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Enlarged Geniculate Ganglion Fossa

Rationale and Objectives

The aim of this study was to preliminarily investigate whether an enlarged geniculate ganglion fossa (GGF) on temporal bone computed tomography can diagnose GGF fracture in patients with traumatic facial paralysis by evaluating the diameter of the GGF.

Materials and Methods

Thirty-six patients who underwent computed tomography before confirmation of GGF fracture on otologic surgery were recruited into a study group. Additionally, a cohort of 107 patients with no histories of head trauma, no structural abnormalities of inner ear, and no clinical symptoms of facial nerve disability who underwent computed tomography for other reasons were selected as a control group. The diameters of the GGFs of the study group were evaluated by two observers and compared retrospectively with those of the control group. Wilcoxon’s test was used to compare discrepancies of both sides, and intraclass correlation coefficients were used to evaluate intraobserver and interobserver reliability.

Results

The measurement of diameters showed good interobserver and intraobserver consistency. The discrepancy in the measurement of transdiameter between both sides of the GGF on reformatted transverse images of the study group was significantly different from that of the control group (Wilcoxon’s test, P < .001). Discrepancy in the GGF on transverse images of the study group was larger than that of the control group. A significant difference existed in the discrepancy in vertical diameter between the study and control groups (Wilcoxon’s test, P < .001) as well.

Conclusions

An enlarged GGF on temporal bone computed tomography offers an additional sign for the diagnosis of GGF fracture in patients with traumatic facial paralysis.

The incidence of temporal bone trauma and associated facial nerve injury has increased with increasing accidents. It has been reported that 14% to 22% of patients with skull fractures have temporal bone fractures , which are frequently attributable to falls, traffic accidents, and assaults . Facial paralysis, one of the most severe complications caused by temporal bone fracture, is usually obvious, affecting facial expression, oral competence, and taste.

Clinically, patients with facial nerve dysfunction are treated either conservatively or surgically. Surgical treatment such as facial nerve decompression is carried out depending on diagnostic and topognostic examination, and the choice of surgical approach is guided by the fracture location. A fracture line of the temporal bone demonstrated on computed tomographic (CT) images is one of the prominent indications for decompression of the facial nerve . Temporal bone CT imaging can depict the facial canal and the direction of temporal bone fractures. Most fracture lines can be depicted, with sensitivity as high as 90% .

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Materials and methods

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Figure 1, Measurement of transdiameter of the geniculate ganglion fossa. The plane crosses the labyrinthine and tympanic segments simultaneously. These two segments make the plane fixed. The transdiameter ( short line ) was measured from the posterior apex ( point a ) of the genu to the proximal lateral wall of the tympanic segment. The location of hiatus canalis facialis ( point b ) is not always easily fixed for the shape variability of hiatus canalis facialis. Thus, the measurement from point a to point b is abandoned.

Figure 2, Measurement of vertical diameter of the geniculate ganglion fossa ( black line ). The swollen tensor tympani muscle locates laterally and inferiorly ( white arrow ). The black arrow represents a fracture of the anterior wall of the tympanic cavity.

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Results

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Figure 3, Fracture line extending to the geniculate ganglion fossa, confirmed intraoperatively ( short arrows ). The geniculate ganglion locates proximally to the tympanic segment. a, greater superficial petrosal nerve; b, geniculate ganglion; c, tympanic segment; d, labyrinthine segment.

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Figure 4, Diameters of left side in the control group and traumatic side in the study group. NT, transdiameter in the nontrauma control group; NV, vertical diameter in the nontrauma control group; TT, transdiameter in the trauma study group; TV, vertical diameter in the trauma study group.

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Analysis of the Transdiameter of the GGF

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Analysis within the control group

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Analysis within the study group

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Analysis between the study and control groups

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Analysis of the Vertical Diameter of the GGF

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Analysis within the control group

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Analysis within the study group

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Analysis between the study and control groups

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Count of Temporal Bone Fractures

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Figure 5, Geniculate ganglion fossa (GGF) depiction on reformatted transverse symmetric computed tomographic image of a patient with GGF fracture confirmed through surgery. The fracture crossing the GGF cannot be recognized clearly. Left-sided GGF enlargement ( long arrow ) can be seen compared to the other side. The longitudinal fracture ( short arrow ) goes through the mastoid, extending into the tympanic cavity.

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Discussion

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Figure 6, Geniculate ganglion fossa (GGF) depiction on reformatted coronal symmetric computed tomographic image ( black arrows ). The tensor tympani muscles locate just below the GGF ( white arrows ). Enlarged GGF of the left side alerts radiologists to the fracture. The left tensor tympani muscle is somewhat swollen compared to the right side.

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Conclusions

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References

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