent cerebellar fissures provided access to the brainstem surface hidden by the cerebellum, while minimizing division of neural tissue. Most of the major cerebellar arteries, veins, and vital neural structures are located in or near these fissures and can be accessed through them.

Longitudinal evaluation of corticospinal tract in patients with resected brainstem cavernous malformations using high-definition fiber tractography and diffusion connectometry analysis: preliminary experience

OBJECT

Brainstem cavernous malformations (CMs) are challenging due to a higher symptomatic hemorrhage rate and potential morbidity associated with their resection. The authors aimed to preoperatively define the relationship of CMs to the perilesional corticospinal tracts (CSTs) by obtaining qualitative and quantitative data using high-definition fiber tractography. These data were examined postoperatively by using longitudinal scans and in relation to patients' symptomatology. The extent of involvement of the CST was further evaluated longitudinally using the automated "diffusion connectometry" analysis.

METHODS

Fiber tractography was performed with DSI Studio using a quantitative anisotropy (QA)-based generalized deterministic tracking algorithm. Qualitatively, CST was classified as being "disrupted" and/or "displaced." Quantitative analysis involved obtaining mean QA values for the CST and its perilesional and nonperilesional segments. The contralateral CST was used for comparison. Diffusion connectometry analysis included comparison of patients' data with a template from 90 normal subjects.

RESULTS

Three patients (mean age 22 years) with symptomatic pontomesencephalic hemorrhagic CMs and varying degrees of hemiparesis were identified. The mean follow-up period was 37.3 months. Qualitatively, CST was partially disrupted and displaced in all. Direction of the displacement was different in each case and progressively improved corresponding with the patient's neurological status. No patient experienced neurological decline related to the resection. The perilesional mean QA percentage decreases supported tract disruption and decreased further over the follow-up period (Case 1, 26%-49%; Case 2, 35%-66%; and Case 3, 63%-78%). Diffusion connectometry demonstrated rostrocaudal involvement of the CST consistent with the quantitative data.

CONCLUSIONS

Hemorrhagic brainstem CMs can disrupt and displace perilesional white matter tracts with the latter occurring in unpredictable directions. This requires the use of tractography to accurately define their orientation to optimize surgical entry point, minimize morbidity, and enhance neurological outcomes. Observed anisotropy decreases in the perilesional segments are consistent with neural injury following hemorrhagic insults. A model using these values in different CST segments can be used to longitudinally monitor its craniocaudal integrity. Diffusion connectometry is a complementary approach providing longitudinal information on the rostrocaudal involvement of the CST.

The 6 thalamic regions: surgical approaches to thalamic cavernous malformations, operative results, and clinical outcomes

OBJECT

The ideal surgical approach to thalamic cavernous malformations (CMs) varies according to their location within the thalamus. To standardize surgical approaches, the authors have divided the thalamus into 6 different regions and matched them with the corresponding surgical approach.

METHODS

The regions were defined as Region 1 (anteroinferior), Region 2 (medial), Region 3 (lateral), Region 4 (posterosuperior), Region 5 (lateral posteroinferior), and Region 6 (medial posteroinferior). The senior author's surgical experience with 46 thalamic CMs was reviewed according to this classification. An orbitozygomatic approach was used for Region 1; anterior ipsilateral transcallosal for Region 2; anterior contralateral transcallosal for Region 3; posterior transcallosal for Region 4; parietooccipital transventricularfor Region 5; and supracerebellar-infratentorial for Region 6.

RESULTS

Region 3 was the most common location (17 [37%]). There were 5 CMs in Region 1 (11%), 9 in Region 2 (20%), 17 in Region 3 (37%), 3 in Region 4 (6%), 4 in Region 5 (9%), and 8 in Region 6 (17%). Complete resection was achieved in all patients except for 2, who required a second-stage operation. The mean follow-up period was 1.7 years (range 6 months-9 years). At the last clinical follow-up, 40 patients (87%) had an excellent or good outcome (modified Rankin Scale [mRS] scores 0-2) and 6 (13%) had poor outcome (mRS scores 3-4). Relative to their preoperative condition, 42 patients (91%) were unchanged or improved, and 4 (9%) were worse.

