Short-latency AEPs, often referred to as auditory brainstem responses (ABRs) ( 19), are generated at the first part of the auditory pathway, from the most distal portion of the auditory nerve to the brainstem.

AEPs are generally categorized in three classes according to their latency: short-, middle- and long-latency AEPs ( S1 figure). It is a technique that is used for the evaluation of neural activity in the auditory pathway, from cochlea to auditory cortex ( 18). It is important to remember that these brainstem structures send signals via multiple pathways to other brainstem and cortical regions, resulting in a cascade of changes directly associated with tinnitus generation ( 5).Īmong clinical procedures to assess various levels of the auditory system, the most widely used involve auditory evoked potentials (AEPs) ( 16, 17). Multiple structures in the brainstem, including the cochlear nuclei and inferior colliculi, display abnormal function linked to tinnitus ( 12, 14, 15). On functional magnetic resonance imaging (fMRI) scans, increased resting state activity is also found in the auditory nuclei in the brainstem ( 12, 13). These disturbances are first found in the cochlear nucleus and inferior colliculus ( 8- 11) and may be relayed to higher levels of the pathway ( 5). More specifically, these changes include increased spontaneous firing rates and bursting activity, which are both forms of hyperactivity, and increased neural synchrony ( 5- 7). Animal studies have consistently shown disturbances in the level and patterns of spontaneous neural activity of brainstem auditory nuclei, linked with the onset of tinnitus. Literature strongly suggests that the brainstem has a role in tinnitus generation and modulation, as well as in nonauditory comorbid conditions associated with tinnitus, such as neck disorders, anxiety, sleep disorders, difficulty concentrating, and depression ( 5). Other possible triggering factors include ototoxic medications, head and neck trauma, temporomandibular dysfunctions, neck pain, neurological and psychological conditions ( 1). There are many factors associated with the onset of tinnitus, the most common one being hearing loss ( 3, 4).

This symptom is often associated with reduced quality of life and psychosocial wellbeing ( 2). It is a very common symptom with a prevalence of 10 to 15% in an adult population ( 1). Tinnitus, or ‘ringing in the ears’, is the conscious perception of an auditory sensation in the absence of a corresponding auditory source.

Auditory pathway flowchart