Iván A. López

OBJECTIVE: To study the pathophysiology of labyrinthine infarction. BACKGROUND: The syndrome of sudden onset vertigo or hearing loss is commonly attributed to inner ear vascular disease, yet histologic studies of isolated labyrinthine infarction in humans have been rare and have not included a complete examination of the vertebrobasilar vascular system. METHODS: Temporal bones, brainstem, cerebellum, and the supplying blood vessels were subjected to gross and microscopic postmortem examinations in a 92-year-old woman who had a sudden onset of vertigo and hearing loss in the right ear 7 years before death. RESULTS: There were prominent atherosclerotic changes at the vertebrobasilar junction, but the internal auditory artery and its branches were patent on both sides. Histologic studies showed degenerative changes in the cochlea and vestibular labyrinth on the right. The posterior canal ampulla and saccular macule were relatively preserved showing partial areas of intact sensory epithelium with underlying nerve fibers. The right vestibulocochlear nerve showed a fibrotic scar and multiple patchy areas of degeneration. These findings are most consistent with a transient period of reduced perfusion of the internal auditory artery. CONCLUSION: The partial sparing of the inferior vestibular labyrinth may indicate a decreased vulnerability to ischemia because of its better collateral blood supply.

Degenerative changes during aging have been identified in the inner ear and in the vestibular nerve, but not in the human vestibular nuclear complex (VNC). Therefore, the purpose of this study was to document quantitative morphometric changes within the VNC in humans as a function of age. The VNC of normal human subjects was examined for age-related changes using computer-based microscopy. Neuronal counts, nuclear volume, neuronal density, and nuclear length of the 4 vestibular nuclei were determined in 15 normal people, age 40 to 93 years. Based on a linear model, there was approximately a 3% neuronal loss per decade from age forty to ninety. VNC volume and neuronal density also decreased significantly with age, although to a lesser degree than did the number of neurons. Neuronal loss as a percentage of the total number of neurons was greatest in the superior vestibular nucleus and least in the medial vestibular nucleus. Despite the overall loss of neurons, the number of giant neurons (> 500 microns2) increased in older people. This increase in giant neurons could be traced to the accumulation of lipofuscin deposits in the cell somata. The overall rate of neuronal loss with aging in the VNC is comparable to that previously observed in hair cells, primary vestibular neurons, and cerebellar Purkinje cells, but is in contrast to prior reports of no age-related loss of neurons in other brain stem nuclei.

The global pandemic of coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 remains a challenge for prevention due to asymptomatic or paucisymptomatic patients. Anecdotal and preliminary evidence from multiple institutions shows that these patients present with a sudden onset of anosmia without rhinitis. We aim to review the pathophysiology of anosmia related to viral upper respiratory infections and the prognostic implications. Current evidence suggests that SARS-CoV-2-related anosmia may be a new viral syndrome specific to COVID-19 and can be mediated by intranasal inoculation of SARS-CoV-2 into the olfactory neural circuitry. The clinical course of neuroinvasion of SARS-CoV-2 is yet unclear, however an extended follow up of these patients to assess for neurological sequelae including encephalitis, cerebrovascular accidents and long-term neurodegenerative risk may be indicated.

BACKGROUND: Auditory and vestibular symptoms and signs are common in patients with migraine, yet little is known about the pathogenesis of these symptoms and signs. OBJECTIVE: To perform clinicopathological correlation in a patient with migraine, sudden deafness, and delayed endolymphatic hydrops. METHODS: A patient with long-standing migraine with aura developed sudden hearing loss in the left ear at the age of 50 years and Ménière disease on the right side at age 73. At age 76, he had a flurry of sudden drop attacks typical of otolithic crisis. He died of unrelated causes at age 81. The brain and temporal bones were removed approximately 24 hours after death. The cochlea and vestibular end organs were dissected after the surrounding bone was carefully removed. RESULTS: The brain and cerebrovasculature were normal. The left cochlea showed prominent fibrosis consistent with an old infarction. The right inner ear showed hydrops, with relatively good preservation of the hair cells in the cochlea, saccular macule, and cristae of the semicircular canals. However, the utricular macule was denuded of hair cells. CONCLUSIONS: The sudden left-sided deafness likely resulted from ischemia, possibly due to migraine-associated vasospasm. Presumably, the right ear suffered only minimal damage when the patient was 50 years old, but this damage later led to the development of delayed endolymphatic hydrops on the right. Otolithic crises are thought to result from pressure changes across the utricular macule. We speculate that loss of hair cells in the utricular macule resulted from a collapse of the utricular membrane onto the macule.