Perioperative Assessment of Cerebellar Masses and the Potential for Cerebellar Cognitive Affective Syndrome.

The cerebellum was long perceived to be a region of limited importance with primary functions in the regulation of motor control. A degree of its functional topography in motor modulation has been traditionally appreciated. However, an evolving body of evidence supports its role in a range of cognitive processes, including executive decision making, language, emotional processing, and working memory. To this end, numerous studies of cerebellar stroke syndromes as well as investigations with functional magnetic resonance imaging and diffusion tensor imaging have given clinicians a better model of the functional topography within the cerebellum and the essential lanes of communication with the cerebrum. With this deeper understanding, neurosurgeons should integrate these domains into the perioperative evaluation and postoperative rehabilitation of patients with cerebellar tumors. This review aims to discuss these understandings and identify valuable tools for implementation into clinical practice.

Assessment of the Endoscopic Endonasal Transclival Approach for Surgical Clipping of Anterior Pontine Anterior-Inferior Cerebellar Artery Aneurysms.

OBJECTIVE: Aneurysms of the anterior pontine segment of the anterior-inferior cerebellar artery (AICA) are uncommon. Their treatment is challenging because critical neurovascular structures are adjacent to it and the available surgical corridors are narrow and deep. Although endoscopic endonasal approaches are accepted for treating midline skull base lesions, their role in the treatment vascular lesions remains undefined. The present study is aimed to assess the anatomic feasibility of the endoscopic endonasal transclival (EET) approach for treating anterior pontine AICA aneurysms and compare it with the subtemporal anterior transpetrosal (SAT) approach. METHODS: Twelve cadaveric specimens were prepared for surgical simulation. The AICAs were exposed using both EET and SAT approaches. Surgical window area and the length of the exposed artery were measured. The distance from the origin of the artery to the clip applied for proximal control was measured. The number of AICA perforators exposed and the anatomic features of each AICA were recorded. RESULTS: The EET approach provided a wider surgical window area compared with the SAT (P < 0.001). More AICA perforators were visualized using the EET approach (P < 0.05). To obtain proximal control of the AICA, an aneurysm clip could be applied closer to the origin of AICA using EET (0.2 ± 0.42 mm) compared with SAT (6.26 ± 3.4 mm) (P < 0.001). CONCLUSION: Clipping anterior pontine AICA aneurysms using the EET approach is feasible. Compared with SAT, the EET approach provides advantages in surgical window area, ensuring proximal control before aneurysm dissection, visualization of perforating branches, and better proximal control.

An anatomical assessment of the supracerebellar midline and paramedian approaches to the inferior colliculus for auditory midbrain implants using a neuronavigation model on cadaveric specimens.

The inferior colliculus (IC) is an alternative site for electrode placement in neural deafness due to its surgical accessibility and its well-known tonotopic stratification. In patients where tumor surgery has already occurred and the cerebellopontine angle contains scar tissue or tumor-remnants, midline and paramedian supracerebellar approaches are alternative routes. They are often avoided due to concerns regarding the venous drainage of the cerebellum, the electrode trajectory and the course of the electrode cable. We studied these surgical routes in five neuronavigated fixed cadaveric specimens. For paramedian and midline approaches, the transverse sinus was exposed 5.8mm on average. A mean of 1.6 cerebellar veins, with an average diameter of 2.0mm, draining to the tentorium were transected to reach the tentorial notch. Only 0.4 arterial branches were met. We conclude that the supracerebellar midline and paramedian approaches provide a good exposure of the IC and offer safe and viable alternative routes to the IC. Additionally, they provide a wider angle of action for optimal electrode placement.

[Microsurgical anatomy and quantitative assessment of suboccipital median transcerebellomedullary fissure keyhole approach].

OBJECTIVE: To assess the suboccipital median transcerebellomedullary fissure keyhole approach in a cadaver model by using a neuronavigation system and explore its feasibility and operative indications. METHODS: Six 10% formaldehyde-fixed adult cadaveric head and neck specimens injected with colored latex were chosen for the study. First the suboccipital median transcerebellomedullary fissure keyhole approach was performed and the anatomical structures were observed under operative microscope. The exposed floor area of the fourth ventricle and the vertical and transverse angles at the point where the line between the lateral apertures crossing the median sulcus, vertical angle at the apertures of midbrain aqueduct and the obex were measured with the aid of a frameless stereotactic navigation device. Parameters were compared with those when C1 posterior arch was removed, and also with those under conventional approach with or without C1 arch. RESULTS: By means of adjusting specimen positions and the angle of operative microscope, as tela choroidea and inferior medullary velum were dissected gradually, the structures of floor, lateral recesses and lateral apertures of the fourth ventrical, vermian and aperture of midbrain aqueduct were exposed. There were no significant difference in the exposed floor area of the fourth ventricle between the keyhole approach and conventional approach (P = 0.06), and the C1 arch removal can't increase the exposed area (P = 0.84). The conventional approach have wider angles than the keyhole approach (P < 0.01), and the C1 arch removal increased the vertical angle (P < 0.05), but not the horizontal angle (P > 0.05). CONCLUSION: The suboccipital median transcerebellomedullary fissure keyhole approach can expose similar anatomic architectures as that of the conventional approach. Thus it can be used to remove the tumors located in the fourth ventricle, dorsum of pons and medullary oblongata and cerebellar vermis.