Differentiation of geniculate ganglion venous malformation from schwannoma: dynamic T1-weighted imaging provides unique diagnostic value.

OBJECTIVE: To distinguish geniculate ganglion venous malformation (GGVM) from schwannoma (GGS) by using high-resolution CT (HRCT), routine MRI, and dynamic T1-weighted imaging (T1WI) characteristics. METHODS: Surgically confirmed GGVMs and GGSs between 2016 and 2021 were retrospectively included. Preoperative HRCT, routine MR, and dynamic T1WI were performed on all patients. Clinical data, imaging characteristics including lesion size, involvement of facial nerve (FN), signal intensity, enhancement pattern on dynamic T1WI, and bone destruction on HRCT were evaluated. Logistic regression model was developed to identify independent factors for GGVMs, and the diagnostic performance was accessed by receiving operative curve (ROC) analysis. Histological characteristics were explored for both GGVMs and GGSs. RESULTS: Twenty GGVMs and 23 GGSs with mean age of 31 were included. On dynamic T1WI, 18 GGVMs (18/20) showed "pattern A" enhancement (a progressive filling enhancement), while all 23 GGSs showed "pattern B" enhancement (a gradual whole-lesion enhancement) (p < 0.001). Thirteen GGVMs (13/20) showed the "honeycomb" sign whereas all GGS (23/23) showed extensive bone changes on HRCT (p < 0.001). Lesion size, involvement of FN segment, signal intensity on non-contrast T1WI and T2-weighted imaging (T2WI), and homogeneity on enhanced T1WI were obviously differed between two lesions (p < 0.001, p = 0.002, p < 0.001, p = 0.01, p = 0.02, respectively). Regression model showed the "honeycomb" sign and "pattern A" enhancement were independent risk factors. Histologically, GGVM was characterized by interwoven dilated and tortuous veins, while GGS was characterized by abundant spindle cells with dense arterioles or capillaries. CONCLUSIONS: The "honeycomb" sign on HRCT and "pattern A" enhancement on dynamic T1WI are the most promising imaging characteristics for differentiating GGVM from GGS. CLINICAL RELEVANCE STATEMENT: The characteristic sign and enhancement pattern on HRCT and dynamic T1-weighted imaging allow preoperative differentiation of geniculate ganglion venous malformation and schwannoma feasible, which will improve clinical management and benefit patient prognosis. KEY POINTS: • The "honeycomb" sign on HRCT is a reliable finding to differentiate GGVM from GGS. • GGVM typically shows "pattern A" enhancement (focal enhancement of the tumor on early dynamic T1WI, followed by progressive contrast filling of the tumor in the delayed phase), while "pattern B" enhancement (gradual heterogeneous or homogeneous enhancement of the whole lesion) is observed in GGS on dynamic T1WI.

Suprameatal-transzygomatic root endoscopic approach to the geniculate ganglion: an anatomical and radiological study.

PURPOSE: To describe the suprameatal-transzygomatic root endoscopic approach (STEA) to the geniculate ganglion (GG), the labyrinthine facial nerve (FN) and epitympanum. METHODS: The feasibility and limits of the STEA, maintaining the integrity of the ossicular chain, were analysed. Ten human cadaveric ears were dissected. Step-by-step description of the technique and relevant measurements were taken during the approach. The visualization and surgical working field on the anterior and posterior medial epitympanum, GG, greater superficial petrosal nerve, the labyrinthine FN and suprageniculate area were evaluated. The range of motion through the approach and the rate of the decompression of the GG and the labyrinthine portion of the FN were assessed as well. CT-scan measurements were compared with those obtained during the dissection. RESULTS: A complete exploration of the epitympanum was possible in every specimen. Decompression of the GG and first portion of the FN was achieved without any trauma to the ossicular chain in nine ears. The endoscope movements were mainly limited by the distance between bony buttress-short process of the incus-tegmen. The working space, during GG and labyrinthine FN decompression, was limited by the distance between malleus head-medial epitympanic wall and malleus head-GG. Radiologic measurements were consistent with those obtained during the dissections. CONCLUSION: The STEA is a promising minimally invasive approach for decompression of the GG and FN's labyrinthine portion. The applications of this corridor include the exploration and surgery of the medial epitympanum, preserving the ossicular chain.

