Resection of the quadrangular lobule of the cerebellum to increase exposure of the cerebellomesencephalic fissure: an anatomical study with clinical correlation.

OBJECTIVE: The lateral aspect of the cerebellomesencephalic fissure frequently harbors vascular pathology and is a common surgical corridor used to access the pons tegmentum, as well as the cerebellum and its superior and middle peduncles. The quadrangular lobule of the cerebellum (QLC) represents an obstacle to reach these structures. The authors sought to analyze and compare exposure of the cerebellar interpeduncular region (CIPR) before and after QLC resection and provide a case series to evaluate its clinical applicability. METHODS: Forty-two sides of human brainstems were prepared with Klingler's method and dissected. The exposure area before and after resection of the QLC was measured and statistically studied. A case series of 59 patients who underwent QLC resection for the treatment of CIPR lesions was presented and clinical outcomes were evaluated at 1-year follow-up. RESULTS: The anteroposterior surgical corridor of the CIPR increased by 10.3 mm after resection of the QLC. The mean exposure areas were 42 mm2 before resection of the QLC and 159.6 mm2 after resection. In this series, ataxia, extrapyramidal syndrome, and akinetic mutism were found after surgery. However, all these cases resolved within 1 year of follow-up. Modified Rankin Scale score improved by 1 grade, on average. CONCLUSIONS: QLC resection significantly increased the exposure area, mainly in the anteroposterior axis. This surgical strategy appears to be safe and may help the neurosurgeon when operating on the lateral aspect of the cerebellomesencephalic fissure.

Three-Dimensional Quantitative Analysis of the Brainstem Safe Entry Zones Based on Internal Structures.

OBJECTIVE: Brainstem safe entry zones (EZs) are gates to access the intrinsic pathology of the brainstem. We performed a quantitative analysis of the intrinsic surgical corridor limits of the most commonly used EZs and illustrated these through an inside perspective using 2-dimensional photographs, 3-dimensional photographs, and interactive 3-dimensional model reconstructions. METHODS: A total of 26 human brainstems (52 sides) with the cerebellum attached were prepared using the Klingler method and dissected. The safe working areas and distances for each EZ were defined according to the eloquent fiber tracts and nuclei. RESULTS: The largest safe distance corresponded to the depth for the lateral mesencephalic sulcus (4.8 mm), supratrigeminal (10 mm), epitrigeminal (13.2 mm), peritrigeminal (13.3 mm), lateral transpeduncular (22.3 mm), and infracollicular (4.6 mm); the rostrocaudal axis for the perioculomotor (11.7 mm), suprafacial (12.6 mm), and transolivary (12.8 mm); and the mediolateral axis for the supracollicular (9.1 mm) and infracollicular (7 mm) EZs. The safe working areas were 46.7 mm2 for the perioculomotor, 21.3 mm2 for the supracollicular, 14.8 mm2 for the infracollicular, 33.1 mm2 for the supratrigeminal, 34.3 mm2 for the suprafacial, 21.9 mm2 for the infrafacial, and 51.7 mm2 for the transolivary EZs. CONCLUSIONS: The largest safe distance in most EZs corresponded to the depth, followed by the rostrocaudal axis and, finally, the mediolateral axis. The transolivary had the largest safe working area of all EZs. The supracollicular EZ had the largest safe area to access the midbrain tectum and the suprafacial EZ for the floor of the fourth ventricle.

Microsurgical approaches to the cerebellar interpeduncular region: qualitative and quantitative analysis.

OBJECTIVE: The cerebellar interpeduncular region (CIPR) is a gate for dorsolateral pontine and cerebellar lesions accessed through the supracerebellar infratentorial approach (SCITa), the occipital transtentorial approach (OTa), or the subtemporal transtentorial approach (STa). The authors sought to compare the exposures of the CIPR region that each of these approaches provided. METHODS: Three approaches were performed bilaterally in eight silicone-injected cadaveric heads. The working area, area of exposure, depth of the surgical corridor, length of the interpeduncular sulcus (IPS) exposed, and bridging veins were statistically studied and compared based on each approach. RESULTS: The OTa provided the largest working area (1421 mm2; p < 0.0001) and the longest surgical corridor (6.75 cm; p = 0.0006). Compared with the SCITa, the STa provided a larger exposure area (249.3 mm2; p = 0.0148) and exposed more of the length of the IPS (1.15 cm; p = 0.0484). The most bridging veins were encountered with the SCITa; however, no significant differences were found between this approach and the other approaches (p > 0.05). CONCLUSIONS: To reach the CIPR, the STa provided a more extensive exposure area and more linear exposure than did the SCITa. The OTa offered a larger working area than the SCIT and the STa; however, the OTa had the most extensive surgical corridor. These data may help neurosurgeons select the most appropriate approach for lesions of the CIPR.

