Anticipating Facial Nerve Position Using Three-Dimensional Tractography During the Preoperative Assessment of Cerebellopontine Angle Tumors.

OBJECTIVE: We aim to evaluate the usefulness of preoperative facial nerve tractography in determining the facial nerve position in cerebellopontine angle tumor resection and its value in helping to preserve facial nerve function during surgery. METHODS: A prospective study was designed to include patients presenting with cerebellopontine angle tumors. Three-dimensional reconstruction of facial nerve tractography was performed and added to the usual preoperative testing in all patients. Facial nerve position was compared between tractography results and surgical findings. Moreover, facial nerve function was evaluated at baseline and during follow-up. RESULTS: Fifteen patients were included for analysis. Complete resection was obtained in 5 patients, near-total resection was achieved in 8 patients, and partial resection in 2 patients. We found a strong statistically significant concordance between the preoperative facial nerve tractography reconstruction and the intraoperative findings (complete concordance in 86.66% of all the cases; κ = 0.784; P < 0.0001). Facial nerve anatomic structure was preserved in all patients during surgery. At 6 months follow-up, 66.66% of patients had a facial nerve normal function or a mild dysfunction. CONCLUSIONS: Preoperative facial nerve tractography reconstruction showed a high correlation with intraoperative findings. Preoperative tractography information regarding facial nerve position and its cisternal course is valuable information and could help the surgeon in increasing the safety of the procedure during cerebellopontine angle tumor surgery.

The Impact of the Location of Chorda Tymapni Nerve Origin on the Round Window Accessibility During Pediatric Cochlear Implantation: A Radioclinical Assessment.

OBJECTIVES: This study assessed the impact of the location of the chorda tympani nerve (CTN) origin on the round window (RW) accessibility during pediatric cochlear implantation (CI). We also tried to validate the radiologic method to measure the length between the origin of the CTN from the facial nerve to the stylomastoid foramen (CF-SM). STUDY DESIGN: It was a prospective observational case-series study. SETTINGS: The included CI surgeries were performed at tertiary referral institutions from November 2018 to August 2021. SUBJECTS: We included 146 pediatric patients who were candidates for CI. INTERVENTION: We measured the CF-SM length in the parasagittal cut of the preoperative high-resolution computed tomography. We also classified the intraoperative RW according to the accessibility through the ordinary posterior tympanotomy approach into accessible or inaccessible. MAIN OUTCOME MEASURE: We correlated the preoperative radiologic CF-SM length with the intraoperative RW accessibility. RESULTS: The radiologic CF-SM length ranged from 2.9 to 7.4 mm with a mean of 4.9 ± 1.03 mm. The RW was accessible in 107 patients and inaccessible in 39 patients. Spearman's correlation coefficient revealed a significant relationship between the location of CTN origin and the RW accessibility as the p value was less than 0.0001. CONCLUSIONS: We found a precise method to measure the CF-SM length in the parasagittal cut of the high-resolution computed tomography. We also found a significant impact of the location of the CTN origin on intraoperative RW accessibility. The radiologic CF-SM length of more than 5.4 mm had a powerful prediction capability of the RW inaccessibility.

Volumetry and Surgical Grading Systems for Vestibular Schwannoma Size Assessment and their Relationship to Postoperative Facial Nerve Function.

BACKGROUND AND STUDY AIMS: Treatment modalities in vestibular schwannoma (VS) are difficult to compare since different techniques for size measurements are used. The purpose of this study was to evaluate the relation between different tumor size grading systems regarding their compatibility as well as the relationship to facial nerve outcome facilitating comparisons of different studies. MATERIAL AND METHODS: In this retrospective study, preoperative magnetic resonance imaging of 100 patients with surgically treated VS was evaluated regarding total tumor volume and anatomical extension based on the Koos and Samii classification, as well as volumetric and maximal diameter measures. Three-dimensional constructive interference in steady state (3D-CISS) and T1 postcontrast volumetric interpolated breath-hold examination (VIBE) sequences were used. Facial nerve function was evaluated according to the House-Brackmann (HB) scale 6 months following complete tumor removal via the retrosigmoid approach. RESULTS: Tumor size showed a moderate influence on postsurgical facial nerve function with correlations not exceeding 0.4. Severe palsy was observed mainly in patients with large tumors with Koos grade 4, Samii grade 4b, respectively a volume of at least 6 cm3 or a maximum diameter of 2.4 cm for HB ≥ 3 and a volume of 7.5 cm3 and maximum diameter of 3.2 cm for HB ≥ 4. In regard to volumetry, the Koos and Samii grading systems were highly comparable, whereas the maximal diameter showed consistently lower correlation values. CONCLUSIONS: The results of our study allow direct comparison of studies on surgery versus radiotherapy of VS. The data allow for translation of tumor sizes based on different grading systems. Comparison of microsurgical, radiotherapeutic and radiosurgical approaches should concentrate on patients with large tumors. Whereas smaller tumors were rarely associated with severe facial palsy, large tumors did not exclude the possibility of weak or no palsy 6 months after surgery.

