1. Supracerebellar Infratentorial Approach to Brainstem Cavernous Malformations Jean G. de Oliveira, Gregory P. Lekovic, Sam Safavi-Abbasi, Cassius V.C. Reis, Ricardo A. Hanel, Randall W. Porter, Mark C. Preul, Robert F. Spetzler Division of Neurological Surgery, Barrow Neurological Institute St. Joseph’s Hospital and Medical Center, Phoenix-AZ.
Introduction
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).
Figure 1. Application of the two-point method. The best trajectories for the (A) median SCIT approach, (B) paramedian SCIT approach, and (C) extreme lateral SCIT approach. Used with permission from Barrow Neurological Institute.
Figure 2. Median variant of the SCIT approach. (A) Patient’s position an d skin incision (dashed line). (B) Craniotomy and dural opening (dashed line). (C) Area of exposure (shaded). (D) Microsurgical view of the anatomy in a cadaveric specimen (3rd Vent.: third ventricle; IC: inferior colliculus; M.P.Ch. A.: medial posterior choroidal artery; P.C.A.: posterior cerebral artery; Pi: pineal; S.C.A.: superior cerebellar artery; SC: superior collic Tent.: tentorium).
Figure 3. Paramedian variant of the SCIT approach. (A) Patient’s position and skin incision (dashed line). (B) Craniotomy and dural opening (dashed line). (C) Area of exposure (shaded). (D) Microsurgical view of the anatomy in a cadaveric specimen (IC: inferior colliculus; P.C.A.: posterior cerebral artery; Pi: pineal; S.C.A.: superior cerebellar artery; SC: superior colliculus; Tent.: tentorium
Figure 4. Extreme lateral variant of the SCIT approach. (A) Patient’s position and skin incision (dashed line). (B) Craniotomy and dural opening (dashed line). (C) Area of exposure. (D) Microsurgical view of the anatomy in a cadaveric specimen (CN IV: fourth cranial nerve; CN V: fifth cranial nerve; IC: inferior colliculus; P.C.A.: posterior cerebral artery; Pet. V.: petrosal vein; S.C.A.: superior cerebellar artery; SC: superior colliculus; Tent.: tentorium).
Methods
Demographic, clinical, radiological 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: 23 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.
Results
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 (DVA). 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.
Figure 5. A: Intraoperative view guided by neuronavigation. B: Superficial aspect of the brainstem. C and D: Microsurgical aspect of the CMBs.
Illustrative Case. A 63-year-old woman presented with left-sided numbness, double vision, dysphagia, gait ataxia, and dizziness. Preoperative (A) sagittal T1-weighted, (B) axial T1-weighted, and (C) T2-weighted MR images showing a CMBs abutting at the posterior incisural space. The extreme lateral variant of the SCIT was recommended based on the best trajectory determined by the two-point method. Postoperative (D) sagittal T1-weighted, (E) axial T1-weighted, andConclusions
Conclusions
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.