The exact mechanisms that cause a migraine or variants of a migraine are not clear. Espinosa-Sanchez and Escamez-Lopez proposed a mechanism for vestibular migraines, which includes inherited brain excitability sensitization and neurogenic inflammation that activates the trigeminal vascular reflex (Front Neurol. 2015; 6:12). Increased sensitivity and vasodilation of blood vessels in the inner ear (caused by the reflex) result in vestibular dysfunction. In theory, apart from the vestibule, we think the same mechanism can be applied to the cochlea. Thus, the cochlea alone can be a possible target for migraine-induced neuroinflammatory effects, and CM patients may present with auditory symptoms, such as hearing loss, tinnitus, and hyperacusis, without involving the balance system.
EXAMINING NOTABLE CASES
Classical presentation of CM is episodic, fluctuated hearing loss without vertigo in migraineurs. Their hearing is variable and hearing loss tends to resolve rather than deteriorate further. We present a 39-year-old female patient with a history of several hemicranias and was diagnosed as having migraines without aura based on the diagnostic criteria of the International Headache Society. She complained of sudden hearing loss and tinnitus in her right ear. Mild sensorineural hearing loss was observed at that time and she was treated with oral fluranazine, a calcium channel antagonist for migraine prophylaxis. Her serial audiograms from each visit during a five-year follow-up period are shown in Figure 1. Her hearing loss fluctuated and was reversible, and she never experienced vertigo.
In some patients, CM can mimic or be mistaken as idiopathic sudden sensorineural hearing loss (ISSHL) because the hearing loss is severe enough to reach the diagnostic criteria of >30 dB in three contagious frequencies. In fact, migraines have been proposed as one etiology for ISSHL in the literature (Otol Neuotol. 2017;38:1411).
We present another case of repeated attacks of ISSHL with good recovery in a migraine patient: a 28-year-old woman with three instances of sudden deafness in her left ear within a six-year period. For the first two episodes (Jan. 18, 2010 and July 21, 2014), oral steroid alone was administered within one week of the attack and hearing loss was completely reversed. However, for the third attack (Feb. 20, 2017), the patient received anti-migraine therapy three days after onset of auditory symptoms. Her serial audiograms can be found on our website: http://bit.ly/2poNsFE (Fig.2). The final hearing test indicated normal hearing in all tested frequencies, except for the 8kHz frequency. Therefore, we suggest that when atypical findings are observed in patients with ISSHL, such as repeated attacks (same or opposite ear) with good recovery or hearing fluctuates over time, CM may be considered as a differential diagnosis.
In addition to hearing loss, migraines may also be closely related to acute and chronic tinnitus in some patients. Two studies by our group provided supporting evidence to this linkage. First, in the population-based association study, patients with a history of migraines had a significantly increased chance (adjusted odds ratio: 3.30) of developing acute and chronic tinnitus compared with those with no history (JAMA Otolaryngol Head Neck Surg. 2018). Secondly, we used low-dose hormone replacement therapy to treat tinnitus in a small group of menopausal women. The improvement of their tinnitus was remarkable and encouraging although the study was uncontrolled (Clin Otolaryngol. 2017 Dec;42(6):1366). The exact mechanism for this treatment is not entirely clear, but we found that these patients all had constant migraines and estrogen deficiency is a common trigger of migraines. The most plausible explanation is that the hormone replacement caused a reduction of migraine-induced tinnitus. Tinnitus may be caused by heterogenic mechanisms, and with this indirect evidence, we think that migraines affecting the cochlea is the etiology of tinnitus for certain patients.
Migraines may target the auditory system alone and cause fluctuations of hearing loss as well as tinnitus in some patients. Diagnosis relies upon awareness of this condition and a longer hearing test follow-up. Once the diagnosis is established, the otologist can start anti-migraine therapy, and hearing loss and tinnitus can be treated.Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.