Relation between volume of sphenoid sinuses and protrusion of Vidian nerve: possible applications to Vidian neurectomy.

PURPOSE: Vidian neurectomy is a surgical procedure applied to different pathological conditions, including chronic rhinitis and sphenopalatine neuralgia. The choice of the correct surgical approach depends upon the possible protrusion of Vidian nerve into the sphenoid sinuses. The present study analyzes the possible relationship between protrusion of Vidian nerve and volume of sphenoid sinuses. METHODS: In total, 320 maxillofacial CT-scans were retrospectively assessed. Subjects equally divided among males and females (age range 18-94 years) were divided into three groups according to the profile of Vidian nerve protrusion: type 1: Vidian nerve inside the sphenoid corpus; type 2: partially protruding into the sphenoid sinus; and type 3: entirely protruding into the sphenoid sinus through a stalk. Volume of sphenoid sinuses was extracted through the ITK-SNAP-free software and automatically calculated. Possible statistically significant differences in prevalence of the three types between males and females were assessed through Chi-squared test (p < 0.05). Differences in volume of sphenoid sinuses in subjects included within the three types were assessed through one-way ANOVA test (p < 0.05), separately for males and females. RESULTS: Type 2 was the most prevalent (46.5%), followed by type 1 (38.8%) and type 3 (14.7%), without significant differences according to sex (p > 0.05). Volume significantly increased passing from type 1 to type 3 both in males (p < 0.01) and in females (p < 0.01). CONCLUSIONS: The results prove the existence of a strict relationship between sphenoid sinuses pneumatization and protrusion of the Vidian canal and give a contribution to the knowledge of this important anatomical variant in endoscopic surgery.

Is the Height of the Arcuate Eminence Related to Body Mass Index?

OBJECTIVES: To determine the relationship, if any, between body mass index (BMI) and attenuation of the arcuate eminence (AE). STUDY DESIGN: Case series with chart review. SETTING: Tertiary neurotologic referral center. SUBJECTS AND METHODS: Submillimeter distances were recorded from high-resolution temporal bone computed tomography (CT) scans of 50 patients (100 sides). The AE (defined as the superiormost location of the petrous bone over the otic capsule), the bony apex of the superior semicircular canal (SSC), and the geniculate ganglion (GG) were identified and 3-dimensional distances measured. The height of the AE relative to the bony apex of the superior semicircular canal was determined using Euclidean geometry using the fixed anatomical landmark of the GG as the origin. Correlations between AE and BMI were calculated using Pearson's, linear mixed effects, and sensitivity analysis models. RESULTS: The mean (SD) BMI was 30 (8.1) kg/m2, with 16 (30%) patients falling in the underweight/normal category (BMI <25 kg/m2), 10 (20%) overweight patients (25 kg/m2≤ BMI ≤ 30 kg/m2), and 24 (48%) patients considered obese (BMI >30 kg/m2). The mean (SD) AE heights for the left and right ears were 2.5 (1.11) and 2.6 (1.09), respectively. The results of the linear mixed-effects models indicated little evidence that BMI is associated with AE height when including all patients (partial R2 = 0.040) and when using BMI categories (partial R2 = 0.025). CONCLUSION: Contrary to other structures within the lateral skull base, the relative prominence of the arcuate eminence does not correlate with BMI or any other demographic variables.

Endoscopic Transcanal Approach to Geniculate Ganglion Hemangioma and Simultaneous Facial Nerve Reinnervation: A Case Report.

