Transmastoid Superior Semicircular Canal Plugging: A Prospective Analysis of Surgical Outcomes

Impaired Vestibulo-Ocular Reflex on Video Head Impulse Test in Superior Canal Dehiscence: "Spontaneous Plugging" or Endolymphatic Flow Dissipation?

Surgical plugging of the superior semicircular canal (SSC) represents an effective procedure to treat disabling symptoms in superior canal dehiscence (SCD), despite resulting in an impaired vestibulo-ocular reflex (VOR) gain for the SSC. On the other hand, SSC hypofunction on video head impulse test (vHIT) represents a common finding in patients with SCD exhibiting sound/pressure-induced vertigo, a low-frequency air-bone gap (ABG), and enhanced vestibular-evoked myogenic potentials (VEMPs). "Spontaneous canal plugging" has been assumed as the underlying process. Nevertheless, missing/mitigated symptoms and/or near-normal instrumental findings would be expected. An endolymphatic flow dissipation has been recently proposed as an alternative pathomechanism for SSC VOR gain reduction in SCD. We aimed to shed light on this debate by comparing instrumental findings from 46 ears of 44 patients with SCD exhibiting SSC hypofunction with post-operative data from 10 ears of 10 patients with SCD who underwent surgical plugging. While no difference in SSC VOR gain values was found between the two groups (p = 0.199), operated ears developed a posterior canal hypofunction (p = 0.002). Moreover, both ABG values (p = 0.012) and cervical/ocular VEMP amplitudes (p < 0.001) were significantly higher and VEMP thresholds were significantly lower (p < 0.001) in ears with SCD compared to operated ears. According to our data, canal VOR gain reduction in SCD should be considered as an additional sign of a third window mechanism, likely due to an endolymphatic flow dissipation.

Postmastoidectomy Hyperacusis Syndrome: Clinical Features and Treatment

OBJECTIVE

We report a novel postmastoidectomy hyperacusis syndrome (PMHS) in patients who have had cortical mastoidectomies and experience hyperacusis to stimuli involving touch of the pinna and periauricular area. This report aims to describe the clinical characteristics of patients predisposed to this disabling complication after mastoid surgery and describes surgical treatment with mastoid cortex resurfacing with hydroxyapatite bone cement.

PATIENTS

Three patients who have undergone intact canal wall mastoidectomies for nonchronic middle ear-related pathologies all reported a similar constellation of postoperative symptoms. None of the patients had any ossicular chain or middle ear abnormalities, and none had preoperative conductive hearing loss. All patients reported disabling hyperacusis related to light touch stimuli in the periauricular area. On examination, all three patients demonstrated synchronous movement of the tympanic membrane when the postauricular area was palpated.

INTERVENTIONS

After a period of observation, none of the patients noted any improvement to their symptoms. Resurfacing of the mastoid cortex with hydroxyapatite bone cement was performed in all patients.

MAIN OUTCOME MEASURES

Presence of touch-induced hyperacusis and audiometry was assessed postoperatively. Patients were also examined for synchronous movement of the tympanic membrane with palpation of the postauricular area.

RESULTS

All patients experienced complete resolution of touch-induced hyperacusis postoperatively. Pure-tone audiometric hearing thresholds remained unchanged after mastoid cortex resurfacing, and there was no longer tympanic membrane movement with palpation of the postauricular area.

CONCLUSIONS

PMHS can occur in patients after cortical mastoidectomy when there is no history of ossicular chain or history of chronic middle ear disease or middle ear abnormalities. PMHS can cause significant distress to patients and remain underrecognized unless synchronous tympanic membrane movement is specifically examined for. Treatment via mastoid cortex surfacing with hydroxyapatite bone cement is safe and effective.

Development of semicircular canal occlusion

Surgical treatment of vertigo is performed with in-depth study of inner ear diseases. Achieving an effective control of vertigo symptoms while reducing damage to hearing and reducing surgical complications is the principle followed by scholars studying surgical modalities. Semicircular canal occlusion is aimed at treatment of partial peripheral vertigo disease and has attracted the attention of scholars because of the above advantages. This article provides a review of the origins of semicircular canal occlusion, related basic research, clinical applications, and the effects of surgery on vestibular and hearing function.