Análise por tomografia computadorizada do teto etmoidal: importante área de risco em cirurgia endoscópica nasal / Computed tomography assessment of the ethmoid roof: a relevant region at risk in endoscopic sinus surgery

OBJETIVO: Avaliar a profundidade das fossas olfatórias e a freqüência de assimetria na altura e na inclinação lateral do contorno do teto etmoidal. MATERIAIS E MÉTODOS: Estudo retrospectivo de 200 tomografias computadorizadas dos seios da face no plano coronal realizadas no período de agosto a dezembro de 2006. As profundidades das fossas olfatórias foram classificadas segundo Keros. O teto etmoidal foi avaliado quanto à simetria entre os lados. RESULTADOS: O tipo de Keros mais encontrado foi o tipo II (73,3 por cento), seguido do tipo I (26,3 por cento) e do tipo III (0,5 por cento). Em 12 por cento (24 exames) havia assimetria entre os lados quanto à altura do teto etmoidal, e em 48,5 por cento (97 exames) observou-se assimetria do contorno do teto, com inclinação lateral da lâmina crivosa de um dos lados. CONCLUSÃO: Em relação à profundidade das fossas olfatórias, o tipo II de Keros foi o mais freqüente. Verificou-se que a assimetria do teto do seio etmoidal, na maioria dos casos, estava relacionada com a inclinação lateral da lamela lateral da lâmina crivosa.

OBJECTIVE: To evaluate the olfactory fossae depth according to the Keros' classification and determine the incidence and degree of asymmetry in the height and contour of the ethmoid roof. MATERIALS AND METHODS: Retrospective analysis of 200 coronal computed tomography studies of paranasal sinuses performed in the period between August and December, 2006. RESULTS: According to the Keros' classification, olfactory fossae type II was most frequently found in 73.3 percent of cases followed by type I in 26.3 percent and type III in 0.5 percent of cases. Asymmetry in the ethmoid roof height was found in 12 percent of cases (24 computed tomography studies), and contour asymmetry was found in 48.5 percent (97 computed tomography studies), with flattening of the ethmoid roof on one of the sides. CONCLUSION: As regards the olfactory fossae depth, the Keros' type II was most frequently found. In most of cases, the ethmoid roof asymmetry was related to angulation of the lateral lamella of the cribriform plate.

Height and Shape of Skull Base as Risk Factors for Skull Base Penetration during ESS

BACKGROUND AND OBJECTIVES: CT/MRI has identified several risk factors for life threatening complications of skull base penetration during endoscopic sinus surgery (ESS). We compared these risk factors in groups of patients with and without penetration. MATERIALS AND METHODS: Retrospective review of direct coronal paranasal sinus computed tomography (CT) scans was done. Using preoperative CT scans of 100 patients without penetration, and 7 with penetration, we classified height into 4 groups and contour into 2 groups. The frequencies of shape and height differences of the right and left skull base were calculated in each group. RESULTS: 6 of the 7 patients who had skull base penetration, ESS was performed by a resident or junior staff member having less than 3 years experience with this technique. Shape asymmetry was significantly higher in with penetration (4 out of 7 patients (57%)) and much less in without penetration (18 out of 100 patients, 18%, p=0.032). The frequencies of low skull base and height difference were seen in 15% and 28%, respectively. CONCLUSION: The most important risk factor for inadvertent skull base penetration during ESS is the surgeon's experience and asymmetric shape of the right and left skull base.

Anatomical Relationship of the Anterior Ethmoid Canal to the Anterior Skull Base: A Computed Tomographic Analysis on the Types of the Fovea Ethmoidalis / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: As the anterior ethmoid canal (AEC) provides a good surgical landmark and its injury may result in serious complications, the anatomical relationship of the AEC to the anterior skull base (ASB) should be evaluated preoperatively. Despite some studies on the ASB, studies analyzing this anatomical relationship and the types of the fovea ethmoidalis (FE) on computed tomography (CT) are rare. The aim of this study is to better understand this anatomical relationship by determining the frequency of each type of the FE and distances between anatomical structures on the CT scans with our new classification. MATERIALS AND METHOD: Four hundred sides of the FE were analyzed from the preoperative coronal CT scans of 200 chronic sinusitis patients (100 males and 100 females, aged 20 to 59 years). The FE was classified into 4 types (I: non-separated type, II: partially separated type, III: completely separated type, IV: unidentifiable type) and 2 subtypes (A: developed medial cranial wall, B: undeveloped medial cranial wall). Heights of the medial cranial wall (a), the AEC (b), and the ethmoid roof (c) were measured on the CT image. RESULTS: Frequencies of the types I-IV were 48.0% (IA: 25.2%, IB: 22.8%), 19.3% (IIA: 4.3%, IIB: 15.0%), 29.5% (IIIA: 29.5%, IIIB: 0%), and 3.2%, respectively. The medial cranial wall of type IIIA was significantly longer than those of the other types, and the AEC of type IIIA was in a significantly lower position than those of the other types. CONCLUSION: On the CT scans, we found the AEC in 96.8% and type IIIA in nearly 30% of all types of the FE. Sinus surgery should be performed only after preoperative evaluation of these anatomical relationship on the CT scans under close scrutiny. For the type IIIA, surgery should be performed with utmost care due to high risk of injury to the AEC and the medial cranial wall.