Hemangioma of the facial nerve (FN) is a very rare benign tumor whose origin is the vascular plexi that surround the nerve. The transpetrous, retrosigmoid, and middle cranial fossa (MCF) routes are the traditional and most widely used approaches to reach these lateral skull base neoformations. However, this very complex region can be reached through an exclusive transcanal endoscopic procedure in selected cases. One of these was a 42-year-old patient who had been presenting a worsening left FN paralysis (grade VI according to the House-Brackmann scale at the time of visit) for 22 months without a history of trauma or infection. Radiological studies showed a lesion in the region of the geniculate ganglion. A suprageniculate endoscopic approach was performed to remove the lesion, with the sacrifice of the FN and a simultaneous hypoglossal-facial anastomosis. The aim of this minimally invasive surgery is the complete excision of the disease, maintaining the hearing function intact and restoration of facial function, whenever possible, avoiding more invasive approaches.

Radiographic Analysis of the Vidian Canal and Its Utility in Petrous Internal Carotid Artery Localization.

BACKGROUND: Endoscopic endonasal surgery of the skull base requires expert knowledge of the anatomy and a systematic approach. The vidian canal is regarded as a reliable landmark to localize the petrous internal carotid artery (pICA) near the second genu, which can be used for orientation in deep skull base approaches. There is controversy about the relationship between the vidian canal and the pICA. OBJECTIVE: To further establish the vertical relationship between the vidian canal and the pICA to aid in surgical approaches to the skull base. METHODS: We utilized a collection of institutional review board-approved computed tomographic (CT) angiograms (CTAs). Fifty CTAs were studied bilaterally for 100 total sides. The vidian canal was visualized radiographically to determine whether it terminates below, at, or above the level of the pICA. RESULTS: Sixty-six of 100 vidian canals terminated inferior to the pICA (66%), which was the most common relationship observed. The average distance inferior to the pICA was 1.01 mm on the right, 1.18 mm on the left, and 1.09 mm of the total 66 sides. Less commonly, the vidian canal terminated at the level of the pICA canal in 34 sides (34%). The vidian canal was not observed to terminate superior to the pICA in any of the 50 CTAs studied. CONCLUSION: The vidian canal terminates inferior to the pICA most commonly, but often terminates at the level of the pICA. Careful drilling clockwise inferior to superior around the vidian canal should allow for safe pICA localization in most cases.

Facial nerve neuroma in the geniculate ganglion extending into the internal auditory canal: A case report.

Facial nerve schwannoma is a very rare benign tumor representing less than 1% of intrapetrous lesions. Our patient is a forty-one year old female who has suffered from recurrent right facial palsy for the last six years. She was first misdiagnosed as having Bell's palsy and received corticosteroids which resulted in little improvement. She then had facial nerve decompression surgery which resulted in a partial improvement. Since then, she has suffered from recurrent attacks of facial palsy. Two years ago, she came to our hospital seeking further treatment options. The final diagnosis made by MRI was a possible facial nerve tumor. To obtain a better facial outcome, total tumor removal was performed through the middle cranial fossa approach along with facial-hypoglossal nerve end-to-side anastomosis through transmastoid approach. Her hearing was preserved, and she obtained a better facial outcome than that of her preoperative level. In conclusion, facial nerve schwannoma has the potential to be misdiagnosed as Bell's palsy which might lead to a delay in diagnosis, and end-to-side neurorrhaphy may be an effective alternative in a selected case.

Temporal Lobe Retraction Provides Better Surgical Exposure of the Peri-Geniculate Ganglion for Facial Nerve Decompression via Transmastoid Approach.

