Effect of Aspirin and Folic Acid for Sudden Sensorineural Hearing Loss

Overview

The annual incidence of sudden sensorineural hearing loss (SSNHL) is 5 to 20 per 100 000 persons. The pathophysiology of SSNHL and acute vestibulo-cochlear syndromes (VCS) is unknown in more than 70% of cases. Hypothesis : an inner ear microvascular disease represents the key element in the pathogenesis of SSNHL and acute VCS. Plasma serotonin has among other tissular effect a vasospastic on microcirculation such as the inner ear microvascularisation. Increased plasma homocysteine has a deleterious effect on vascular endothelium. Inner ear microvascularisation sensitized by an increased homocysteine level and the vascular wall would vasoconstrict under serotonin stimulation inducing ischemia of the vestibular and/or cochlear organs.

Sudden sensorineural hearing loss (SSNHL) is defined as sensorineural hearing loss of 30dB or greater over at least three contiguous audiometric frequencies occurring over 72 hr 9,10. SSNHL is a relatively common disorder in otologic and audiologic practices (1.5-1.7 per 100 new patients presenting in ENT practice. Most patients with sudden SSNHL have no identifiable cause for hearing loss and are classified as "idiopathic". Despite extensive research, the etiology and therapeutic management of SSNHL and acute VCS remain elusive. Regardless of the etiology, complete or partial recovery of hearing thresholds following SSNHL may not occur. Factors influencing hearing recovery include the age at onset of hearing loss, severity and frequencies affected, the presence of vertigo, and the delay of treatment. The incidence of SSNHL is 5-20 per 100, 000. The true incidence of SSNHL may be higher than these estimates because affected individuals who recover spontaneously do not present for medical care. Although individuals of all ages can be affected, the peak incidence is between the fifth and sixth decade of life. Men and women are equally affected. Nearly all cases of SSNHL are unilateral; less than 2% of patients have bilateral involvement and typically bilateral involvement is sequential. Accompanying symptoms include tinnitus (41% to 90%) and dizziness (29% to 56%) New vestibular function assessment now allows us to specify the vestibular damage associated with SSNHL. Until now, the association with dizziness was a poor prognostic factor for hearing. In a recent study in 2023, more than 60% of patients treated for SSNHL had associated vestibular damage even if they did not complain of vestibular symptoms. 20. Vestibular involvement has often been under-diagnosed and could be a way of targeting more precisely the pathophysiological mechanisms behind SSNHL. Vestibular and cochlear damage can be secondary to a pressure disorder of the endolymphatic system (endolymphatic atelectasis or endolymphatic hydrops) or to microvascular damage of cochlear and/or vestibular arteries (e.g. cochlear artery syndrome), but also to inflammatory damage of the labyrinth. 3D-Flair Endolymph magnetic resonance imaging highlighted the different mechanisms involved in deafness: endolymphatic hydrops or atelectasis, microvascular or inflammatory involvement the presence or absence of a rupture of the blood-labyrinth barrier. For all these disorders, increase serum homocysteine and plasma serotonin levels would be a predisposing factor, weakening the microvascularisation inner ear's vascular endothelium.