A systematic review and meta-analysis of 25 studies show that the incidence of symptomatic hemorrhage or rehemorrhage is higher in brainstem lesions. First symptomatic hemorrhage increases the chance of symptomatic rehemorrhage, which decreases after 2 years 1). But reported variance in the literature may also be due to study limitations along with selection, patient and disease-specific; follow-up; and recall bias. An accurate assessment of hemorrhagic risk along with evaluation of patient and lesion-specific characteristics is critical in the decision-making process for potential intervention, as microsurgical intervention can significantly decrease the risk of future hemorrhage, but may be associated with significant complications 2).
Rather than developing a grading system for all cerebral cavernous malformations that is weak with BSCMs, Garcia et al. propose a system for the patients who need it most. The BSCM grading system differentiates patients who might expect favorable surgical outcomes and offers guidance to neurosurgeons forced to select these patients 3).
Preoperative diffusion tensor imaging DTI and diffusion tensor tractography (DTT) should be considered in the resection of symptomatic BSCMs. These imaging studies may influence the selection of surgical approach or brainstem entry zones, especially in deep-seated lesions without pial or ependymal presentation. DTI/DTT findings may allow for more aggressive management of lesions previously considered surgically inaccessible. Preoperative DTI/DTT changes do not appear to correlate with functional postoperative outcome in long-term follow-up 4)
Intact corticospinal tract (CST) morphology in diffusion tensor imaging DTI predicts a favorable postoperative outcome in patients with BSC. Interrupted CSTs and decreased Fractional anisotropy (FA)-values correlate well within lesion level, nevertheless morphologic characteristics and diffusion parameter changes cannot predict poor prognosis. Caudal and rostral diffusion parameters can provide more information of the integrity of CSTs compared with morphological study alone 5).
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 6).
Brainstem cavernous malformations are associated with a considerable risk of hemorrhage and subsequent morbidity, with significant focal impairment caused by hemorrhages leading to facial nerves damage 7).
Favorable surgical outcomes can be predicted in brainstem CM patients with early age at presentation, pontine cavernous malformationlocation of the cavernoma, favorable preoperative mRS and those undergoing early surgery. The outcomes at long-term follow-up were associated with location of the CM in the brainstem, size of the CM and the preoperative mRS 8).
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 ± 13.0 years with microsurgical resection of a total of 37 different BSCMs between 2002 and 2011. Median clinical follow-up was 44.0 months (range 8-116 months). 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 6 months after surgery 9).
Consecutive patients with brainstem cavernomas who underwent surgical removal from June 2007 to December 2014 were retrospectively analysed. Transcranial motor-evoked potential (MEP) and somatosensory-evoked potential (SSEP) monitorings were performed in all cases. The evoked potential (EP) monitoring data were reviewed and related to new postoperative motor and sensory deficits and postoperative imaging. Clinical outcomes were assessed during follow-up.
Twenty-six consecutive patients with brainstem cavernoma underwent 27 surgical resections within this study. MEP and SSEP monitoring was technically feasible in 26 and 27 cases, respectively. MEP sensitivity and specificity were 33 and 88 %, respectively. MEP positive and negative predictive values were 28 and 78 %, respectively. SSEP sensitivity and specificity were 20 and 81 %, respectively. SSEP positive and negative predictive values were 20 and 81 %, respectively 10)
A consecutive, single-surgeon series of 104 patients was used to assess preoperative clinical and imaging predictors of microsurgical outcomes. Univariable logistic regression identified predictors and a multivariable logistic regression model tested the association of the combined predictors with final modified Rankin Scale scores. A grading system assigned points for lesion size, location crossing the brainstem's midpoint, presence of developmental venous anomaly, age, and time from last hemorrhage to surgery.
Average maximal diameter of BSCMs was 19.5 mm; 50% crossed the axial midpoint; 54.8% had developmental venous anomalies; mean age was 42.1 years; and median time from last hemorrhage to surgery was 60 days. One patient died (0.96%), and 15 patients (14.4%) experienced worsened cranial nerve or motor dysfunction, of which 10 increased their modified Rankin Scale scores (9.6%). BSCM grades ranged from 0 to 7 points and predicted outcomes with high accuracy (receiver operating characteristic = 0.86, 95% confidence interval: 0.78-0.94) 11).
Maurer et al. present case series of patients who underwent surgical resection of brainstem cavernous malformations using minimally invasive approaches at our institution from January 2012 to August 2014, all of whom had experienced at least one hemorrhage prior to presentation. Approach choice was determined by location of the cavernous malformation in relation to the brainstem surface. Postoperatively, there were three instances of transient neurologic symptoms, all of which resolved at time of last follow-up. All eight patients experienced neurologic improvement after surgery, with four patients showing no deficits at last follow-up. Approach selection rationale and technical nuances are presented on a case-by-case basis. With carefully planned keyhole approaches to cavernous malformations presenting to the brainstem surface, excellent results may be achieved without the necessity of larger conventional craniotomies. They believe the nuances presented may be of use to others in the surgical treatment of these lesions 12).
36 consecutive patients (12 men, 24 women; mean age, 42 years) who underwent microsurgical resection of brainstem cavernomas between 1996 and 2006. Medical records, surgical records, and neuroimaging examinations were evaluated. All 36 patients presented with > or =1 hemorrhage from the cavernomas and preoperatively displayed some neurological symptoms. Surgical approach was midline suboccipital for 16 pontine and/or medullary cavernomas under the floor of the fourth ventricle, retrosigmoid for 10 lateral mesencephalic, pontine, and/or medullary cavernomas, occipital transtentorial approach for 2 thalamomesencephalic and 3 mesencephalic cavernomas, combined petrosal for 2 pontine cavernomas, and other for 3 cavernomas. Complete resection according to postoperative magnetic resonance imaging was achieved in 33 of 36 patients. No mortality was encountered in this study. New neurological deficit occurred in the early postoperative period for 18 patients, but was transient in 15 of these. Neurological state as of final follow-up was improved in 16 patients (44%), unchanged in 17 (47%), and worsened in 3 (8%) compared with preoperatively. In conclusion, symptomatic brainstem cavernomas should be considered for surgical treatment. Careful selection of the optimal operative approach and a meticulous microsurgical technique are mandatory 13).