Vestibular atelectasis: Myth or reality?

Perilymphatic fistula with characteristic findings of the inner ear by contrast-enhanced magnetic resonance imaging: a case report

A perilymphatic fistula (PLF) presents with abnormal traffic in the otic capsule, causing cochlear and vestibular symptoms. However, the mechanisms underlying symptom recurrence remain controversial. Herein, we report the case of a 27-year-old female who complained of hearing disturbance in her right ear and recurrent vertigo after sudden onset of hearing loss with vertigo. The caloric test revealed unilateral weakness in the right ear, and the video head impulse test (vHIT) showed decreased vestibulo-ocular reflex (VOR) gain. Contrast-enhanced magnetic resonance imaging (MRI) using hybrid of reversed image of positive endolymph signal and negative image of perilymph signal (HYDROPS) indicated a collapsed endolymphatic space. As the vestibular symptoms did not improve, an exploratory tympanotomy was performed on the right ear. Although perilymph leakage was not noted in the oval or round windows, both windows were sealed with connective tissue. The patient's vestibular symptoms rapidly improved after surgery, and postoperative contrast-enhanced MRI showed improvement in the collapsed endolymphatic space. Although the caloric test revealed unilateral weakness, the VOR gain on the vHIT improved to normal on the right side. Thus, these findings indicated that recurrent symptoms caused by PLF are associated with a collapsed endolymphatic space. We speculate that the collapsed endolymphatic space was due to a ruptured Reissner's membrane. We hypothesized that sealing the fistula would promote normalization of perilymph pressure. The ruptured Reissner's membrane may have been gradually repaired as vestibular symptoms improved. This case adds to the existing literature on the occurrence of the "double-membrane break syndrome". Collapse of the endolymph due to a ruptured Reissner's membrane may be the cause of PLF symptoms.

Increased signal intensity with delayed post contrast 3D-FLAIR MRI sequence using constant flip angle and long repetition time for inner ear evaluation

PURPOSE

The purpose of this study was to compare the degree of perilymphatic enhancement between 4 hour post-contrast constant flip angle three-dimensional fluid attenuated inversion recovery (3D-FLAIR) images obtained with short repetition time (TR) and those obtained with long TR.

MATERIALS AND METHODS

This single-center, prospective study included patients who underwent MRI of the inner ear with heavily T2-weighted sequence, 3D-FLAIR sequence with a "short" TR of 10,000 ms (s3D-FLAIR) and with a "long" TR of 16,000 ms (l3D-FLAIR). Signal intensity ratio (SIR) and contrast-to-noise ratio (CNR) obtained with s3D-FLAIR and l3D-FLAIR were quantitatively assessed using region of interest (ROI) method and compared. The morphology of the endolymphatic space on both sequences was also evaluated.

RESULTS

From March 2020 to July 2020, 20 consecutive patients were enrolled (9 women and 11 men; mean age, 52.1 ± 14.5 [SD] years; age range: 29-75 years). On l3D-FLAIR images, mean SIR (21.1 ± 8.8 [SD]; range: 7.6-46.1) was significantly greater than that on s3D-FLAIR images (15.7 ± 6.7 [SD]; range: 5.9-33.4) (P < 0.01). On l3D-FLAIR images, mean CNR (17 ± 8.5 [SD]; range: 2-40) was significantly greater than that on s3D-FLAIR images (12 ± 6.3 [SD]; range: 3.2-29.8) (P < 0.01). Kappa value for inter-rater agreement for endolymphatic hydrops, vestibular atelectasis and perilymphatic fistula were 0.93 (95% CI: 0.74-1), 1 (95% CI: 0.85-1) and 1 (95% CI: 0.85-1) respectively.

CONCLUSION

This study demonstrates that the sensitivity of 3D-FLAIR sequences to low concentration gadolinium in the perilymphatic space is improved by elongation of the TR, with SIR and CNR increased by +34.4% and +41.3% respectively.

MRI characteristics of intralabyrinthine schwannoma on post-contrast 4 h-delayed 3D-FLAIR imaging

PURPOSE

The purpose of this study was to describe the MRI characteristics of intralabyrinthine schwannoma (ILS) on post contrast three-dimensional (3D) fluid-attenuation-inversion-recovery (FLAIR) images obtained four hours after intravenous administration of a gadolinium-based contrast agent (4h-3D-FLAIR).

