Diving Ear: Anatomy and Physiology (External, Middle and Inner Ear).

Diving ear problems are the most common occupational diseases of diving, and the diving physician should have a working knowledge of otology– to know ear anatomy and ear physiology.

 It is not always possible to obtain specialist assistance at an early stage in the assessment of a diving accident, i.e. when effective therapeutic decisions are made.

The ideal combination is a diving physician and an otologist, both of whom have an appreciation of the other's specialty. It is for the diving physician that this section is included.

 External Ear Physiology and Anatomy

Anatomy of External Diving Ear

The external ear comprises the pinna and the external diving ear canal, which captures sound waves and directs them to the middle ear, which is separated from the external ear by the ear drum or tympanic membrane.

The external ear canal is approximately 3 cm long; the outer one-third is surrounded by cartilage and the inner two-thirds by bone. It is lined bystratified squamous epithelium which tends to migrate outwards, carrying casts of dead epithelial cells, foreign bodies such as dust, and cerumen.

Cerumen or ear-wax forms in the outer one-third of the canal. At body temperature the wax contains fatty acids which become bacteriostatic. It produces a hydrophobic lining which prevents the epithelium from being wetted, becoming soggy and creating a culture medium for infections of the external canal-referred to as otitis externa. The pH of the external canal lining is usually slightly acidic, which also serves as a bacteriostatic factor.

Interference (external ear anatomy) with the function of the external canal can be produced by removal of the cerumen, either by syringing of the ear, long periods of immersion, or traumatic gouging of the canal with cotton buds, finger nails, hair pins, etc. The mere presence of cerumen or wax should not be an indication for external ear toilet, or syringing. On the contrary, it is likely to increase the degree of subsequent otitis externa if performed before diving.

By immersion, divers can lose most of the cerumen from their ears, and it is rare, to see a subject who is in frequent diving practice who has any significant amount of cerumen blockage, unless he wears a hood that prevents the entry of water (diving ear physiology).

Patients with seborrhoeic dermatitis (often presenting as dandruff) may have episodes of external ear itchiness. If they respond to this by scratching the diving ear, they gouge out furrows of wax and excoriate the skin - breaking the two protec­tive linings (best diving). Otitis externa may develop within hours. If the diver refrains from inflicting this trauma, and especially if they treat the inflamma­tion and itch with the use of a non-water based anti-inflammatory steroid ointment (e.g. Ultralan, Kenacomb), then this unpleasant sequence of events does not eventuate.

Patients with an occluding cerumen plug or otitis externa should not dive, but they sometimes do. The obstruction of one external auditory canal may greatly restrict water entry, resulting in asymmetrical caloric stimuli and vertigo while diving, and/or con­ductive hearing loss on the surface.

A long-term reaction to cold water in the external ear canal is the development of exostoses - usually from three sites around the canal. Being osteomata, they are very hard white masses, and are tightly covered by epithelium. Sometimes they grow to such a size that they occlude the external canal and cause a conductive deafness and may need to be removed by an otological surgeon. Less extensive lesions can still produce problems by interfering with the drainage of cerumen, debris and water - predisposing to otitis externa. Otitis externa may complete the partial occlusion of the canal, initiated by the exostoses.

Diving Ear Case Report

During a diving medical seminar at Tahiti, a heated discussion ensued on the value of ear syringing to remove cerumen. Of the 44 divers present, only three were required by a Club Mediteranee physician to have cerumen removed from their ears, even though in none of these cases was the external ear obstructed. Otitis externa developed in four ears during the subsequent week, one bilateral and two unilateral - in the three subjects who had their ears syringed. It demonstrated statistically what most of us knew clinically.

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