Evaluation of Semicircular Canal Function by Video Head Impulse Test in Patients With Facial Nerve Schwannoma

Evaluation of Semicircular Canal Function by Video Head Impulse Test in Patients With Labyrinthine Fistula Due to Cholesteatoma

OBJECTIVES

To evaluate semicircular canal function in patients with labyrinthine fistula (LF) due to cholesteatoma by the video Head Impulse Test (vHIT).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Ten patients with LF due to cholesteatoma and six without LF underwent vestibular examination.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURES

The gain in vestibulo-ocular reflex (VOR) and the presence of catch-up saccade were examined for the semicircular canals in patients with LF.

RESULTS

Seven of 10 cases (70.0%) in the fistula group were judged to have semicircular canal dysfunction based on preoperative evaluation. VOR gains in the patients with LF were significantly lower than those in the patients without LF. VOR gain decreased significantly in accordance with the severity of the LF. The postoperative VOR gain more than 6 months after surgery was significantly improved compared with the preoperative VOR gain.

CONCLUSIONS

The vHIT is thought to be the most suitable method for evaluating semicircular canal function in patients with LF due to cholesteatoma as it is not influenced by middle ear pathology and can evaluate the function of the vertical canals. The vHIT could predict whether a LF is present or not before surgery, and the vHIT is essential for surgery for patients with LF.

Preoperative Differences in Intracranial Facial Versus Vestibular Schwannomas: A Four Nerve Assessment

OBJECTIVES

Assesses whether preoperative functional testing can distinguish vestibular schwannomas from facial nerve schwannomas medial to the labyrinthine segment.

STUDY DESIGN

Retrospective cohort.

METHODS

Retrospectively review surgically managed intracranial facial and vestibular schwannomas between January 2015 and December 2019 at two tertiary care centers. Patients with neurofibromatosis 2 and surgery for recurrence were excluded. Preoperative functional testing to include House-Brackmann scores, electroneuronography (ENoG), cervical vestibular evoked myogenic potentials (cVEMP), caloric testing, acoustic brainstem responses (ABRs), acoustic reflexes, and audiograms was compared between the two groups of schwannomas.

RESULTS

Twelve facial and 128 vestibular schwannomas met inclusion criteria. In only one case was a facial schwannoma diagnosed preoperatively from imaging. No statistically significant difference was found in preoperative House-Brackmann scores, ENoG, cVEMP, caloric testing, ABRs, or acoustic reflexes. Pure tone average was worse in the vestibular schwannoma group (63 dB [95% CI: 58-68 dB] vs. 46 dB [95% CI: 34-58 dB], P = .01), and the difference was more apparent in the lower frequencies. Word recognition score was better in the facial schwannoma group (66% [95% CI: 45-86%] vs. 41% [95% CI: 34-47%], P = .02).

CONCLUSION

Specialized preoperative functional evaluation of the nerves of the internal auditory canal cannot reliably predict the presence of an intracranial facial schwannoma. Hearing is better in facial schwannomas, particularly in the lower frequencies. This should raise the index of suspicion for an intracranial facial schwannoma, especially in candidates for hearing preservation vestibular schwannoma surgery.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:2098-2105, 2021.

Usefulness of the Video Head Impulse Test for the Evaluation of Vestibular Function in Patients With Otitis Media With Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

OBJECTIVES

To investigate usefulness of the video Head Impulse Test (vHIT) as a method for evaluating semicircular canal function in patients with otitis media with antineutrophil cytoplasmic antibody-associated vasculitis (OMAAV).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Fourteen patients with OMAAV underwent vestibular examination.

MAIN OUTCOME MEASURES

The gain in vestibulo-ocular reflex (VOR) and the presence of catch-up saccade were examined for each semicircular canal.

RESULTS

Seven (50.0%) of the 14 patients felt subjective symptoms of disequilibrium. Dysfunction in at least one semicircular canal was detected in all ears of the OMAAV patients evaluated by vHIT. Dysfunction in posterior semicircular canal was detected more frequently than that in the anterior or horizontal canal. There were no significant correlations between the gain in VOR and hearing loss.

CONCLUSIONS

vHIT is thought to be the most suitable method for evaluating semicircular canal function in patients with OMAAV as vHIT is not influenced by middle ear pathology and was able to evaluate vertical canal function including the posterior canal.