Cassius Reis

Supracerebellar infratentorial approach to cavernous malformations of the brainstem: surgical variants and clinical experience with 45 patients.

OBJECTIVEThe 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). METHODSDemographic, 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. RESULTSTwenty-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. CONCLUSIONSCIT 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.

Anatomy of the Mastoid Emissary Vein and Venous System of the Posterior Neck Region: Neurosurgical Implications

OBJECTIVE The superficial venous system of the posterior neck (suboccipital venous plexus) is a potential source of complications from bleeding and air embolism. Because there is little information available about this in the literature, an anatomic study of the superficial posterior neck venous system and a morphometric analysis of the mastoid emissary vein (MEV) complex were undertaken. Both surgical and endovascular implications were considered. METHODS The posterior craniocervical regions of 15 silicon-injected human cadaveric specimens were dissected. The patterns and variances of venous anatomy were observed. Distances between fixed bony landmarks were measured with a caliper. RESULTS The suboccipital venous plexus, which forms a complex venous network located between the posterior muscular layers of the neck, drains to the anterior vertebral vein and deep cervical vein. The MEV connects this plexus to the sigmoid sinus. Its average diameter was 2.15 mm, and it was located a mean of 21.14 mm from the asterion and a mean of 33.65 mm from the mastoid tip. However, the size of the MEV complex varied considerably. CONCLUSION The suboccipital venous plexus in the posterior neck region may be very large. The size of the veins in the plexus varies, but the drainage pattern remains consistent. The plexus is a potential source of intense bleeding and air embolism during posterior fossa approaches. The risks are greatest for lateral surgical approaches, as a result of the anatomic position of the venous system. The described measurements can be used to approach the MEV in endovascular procedures that involve the sigmoid sinus.

ANATOMY OF THE SUPERIOR OPHTHALMIC VEIN APPROACH FOR DIRECT ENDOVASCULAR ACCESS TO VASCULAR LESIONS OF THE ORBIT AND CAVERNOUS SINUS.Commentary

OBJECTIVE The superior ophthalmic vein (SOV) provides an alternative venous access for the treatment of carotid-cavernous fistulae. Its direct surgical exposure and cannulation can be difficult. This study was performed to identify anatomic landmarks to facilitate localization and exposure of the SOV. METHODS The vascular tree of 6 formalin-fixed human cadaveric heads was injected with colored silicone. The SOV was exposed using a periorbital incision. The diameter of the SOV, its distance to the inferior border of the incision, and the angle formed by the SOV and sagittal midpupillary line were measured. The tributaries of the SOV and its orbital anatomy and relationship to the supraorbital notch/foramen were evaluated. RESULTS The SOV was located in the superomedial quadrant of the orbit. Its mean diameter was 2.2 mm (standard deviation, ±1.2 mm). The mean distance from the SOV to the superior sulcus of the eyelid nasally was 5.9 mm (standard deviation, ±2.0 mm). The mean angle formed by the SOV and the sagittal midpupillary line was 27.9 degrees (standard deviation, ±5.4 degrees). The tributaries of the SOV were the angular vein and supraorbital vein (SPOV). The SPOV, identified in all 12 dissections, could be followed to the SOV within the orbit. The SPOV was always located inside the supraorbital notch/foramen when the latter was present. CONCLUSION The SOV is located at the superomedial quadrant of the orbit. The SPOV is a reliable reference during surgical exposure. A lid crease or subbrow incision centered over the supraorbital notch simplifies identification of the SOV.

THE ASCENDING PHARYNGEAL ARTERY AND ITS RELEVANCE FOR NEUROSURGICAL AND ENDOVASCULAR PROCEDURES. COMMENTARIES

OBJECTIVE: The ascending pharyngeal artery (APA), a branch of the external carotid artery (ECA), supplies the lower cranial nerves, superior cervical ganglion, and nasopharyngeal structures. The APA can also supply blood to various intracranial lesions. We studied the anatomy of the APA in the context of its neurosurgical and endovascular relevance. METHODS: The cervical origin, branching pattern, and course of the APA were studied in 20 human cadaveric craniocervical sides. The diameter of the APA, the extension of its main trunk, and the distance of its origin from the common carotid artery bifurcation were measured. The relationships between the APA and surrounding structures were also observed. RESULTS: In 80% of the specimens, the APA originated from the ECA. It originated from its medial wall in 56% and from the posterior wall in 44%. The APA originated from the internal carotid artery, common carotid artery bifurcation, occipital artery, and a trunk common to the lingual and facial arteries in 5% each. The APA was usually the third branch of the ECA (40%). The mean distance from the origin of the APA to the common carotid artery bifurcation was 15.3 mm (range, 0-32; standard deviation, ± 8.3 mm). The APA was frequently the second smallest branch of the ECA (caliber, 1.54 mm; range, 1.1-2.1; standard deviation, ± 0.25 mm). CONCLUSION: The APA is an important channel for supplying neural structures of the posterior fossa. Knowledge of its anatomy, variants, and anastomotic channels is essential in the treatment of lesions supplied by its branches and to avoid complications related to its inadvertent injury.

