MEDICAL REPORTS

Non syndromic hearing loss

Nonsyndromic hearing loss refers to an isolated hearing impairment, devoid of other associated medical symptoms. This type of hearing loss is multifaceted and can be categorised based on its inheritance pattern: autosomal dominant (DFNA), autosomal recessive (DFNB), X-linked (DFNX), or mitochondrial. Each category comprises multiple subtypes. For instance, the DFNA, DFNB, and DFNX classifications are sequentially numbered based on their order of discovery, with DFNA1 being the inaugural type of autosomal dominant nonsyndromic hearing loss identified.

The manifestations of nonsyndromic hearing loss differ across types. It can be unilateral (affecting one ear) or bilateral (both ears), with the severity ranging from mild, where soft speech might be challenging to decipher, to profound, marked by an inability to detect even loud sounds. The latter is often termed “deafness.” The progression can be stable or intensify with age, and the impairment can be more pronounced for certain sound frequencies, whether they be high, mid, or low tones.

Most nonsyndromic hearing losses are sensorineural, indicating permanent impairment stemming from inner ear damage. The inner ear’s function is to convert sound into electrical nerve impulses directed towards the brain. Less frequently, the loss is conductive, arising from middle ear alterations. In some cases, especially with the DFNX2 type, both the inner and middle ear are affected, leading to mixed hearing loss.

Nonsyndromic hearing loss can manifest at any life stage, from infancy to advanced age. If it emerges before speech development, it’s termed prelingual or congenital. Postlingual hearing loss sets in post speech development.