Ear, nose and throat surgery

26 Ear, nose and throat surgery





Ear



Anatomy



External ear


The pinna (Fig. 26.1) is made of fibroelastic cartilage. The external auditory meatus has an outer cartilage portion; the inner part is formed by the tympanic bone (Fig. 26.2). It is lined by squamous epithelium and contains ceruminous glands that produce wax. There is very little subcutaneous tissue and soft tissue swelling is very painful.





Middle ear


The vibrating tympanic membrane is conical and attached to the margin of the bony ear canal laterally and to the handle of the malleus, the first of the three ossicles, medially (Fig. 26.2). The head of the malleus is attached to the body of the incus in the space superior to the middle ear known as the attic. The long process of the incus attaches to the head of the stapes via its lenticular process. The stapes is joined to the oval window margin by the annular ligament. The middle ear is lined by simple cuboidal epithelium containing some mucus-secreting cells. The middle ear space is connected to the nasopharynx by the Eustachian tube, which maintains the middle ear at atmospheric pressure.





Assessment





Audiometry


Hearing by air conduction can be assessed by pure tone audiometry, in which sounds of known pitch and loudness are presented to each ear in turn via headphones. Bone conduction (cochlear function) can be separately tested by applying sounds to the mastoid process. A masking tone is needed if the two cochleae are to be tested separately. The difference between the air and bone conduction gives the level of conductive hearing loss (Figures 26.4 and 26.5). The patient’s ability to hear speech can be tested by presenting lists of words via headphones. The percentage correctly identified at different loudness levels allows derivation of a speech reception threshold (50% of words correct) and a discrimination score. Middle ear function (compliance) can be assessed by tympanometry. The amount of sound from a probe reflected back from the drum is measured while the pressure in the ear canal is made to vary. The compliance is maximal when the pressure in the ear canal equals the pressure in the middle ear, because when pressure is the same on both sides of the drum it is maximally mobile. Tympanometry is most often used to confirm the presence of fluid in the middle ear.








Diseases of the middle ear





Chronic suppurative otitis media


This causes aural discharge and deafness.




Atticoantral or squamous disease


A cholesteatoma forms as a retracted area of the drum in which keratin accumulates. The drum tissue at the periphery of the cholesteatoma produces a number of chemical mediators that stimulate osteoclast activity. Hence the cholesteatoma can erode surrounding bone and cause complications such as disruption of the ossicular chain, facial palsy and intracranial sepsis. The primary treatment goal is to eliminate the disease. Surgical treatment (mastoidectomy) is mandatory in all but the very elderly and those who are medically unfit.





Diseases of the inner ear




Vertigo


In some cases, balance disorders may arise from abnormalities of the vestibular portion of the inner ear.


Benign paroxysmal positional vertigo is a very common condition in middle age and is due to debris floating in the posterior semicircular canal which stimulates the ampulla hair cells, producing vertigo. Episodes are triggered when the affected ear is down-most – as when the patient turns over in bed. Debris can be displaced therapeutically from the posterior canal by positioning the head so that it floats out of the canal into the vestibule (Epley’s particle repositioning manoeuvre). If this fails, division of the ampullary (singular) nerve or occlusion of the posterior semicircular canal is beneficial.


Vestibular neuronitis causes severe vertigo lasting for as long as several weeks. The hearing remains normal. It is due to severe temporary reduction of vestibular function in the affected ear. Patients are managed by bed rest and vestibular sedatives, such as prochlorperazine.


Abnormal fluctuations of fluid pressure within the inner ear (endolymphatic hydrops) produce a combination of fluctuating deafness, tinnitus and vertigo known as Ménière’s disease. This uncommon condition is initially treated medically, using either a vasodilator agent (e.g. betahistine) or a diuretic. If medical treatment fails, the vestibular portion of the labyrinth may be destroyed by a middle ear injection of gentamicin. Procedures of last resort are surgical destruction of the labyrinth, or section of the vestibular nerve.




Nose



Anatomy


The nasal skeleton consists of two nasal bones superiorly and two pairs of cartilages inferiorly (Fig. 26.9). The nasal cavity is divided in two by a partition composed of cartilage anteriorly and bone posteriorly (the nasal septum). Three turbinate bones protrude from the lateral wall of the nose (Fig. 26.10). Between the inferior and middle turbinates is the middle meatus of the nose. Most of the paranasal sinuses open into this area under cover of a soft tissue flap known as the uncinate process. Obstruction of the sinus ostia in this area can cause sinus pain and may lead to sinus infection. Superior to the superior turbinate is an area of olfactory epithelium from which arise the nerve fibres of the olfactory nerve. The anterior portion of the nasal septum is called Little’s area. Here prominent veins are often found, and nose bleeds most often arise from this part of the nose.






Assessment




Mar 20, 2017 | Posted by in GENERAL SURGERY | Comments Off on Ear, nose and throat surgery

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