Cortical deafness
| Cortical deafness | |
|---|---|
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| Location of the primary auditory cortex in the brain | |
| Classification and external resources | |
| MeSH | D006313 |
Cortical deafness is a rare form of sensorineural hearing loss caused by damage to the primary auditory cortex. Cortical deafness is an auditory disorder where the patient is unable to hear sounds but has no apparent damage to the anatomy of the ear (see auditory system), which can be thought of as the combination of auditory verbal agnosia and auditory agnosia. Patients with cortical deafness cannot hear any sounds, that is, they are not aware of sounds including non-speech, voices, and speech sounds. Although patients appear and feel completely deaf, they can still exhibit some reflex responses such as turning their head towards a loud sound.
Cortical deafness is caused by bilateral cortical lesions in the primary auditory cortex located in the temporal lobes of the brain. The ascending auditory pathways are damaged, causing a loss of perception of sound. Inner ear functions, however, remains intact. Cortical deafness is most often cause by stroke, but can also result from brain injury or birth defects. More specifically, a common cause is bilateral embolic stroke to the area of Heschl's gyri. Cortical deafness is extremely rare, with only twelve reported cases. Each case has a distinct context and different rates of recovery.
It is thought that cortical deafness could be a part of a spectrum of an overall cortical hearing disorder. In some cases, patients with cortical deafness have had recovery of some hearing function, resulting in partial auditory deficits such as auditory verbal agnosia. This syndrome might be difficult to distinguish from a bilateral temporal lesion such as described above.
Early reports, published in the late 19th century, describe patients with acute onset of deafness after experiencing symptoms described as apoplexy. The only means of definitive diagnosis in these reports were postmortem dissections. Subsequent cases throughout the 20th century reflect advancements in diagnoses of both hearing loss and stroke. With the advent of audiometric and electrophysiologic studies, investigators could diagnose cortical deafness with increasing precision. Advances in imaging techniques, such as MRI, greatly improved the diagnosis and localization of cerebral infarcts that coincide with primary or secondary auditory centers. Neurological and cognitive testing help to distinguish between total cortical deafness and auditory agnosia, resulting in the inability to perceive words, music, or specific environmental sounds.
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