Ear & Hearing

The ear constitutes an important component of the sensory system. The main function of the ear is to maintain balance and convert sound into electrical impulses after amplifying them. These electrical impulses are than transmitted into the brain.

For descriptive purpose the ear is divided in to:

• The External ear
• The Middle ear
• The Inner ear

External Ear

The external ear consists of pinna or auricle and the external auditory canal.

Pinna: This is the part of the ear that projects from the side of the head. It helps in collecting sound and directing the traveling sound waves in to the external auditory canal. It consists of elastic cartilage that is covered by skin.

External auditory canal: It measures about 2.5cm and extends from pinna to tympanic membrane. Its outer part is cartilaginous while the inner part is bony. At its medial end (inner) is the eardrum or Tympanic membrane. It is lined by skin. The skin is rich in sebaceous and ceruminous glands (sweat glands). The products of these glands mix to form wax.

Middle Ear

The middle ear resembles a matchbox with a vertical diameter of 15mm and transverses diameter of 4mm. It consists of the tympanic membrane and middle ear bones or ossicles. The middle ear communicates with the nasopharynx (area behind the nose) through the Eustachian tube.

Tympanic membrane: A transparent disc situated between the external ear and the middle ear. The eardrum has a diameter of approximately 8 to 9mm. It has an outer skin layer and an inner mucous layer.

Middle ear ossicles (bones): These consist of a chain of three movable bones; malleus, incus and stapes.

Malleus: It is the largest of the three ossicles measuring about 8mm in length. The malleus resembles a hammer and is the outer most (lateral) ossicle. It is firmly fixed to the eardrum at one end while the other end articulates with the incus.

Incus: It is present between the malleus and stapes. It is shaped like an anvil.

Stapes: – It is the smallest of the three ossicles resembling a stirrup. It is attached to the incus at one end and its other end i.e. the footplate articulates with the inner ear via the oval window.

Inner Ear

The inner ear lies in the temporal bone. It consists of three semicircular canals (anteriorly), cochlea (posteriorly) and the vestibule (middle).

All the inner ear structures have an outer bony shell inside which the membranous end organs (receptors and nerve endings) of hearing and balance are suspended. Two fluids surround this membranous end organ. The fluid inside the membranous end organ is called endolymph and the fluid outside the end organ between the bony shell and the end organ is called perilymph. These fluids protect the membranous end organ and help in normal functioning of the membranous end organ.

Semicircular canals: These are three semi-circled tubes set at right angles to each other. The canals are named horizontal, anterior vertical and posterior vertical. The membranous end organ here contains the organ of balance or equilibrium.

Cochlea: This is a snail like structure within the inner ear from which the organ of hearing is suspended. It is coiled for two and half turns.

From these membranous end organ the auditory nerve arises which carries impulses into the brain.

Middle ear is most commonly affected part of the ear. In healthy children, the middle ear is filled with air, but if your child has an infection or any diseases, fluid or mucous will get accumulated.

Pediatric Hearing Problems

Hearing problems can be congenital or acquired. Congenital causes include genetic defects, prematurity, maternal diabetes, lack of oxygen supply to the foetus. Acquired causes include ear infections, meningitis, measles, noise exposure, chicken pox, influenza, head injury, and overuse of ototoxic drugs. Hearing problems can be temporary or permanent.

In children, hearing problems are not easily noticed until the age of 12 to 18 months. Hearing problems in new born can be diagnosed with hearing screening test and some new born babies may have undergone a hearing screening assessment. One of the conditions that cause hearing loss is glue ear.

Causes

Children are at more risk of developing glue ear because the eustachian tube is small in size and can be easily blocked.

Enlarged or infected adenoids may also block the eustachian tube. Adenoid glands are situated at the back of the nose and throat that fight against germs and bacteria which invade the body. Infection of these glands may cause glue ear.

Symptoms

Your child will not be able to hear properly because of the blockage by glue like fluid. Because of hearing loss, your child may not be able to pay attention or interact with others. Your child may also experience problems while talking.

Diagnosis and treatment

Your ENT doctor primarily examines your child’s ear by an instrument called otoscope. In addition an audiogram (to check if your child can hear) and tympanogram (to check how flexible the eardrum is at different pressures) may also be ordered to assess the condition.

Surgery is recommended if the fluid persists for longer than 3 months. The surgical procedure is called a myringotomy where a small incision is made in your child’s eardrum to drain out the fluid. Ventilation tubes (grommets) or tympanostomy tubes are inserted into the incision created which allows the air to pass in and out. It also helps to improve hearing by clearing the fluid in the ear drum.

Surgery may also be done to remove the enlarged adenoid gland, and the procedure is called as adenoidectomy and the surgery may not improve your child’s hearing if grommets are not inserted.

Adult Hearing Problems

Hearing loss is common with advancing age. Most of the causes of adult hearing loss are irreversible as the damage is in the inner ear, and not amenable tosurgical intervention. However, wax impaction, fluid in the ear, perforations in the eardrum, abnormalities of the bones of the ear are all reversible causes of adult hearing loss. These can usually be determined by an examination and a hearing assessment. If a hearing assessment is required, my secretary can be contacted, and she will be able to put you in touch with a local audiologist. The audiologist will know if you then need to see an ENT surgeon.