Postoperative radiological assessment of the mastoid facial canal in cochlear implant patients in correlation with facial nerve stimulation.

OBJECTIVES: To correlate the radiological assessment of the mastoid facial canal in postoperative cochlear implant (CI) cone-beam CT (CBCT) and other possible contributing clinical or implant-related factors with postoperative facial nerve stimulation (FNS) occurrence. METHODS: Two experienced radiologists evaluated retrospectively 215 postoperative post-CI CBCT examinations. The mastoid facial canal diameter, wall thickness, distance between the electrode cable and mastoid facial canal, and facial-chorda tympani angle were assessed. Additionally, the intracochlear position and the insertion angle and depth of electrodes were evaluated. Clinical data were analyzed for postoperative FNS within 1.5-year follow-up, CI type, onset, and causes for hearing loss such as otosclerosis, meningitis, and history of previous ear surgeries. Postoperative FNS was correlated with the measurements and clinical data using logistic regression. RESULTS: Within the study population (mean age: 56 ± 18 years), ten patients presented with FNS. The correlations between FNS and facial canal diameter (p = 0.09), wall thickness (p = 0.27), distance to CI cable (p = 0.44), and angle with chorda tympani (p = 0.75) were statistically non-significant. There were statistical significances for previous history of meningitis/encephalitis (p = 0.001), extracochlear-electrode-contacts (p = 0.002), scala-vestibuli position (p = 0.02), younger patients' age (p = 0.03), lateral-wall-electrode type (p = 0.04), and early/childhood onset hearing loss (p = 0.04). Histories of meningitis/encephalitis and extracochlear-electrode-contacts were included in the first two steps of the multivariate logistic regression. CONCLUSION: The mastoid-facial canal radiological assessment and the positional relationship with the CI electrode provide no predictor of postoperative FNS. Histories of meningitis/encephalitis and extracochlear-electrode-contacts are important risk factors. KEY POINTS: • Post-operative radiological assessment of the mastoid facial canal and the positional relationship with the CI electrode provide no predictor of post-cochlear implant facial nerve stimulation. • Radiological detection of extracochlear electrode contacts and the previous clinical history of meningitis/encephalitis are two important risk factors for postoperative facial nerve stimulation in cochlear implant patients. • The presence of scala vestibuli electrode insertion as well as the lateral wall electrode type, the younger patient's age, and early onset of SNHL can play important role in the prediction of post-cochlear implant facial nerve stimulation.

Peri-operative electrically evoked auditory brainstem response assessment of facial nerve/cochlea interaction at cochlear implantation.

OBJECTIVES: Dehiscence between the cochlear otic capsule and the facial nerve canal is a rare and relatively newly described pathology. In cochlear implantation (CI), this dehiscence may lead to adverse electric facial nerve stimulation (FNS) already at low levels, rendering its use impossible. Here, we describe an assessment technique to foresee this complication. METHODS: Pre- and postoperative computed tomography (CT) scans and intraoperative electrically evoked auditory brainstem response (e-ABR) measurements were analyzed in two patients with cochlear-facial dehiscence (CFD). RESULTS: Because of the relatively low resolution, the confirmation of CFD with a clinical CT was difficult. The e-ABR displayed a large potential with 6 and 7.5 ms latency, respectively, which did not occur otherwise. DISCUSSION: Potential strategies to resolve and manage FNS are described. CONCLUSION: Prediction of FNS by assessing the distance between the labyrinthine portion of the facial nerve and the cochlea is difficult using conventional CT scans. A large evoked late myogenic potential at low stimulation levels during intraoperative e-ABR measurement may foresee FNS at CI activation.

Assessment of the cochlear nerve to facial nerve size ratio using MR multiplanar reconstruction of the internal auditory canal in patients presenting with acquired long-standing hearing loss.

OBJECTIVE: To test using the facial nerve as a reference for assessment of the cochlear nerve size in patients with acquired long-standing sensorineural hearing loss (SNHL) using MRI multiplanar reconstruction. METHODS: The study was retrospectively performed on 86 patients. Group 1 (study group, n = 53) with bilateral long-standing SNHL. Group 2 (control group, n = 33) without hearing loss. The nerve size was measured by drawing a region of interest around the cross-sectional circumference of the nerve in multiplanar reconstruction images. RESULTS: No significant correlation was noted between the cochlear nerve and facial nerve size, and the patient's age, gender and weight (p > 0.05). In Group 1, the mean ratio of the cochlear to facial nerve size was 0.99 ± 0.30 (range: 0.52-1.86) and 1.12 ± 0.35 (range: 0.34-2.3) for the right and left sides, respectively. In Group 2, it was 1.18 ± 0.23 (range: 0.78-1.71) and 1.25 ± 0.25 (range: 0.85-1.94) for the right and left sides, respectively. The cochlear nerve size was statistically (p = 0.0004) smaller in Group 1 than in Group 2. CONCLUSION: The cochlear nerve size and the cochlear to facial nerve size ratio are significantly smaller in patients with acquired long-standing SNHL. Advances in knowledge: The facial nerve can be used as a reference for assessment of the cochlear nerve in patients with acquired long-standing SNHL.

