Frequency and Diagnostic Utility of Intralabyrinthine FLAIR Hyperintensity in the Evaluation of Internal Auditory Canal and Inner Ear Pathology

Rationale and Objectives

Fluid-attenuated inversion recovery (FLAIR) imaging can detect elevated protein levels in fluid that may be difficult or impossible to detect with T1- or T2-weighted imaging. The purpose of this study is to evaluate the frequency and asses the diagnostic utility of abnormal FLAIR signal in various types of inner ear and internal auditory canal (IAC) pathology.

Materials and Methods

A retrospective review of medical records and magnetic resonance images from 187 consecutive patients who underwent imaging of the temporal bones for possible inner ear or IAC pathology over a 1-year period were reviewed for abnormal increased FLAIR signal, increased intrinsic T1 signal, abnormal enhancement after gadolinium administration, and the presence of a mass lesion within the cerebellopontine angle, IAC, or inner ear. Reviewers were blinded to clinical diagnosis.

Results

Twenty-five of 32 (78%) patients with schwannomas restricted to the IAC and cerebellopontine angle demonstrated associated increased FLAIR signal within the ipsilateral inner ear structures. The sensitivity, specificity, positive predictive value, and negative predictive value of inner ear FLAIR hyperintensity for a schwannoma were 80%, 95%, 78%, and 95%, respectively. Inner ear FLAIR hyperintensity was also seen in cases of intracochlear hemorrhage, labyrinthitis, and labyrinthitis ossificans, but these conditions did not occur with sufficient frequency in our study population to determine statistical significance.

Conclusion

Identification of inner ear FLAIR hyperintensity can alert the radiologist to scrutinize pre- and post-gadolinium T1-weighted images and T2-weighted images for subtle IAC and inner ear abnormalities. Although enhancement after the administration of gadolinium contrast media is the gold standard for detection of schwannoma, inner ear FLAIR hyperintensity may be a helpful diagnostic adjunct for vestibular schwannoma. This may be particularly helpful when gadolinium was not administered and the T2-weighted images are equivocal, especially when dedicated thin-section imaging of the IACs and temporal bones was not performed.

The fluid-attenuated inversion recovery (FLAIR) pulse sequence nulls signal from cerebrospinal fluid and produces T2-weighted images. It has been shown to detect elevated protein levels, hemorrhage, and other cerebrospinal fluid abnormalities that are difficult or impossible to detect with standard T1- or T2-weighted imaging . Although inner ear FLAIR signal abnormality has been described in a number of conditions including schwannomas, labyrinthitis, and in cases of deafness from mumps (paramyxovirus) infection, the frequency of this finding and its potential utility as a secondary marker for various types of internal auditory canal (IAC) or inner ear pathology has not been fully described . In our study, we evaluated the frequency of IAC and inner ear FLAIR hyperintensity in various types of IAC and inner ear pathology by studying a series of consecutive patients who underwent dedicated magnetic resonance imaging (MRI) of the temporal bone for a variety of clinical indications.

Materials and methods

The study was conducted as a retrospective review of medical records and MRI studies. The reviewers were blinded to the clinical history and diagnosis.

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Results

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Table 1

Clinical Diagnoses and Inner Ear FLAIR Hyperintensity

Clinical Diagnosis for Cause of Symptoms that Prompted Magnetic Resonance Imaging Examination Number of Patients Number of Patients with Inner Ear Fluid-attenuated Inversion Recovery Hyperintensity Vestibular schwannoma 35 28 Endolymphatic hydrops 9 0 Benign paroxysmal positional vertigo 5 0 Noise-induced hearing loss 5 0 Migraine-associated vertigo 4 0 Presbycusis 4 0 Otitis media/eustachian tube dysfunction 3 0 Labyrinthitis 3 1 Barotrauma 2 0 Remote trauma 2 0 Vancomycin vestibulopathy 1 0 Presumed cochlear hemorrhage 1 1 Labyrinthitis ossificans 1 1 Petrous apex granuloma 1 0 Orthostatic hypotension 1 0 Vascular compression 1 0 Meningioma 1 0 Hyperacusis/stapedius reflex 1 0 Attic cholesteatoma 1 0 Bell’s palsy 1 0 Rubella-related hearing loss 1 0 High-riding jugular bulb 1 0 Otosclerosis 1 0 Inflammatory paranasal sinus disease 1 0 Postsurgical changes of transmastoid surgery 1 1 Multiple sclerosis and/or sarcoidosis 1 0 Migraines and benign paroxysmal positional vertigo 1 0 Endolymphatic hydrops and benign paroxysmal positional vertigo 1 0 No final clinical diagnosis in medical record to explain patient’s symptoms 97 3 Total 187 0

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Table 2

Inner Ear FLAIR Hyperintensity and Presence or Absence of Schwannoma

Schwannoma No Schwannoma Inner ear FLAIR hyperintensity 28 8 No inner ear FLAIR hyperintensity 7 144

FLAIR, fluid-attenuated inversion recovery.

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Discussion

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Conclusion

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References

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Frequency and Diagnostic Utility of Intralabyrinthine FLAIR Hyperintensity in the Evaluation of Internal Auditory Canal and Inner Ear Pathology

Rationale and Objectives

Materials and Methods

Results

Conclusion

Materials and methods

Results

Discussion

Conclusion

References

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