The accessory middle cerebral artery: anatomic report.

OBJECTIVE An accessory middle cerebral artery (MCA) usually originates between the A1 and proximal A2 segment of the anterior cerebral artery, reaches the sylvian fissure, and supplies the territory of the MCA. This anomaly has been associated with cerebral aneurysms and Moyamoya disease. We report an accessory MCA arising from the A2 segment. METHODS A cadaveric head, fixed in formalin solution and injected with red and blue silicone on its vascular tree to trace intracranial and extracranial vessels, was dissected. RESULTS An accessory MCA was found arising from the A2 segment of the anterior cerebral artery and feeding the basal and inferior surface of the inferior frontal gyrus. In our specimen, the vessel was associated with intracranial aneurysms at other locations. CONCLUSION Although anomalies of the MCA are rare, neurosurgeons must be familiar with such anatomic variations. An accessory MCA can be associated with Moyamoya disease and aneurysms at its junction with the anterior cerebral artery. Patients with this anomaly may, therefore, have an increased risk for developing aneurysms and other neurovascular complications. By obstructing the surgical view, an accessory MCA may increase the difficulty of exposing lesions in the vicinity of the optic chiasm.

Comparative study of cranial topographic procedures: Broca's legacy toward practical brain surgery.

OBJECTIVE In many locations, neurosurgeons still use stereotactic- or anatomic-based craniocerebral topography systems to identify cortical landmarks. However, their predictive value for identifying two key landmarks--the central sulcus (CS) and lateral sulcus (LS)--has never been evaluated. We quantitatively compare leading craniocerebral topographic methods and review their historical significance for neurosurgery. METHODS On 12 cadaveric head sides, the methods of Broca, Reid, Poirier, Taylor-Haughton, and Rhoton were used to predict positions of the CS and LS. After craniotomy, the actual CS, LS, and the superior and inferior Rolandic points were identified. Distances between predicted positions and actual structures were measured, and the systems were compared. RESULTS The actual superior Rolandic point was 4.6 +/- 2.9 mm anterior to prediction by Brocas method; 4.3 +/- 2.13 mm anterior to the Poirier, Taylor-Haughton, and Rhoton methods; and 3.26 +/- 3.17 mm anterior or posterior using Reids method. The actual inferior Rolandic point was anteroinferior to all predictions: 5.87 +/- 3.1 mm by Rhoton, 6.97 +/- 3.55 mm by Broca, 7.64 +/- 2.54 mm by Poirier, and 7.61 +/- 3.85 mm by Reid and Taylor-Haughton. The actual LS was 2.33 mm away from the predicted point using Poiriers method, and 2.00 mm away from the predicted point using the Reid, Taylor-Haughton, and Rhoton methods. CONCLUSION Predicting positions of the CS and LS to within a few millimeters, these landmark methods remain reliable for cerebral localization. Largely initiated by the work of Paul Broca, these systems lay at the development of a practical method of neurosurgery in the late 19th century.

Midline as a landmark for the position of the superior sagittal sinus on the cranial vault: An anatomical and imaging study

Background: Craniotomies involving the midline are regular practice in neurosurgery, during which injury to the superior sagittal sinus (SSS), an uncommon yet devastating event, may occur. The midline tends to be the most common landmark used to identify the position of the SSS. In this study we examined the reliability of the midline as a landmark for the SSS. Methods: We performed bilateral craniectomies on eight cadaveric heads, preserving the coronal, sagittal, and lambdoid sutures. The width of the SSS and its displacement from midline were measured on the cadaveric specimens and on 105 normal magnetic resonance images (MRIs) of the head at the following locations: halfway between nasion and bregma (NB), bregma (B), halfway between bregma and lambda (BL), lambda (L), and inion (I). Results: In all cadaveric specimens, the SSS was partially or totally displaced toward one side of midline, usually to the right. It tended to be closer to midline in the frontal region and more displaced posteriorly. The SSS usually drained into the right-side transverse sinus. The mean width of the SSS was 4.3, 5.9, 6.9, 7.9, and 7.8 mm, and the average displacement from midline was 4.3, 6.3, 5.5, 6.9, and 6.0 mm for NB, B, BL, L, and I, respectively. These measurements were then compared with those obtained from the MRIs. Conclusion: The SSS was consistently displaced on either side of midline. Thus, the midline is not reliable for identifying the SSS, and caution should be used within 6–10 mm on either side of midline.

ESTUDO DAS ESTRUTURAS NEUROVASCULARES DA FACE POSTERIOR DA PIRÂMIDE PETROSA Aplicações nas abordagens do ângulo pontocerebelar

A topographic study of posterior surface of the petrous pyramid was performed in 20 human cadaveri heads. The distances between the neurovascular structures were measured in the points where they contact the posterior surface of the petrous pyramid. The study also points out the relationship between the bone landmarks and the transverse and the superior petrous sinuses. The result of this study was correlated with the approaches to the cerebellopontine angle.