CONCLUSIONS

The authors have presented the largest series reported to date of surgically treated thalamic CMs, achieving excellent results using this methodology. In the authors' experience, conceptually dividing the thalamus into 6 different regions aids in the selection of the ideal surgical approach fora specific region.

Endoscopic approaches to brainstem cavernous malformations: Case series and review of the literature

Background:

Symptomatic cavernous malformations involving the brainstem are frequently difficult to access via traditional methods. Conventional skull-base approaches require significant brain retraction or bone removal to provide an adequate operative corridor. While there has been a trend toward limited employment of the most invasive surgical approaches, recent advances in endoscopic technology may complement existing methods to access these difficult to reach areas.

Case Descriptions:

Four consecutive patients were treated for symptomatic, hemorrhagic brainstem cavernous malformations via fully endoscopic approaches (endonasal, transclival; retrosigmoid; lateral supracerebellar, infratentorial; endonasal, transclival). Together, these lesions encompassed all three segments of the brainstem. Three of the patients had complete resection of the cavernous malformation, while one patient had stable residual at long-term follow up. Associated developmental venous anomalies were preserved in the two patients where one was identified preoperatively. Three of the four patients maintained stable or improved neurological examinations following surgery, while one patient experienced ipsilateral palsies of cranial nerves VII and VIII. The first transclival approach resulted in a symptomatic cerebrospinal fluid leak requiring re-operation, but the second did not. Although there are challenges associated with endoscopic approaches, relative to our prior microsurgical experience with similar cases, visualization and illumination of the surgical corridors were superior without significant limitations on operative mobility.

Conclusion:

The endoscope is a promising adjunct to the neurosurgeon's ability to approach difficult to access brainstem cavernous malformations. It allows the surgeon to achieve well-illuminated, panoramic views, and by combining approaches, can provide minimally invasive access to most regions of the brainstem.

The Far Lateral Transpontomedullary Sulcus Approach to Pontine Cavernous Malformations: Technical Report and Surgical Results

BACKGROUND:

Pontine cavernous malformations (CMs) located on a peripheral pontine surface or the fourth ventricular floor are resectable lesions, but those deep within the pons away from a pial surface are typically observed. However, the anterior bulge of the pons formed by the brachium pontis creates a unique entry point for access to deep pontine lesions from below, working upward through the pontomedullary sulcus.

OBJECTIVE:

We developed a transpontomedullary sulcus (TPMS) approach to these lesions.

METHODS:

The TPMS approach used the far lateral craniotomy and upper vagoaccessory triangle to define the surgical corridor. The entry point was above the olive, lateral to the pyramidal tracts and cranial nerve (CN) VI, above the preolivary sulcus and CN XII, and medial to CNs VII and VIII and CNs IX through XI.

RESULTS:

Four patients underwent this approach. All presented with hemorrhage and CN VI palsies. All pontine CMs were resected completely. Three patients were improved or unchanged, with good outcomes (modified Rankin Scale score ⩽2) in all patients.

CONCLUSION:

The central pons remains difficult territory to access, and new surgical corridors are needed. The bulging underbelly of the pons allows access to pontine lesions deep to the pial surface from below. The far lateral TPMS approach is a novel and more direct alternative to the retrosigmoid transmiddle cerebellar peduncle approach. Unlike the retrosigmoid approach, the TPMS approach requires minimal parenchymal transgression and uses a brainstem entry point medial to most lower CNs. Favorable results demonstrate the feasibility of resecting pontine CMs that might have been previously deemed unresectable.

Surgical management of pediatric brainstem cavernous malformations

OBJECT

The goal of this study was to evaluate surgical outcomes of pediatric brainstem cavernous malformations (CMs) and identify the risk factors associated with postoperative full recovery and rebleeding.

