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.

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.

CT volumetric assessment of pulmonary neoplasms after radiofrequency ablation: when to consider a second intervention?

PURPOSE: To determine the minimal follow-up time point to predict therapeutic response to radiofrequency (RF) ablation of lung tumors. MATERIALS AND METHODS: A retrospective study design was approved by the institutional review board. From January 2008 to January 2010, 78 patients (46 men and 32 women; mean age, 58.9 y) underwent computed tomography (CT)-guided percutaneous RF ablation of pulmonary malignancies. A single RF multitined electrode was used to treat 100 index tumors, 6 primary lesions, and 94 metastatic lesions. CT volumetric measurements of ablated tumors were made before ablation and 24 hours, 3-6 weeks, 3 months, 6 months, 9 months, and 12 months after ablation. An unpaired t test and Spearman rank correlation coefficient were used to analyze the volumetric changes. RESULTS: Complete successful ablation was achieved in 80% of index tumors. The mean time to detection of tumor residue or recurrence tumor residue or recurrence was 6.7 months after ablation. In successfully ablated lesions, the mean volume before ablation was 1.81 cm(3) (standard deviation [SD], 1.71); in failed ablation lesions, the mean volume before ablation was 2.58 cm(3) (SD, 2.8) (P = .42). The earliest statistically significant follow-up time point that showed a difference in the volumetric measurements of failed and successful ablations as well as the earliest significant correlation with the 12-month point was 3 months (P = .025, Spearman R = 0.72). Secondary tumor control after repeat ablation was statistically significant for lesions ablated at a 3-month interval (four out of five lesions) (P = .04). CONCLUSIONS: CT volumetric assessment of ablated tumors revealed that 3 months was the earliest time point that may determine the response of a pulmonary ablation or repeat intervention.