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Objective To hierarchize the anterior inferior cerebellar artery (AICA)-subarcuate artery (SAA) complex's variations in the surgical field. Background The AICA's "subarcuate loop" (SL) presents multiple variations, closely related to the SAA. AICA-SAA complex's variations may represent major issues in cerebellopontine angle (CPA) surgery. As the spectrum of configurations is originated during the development, a systematized classification was proposed based on the interaction between the petrosal bone and the AICA in the embryonic period. Methods The variations were defined as follow: Grade 0: free, purely cisternal AICA, unidentifiable or absent SAA; Grade 1: purely cisternal AICA, loose SL, SAA > 3 mm; Grade 2: AICA near the subarcuate fossa, pronounced SL, SAA <3 mm; Grade 3: "duralized" AICA, unidentifiable SAA, or included in the petromastoid canal (PMC); and Grade 4: intraosseous AICA, unidentifiable SAA, or included in the PMC. The classification was applied to a series of patients assessed by magnetic resonance constructive interference in steady state sequence. Surgical examples were also provided. Results Eighty-four patients were evaluated, including 161 CPA. The proportions found in the gradation remained within the range of previous publications (Grade 0: 42.2%; Grade 1: 11.2%; Grade 2: 35.4%; Grade 3: 10.6%; and Grade 4: 0.6%). Moreover, the degrees of the classification were related to the complexity of the anatomical relationships and, therefore, to the difficulty of the maneuvers required to overcome them. Conclusion The proposed AICA-SAA complex classification allowed to distinguish and objectify pre- and intraoperatively the spectrum of variations, to thoroughly plan the required actions and instrumentation.
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Introducción: El recorrido del "loop subarcuato" de la arteria cerebelosa anteroinferior (ACAI) presenta múltiples variaciones que condicionan además su principal eferencia, la arteria subarcuata (ASA). El espectro de variaciones de este complejo ha sido referido en la literatura de forma inconexa y desorganizada. Material y Métodos: Se propuso una clasificación sistematizada de las variantes del complejo ACAI-ASA, basada en la interacción del hueso petroso y la ACAI en el periodo embrionario. La misma fue aplicada en una serie de pacientes estudiados mediante secuencia CISS (constructive interference in steady state) de resonancia magnética para categorizar las relaciones presentes en el ángulo pontocerebeloso (APC). Resultados: Se evaluaron 84 pacientes, incluyendo 161 APC. Todos los grados propuestos fueron identificados en la serie evaluada. Las proporciones encontradas en la gradación propuesta se mantuvieron en el rango de las publicaciones aisladas. Conclusión: La clasificación propuesta para el complejo ACAI-ASA permitió distinguir y objetivar consistentemente el espectro de variaciones.
Introduction: The pathway of the anterior inferior cerebellar artery's (AICA) "subarcuate loop" can vary extensively. This variability also affects its main branch, the subarcuate artery (SAA). The spectrum of variations observed with this combination of vessels is inadequately described in the literature. Methods and Materials: A systematized classification system for AICA-SAA complex variants was proposed, based upon interactions between the petrosal bone and the AICA in embryos. This classification scheme then was applied to a series of patients assessed by magnetic resonance CISS (constructive interference in steady state) sequences, to categorize the cerebellopontine angle (CPA) relationships. Results: Eighty-four patients were evaluated, encompassing 161 CPA. All the proposed grades were identified in the evaluated series. The proportions found with the proposed gradation system were within the range of previous publications. Conclusions: The AICA-SAA complex classification system that we proposed allowed for consistently distinguishing and objectifying the spectrum of variations seen in the subarcuate loop.
Assuntos
Humanos , Síndrome Medular Lateral , Artérias , Ângulo CerebelopontinoRESUMO
Literature describes that on the 25th gestational week the labyrinth is fully formed and with adult size. However, recent studies have shown that the cranial and labyrinth development continues until 3 years of age. OBJECTIVES: To demonstrate through tomographic study the frequency of semicircular canal dehiscence on nine specimens of stillbirths between 32 and 40 weeks and, through literature review, present another possible etiology for its cause. METHODS: Tomographic study of the temporal bone of 9 specimens of stillbirths between 32 and 40 weeks. RESULTS: A frequency of 88.89% of alterations were found in our study, with 44% presenting bilateral alterations and 44% unilateral alteration; 11.11% had no dehiscence. CONCLUSION: The tomographic study showed superior semicircular canal dehiscence (SSCD) in 88% of the specimens studied, protrusion of the superior semicircular canal (SSC) in all fetuses, and an enlarged SSC that may be caused by the expansion process provoked by the subarcuate artery entering the subarcuate canaliculus, leading to SSCD.