PURPOSE: For the exposure of the labyrinthine segment of the facial nerve, transmastoid approach is not usually considered due to being situated behind the superior semicircular canal. To obtain a better view and bigger field for manipulation in the peri-geniculate area during facial nerve decompression, retraction of temporal lobe after bony removal of tegmen mastoideum was designed via transmastoid approach. MATERIALS AND METHODS: Fifteen patients with traumatic facial paralysis [House-Brackmann (HB) grade IV-VI], 3 patients with Bell's palsy (HB grade V-VI), and 2 patients with herpes zoster oticus (HB grade V-VI) underwent facial nerve decompression surgery between January 2008 and July 2014. In all patients, we performed temporal lobe retraction for facial nerve decompression via the transmastoid approach. Patients were examined using pre operative tests including high-resolution computed tomography, temporal magnetic resonance imaging, audiometry, and electroneurography (degenerative ratio >90%). Facial function was evaluated by HB grading scale before and 6 months after the surgery. RESULTS: After the surgery, facial function recovered to HB grade I in 9 patients and to grade II in 11 patients. No problems due to surgical retraction of the temporal lobe were noted. Compared to the standard transmastoid approach, our method helped achieve a wider surgical view for improved manipulation in the peri-geniculate ganglion in all cases. CONCLUSION: Facial nerve decompression via the transmastoid approach with temporal lobe retraction provides better exposure to the key areas around the geniculate ganglion without complications.

Anterior Displacement of the Geniculate Ganglion.

We present the case of a 34-year-old Japanese woman with cholesteatoma of the middle ear. During the operation, this patient showed an unusual position of the geniculate ganglion. We reviewed the computed tomography (CT) images targeting the ear of the present case after the operation. We found that the shortest ranges from the ampullated end of the superior semicircular canal to the geniculate ganglion fossa were 5.1 mm on both sides. We did not find any cases with obvious dislocation of the geniculate ganglion among the 67 cases for which we had performed tympanoplasty. Displacement of the geniculate ganglion is either extremely rare or typically unnoticed because this abnormality is asymptomatic. We speculated that the unusual position of the geniculate ganglion was due to an incomplete development of the tympanic tegmen. When surgical treatment such as decompression of the facial nerve or tympanoplasty is performed, close attention should always be paid to the anatomy of the facial nerve from the labyrinthine segment to the geniculate ganglion. In the present case, although connective tissues existed around the anterior epitympanic recess, we left this lesion to avoid iatrogenic facial palsy.

Facial nerve hemangiomas at geniculate ganglion: preservation of nerve integrity is correlated with duration of facial palsy.

OBJECTIVE: To study preservation of nerve integrity in 16 cases with facial nerve hemangiomas at geniculate ganglion (GG). METHODS: 16 cases with facial nerve hemangiomas at GG, who presented with facial palsy, were included in the study. Preservation of nerve integrity was attempted by the same surgeon during surgical removal, and those who failed to preserve nerve integrity underwent nerve grafting. The patients were divided into longer duration group (>12months) and shorter duration group (≤12months) according to duration of facial palsy, and preservation of nerve integrity in the couple of groups was compared. RESULTS: Nerve integrity was preserved in 2 of 10 cases (20%) among longer duration group, while it was preserved in 5 of 6 cases (83.3%) among shorter duration group (p<0.05). All the cases with nerve integrity preserved recovered to grade III or better, among which 3 cases recovered to grade I or grade II, while only 3 of 9 cases (33.3%) with nerve grafting recovered to grade III at the best. CONCLUSIONS: Preservation of nerve integrity was correlated with duration of facial palsy in cases with hemangiomas at GG. Patients with nerve integrity preserved showed better outcomes of facial nerve.

Measurement and analysis of facial nerve on fully displayed multislice computed tomographic multiplanar reconstruction image.

The objectives of this study were to measure the length of horizontal segment of facial nerve (HFN), the length of vertical segment of facial nerve (VFN), and the angle between these 2 segments on a fully displayed multislice computed tomographic multiplanar reconstruction (MPR) images of HFN and VFN and to analyze the data with respects to side, sex, and age. Parameters of 234 patients (468 observations, 118 men and 116 women, aged 4-70 years) with intact temporal bone were measured on multislice computed tomographic multiplanar reconstruction images. The data gained were analyzed by statistical method. The left and right lengths of VFN were significantly different (P < 0.05). And the length of HFN, the length of VFN, and the angle between males and females were significantly different (P < 0.05). We divided the data into 3 groups to study correlations between measurements and age. In underaged group, there was a strong positive correlation between the length of VFN and age; the value of Pearson correlation was 0.645. And there was a weak correlation between the angle and the age; the value of Pearson correlation was 0.270. In older-aged group, there was a moderate negative correlation between the length of VFN and age; the value of Pearson correlation was -0.408. Our results are of high potential to expand the visual field to facial nerve and may provide more detailed information to surgeries of facial nerve, middle ear, and temporal bone.