Tumor teratoide/rabdoide atípico con diferenciación tipo ganglioglioma: reporte de caso / Atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation: Case report

Antecedentes El tumor teratoide/rabdoide atípico es una entidad muy rara y agresiva que se presenta principalmente en pacientes pediátricos. Hasta donde sabemos, la presentación inicial de este tipo de tumor con diferenciación tipo ganglioglioma es rara dentro de la literatura. Descripción del caso Presentamos el caso de una paciente de nueve meses de edad con parálisis facial izquierda. Se realizó resonancia magnética, la cual reveló una lesión a nivel del ángulo pontocerebeloso izquierdo. Se realizó resección quirúrgica total macroscópica. Los estudios histopatológico e inmunohistoquímico revelan un tumor teratoide/rabdoide atípico con diferenciación de tipo ganglioglioma. Conclusiones El presente reporte de caso presenta un tumor teratoide/rabdoide atípico con una diferenciación inicial de tipo ganglioglioma. Este trabajo aumenta la base de datos literaria y promueve el estudio de este tipo de histogénesis. Creando bases para incentivar estudios mayores que permitan determinar si deben realizarse modificaciones en los protocolos de manejo existentes, y a la vez determinar si existiría variación en cuanto a pronóstico de la patología (AU)

Background Atypical teratoide/rhabdoid tumor is a very rare and aggressive disease that primarily presents in pediatric patients. To the best of our knowledge, the initial presentation of this type of tumor with ganglioglioma-like differentiation is rare in the literature. Case report We present the case of a 9-month-old patient with left facial paralysis. An MRI revealed a lesion at the left cerebellopontine angle. Complete macroscopic surgical resection was performed. Histopathology and immunohistochemistry testing revealed an atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation. Conclusions This case report presents an atypical teratoid/rhabdoid tumor with initial gangligioma-like differentiation. This study adds to the data in the literature and promotes the study of this type of histogenesis. It lays a foundation for encouraging further studies to determine whether changes should be made to existing management protocols and, at the same time, determine whether there would be any variation with regard to disease prognosis (AU)

Combined treatment for a hemispheric cerebellar AVM.

Posterior fossa arteriovenous malformations (AVMs) can be a challenging disease, especially those large in size. AVMs can be treated with a combination of endovascular treatment and microsurgery. Here, the authors present the case of a 16-year-old female patient with progressive dizziness and episodic syncope. The workup of the patient showed a hemispheric cerebellar AVM, Spetzler-Martin grade IV. She underwent combined treatment (endovascular and microsurgery) with no complications and cure of the malformation. The video can be found here: https://youtu.be/rNw_Kyd76Mg.

Anterior Clinoidectomy: Intradural Step-by-Step En Bloc Removal Technique.

OBJECTIVE: Anterior clinoidectomy is an important and essential skill for skull base and cerebrovascular neurosurgeons. We present a 1-piece intradural anterior clinoidectomy, providing a step-by-step description of the technique, independently of anatomic variations. METHODS: Between 2014 and 2020, 128 patients (119 women and 9 men; average age, 54.6 years) underwent intradural anterior clinoidectomy during microsurgical clipping of carotid-ophthalmic aneurysms. RESULTS: The anterior clinoid process continues medially with the planum sphenoidale, over the optic nerve, laterally with the lesser wing of the sphenoid bone, and inferiorly with the optic strut, which is always found anteriorly to the clinoid segment of the internal carotid artery, and separates the optic canal from the superior orbital fissure. The proposed anterior clinoidectomy followed, one after the other, these 3 fixation points for the detachment of the anterior clinoid process. The main indication for intradural anterior clinoidectomy was the management of vascular lesions around paraclinoid (clinoidal and ophthalmic) segments of the internal carotid artery. Complications of the procedure included injury to the internal carotid artery or the ophthalmic artery, thermal damage to the optic nerve, and invasion of the sphenoid sinus or a pneumatized anterior clinoid process, which could lead to postoperative cerebrospinal fluid leakage. CONCLUSIONS: The anterior clinoidectomy technique described here minimizes the drilling surface for detachment of the anterior clinoid process and reduces operative time as well as the amount of bone dust produced by drilling. It also precisely delineates the localization of the optic strut, preventing carotid or optic nerve damage.

Atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation: Case report. / Tumor teratoide/rabdoide atípico con diferenciación tipo ganglioglioma: reporte de caso.

BACKGROUND: Atypical teratoide/rhabdoid tumor is a very rare and aggressive disease that primarily presents in pediatric patients. To the best of our knowledge, the initial presentation of this type of tumor with ganglioglioma-like differentiation is rare in the literature. CASE REPORT: We present the case of a 9-month-old patient with left facial paralysis. An MRI revealed a lesion at the left cerebellopontine angle. Complete macroscopic surgical resection was performed. Histopathology and immunohistochemistry testing revealed an atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation. CONCLUSIONS: This case report presents an atypical teratoid/rhabdoid tumor with initial gangligioma-like differentiation. This study adds to the data in the literature and promotes the study of this type of histogenesis. It lays a foundation for encouraging further studies to determine whether changes should be made to existing management protocols and, at the same time, determine whether there would be any variation with regard to disease prognosis.