ASSIGNMENT 8: SENSORY HEARING LOSS

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HEARING

The process of hearing can be divided into two components:

1. The conduction of sound as mechanical waves

2. The conversion of mechanical waves to electrical signals and their subsequent passage to the brain

The external and middle ear are responsible for the first part (the conduction of sound waves). The internal ear is responsible for the second part.

The following videos (also available from the "VIDEOS" section) demonstrate these two components of hearing

HEARING LOSS

Hearing can be impaired if either or both of the above components are affected. If the first component is affected the resultant deafness is called "conductive"; if the second component is affected the deafness is called "sensori-neural (sensory)" hearing loss (SNHL)

The following video provides an "over-view" of the types of hearing loss

SENSORI-NEURAL HEARING LOSS (SNHL)

Sensori-neural (sensory, SNHL) is due to a defect in the functioning of the internal ear, the CN VIII or the central pathways of hearing (including the hearing center). This type of hearing loss has many causes including defect from birth (congenital), exposure to loud noise (jack hammers, music), aging (called presbyacusis; the equalent of presbyopia of the eye), chemicals etc.

Majority of SNHL is due to a defect in the cochlea, the hair cells in organ of Corti to be exact (see videos above and picture below). The cells fail to function normally.

Recently it has been suggested that elevated levels of antibodies against Thyroid peroxidase (TPO) in pregnant mothers may be linked to SNHL in their (to be born) children.

Your task is to find evidence linking the two (TPO antibodies and SNHL) together.