The prognostic value and pathophysiologic significance of three‐dimensional fluid‐attenuated inversion recovery (3D‐FLAIR) magnetic resonance imaging in idiopathic sudden sensorineural hearing loss: A systematic review and meta‐analysis

Abstract

Background The underlying pathophysiology of idiopathic sudden sensorineural hearing loss (ISSNHL) is still unknown. However, an increasing number of observational studies report intralabyrinthine signal alterations in patients with ISSNHL using three‐dimensional fluid‐attenuated inversion recovery (3D‐FLAIR) magnetic resonance imaging (MRI). These findings warrant a meta‐analysis. Objective of review To conduct a meta‐analysis assessing the value of 3D‐FLAIR MRI in identifying possible underlying labyrinthine pathophysiologic mechanisms and prognostication in patients with ISSNHL. Search strategy Two reviewers independently searched the Pubmed, Embase and Cochrane Library from inception until October 10, 2018 and evaluated eligibility based on titles and abstracts of all retrieved studies. All studies reporting on 3D‐FLAIR imaging in ISSNHL were included. Subsequently, the full text of eligible studies were evaluated. Evaluation method Adhering to the MOOSE guideline, two independent reviewers extracted data, assessed risk of bias and evaluated the relevance and quality of evidence. Data on the number of patients and events were extracted and hearing levels were converted to standardised mean differences (SMD) for conducting meta‐analyses. Random effects models for meta‐analyses were applied. Results Eight observational studies met our inclusion criteria (n = 638 patients). In 29%, high signal intensity was found on 3D‐FLAIR imaging, suggesting labyrinthine pathology (labyrinthitis [79%], intralabyrinthine haemorrhage [21%]). High signal intensity on 3D‐FLAIR was associated with poorer hearing (SMD: 14 dB, 95% CI 5.67‐22.94) and vertigo (RR: 1.92, 95% CI 1.16‐3.17) at baseline. Multivariate analyses demonstrated that patients with high 3D‐FLAIR signal intensity had 21 dB lower final hearing pure‐tone averages (SMD: 21 dB, 95% CI 9.08‐33.24). Conclusions Three‐dimensional fluid‐attenuated inversion recovery MR imaging can identify an underlying labyrinthine condition in up to 29% of patients with sudden hearing loss in whom previously no cause could be identified. Their final pure‐tone averages are more than 20 dB worse than 3D‐FLAIR–negative patients, suggesting more severe labyrinthine damage. Findings such as these may contribute to our understanding of pathophysiologic mechanisms of ISSNHL.

Anatomical and Pathological Findings of Magnetic Resonance Imaging in Idiopathic Sudden Sensorineural Hearing Loss

“…As previously shown [11,13,14], labyrinthine lesions such as intralabyrinthine hemorrhage were associated with worse hearing with or without treatment in our study. Labyrinthine lesions on IAC MRI should be considered to be an important prognostic factor for SSNHL.…”

“…Especially, using fluid-attenuated inversion recovery (FLAIR) MRI, we can identify underlying pathologies in ISSNHL cases that were previously designated as being idiopathic. FLAIR MRI can assist clinicians in detecting increased protein concentrations or hemorrhage in the labyrinth that can contribute to hearing loss [11].…”

“…Therefore, FLAIR MRI sequences can be used to identify methemoglobin in the cerebrospinal fluid in addition to revealing elevated protein and cellular concentrations. On FLAIR images, the hypersignal intensity in the labyrinth may reflect the presence of blood and protein within the inner ear [11].…”

“…This can be explained by the course of hemoglobin decomposition: specifically, the hemoglobin in hemorrhage is metabolized from oxyhemoglobin to deoxyhemoglobin, methemoglobin, and then hemosiderin. Thus, after two weeks, the hemoglobin has become hemosiderin which produces a hyposignal intensity on FLAIR images [11]. Thus, we recommend conducting IAC MRI within two weeks of SSNHL onset to detect not only chronic retrocochlear lesions but also acute or subacute labyrinthine lesions.…”

State of the Art Imaging in Menière’s Disease. Tips and Tricks for Protocol and Interpretation

“…This hypothesis is corroborated by histopathological studies in MD that demonstrated BLB dysfunction in the microvasculature of vestibular end organs in MD patients [73]. The observation of BLB impairment on MRI is, however, not exclusive for MD as similar findings have been reported in vestibular neuritis [74,75], sudden sensorineural hearing loss [76] and vestibular schwannoma [77]. As such, increased perilymph signal intensity on its own is non-specific.…”