Anatomic Assessment of Petrous Internal Carotid Artery, Facial Nerve, and Cochlea Through the Anterior Transpetrosal Approach.

The aim of this study was to measure the related parameters of the cochlea, so as to allow preoperative assessment of the anatomic relationship of the petrous internal carotid artery (ICA), the facial nerve (FN), and the cochlea during skull base surgery. Seven parameters of these 3 structures were examined in the computed tomographic scan of 120 patients. The shortest distance from the cupula cochleae to the petrous ICA and the FN is as follows: 19.39 (1.01) mm to the stylomastoid foramen (D2), 10.27 (0.80) mm to the midpoint of the genu of FN canal (D3), 13.66 (0.88) mm to the exocranial opening of the carotid canal (D4), and 5.64 (1.03) mm to the midpoint of carotid knee (D5). The shortest distance between the mastoid segment of FN canal and the vertical segment of the petrous ICA (D6) was 13.33 (1.25) mm. The angle between D2 and D3 was measured at 45.66 (3.31)°, and the angle between D4 and D5 was measured at 41.08 (2.64)°. Clinically, it is relatively safe to work within the distances and angles measured in this research, and these results may give surgeons a practical and specific view of these 3 structures in the skull base approaches such as anterior transpetrosal approach to achieve the best possible surgical outcome and maximize safety.

[Facial palsy rehabilitation: Assessment before surgery]. / Réhabilitation de la face paralysée. Bilan préthérapeutique du patient.

A patient who needs a surgery for facial rehabilitation must have a complete assessment. The etiology of the facial palsy must be clear. It is necessary to have a MRI of the facial nerve for the statement of the initial pathology or to search a lesion on the nerve. The facial palsy must be definite which is depending of the delay of the palsy and the etiology. An electromyography must be done. The choice of the procedure depends on the delay of the palsy, the site on the nerve, the associated diseases and the opinion of the patient after a good explanation.

[The diagnostic value of high resolution CT in assessment of temporal bone traumatic facial nerve paralysis].

OBJECTIVE: To investigate the diagnostic value of high resolution CT for temporal bone traumatic facial nerve paralysis and the guidance significance for surgery. METHOD: Twenty-nine patients of traumatic facial nerve paralysis were investigated. The predictive diagnosis was made according to the clinical data and the image features of HRCT, then a comparative analysis of the preoperative image features and the surgical findings were carried out. RESULT: The trend of temporal bone fracture displayed on the CT scan was basically consisted with the surgical findings. The direct CT signs of facial nerve injury include the bone fracture line went through the tube, bone tube rupture or continuity interruption, while the indirect CT signs include local incrassation of the facial nerve, lower bone density of the tube, geniculate fossa expansion, oppressed facial nerve, et al. The predictive diagnostic accordance rates of all the image features were above 90% as to the surgical findings. CONCLUSION: High resolution CT could localize the trend of temporal bone fracture,and is helpful to estimate the extent of facial nerve injury and other complications. High resolution CT could provide reliable basis for clinical diagnosis and treatment.

Acoustic neuroma. Assessment and management.

Acoustic neuroma results from abnormal proliferation of Schwann cells. These tumors originate in the region of Scarpa's ganglion at the junction of peripheral and central myelin of the vestibular nerve located in the internal auditory canal (IAC). The bony confine of the IAC houses the VII and the VIII cranial nerves. The presence of tumor mass compresses these structures. The growing tumor mass may also prolapses into the cerebellopontine angle (CPA). With continued growth, the tumor eventually compresses on the brain stem and cerebellum. Despite the benign nature of these tumors, the clinical course of this disease may be fraught with complications.

[The assessment of the function of the nervus intermedius by means of functional salivary gland-scintigraphy]. / Beurteilung der Nervus-Intermedius-Funktion mit Hilfe der funktionellen Speicheldrüsenszintigraphie.

Using functional scintigraphy of the salivary glands, the function of the nervus intermedius can be assessed by estimating excretory quotients for both submandibular glands. This method is preferred to the standard salivation test method of Magielski and Blatt, despite a minimal exposure of the patient to radiation from the injected Natriumpertechnetat. The technical course of this investigation, along with the indications for its use, will be presented.