Abstract
We describe a rare case of posterior semicircular canal (PSC) fibrosis following acute labyrinthine ischemia in the territory supplied by the common cochlear artery (CCA) and review the relevant literature. A 71-year-old man with multiple vascular risk factors presented 12 days after the onset of acute vertigo and profound left-sided hearing loss. Right-beating spontaneous nystagmus with downbeat components elicited by mastoid vibrations and headshaking was detected. The video head impulse test (vHIT) revealed an isolated hypofunction of the left PSC, whereas vestibular evoked myogenic potentials (VEMPs) showed ipsilateral saccular loss. The clinical presentation and instrumental picture were consistent with acute ischemia in the territory supplied by left CCA. Compared to previous imaging, a new MRI of the brain with 3D-FIESTA sequences highlighted a filling defect in the left PSC, consistent with fibrosis. Hearing function exhibited mild improvement after steroid therapy and hyperbaric oxygen sessions, whereas vHIT abnormalities persisted over time. To the best of our knowledge, this is the only case in the literature reporting a filling defect on MRI, consistent with semicircular canal fibrosis following acute labyrinthine ischemia. Moreover, PSC fibrosis was related with poor functional outcome. We therefore suggest using balanced steady-state gradient-echo sequences a few weeks following an acute lesion of inner ear sensors to detect signal loss within membranous labyrinth consistent with post-ischemic fibrosis. Besides addressing the underlying etiology, signal loss might also offer clues on the functional behavior of the involved sensor over time. In cases of acute loss of inner ear function, a careful bedside examination supplemented by instrumental assessments, including vHIT and VEMPs, of vestibular receptors and afferents may be completed by MRI with balanced steady-state gradient-echo sequences at a later time to confirm the diagnosis and address both etiology and functional outcome.
Highlights
Inner ear fibrosis and ossification result from fibrous tissue deposits and new bone formation, respectively, in labyrinthine structures
We describe the onset of posterior semicircular canal (PSC) fibrosis on Magnetic resonance imaging (MRI) in a patient with a clinical presentation and instrumental findings consistent with acute stroke in the territory supplied by the common cochlear artery (CCA)
Thanks to the introduction in clinical practice of fast modern devices such as video head impulse test (vHIT) and vestibular evoked myogenic potentials (VEMPs), which provide a precise assessment for each SC and the otolith end organs in the high-frequency domain, instrumental testing has demonstrated its pivotal role in the topographical diagnosis of selective dysfunction of inner ear structures, including in the acute stage [8, 9]
Summary
Inner ear fibrosis and ossification result from fibrous tissue deposits and new bone formation, respectively, in labyrinthine structures. We describe the onset of posterior semicircular canal (PSC) fibrosis on MRI in a patient with a clinical presentation and instrumental findings consistent with acute stroke in the territory supplied by the common cochlear artery (CCA). A 71-year-old man was admitted to our institution for evaluation of sudden onset of left-sided hearing loss (HL), vertigo, and severe unsteadiness persisting for over 12 days His clinical history was consistent with arterial hypertension, atrial fibrillation (in treatment with oral anticoagulants), and myelodysplastic syndrome (regular hematologic follow-ups). No cervical responses could be detected on the pathologic side consistent with left-sided isolated saccular loss, symmetrical potentials were evoked for ocular testing (Figures 2C,D). Written informed consent was obtained from the patient for the publication of this case report, including all data and images
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