The presigmoid retrolabyrinthine approach: Technical note.

BACKGROUND: The retrolabyrinthine approach is classified among the posterior petrosectomies. Its goal is to achieve an enlarged mastoidectomy while sparing the intrapetrous neurotologic structures in order to offer maximal exposure of the posterior cerebellopontine angle compound. METHODS: The stages of the procedure are subsequently the skeletonization of the sigmoid sinus, wide opening of the mastoid antrum and exposure of the semicircular canals. We present herein the technique, indications and limitations of the retrolabyrinthine approach. CONCLUSION: The retrolabyrinthine approach is a demanding technique. Nowadays the retrolabyrinthine approach is routinely combined to additional resections of the petrous bone, so-called "combined petrosectomies", to target the jugular foramen or the petroclival area.

The Retrolabyrinthine Presigmoid Approach to the Anterior Cerebellopontine Region: Expanding the Limits of Trautmann Triangle.

OBJECTIVE: The anatomic area exposed through exposure of Trautmann triangle may not be sufficient. We studied the additional exposure provided by skeletonizing the sigmoid sinus (SS). METHODS: In 5 human cadaveric heads, thin-cut computed tomography images of 2 sides of the temporal bone were obtained for a total of 10 sides. The estimated surgical working angle was calculated based on the relationship of the SS to the posterior semicircular canal (PSC), superior petrosal sinus, and jugular bulb on imaging. Mastoidectomy was performed, and heads with and without SS skeletonization were remeasured. RESULTS: Working angle calculated on computed tomography was 56° ± 11.3. Skeletonization of the SS increased the distance between the PSC and SS by 5 mm (P = 0.01) and between the lateral semicircular canal and SS by 4 mm (P = 0.01). Skeletonization and retraction of the SS significantly increased the distance between the PSC and lateral semicircular canal to the SS. On images obtained after mastoidectomy, skeletonizing the SS helped improve anterior visibility on most samples that had an SS that was lateral to the PSC on axial imaging. In samples in which the SS was medial to the PSC or had only minimal lateral displacement, skeletonizing the SS did not markedly improve visibility of the retrolabyrinthine space. CONCLUSIONS: Working area and visibility improved as the PSC and SS approached the same plane on axial imaging. Preoperative evaluation of the laterality of the SS to the PSC may assist a surgeon in determining the need for skeletonizing the SS and avoiding possible vascular injuries.

Comparative morphometric study of the sigmoid sinus sulcus and the jugular foramen / Estudo morfométrico comparativo do sulco do seio sigmóideo e do forame jugular

Objective To compare the right and left sides of the same skulls as far as the described landmarks are concerned, and establish the craniometric differences between them. Method We carried out measurements in 50 adult dry human skulls comparing both sides. Results The sigmoid sinus width at the sinodural angle level was larger on the right side in 78% of the cases and at the level of the digastric notch in 72%. The jugular foramen width was also larger on the right side in 84% of the cases. The sigmoid sinus distance at the level of the digastric notch was larger on the right side in 64% of the cases, and the sigmoid sinus distance at the level of the digastric notch to the jugular foramen was larger on the right side in 70% of the cases. Conclusion Significant craniometric differences were found between both sides of the same skulls. .

Objetivo Comparar os lados direito e esquerdo no mesmo crânio nos pontos referenciais descritos e definir as diferenças craniométricas entre ambos. Método Realizamos mensurações em 50 crânios secos de humanos adultos comparando os lados direito e esquerdo. Resultados Como resultado, obtivemos as medidas da largura do seio sigmóideo na altura do ângulo sinodural maiores no lado direito em 78% dos casos e na altura do ponto digástrico em 72%. A largura do forame jugular foi também maior no lado direito em 84% dos casos. A distância do seio sigmóideo na altura do ângulo sinodural até a altura do ponto digástrico foi maior do lado direito em 64% dos casos, e a distância do seio sigmóideo na altura do ponto digástrico até o forame jugular foi maior do lado direito em 70% dos casos. Conclusão Diferenças craniométricas significativas foram encontradas entre os dois lados do crânio. .

Bases anatômicas do acesso petroso / Anatomical landmarks of petrosal approach

Sob técnica microcirúrgica, foram dissecadas 10 cabeças cadavéricas, permitindo o estudo de 20 regiöes petroclivais e as estruturas nervosas e vasculares envolvidas neste acesso. Medidas referentes a distâncias em milimetros entre o ângulo sinodural e a veia de Labbé e entre a origem e a emergência dos VII, VIII, IX, X e XI nervos cranianos, seus orifícios e envoltórios durais foram tomados antes e após "drilagem" do osso temporal. A veia de Labbé desemboca no seio transverso a uma distância segura do ângulo sinodural. No material estudado, a distância minima entre estes pontos foi de 11,0 mm. A distância média entre a emergência dos VII e VIII nervos cranianos e o meato acústico interno foi de 11,5 mm à direita e 11,8 mm à esquerda. Após "drilagem" do osso temporal, a distância média foi de 15,41 mm à direita e 16,0 mm à esquerda. Para os IX, X e XI nervos cranianos, a distância média foi de 11,92 mm à direita e 11,43 mm à esquerda antes da "drilagem", e 14,21 mm à direita e 15,37 mm à esquerda depois da "drilagem". Estes resultados confirmam o ganho em campo cirúrgico, através do acesso petroso a regiâo petroclival