Cochlear modiolus and lateral semicircular canal in sudden deafness

Vestibular dysfunction in lateral semicircular canal dysplasia

Introduction

Lateral semicircular canal (LSCC) dysplasia is the most common inner ear malformation. The severity of dysplasia can appear in various spectrums, from a short and broad LSCC with normal or small-sized central bony island (CBI) to a single fluid-filled cavity confluent with the vestibule without CBI. However, reports on the association between LSCC dysplasia and the loss of vestibular function are still lacking. In this study, the results of vestibular function tests [caloric test and video-head impulse test (vHIT)] in patients with LSCC dysplasia were analyzed and compared between groups with and without CBI.

Methods

This study retrospectively enrolled 17 patients (23 ears) who had LSCC dysplasia following computed tomography or magnetic resonance imaging and underwent vestibular function tests.

Results

LSCC dysplasia was observed unilaterally in 11 patients and bilaterally in six patients. Nine of 23 ears had CBIs, and 14 ears had no CBI. Three of 17 patients experienced dizziness. Abnormal caloric tests were detected in 11 of the 16 patients who underwent the caloric tests (69%); in contrast, 11 of 12 patients who underwent the vHIT (92%) had normal LSCC vestibulo-ocular reflex (VOR) gain on vHIT. A significant correlation was found between the maximum slow-phase velocity of the caloric test and LSCC VOR gain of the vHIT (correlation coefficient 0.792, p = 0.004). The CBI-absent group showed significantly lower SPV and LSCC VOR gains than the CBI-present group (p = 0.001 and 0.004, respectively).

Discussion

LSCC dysplasia impairs VOR function, especially in the absence of CBI.

Augmented Reality Based Transmodiolar Cochlear Implantation

HYPOTHESIS

Transmodiolar auditory implantation via the middle ear cavity could be possible using an augmented reality system (ARS).

BACKGROUND

There is no clear landmark to indicate the cochlear apex or the modiolar axis. The ARS seems to be a promising tool for transmodiolar implantation by combining information from the preprocedure computed tomography scan (CT-scan) images to the real-time video of the surgical field.

METHODS

Eight human temporal bone resin models were included (five adults and three children). The procedure started by the identification of the modiolar axis on the preprocedure CT-scan followed by a 3D reconstruction of the images. Information on modiolar location and navigational guidance was supplemented to the reconstructed model, which was then registered with the surgical video using a point-based approach. Relative movements between the phantom and the microscope were tracked using image feature-based motion tracking. Based on the information provided via the ARS, the surgeon implanted the electrode-array inside the modiolus after drilling the helicothrema. Postprocedure CT-scan images were acquired to evaluate the registration error and the implantation accuracy.

RESULTS

The implantation could be conducted in all cases with a 2D registration error of 0.4 ± 0.24 mm. The mean entry point error was 0.6 ± 1.00 mm and the implant angular error 13.5 ± 8.93 degrees (n = 8), compatible with the procedure requirements.

CONCLUSION

We developed an image-based ARS to identify the extremities and the axis of the cochlear modiolus on intraprocedure videos. The system yielded submillimetric accuracy for implantation and remained stable throughout the experimental study.

Nystagmus in patients with lateral semicircular canal dysplasia

BACKGROUND

Dizziness is not a common symptom in the lateral semicircular canal (LSCC) dysplasia, and nystagmus findings has been rarely described in LSCC dysplasia.

OBJECTIVE

To investigate the characteristics of spontaneous and positional nystagmus in patients with LSCC dysplasia.

METHODS

Patterns of spontaneous and positional nystagmus of twelve patients with LSCC dysplasia, who visited our clinic with a chief complaint of dizziness, were investigated.

RESULTS

LSCC dysplasia was observed unilaterally in 4, and bilaterally in 8 patients. Non-rotatory dizziness with various onset times was the most common description of dizziness, and unilateral caloric weakness was observed in 82% of patients. Direction-fixed nystagmus, in which the direction of spontaneous nystagmus was same with that of positional nystagmus, was observed in 9 patients, and direction-changing positional nystagmus, in which the direction of nystagmus was changed from that of spontaneous nystagmus by positioning maneuvers, was observed in 3 patients, of whom down-beating or direction-changing spontaneous nystagmus was observed in one patient each.

