Case Report: Filling Defect in Posterior Semicircular Canal on MRI With Balanced Steady-State Gradient-Echo Sequences After Labyrinthine Ischemia in the Common Cochlear Artery Territory as an Early Sign of Fibrosis

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.

Posterior semicircular canal ossification following acute vestibular loss mimicking inferior vestibular neuritis: A case report

“…Therefore, the clinical and instrumental effects of PVA occlusion perfectly overlap with IVN. While in the case described by Castellucci et al (38), an occlusion of CCA was suggested to explain the involvement of the lower labyrinthine structures and PSC fibrosis, a possible PVA terminal occlusion seems to represent the possible site of vascular lesion in our case, resulting in acute PSC and saccular impairment without auditory symptoms. Since our patient denied previous infections, trauma, surgery, and middle/inner ear dysfunctions other than previous contralateral sudden sensorineural HL, most conditions accounting for LO could be reasonably excluded, while inner ear ischemia seems to represent the most likely pathomechanism.…”

“…Selective ossification of a single semicircular canal is very rare. Castellucci et al (38) were recently able to demonstrate a filling defect in the PSC on MRI, consistent with early fibrosis of the canal, in a patient with a sudden cochleovestibular loss likely due to CCA ischemia. A labyrinthine ossification was clearly demonstrated two months after vascular inner ear occlusion in guinea pigs by Kimura and Perlman (39,40).…”

Video Head Impulse Test Findings in Patients With Benign Paroxysmal Positional Vertigo Secondary to Idiopathic Sudden Sensorineural Hearing Loss

“…It has been suggested that posterior SCC paresis associated with ipsilateral sudden hearing loss could possibly be caused by ischemia of the common cochlear artery ( 37 ), while the lesion pattern of hearing loss and ipsilateral paresis of the posterior and horizontal SCCs may indicate viral neurolabyrinthitis ( 16 ). Recently, a selective vHIT gain reduction of the ipsilateral posterior SCC in a SSNHL patient with acute vertigo has been reported, in which posterior SCC fibrosis has been detected by inner ear MRI, thus lend further support to vascular etiology ( 38 ). Although recent application of instrumental testing (vHIT and VEMP) can facilitate topographical diagnosis of selective dysfunction of inner ear end-organs, the underlying mechanisms require further investigations for patients with vertigo in SSNHL ( 3 , 38 ).…”

“…Recently, a selective vHIT gain reduction of the ipsilateral posterior SCC in a SSNHL patient with acute vertigo has been reported, in which posterior SCC fibrosis has been detected by inner ear MRI, thus lend further support to vascular etiology ( 38 ). Although recent application of instrumental testing (vHIT and VEMP) can facilitate topographical diagnosis of selective dysfunction of inner ear end-organs, the underlying mechanisms require further investigations for patients with vertigo in SSNHL ( 3 , 38 ).…”

Video Head Impulse Test in Persons with Blindness: Feasibility and Outcomes

“…Isolated posterior canal dysfunction has also been reported in other conditions such as idiopathic sudden sensorineural hearing loss, 21 posterior semicircular canal aplasia, 22 and labyrinthine ischemia in the common cochlear artery territory. 23 The participants in our study were neither elderly individuals nor did they have any history of vestibular complaints or any of the vestibular pathologies just mentioned. Thus, it is unlikely that the reduced VOR gain in the posterior SCC (in our study) could have been due to isolated posterior canal lesions, as seen in some elderly individuals with vestibular complaints.…”