Enlarged geniculate ganglion fossa: CT sign of facial nerve canal fracture.

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.

Use of computed tomography to predict the possibility of exposure of the first genu of the facial nerve via the transmastoid approach.

HYPOTHESIS: The purpose of this study was to investigate whether computed tomography (CT) could predict the possibility of first genu exposure of the facial nerve via the transmastoid approach in patients with acute facial paralysis. BACKGROUND: Temporal bone CT is the best method for visualizing the intratemporal segment of the facial nerve canal, which is known to have diverse anatomic variations. METHODS: A prospective study was conducted on 11 patients who underwent facial nerve decompression via the transmastoid approach. Two groups of patients underwent surgery to expose the perigeniculate area via the transmastoid approach. One group included patients who had anatomic parameters of the temporal bone that met the CT criteria, including length of the labyrinthine segment, level of the geniculate ganglion, bony thickness of the lateral semicircular canal, and height interval between the tympanic and labyrinthine segments. The other group included patients with facial paralysis who required facial nerve exploration, especially distal to the geniculate ganglion. Facial nerve decompression was performed in all patients as far proximal in the transmastoid view as was possible without causing damage to the semicircular canals. RESULTS: We correlated the temporal bone CT images and surgical findings in 11 patients who underwent facial nerve decompression via the transmastoid approach. The facial nerves of 6 patients who had anatomic structures that met the CT criteria were successfully exposed to the proximal labyrinthine segment without labyrinthine damage. The facial nerves of another 4 patients who did not have anatomic structures that met the CT criteria could be decompressed only to the geniculate ganglion. CONCLUSION: CT scan can predict the possibility of first genu exposure of the facial nerve via the transmastoid approach based on the CT parameters suggested in this study.

Using greater superficial petrosal nerve and geniculate ganglion as the only two landmarks for identifying internal auditory canal in middle fossa approach.

The middle fossa approach is a surgical technique indicated for acoustic neuroma with advantages of complete tumor removal and hearing preservation. Various methods have been developed for identifying internal auditory canal (IAC). Here, we describe a new method, which uses greater superficial petrosal nerve (GSPN) and geniculate ganglion (GG) as the only two landmarks to identify IAC. In this study, the surgical anatomy and relations between GSPN, GG, petrous ridge, and IAC were measured on 20 temporal bone specimens and 40 HRCT scans of normal inner ear structures. The temporal bone study showed that the GSPN is nearly parallel to the petrous ridge, with an average angle of about 6 degrees. The line perpendicular to the GSPN from the tip of the GG to the petrous ridge reaches at the porus acousticus, with an average distance of 12.95 mm. The temporal bone HRCT scan study revealed that the length from the tip of the GG to the midpoint of the IAC portion on the line perpendicular to the petrous ridge is about 9.9 mm. We applied this method on 20 temporal bones by drilling the point away from the tip of the GG about 9.9 mm on a line angled with the GSPN about 96 degrees. All IACs were safely identified without damaging the cochlea, the labyrinthine portion of the facial nerve, or the vestibule. In conclusion, the GSPN and GG can be the only two landmarks for safely identifying the IAC without injury to the inner ear structures in the middle fossa approach.

Geniculate ganglion hemangiomas: clinical results and long-term follow-up.