CONCLUSION

While direction-fixed horizontal nystagmus is the most commonly observed type of nystagmus in LSCC dysplasia, atypical spontaneous nystagmus, such as down-beating nystagmus or direction-changing spontaneous nystagmus, may be observed in patients with bilateral LSCC dysplasia.

Volumetric measurements of the inner ear in patients with Meniere's disease using three-dimensional magnetic resonance imaging

CONCLUSION

This study described the lateralities of axial length of inner ear (ALIE), of the volume of inner ear (VIE) and age-related differences of the volume of inner ear components in patients with chronic rhinosinusitis (CRS). Age-related differences were found in ALIE and the positive correlation in ALIE and the volume of the cochlea (VC) of the affected ear in patients with Meniere's disease (MD).

OBJECTIVE

To identify side or sex-related differences in the ALIE, the length of the spiral canal of cochlea (LSCC), and the volume of components of the inner ear in MD and CRS.

METHODS

Thirty-two with unilateral MD and 14 with CRS were included. Images were acquired with a 3.0-tesla unit using SPACE sequences. The ALIE was measured and the VIE, VC, the volume of the vestibule (VV), and of the semi-circular canals (VSC) were also measured.

RESULTS

In CRS, ALIE of the right ear in males was significantly longer than in females. Patients younger than 60 years old with CRS had a significantly larger VIE, VC, and VSC than older than 60. In MD, the ALIE in older than 60 was longer than below 60.

Ratio of Vestibular Endolymph in Patients with Isolated Lateral Semicircular Canal Dysplasia

PURPOSE

Isolated vestibular-lateral semicircular canal dysplasia (LSCCD) is one of the most common anomalies of the inner ear. However, endolymphatic size in LSCCD is unknown. We measured the size of the endolymph in the vestibule of patients with LSCCD and compared it with that measured in patients without LSCCD.

METHODS

We extracted 1102 magnetic resonance (MR) studies for the evaluation of endolymphatic hydrops (EH) from our database of radiology reports. Among these, we found 15 ears from 11 patients with LSCCD; 4 patients had bilateral abnormalities. Seven of the 15 ears demonstrated aplasia and 8 ears, hypoplasia of the lateral semicircular canal (LSCC). The control group consisted of 26 ears from 13 randomly selected patients without LSCCD. We measured the area of endolymph in the vestibule (ELA), total area of vestibular lymph fluid (TLA), and area of the central bony island (CBI) of the LSCC from axial MR images obtained after intratympanic or intravenous administration of gadolinium-based contrast material. The ratio of endolymphatic area to total lymphatic area (%EL) was defined as %EL = ELA/TLA × 100.We evaluated the correlation between %EL and the area of the CBI and compared age, %EL, degree of cochlear EH, hearing level, and presence of rotating vertigo among the 3 groups (aplasia, hypoplasia, control).

RESULTS

The mean %EL was 76.7% in the aplasia group, 50.0% in the hypoplasia group, and 27.8% in the control group (P < 0.001). There was a relatively strong linear correlation between the area of the CBI and %EL (r = -0.767). Patient age, mean hearing level, degree of cochlear EH, or presence of vertigo attacks did not differ significantly among the groups (P > 0.05).

CONCLUSION

The size of vestibular endolymph was larger in the groups with aplasia or hypoplasia than the control group. Thus, the current diagnostic cut-off value for significant vestibular EH (>50%) might not be appropriate for ears with LSCCD.

Sudden Sensorineural Hearing Loss: MR Imaging

Hearing loss greater than 30 dB over three contiguous pure-tone frequencies occurring within a three day period is defined as sudden hearing loss. It is usually sensorineural (SSNHL), unilateral and appears as an otologic emergency. SSNHL has many possibile etiologies such as: labyrinthine viral infection, ischemic or hemorrhagic illness, trauma, immuno-mediated inner ear disease, tumor, inner ear malformation, and an imbalance between perilymphatic and endolymphatic fluid pressure. Nevertheless in almost 80% of cases SSNHL belongs to the idiopathic category because the etiology is unknown. The aim of this study was to test the diagnostic impact of two MR devices. Fifteen cases of SSNHL studied with a 1.5 T unit in our hospital between January 2006 and December 2008 within two weeks of the onset were retrospectively evaluated. Since January 2009 three more patients affected by SSNHL have been scanned with a 3T MR unit. We discuss the diagnostic sensitivity, clinical usefulness and the cost-benefit ratio of the MR systems.