MATERIALS AND METHODS

This IRB-approved retrospective multi-center study included patients presenting with typical ILS from January 2016 to October 2020. All medical charts were systematically collected. All MRI examinations, including 4h-3D-FLAIR images, were reviewed by two board-certified neuroradiologists. Main outcome measures were location, signal intensity and associated anomalies of ILS.

RESULTS

Twenty-seven out of 8730 patients (0.31%) referred for the investigation of a cochleovestibular disorder had a final diagnosis of ILS. There were 13 men and 14 women with a mean age of 52 ± 17 (SD) years (age range: 20-86 years). The most common clinical presentation was unilateral progressive sensorineural hearing loss (16/27; 59%). All ILS were unilateral and 15 (15/27; 55%) were intracochlear. All ILS presented as a hypointense filling defect within the labyrinth on T2-weighted images that enhanced on post-contrast T1-weighted images. On 4h-3D-FLAIR images, all ILS presented as a hypointense filling defect, associated with diffuse perilymphatic hyperintensity. Two patients (2/27; 7%) presented with ipsilateral endolymphatic hydrops.

CONCLUSION

ILS displays consistent features on post-contrast 4h-3D-FLAIR images. ILS should not be confused with endolymphatic hydrops and requires a systematic analysis of the corresponding T2-weighted images.

Unilateral decrease in inner ear signal in fluid-attenuated inversion recovery sequences in previously suspected canine idiopathic vestibular syndrome

The aetiology of canine idiopathic vestibular syndrome (IVS) remains unclear. In human medicine, characteristic magnetic resonance imaging (MRI) techniques are used to demonstrate differences in endolymph composition between affected and unaffected inner ears. The purpose of this study was to determine whether similar MRI techniques could help to detect changes in the inner ears of canine IVS patients. Medical records from two veterinary referral clinics were reviewed retrospectively. Dogs were included if they had a diagnosis of IVS, obvious lateralisation of clinical signs, and an MRI of the vestibular system. A region of interest (ROI) was manually outlined by defining the anatomical area of the inner ear in T2-weighted and fluid-attenuated inversion recovery (FLAIR) images. In order to calculate the ratio of FLAIR suppression of each ear, the mean grey value of the ROI was determined in both sequences. If a unilateral decrease in suppression was identified, it was compared with the direction of clinical signs. In total, 80 dogs were included in the study. There was a significantly lower degree of suppression on the affected compared to the unaffected side (0.8886 vs. 0.9348, respectively; P = 0.0021). In 92.5% of cases, there was agreement between the most suppressed side on MRI and the direction of clinical signs. This study provides preliminary evidence about the appearance of endolymph on MRI of dogs with IVS. Further studies are needed to investigate associations between the severity of MRI changes and prognosis.

Advanced Magnetic Resonance Imaging of the Skull Base

Magnetic resonance (MR) imaging is a crucial tool for evaluation of the skull base, enabling characterization of complex anatomy by utilizing multiple image contrasts. Recent technical MR advances have greatly enhanced radiologists' capability to diagnose skull base pathology and help direct management. In this paper, we will summarize cutting-edge clinical and emerging research MR techniques for the skull base, including high-resolution, phase-contrast, diffusion, perfusion, vascular, zero echo-time, elastography, spectroscopy, chemical exchange saturation transfer, PET/MR, ultra-high-field, and 3D visualization. For each imaging technique, we provide a high-level summary of underlying technical principles accompanied by relevant literature review and clinical imaging examples.