OBJECTIVE: To review the clinical presentation, evaluation, and management of 18 patients with geniculate ganglion hemangiomas seen at the House Clinic. STUDY DESIGN: Retrospective case review. SETTING: Private neurotological tertiary referral center. PATIENTS: Eighteen patients with geniculate ganglion hemangiomas treated at the House Clinic between 1986 and 2008. INTERVENTION: Observation or surgical intervention using the middle fossa or translabyrinthine craniotomy for decompression or excision of the hemangioma with or without facial nerve resection and grafting. MAIN OUTCOME MEASURES: Postoperative facial function using the House-Brackmann grading system, postoperative audiograms and postoperative follow-up magnetic resonance imaging or computed tomographic scan of the temporal bone. RESULTS: Approximately 13 patients (72%) were female subjects, and 5 (28%) were male subjects. Mean age was 54 years, and follow-up was 73 months. 17 (94%) of 18 patients presented with facial paresis or paralysis. Facial twitching was present in 10 (56%) of 18 cases. Four patients (22%) presented with hearing loss. Facial nerve function was House-Brackmann grade I/II in 7(38%), III/IV in 5 (28%), and V/VI in 6 (34%) patients, respectively. Approximately 13 patients (72%) underwent middle fossa craniotomy for excision or decompression of their hemangiomas, and 2 (11%) underwent translabyrinthine removal. The facial nerve was preserved in 11 (73%) of 15 patients and was excised and grafted in 4 (27%) of 15. Recovery to a House-Brackmann grade I/II was seen in 8 (72%) of 11 patients in whom the integrity of the facial nerve was preserved. In the surgical group, hearing remained stable in 64% of hearing preservation cases and worsened in 38%. Facial function remained stable in the nonsurgical group. CONCLUSION: Geniculate ganglion hemangiomas are rare vascular malformations that produce facial paralysis despite their relative small size at presentation. When possible, excision with neural preservation yields better long-term facial function. Recurrences are rare.

Zygomatic root approach.

CONCLUSIONS: The zygomatic root (ZR) approach provides improved intraoperative exposure of the key areas around the geniculate ganglion without a craniotomy, combining the advantages of middle cranial fossa (MCF) and transmastoid extralabyrinthine (TMEL) approaches. The ZR approach may be useful in cases of traumatic facial palsy, Bell's palsy, iatrogenic facial palsy, superior semicircular canal dehiscence and primary cholesteatoma. OBJECTIVES: To describe and evaluate the new ZR approach technique in the treatment of traumatic intratemporal facial nerve injuries. PATIENTS AND METHODS: This is a prospective clinical study of three consecutive procedures performed between July 2007 and January 2008, and a detailed discription of the surgical technique. The setting is a tertiary referral center. The patients' age range was 3-7 years. Interventions were based on drilling the ZR area extensively, so that the perigeniculate area was exposed through the space created between the middle cranial fossa basal dura and skeletonized external auditory canal. The ZR approach can be performed as an isolated technique or can be combined with an inferior mastoidectomy protecting the bony bridge between. RESULTS: Two patients had a mixed-type fracture and one patient had a transverse fracture. All three patients received a ZR combined approach. There was no cerebrospinal fluid leak, hearing loss, tympanic membrane perforation or meatal stenosis.

Quantitative morphology of facial nerve based on three-dimensional reconstruction of temporal bone.

OBJECTIVE: To investigate an effective method of quantitative analysis of the facial nerve and its adjacent structures on the basis of three-dimensional (3D) CT image reconstruction of the temporal bone. METHODS: The inner structures of the temporal bone from CT images of 34 healthy adults were reconstructed. Precise measurement of the facial nerve and its adjacent structures were accomplished by using Able Software 3D-DOCTOR. RESULTS: 3D images of temporal bone structures, including facial nerve, tympanic annulus, cochleariform process, cochlea, semicircular canals, jugular fossa, and carotid artery, were reconstructed. Quantitative data of the facial nerve and its adjacent structures were analyzed, especially the detailed spatial relationships between the facial nerve and the surface of the mastoid process or tympanomastoid fissure. CONCLUSION: 3D reconstruction of CT images clearly displayed the detailed structures of the temporal bone. Quantitative data of the facial nerve and its adjacent structures are very useful for temporal bone surgery.