METHODS

The clinical charts and radiographs from a series of 52 pediatric patients (37 male and 15 female; mean age 12.2 years; range 1-17 years) who underwent surgery for brainstem CMs between 1996 and 2011 were reviewed. Follow-up evaluation measures were obtained retrospectively. Neurological function was evaluated using the modified Rankin Scale (mRS) score.

RESULTS

The lesion locations among the 52 patients included the midbrain (n = 7, 13.5%), pons (n = 38, 73.1%), and medulla (n = 7, 13.5%). The mean duration of symptoms was 18.5 months, and the preoperative annual hemorrhage and rebleeding rates were 12.3% and 32.5% per patient-year, respectively. The mean lesion size was 2.1 cm. Gross-total resection without surgery-related death was achieved in 49 patients (94.2%). Immediate postoperative reduced neurological function was observed in 17 patients (32.7%). Surgical morbidities developed in 25 patients (48.1%) and remained in 11 patients (21.2%) after 7.9 years of follow-up. The mean mRS scores at admission, discharge after surgery, 3 and 6 months postsurgery, and recent evaluation were 2.0, 2.3, 2.0, 1.5, and 1.0, respectively. The postoperative mRS scores at 6 months (p < 0.001) and on recent evaluation (p < 0.001) were significantly lower than those at admission. Postoperative rebleeding occurred in 2 patients, and the postoperative annual rebleeding rate was 0.5% per patient-year. By the most recent evaluation, 10 patients (19.2%) had achieved full recovery and all patients were either improved (n = 32, 61.5%) or unchanged (n = 20, 38.5%). The adverse predictors for full recovery included age ≥ 12 years (HR 0.230, p = 0.021), ≥ 2 preoperative hemorrhages (HR 0.124, p = 0.048), and poor preoperative status (HR 0.197, p = 0.040). An HR < 1 predicted poor complete recoveries. The single risk factor predicting postoperative rebleeding was incomplete resection (χ2 = 4.340, p = 0.037).

CONCLUSIONS

Fair outcomes for pediatric brainstem CMs could be obtained through surgery, but only a few patients achieved full recovery. Thus, to minimize surgical morbidity, surgical planning must be tailored to individual patients in all cases in which an operation is warranted. Complete resection must be attempted to reduce the risk of postoperative rebleeding. The predictors associated with complete postoperative recovery were referential for determining treatment.

Microsurgery and radiosurgery for brainstem cavernomas: effective and complementary treatment options

OBJECTIVE

To evaluate treatment options for brainstem cavernous malformations (BSCMs) using the results from a center with long-standing experience in microsurgical resection and Gamma Knife radiosurgery (GKRS) treatment of BSCMs.

METHODS

Study participants were 67 symptomatic patients with BSCMs who were treated either microsurgically (n = 29) or radiosurgically (n = 38). Patients were followed for a minimum of 2 years (median, 7.7 years). A recent follow-up was performed.

RESULTS

Patients receiving surgical treatment had mainly large, superficially seated lesions and experienced preoperative hemorrhages more often and presented with higher preoperative modified Rankin Scale scores. Patients receiving GKRS harbored smaller, deep-seated lesions, reflecting a selection bias. In both treatment groups, patients presented with significantly better modified Rankin Scale scores at follow-up than before intervention. Overall annual preoperative hemorrhage rates were 3.2% in microsurgery patients and 2.3% in radiosurgery patients. In the preoperative observation period, the rehemorrhage rate was 25.1% for microsurgery patients and 7.2% for radiosurgery patients. Hemorrhage rate after GKRS decreased significantly to 0.6% after 2 years. The postoperative hemorrhage rate was 8.8% but only for microsurgery patients with residual lesions. Advancements in microsurgical techniques improved surgical outcomes, resulting in a high total excision rate in the modern era.

CONCLUSIONS

In the treatment of BSCM, patient selection and timing of surgery are crucial. If applied in a multidisciplinary neurosurgical center, microsurgery and radiosurgery are complementary treatment options that both result in reduced bleeding rates and improvement of clinical outcome.