Otolithic membrane damage in patients with endolymphatic hydrops and drop attacks.

OBJECTIVES: 1. Evaluate the otolithic membrane in patients with endolymphatic hydrops (EH) and vestibular drop attacks (VDA) undergoing ablative labyrinthectomy. 2. Correlate intraoperative findings to archival temporal bone specimens of patients with EH. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. SPECIMEN SOURCE: 1. Patients undergoing labyrinthectomy for incapacitating Ménière's disease (MD), delayed EH, VDA, or acoustic neuroma (AN) between 2004 and 2011. 2. Archival temporal bone specimens of patients with MD. INTERVENTIONS: Ablative labyrinthectomy. MAIN OUTCOME MEASURES: Examination of the utricular otolithic membrane. RESULTS: The otolithic membrane of the utricle was evaluated intraoperatively in 28 patients undergoing labyrinthectomy. Seven (25%) had a history of VDA, 6 (21%) had delayed EH, 9 (32%) had MD, and 6 (21%) had AN. All patients with VDA showed evidence of a disrupted utricular otolithic membrane, whereas only 50% and 56% of patients with delayed EH and MD, respectively, demonstrated otolithic membrane disruption (p = 0.051). None of the patients with AN showed otolithic membrane disruption (p = 0.004). The mean thickness of the otolithic membrane in 5 archival temporal bone MD specimens was 11.45 micrometers versus 38 micrometers in normal specimens (p = 0.001). CONCLUSION: The otolithic membrane is consistently damaged in patients with VDA. In addition, there is a significantly higher incidence of otolithic membrane injury in patients with MD and delayed EH compared with patients without hydrops, suggesting that the underlying pathophysiology in VDA results from injury to the otolithic membrane of the saccule and utricle, resulting in free-floating otoliths and atrophy.

Impact of endolymphatic mastoid shunt surgery on saccule and lateral semicircular canal function.

Endolymphatic mastoid shunt surgery (EMSS) is widely performed in patients with medically intractable Meniere's disease. Although many patients report an improvement of symptoms after surgery, the mechanisms which are responsible for the relief of complaints are not known. To date, only few studies exist which studied the influence of EMSS on vestibular function. The present study examines the effect of EMSS on saccule function by measuring vestibular evoked myogenic potentials and the effect on lateral semicircular canal function by sinusoidal harmonic acceleration (SHA) testing. No changes in vestibulo-collic reflexes were found after surgery compared to before surgery. SHA testing resulted in comparable phase lag and gain pre- and postoperatively. Although central compensation is clinically evident no effect in specific vestibular diagnostic testing is seen. Modulations of canal-otolith interaction might suggest a change of symptoms. The only method so far to evaluate the success of EMSS is the patient's subjective assessment.

Analysis of residual symptoms after treatment in benign paroxysmal positional vertigo using questionnaire.

OBJECTIVES: Canalith repositioning procedure (CRP) provides rapid and long-lasting relief of symptoms in most patients with benign paroxysmal positional vertigo. However, some patients express nonspecific symptoms such as anxiety or discomfort after treatment, even after the disappearance of nystagmus and vertigo. The purpose of this study was to assess the residual symptoms after CRP in patients with benign paroxysmal positional vertigo using the Dizziness Handicap Inventory (DHI) in a questionnaire format. STUDY DESIGN AND SETTING: Controlled, prospective study. SUBJECTS AND METHODS: CRP was performed in 135 patients until nystagmus and vertigo disappeared. Patients were asked to complete the questionnaire before and 5 to 7 days after treatment. A control group of 135 normal volunteers was selected and cross-matched according to the age and sex of the patient group. The data were compared for the pre-CRP, post-CRP, and control groups. RESULTS: There was a significant improvement in the DHI scores when comparing the pre- and post-CRP groups (P=0.000), although six items showed incomplete improvement. Subsequent comparison of DHI scores between the control group and the post-CRP group still showed a difference in some items so that the improvement was incomplete. CONCLUSION: Even after successful CRPs, Dizziness Handicap Inventory scores indicated that residual subjective symptoms may remain. Thus, additional follow-up and management are important for these patients.

Carp experiment in space microgravity--a visual-vestibular sensory conflict model.

In the 8-d flight mission of Spacelab-J (STS-47) conducted in 1992, behavior of the dorsal light response (DLR) and EEG activity of the cerebellum were intermittently examined for two carp, normal and otolith-removed. The latter carp had immobilization trouble caused by twisting of the EEG cable on day 2 inflight. The problem continued for the remainder of the experiment. Analyses made on the normal carp provided additional evidence in fish for sensory-motor disorder and readjustment during early phase of microgravity, thus supporting the sensory conflict hypothesis for space motion sickness. In the present report, why and how this space experiment was conducted were reviewed with a brief summary of the results.

Mechanism of vestibular adaptation of fish under microgravity.

In a space experiment, the adaptation of goldfish behavior during flight and readaptation after landing were investigated. Six goldfish (1 normal, 1 with otoliths removed on both sides, 4 with otoliths removed on one side) were flown in a fish package (F/P) of Aquatic Animal Experiment Unit (AAEU). The dorsal light responses (DLRs) of fish with otoliths removed were recorded after operation until launch and after landing. The behaviors of the fish were recorded with a video camera on Mission Elapsed Time (MET) Day-00, 02, 05, 08, 12. On MET Day-00, two fish with otoliths removed on one side showed flexion of body toward the operated side. These fish also showed rolling behavior toward the operated side. However, the body flexion disappeared on MET Day-05 or MET Day-08. No rolling behaviors were observed after that time. Five fish showed backward looping behaviors during the mission. Although the frequency of looping episodes decreased after MET Day-08, five fish still showed looping behavior on MET Day-12, that was the last day of video recording on orbit. In microgravity, visual system of fish did not seem to provide sufficient cues to prevent them from looping or rolling. After landing, no looping and rolling behavior was observed. However, the tilt angle of the DLR increased in the fish with otolith removed 5 month before launch but not in normal fish and those with otoliths removed 2 weeks before launch. These results suggest that the behavioral dysfunction and the adaptational process in space are dependent on vestibular inputs.

Ablation of otolithic organs with argon laser.

Utricular maculae of guinea pigs were irradiated by argon laser through the oval window without touching the perilymph. The stapes was replaced in the oval window after irradiation. The inner ear was studied morphologically and physiologically. Argon laser beam caused detachment of the sensory epithelium from the basement membrane of the utricular macula. The lesion was round and localized at the site of irradiation. The epithelium changed to a layer of cuboidal cells after 2 to 3 weeks at the irradiated spot. Degeneration of the epithelium gradually spread to the periphery, and total loss of sensory epithelium was observed 10 weeks after irradiation. Hearing was preserved, and caloric test showed normal response.