Rare Disorders of the Vestibular Labyrinth: of Zebras, Chameleons and Wolves in Sheep's Clothing

The differential diagnosis of vertigo syndromes is a challenging issue, as many - and in particular - rare disorders of the vestibular labyrinth can hide behind the very common symptoms of "vertigo" and "dizziness". The following article presents an overview of those rare disorders of the balance organ that are of special interest for the otorhinolaryngologist dealing with vertigo disorders. For a better orientation, these disorders are categorized as acute (AVS), episodic (EVS) and chronic vestibular syndromes (CVS) according to their clinical presentation. The main focus lies on EVS sorted by their duration and the presence/absence of triggering factors (seconds, no triggers: vestibular paroxysmia, Tumarkin attacks; seconds, sound and pressure induced: "third window" syndromes; seconds to minutes, positional: rare variants and differential diagnoses of benign paroxysmal positional vertigo; hours to days, spontaneous: intralabyrinthine schwannomas, endolymphatic sac tumors, autoimmune disorders of the inner ear). Furthermore, rare causes of AVS (inferior vestibular neuritis, otolith organ specific dysfunction, vascular labyrinthine disorders, acute bilateral vestibulopathy) and CVS (chronic bilateral vestibulopathy) are covered. In each case, special emphasis is laid on the decisive diagnostic test for the identification of the rare disease and "red flags" for potentially dangerous disorders (e. g. labyrinthine infarction/hemorrhage). Thus, this chapter may serve as a clinical companion for the otorhinolaryngologist aiding in the efficient diagnosis and treatment of rare disorders of the vestibular labyrinth.

Clinical characteristics in unilateral vestibular atelectasis

INTRODUCTION

Unilateral vestibular atelectasis (UVA), an entity first described by Merchant and Schuknecht in 1988, has rarely been reported in vivo as of yet. We specify here the clinical characteristics of 22 patients diagnosed with UVA.

MATERIALS AND METHODS

Patients with a radiological diagnosis of UVA who underwent delayed inner ear MRI were included between April 2017 and January 2020. Full clinical testing including ocular infrared video-oculography, oVEMPs, cVEMPs, vHIT, bithermal caloric testing and auditory testing was performed.

RESULTS

There were 13 men and 9 women, of mean age 58.6 ± 13.7 years. Onset was more frequently sudden (73%) than insidious (27%) though both clinical presentations were reported, and positional vertigo was described in 41% of cases. There were only two (9%) patients reporting Tullio's phenomenon. Vestibular testing showed that in 90% of cases, there was utricular dysfunction on oVEMP, while in 77% of cases, saccular function was preserved on cVEMP. vHIT showed high-velocity canal function impairment in all 22 patients: 8 patients (36%) had one impaired canal, 5 (23%) had two and 9 (41%) had all three canals affected. Caloric tests found complete unilateral areflexia, in 65% of tested cases, and partial deficiency in 35% of cases. Nine patients (40%) displayed asymmetrical hearing.

CONCLUSION

We described in this study the various clinical presentations of a disease rarely reported in vivo, UVA. Initial clinical presentation can appear similar to an acute vestibular deficit, a recurrent positional vertigo, or fluctuating dizziness.

The round window sign: a sensitive sign to detect perilymphatic fistulae on delayed postcontrast 3D-FLAIR sequence

OBJECTIVES

The aim of this study is to assess the diagnostic performance of a new MR sign, named the round window sign (RWS), to diagnose perilymphatic fistula (PLF) in a population of patients with chronic cochleo-vestibular symptoms, classified as definite or probable Menière's disease (MD).

METHODS

A total of 164 patients (mean age 52 ± 35 years) with chronic cochleo-vestibular symptoms underwent MRI, between 4 and 5 h after intravenous gadoteric acid injection (Dotarem®, 0.1 mmol/kg). MRI exploration was carried out on a 3-T Achieva® TX scanner. We analyzed the presence of the RWS, defined as a nodular FLAIR high signal in the round window (RW) and the presence of associated saccular hydrops. When this RWS was present, a temporal bone CT scan was performed and the RW was analyzed.

RESULTS

Of the 164 patients with definite MD (85 patients) or probable MD (79 patients), we found the RWS in 18 (11%), and 17/18 were classified into the group of probable MD. All these 18 patients showed other MR sequences considered as normal, including heavily weighted T2 imaging. Among these 18 patients, the temporal bone CT examination presented a filling of the RW in 13 patients (72%) and no filling of the RW in 5 patients (28%). Seven patients were surgically managed confirming in vivo the PLF diagnosis. The RWS was associated with the presence of a saccular hydrops in 4 cases.

