A Comparison of Diagnostic Accuracy of Superior Semicircular Canal Dehiscence in MDCT and MRI, and Coexistence with Tegmen Tympani Dehiscence.

Objective Tegmen tympani dehiscence in temporal multidetector computed tomography (MDCT) and superior semicircular canal dehiscence may be seen together. We investigated superior semicircular canal dehiscence in temporal MDCT and temporal magnetic resonance imaging (MRI). Methods In this retrospective study, 127 temporal MRI and MDCT scans of the same patients were reviewed. In all, 48.8% ( n = 62) of cases were male, and 51.2% ( n = 65) of cases were female. Superior semicircular canal dehiscence and superior semicircular canal-temporal lobe distance were evaluated by both MDCT and MRI. Tegmen tympani dehiscence was evaluated by MDCT. Results Superior semicircular canal dehiscence was detected in 14 cases (5.5%) by temporal MDCT and 15 cases (5.9%) by temporal MRI. In 13 cases (5.1%), it was detected by both MDCT and MRI. In one case (0.4%), it was detected by only temporal MDCT, and in two cases (0.8%), it was detected by only temporal MRI. Median superior semicircular canal-to-temporal distance was 0.66 mm in both males and females in temporal MDCT and temporal MRI. In both temporal MDCT and temporal MRI, as superior semicircular canal-to-temporal lobe distance increased, the presence of superior semicircular canal dehiscence in temporal MDCT and temporal MRI decreased. Tegmen tympani dehiscence was detected in eight cases (6.3%) on the right side and six cases (4.7%) on the left side. The presence of tegmen tympani dehiscence in temporal MDCT and the presence of superior semicircular dehiscence in MDCT and MRI increased. Conclusion Superior semicircular canal dehiscence was detected by both MDCT and MRI. Due to the accuracy of the MRI method to detect superior semicircular dehiscence, we recommend using MRI instead of MDCT to diagnose superior semicircular canal dehiscence. Moreover, there is no radiation exposure from MRI.

The Pitfalls and Important Distances in Temporal Bone HRCT of the Subjects with High Jugular Bulbs - Preliminary Report.

BACKGROUND: High jugular bulb (HJB) may be detected unilaterally or bilaterally in temporal bone high resolution computerized tomography (HRCT). OBJECTIVES: In this retrospective study, we investigated the pitfalls and important surgical distances in patients with unilateral and bilateral HJB via temporal bone HRCT. MATERIAL AND METHODS: In this preliminary report, the study group consisted of 20 adult patients (12 male, 8 female), or 40 ears, all of which underwent temporal bone HRCT. We divided them into groups that consisted of bilateral HJB (14 ears), unilateral HJB (13 ears), and control (No HJB, 13 ears). The anotomical relationships of the sigmoid sinus, jugular bulb, and carotid artery with several landmarks in the temporal bone were studied via temporal bone axial and coronal HRCT. The shortest distances between certain points were measured. These measurements were analyzed in respect to pneumatization. Dehiscence on the jugular bulb (JB) and internal carotid artery (ICA) and the dominance of JB were also evaluated for all of the groups. RESULTS: In the axial sections of the temporal bone HRCTs, the sigmois sinus (SS)-external auditory canal (EAC) distance of the bilateral HJB group (14.00±1.17 mm) was significantly lower than that of the control group (16.46±2.14 mm). The JB-posteromedial points of the umbo on the ear drum (ED) distance of the bilateral HJB (6.28±1.72 mm) and the unilateral HJB groups (7.23±2.00 mm) were significantly lower than that of the control group (11.15±2.30 mm). In the coronal sections of the temporal bone HRCT, the JB-F distance of the bilateral HJB group (5.42±2.10 mm) was significantly lower than that of the control group (8.30±2.28 mm). As the mastoid pneumatisation and mastoid volume increased, the percentage of ICA-dehiscence and the percentage of JB-dehiscence increased. CONCLUSIONS: In subjects with well-pneumatised mastoids, the doctors should be aware of the increased risk of ICA-dehiscence and JB-dehiscence. These measurements should be done in greater series to yield more thorough knowledge.

Anatomic variations of the sphenoid sinus on computed tomography.

Anatomic variations of the vital structures adjacent to the sphenoid sinus can be jeopardized during functional endoscopic sinus surgery (FESS). The knowledge of the size and extent of pneumatization of the sphenoid sinus (SS) is an important condition for adequate surgical treatment of its disease. The bony anatomic variations of SS as well as its relationship with adjacent vital structures were reviewed in this paper. The study was performed on 267 patients with a complaint of chronic or recurrent sinusitis. Computed tomographic (CT) scans were obtained upon completion of therapy. The evaluations of the sphenoid sinuses were regarded separately, so as 534 sides were examined. Especially bony anatomic variations as well as mucosal abnormalities of the sphenoid sinuses were examined. Pneumatization of the pterygoid process and anterior clinoid process were found in 39.7% and 17.2% of the patients respectively. Vidian canal protrusion was found in a total of 158 sides of which 60 were bilateral. These entities were encountered usually when pneumatization of the pterygoid process occurred. Carotid canal and optic canal protrusions were found in 5.2% and 4.1% of the patients respectively. Mucosal thickening, and polyps or cysts of sphenoid sinuses were detected in 20.6% and 4.5% of the patients respectively. There was a statistically significant correlation between pterygoid pneumatization and vidian canal protrusion (p < 0.001), and vs. foramen rotundum protusion (p = 0.004). While the optic canal protrusion was found significantly associated with the anterior clinoid pneumatization (p < 0.001), there was no statistically significant correlation between a carotid canal protrusion and anterior clinoid pneumatization (p = 0.250). Sphenoid sinus surgery is very risky, because of changing variations of the cavity. We are in the opinion that detailed data from CT scans of SS will enable the surgeon to interpret any anatomic variations and pathological conditions before initiation of the surgical therapy.