Neurosurgery Blog

Acta Neurochir (2011) 153:1753–1759. DOI 10.1007/s00701-011-1065-7

Brainstem surgery bears a risk of damage to the corticospinal tract (CST). Motor-evoked potentials (MEPs) are used intraoperatively to monitor CST function in order to detect CST damage at a reversible stage and thus impede permanent neurological deficits. While the method of MEP is generally accepted, warning criteria in the context of brainstem surgery still have to be agreed on.

Method We analyzed 104 consecutive patients who underwent microsurgical resection of lesions affecting the brainstem. Motor grade was documented prior to surgery, early postoperatively and at discharge. A baseline MEP stimulation intensity threshold was defined and intraoperative testing aimed to keep MEP response amplitude constant. MEPs were considered deteriorated and the surgical team was notified whenever the threshold was elevated by ≥20 mA or MEP response fell under 50%.

Findings On the first postoperative day, 18 patients experienced new paresis that resolved by discharge in 11. MEPs deteriorated in 39 patients, and 16 of these showed new postoperative paresis, indicating a 41% risk of new paresis. In the remaining 2/18 patients, intraoperative MEPs were stable, although new paresis appeared postoperatively. In one of these patients, intraoperative hemorrhage caused postoperative swelling, and the new motor deficit persisted until discharge. Of all 104 patients, 7 deteriorated in motor grade at discharge, 92 remained unchanged, and 5 patients have improved.

Conclusions Adjustment of surgical strategy contributed to good motor outcome in 33/39 patients. MEP monitoring may help significantly to prevent motor deficits during demanding neurosurgical procedures on the brainstem.

Neurosurgery 66:389-399, 2010. DOI: 10.1227/01.NEU.0000363702.67016.5D

OBJECTIVE: The supracerebellar infratentorial (SCIT) approach can be performed at the midline (median variant), lateral to the midline (paramedian variant), or at the level of the angle formed by the transverse and sigmoid sinuses (extreme lateral variant). We analyzed our experience with SCIT approaches for the surgical treatment of cavernous malformations of the brainstem (CMBs).

METHODS: Demographic, clinical, radiologic, and surgical data from 45 patients (20 males and 25 females; mean age, 36.2 years) with CMBs surgically removed through SCIT approaches were reviewed retrospectively. Anatomic information was explored using cadaver head dissection.

RESULTS: Twenty-three lesions were in the midbrain, 3 were at the midbrain and extended to the thalamus, 9 were at the pontomesencephalic junction, and 10 were in the upper pons. All patients presented with hemorrhage. The median variant was used in 13 patients, the paramedian variant in 9, and the extreme lateral variant in 23. Intraoperatively, all CMBs were associated with a developmental venous anomaly. At last follow-up, 88% of the patients were the same or better. After a mean follow-up of 20 months, their mean Glasgow Outcome Scale score was 4.1.

CONCLUSION: SCIT approaches provide excellent exposure to CMBs located at the posterior incisural space, not only in the midline but also in the posterolateral surface of the upper pons and midbrain. Careful preoperative planning and neuronavigational assistance are needed to determine the best angle of attack and trajectory for SCIT approaches. Refined microsurgical techniques are paramount to achieve safe surgical removal of CMBs with good outcomes.

J Neurosurg Pediatrics 4:040580–400640, 2009.DOI: 10.3171/2009.6.PEDS0923

Because of their location and biological behavior, brainstem cavernous malformations (CMs) pose a formidable clinical challenge to the neurosurgeon. The optimal management of these lesions requires considerable neurosurgical judgment. Accordingly, the authors reviewed their experience with the management of pediatric brain- stem CMs at the Hospital for Sick Children.

Methods. The authors performed a retrospective chart review of pediatric patients who had received diagnoses of a brainstem CM at the Hospital for Sick Children over the past 20 years.

Results. Twenty patients were diagnosed with brainstem CMs. The mean age at diagnosis was 10.1 ± 5.4 years, and the patients included 13 boys and 7 girls. The mean maximal diameter of the CM was 14.3 ± 11.2 mm. The le- sions were evenly distributed on the right and left sides of the brainstem with 4 midbrain, 13 pontine, and 3 medullary lesions. Seven patients underwent surgery for the management of their CMs, with a mean age at presentation of 5.2 years, and a mean CM size of 21.0 mm. Of note from the surgical group, 2 patients had a family history of CMs, 2 lesions were medullary, the CM reached a pial surface in 6 of 7 patients, and 6 of 7 lesions were located on the right side. The mean age at presentation among the 13 patients in the nonsurgical group was 12.7 years, and the mean CM size was 10.6 mm. Seven of these patients had a prior history of radiation for tumor, and only 3 had lesions that reached a pial surface.

Conclusions. The management of brainstem CMs in children is influenced by multiple factors. The majority of patients received conservative management and tended to be asymptomatic with smaller lesions. Patients with larger lesions and direct pial contact, in whom symptoms arose at a younger age were more likely to undergo surgical management. A history of familial CM was also a predictor for receiving surgical treatment. No patients with a prior history of radiation therapy underwent surgery for CMs. The presence of multiple lesions seemed to have no impact on the type of management chosen. Patients who underwent surgery did suffer morbidity related to the procedure, and tended to improve clinically over time. Conservative management was associated with new deficits arising in children, some of which improved with time. Consideration of many clinical and radiological parameters is thus prudent when managing the care of children with brainstem CMs.