CONCLUSION

Delayed postcontrast 3D-FLAIR may reveal perilymphatic fistulae in patients with probable Menière's disease using the round window sign.

KEY POINTS

• MRI with delayed acquisition can detect perilymphatic fistulae with perfect sensitivity, based on the presence of the round window sign. • This visual sign is only visible on a 3D-FLAIR sequence. • 3D-FLAIR sequence with delayed acquisition is more sensitive than temporal bone CT scan examination in detecting PLF.

Comparison of Enhancement of the Vestibular Perilymph between Variable and Constant Flip Angle-Delayed 3D-FLAIR Sequences in Menière Disease

BACKGROUND AND PURPOSE

Endolymphatic hydrops in patients with Menière disease relies on delayed postcontrast 3D-FLAIR sequences. The purpose of this study was to compare the degree of perilymphatic enhancement and the detection rate of endolymphatic hydrops using constant and variable flip angles sequences.

MATERIALS AND METHODS

This was a retrospective study performed in 16 patients with Menière disease who underwent 3T MR imaging 4 hours after gadolinium injection using two 3D-FLAIR sequences with a constant flip angle at 140° for the first and a heavily-T2 variable flip angle for the second. The signal intensity ratio was measured using the ROI method. We graded endolymphatic hydrops and evaluated the cochlear blood-labyrinth barrier impairment.

RESULTS

Both for symptomatic and asymptomatic ears, the median signal intensity ratio was significantly higher with the constant flip angle than with the heavily-T2 variable flip angle (7.16 versus 1.54 and 7.00 versus 1.45, P < .001). Cochlear blood-labyrinth barrier impairment was observed in 4/18 symptomatic ears with the heavily-T2 variable flip angle versus 8/19 with constant flip angle sequences. With heavily-T2 variable flip angle sequences, endolymphatic hydrops was observed in 7-10/19 symptomatic ears versus 12/19 ears with constant flip angle sequences. We found a significant association between the clinical symptomatology and the presence of endolymphatic hydrops with constant flip angle but not with heavily-T2 variable flip angle sequences. Interreader agreement was always perfect with constant flip angle sequences while it was fair-to-moderate with heavily-T2 variable flip angle sequences.

CONCLUSIONS

3D-FLAIR constant flip angle sequences provide a higher signal intensity ratio and are superior to heavily-T2 variable flip angle sequences in reliably evaluating the cochlear blood-labyrinth barrier impairment and the endolymphatic space.

Electrophysiological and inner ear MRI findings in patients with bilateral vestibulopathy

PURPOSE

Bilateral vestibulopathy (BV) is an uncommon disorder and the etiology remained idiopathic in most cases. Delayed 3D-FLAIR sequences have provided new insights into various inner ear diseases, allowing the evaluation of the endolymphatic space and the permeability of the blood-labyrinthine barrier (BLB). The aim of this study was to assess both the morphology of the endolymphatic space and the permeability of the BLB in patients with BV as evaluated by delayed 3D-FLAIR sequences.

METHODS

In this retrospective study, we performed 3D-FLAIR sequences 4 h after administering contrast media to 42 patients with BV. Two radiologists independently evaluated the morphology of the endolymphatic space (either vestibular atelectasis or endolymphatic hydrops) and the permeability of the BLB.

RESULTS

Morphologic anomalies of the endolymphatic space and vestibular blood-labyrinthine barrier impairment were observed in 59.6% of patients with BV. Bilateral vestibular atelectasis (VA) was found in 21 patients (50%), involving only the utricle and all three ampullas while the saccule was always observed with no sign of collapse: idiopathic BV (n = 19), aminoglycoside administration (n = 1) and few days following abdominal surgery (n = 1). One patient had bilateral vestibular malformation. BLB impairment was observed in five patients (11.9%): paraneoplastic (n = 1), lymphoma (n = 1), autoimmune (n = 1), and vestibular "neuritis" (n = 2). Seventeen patients (40.4%) had normal MRI with no endolymphatic space anomaly or BLB impairment.

CONCLUSION

Patients with BV presented with morphologic anomalies of the endolymphatic space or BLB impairment in 59.6% of patients.