well-marked lymph space. In young subjects, remains of fetal cartilage are
sometimes to be found in the promontory near the anterior margin of the oval
window.
Otosclerosis is a very common disease. Probably 1 person in every 200 suffers
from the affection. In many cases otosclerosis is present, unsuspected, in the
labyrinth capsule and only becomes manifest when it involves the hearing
mechanism.
AETIOLOGY. The disease is much more common in the female than the male sex.
There is a marked hereditary tendency to otosclerosis in certain families, and
in nearly 50% of cases a history of deafness in the family can be obtained. The
disease usually becomes manifest between the ages of 18 and 30, but it may begin
earlier. There appears to be a close relationship between the onset of deafness
and the onset of puberty or the occurrence of pregnancy.
PATHOLOGY. The bony changes vary according to the duration of the disease. At
first the normal bone is absorbed and replaced by vascular spongy osteoid
tissue. The process advances along the blood vessels. Later the new bone becomes
thicker and less vascular. The most common site of disease is the promontory in
the region of the anterior margin of the oval window, and in advanced cases the
stapes becomes ankylosed in position by a mass of spongy new bone. Various
reasons have been given to explain this "site of election" for bone disease in
otoscleroisis. It may be worthy of note that there is in this region an
anastomosis between the vessels of the middle ear and those of the labyrinth
capsule.
SYMPTOMS. The chief symptoms are gradually increasing deafness and tinnitus. The
noises are often refereed to the head rather than the ear and occasionally cause
the patient more discomfort than the deafness. If tinnitus is marked, the case
is likely to progress rapidly. Paracusis Willisii is frequently present,, i.e.
the patient states that he can hear better in a noisy place such as a railway
carriage or motor car. Various explanations have been put forward to account for
paracusis, the most probable being that patients suffering from otosclerosis,
and consequently unable to hear lower tones, obtain more advantages than normal
people from the raising of their friends' voices in a noisy place, as they
(otosclerotics) are not distracted by the low-pitched hum of machinery to the
same extent as people with perfect hearing. Giddiness is a rare symptom, but may
be present in varying degree even to the extent of true paroxysmal vertigo.
EXAMINATION. In otosclerosis the tympanic membrane is usually normal. In about
10% of cases a flamingo-pink blush may be seen through the membrane, usually
behind the handle of the malleus. This is due to hyperaemia of the promontory
and affords good evidence that the otosclerotic process is in an active phase.
The Eustachian tube is usually patent. On the other hand, the presence of scars
in, or opacity or retraction of, the drumhead in association with Eustachian
obstruction by no means negatives the diagnosis of otosclerosis. Otosclerosis
may be complicated by middle-ear suppuration. There are three types of
otosclerosis: tympanal, cochlear and mixed.
In tympanal type tuning-fork tests show a negative Rinne's test and Weber's test
is lateralized to the more affected ear. Audiometry confirms the presence of a
conductive deafness with, usually, normal inner-ear function. Sometimes there
may be a diminution of inner-ear function, earlier than can be accounted for by
presbyacusis.
There are rare cases of otosclerosis (cochlear type) in which the focus of
spongification does not affect the region of the oval window but involves the
capsule of the cochlea at a separate spot. In such cases there is no paracusis,
and tuning-fork tests give the results normally obtained in a case of
sensorineural deafness. It has been suggested that if a young or middle-aged
patient suffers from nerve deafness for which no other cause can be found, and
if in her or his family there are individuals suffering from typical
otosclerosis, the case should be regarded as one of spongification of the
labyrinth capsule.
TREATMENT. Patients with otosclerosis hear well with a hearing aid, but as
treatment is usually sought in early adult life or in middle age, surgical
treatment is usually preferred.
The surgical treatment of otosclerosis was revolutionized by the introduction of
direct mobilization of the stapes by Rosen in 1953. This gave excellent results
initially, but it soon became apparent that the stapes refixed in practically
all cases. In 1960 the operation of stapedectomy (or stapedoplasty) was
introduced when the stapes was removed and replaced by a prosthesis. The
operation is best carried out under general anaesthesia using controlled
hypotension, although it can also be done under local anaesthesia. It is
essential to use a good operating microscope. The exposure is achieved using an
aural speculum. The skin of the posterior bony meatal wall is incised to form a
U-shaped flap, which is elevated towards the annulus tympanicus which is then
elevated from the underlying bone so that the posterior half of the tympanic
membrane can be folded forwards, hinged on the handle of the malleus, to expose
the posterior half of the tympanic cavity. Extra exposure is obtained by
removing bone around the posterosuperior margin of the bony rim. The
superstructure of the stapes is removed; a limited opening is made through the
footplate of the stapes and a teflon piston is inserted with its looped end
around the long process of the incus and its free end inserted into the opening
through the stapes footplate. The opening in the footplate may be sealed by a
vein graft.
There are many modifications of technique in stapedectomy but satisfactory
improvement in hearing is obtained in more than 80% of cases with closure of the
air-bone gap in the great majority. The extent of the improvement will, of
course, be limited by any sensorineural loss. This high success rate has to be
balanced against a possible postoperative deterioration of hearing, sometimes
total loss of hearing, in under 5% of cases. Because of this risk to the hearing
the operation should only be carried out on the ear with the poorer hearing.
COMPLICATION. The most important complication is loss of hearing and this may
occur at the time of the operation but it may not occur until many months later.
For this reason operation on the second ear should only be considered after at
least 6 months. Sudden hearing loss is particularly liable to occur after sudden
changes in pressure and patients should avoid diving. In a small number of cases
a fistula may develop between the fluids of the inner ear and the middle ear via
the new opening in the footplate of the stapes. This will give rise to
fluctuating hearing and to intermittent vertigo. When such symptoms occur the
ear should be explored and the operation revised with closure of the opening
into the labyrinth.
PROGNOSIS. Patients should be assured that the progress of the disease is
usually very slow, that no brain disease is present, that the condition is not
dangerous to life and does not result in absolute deafness. Pregnancy, illness
and accident may cause a rapid increase of the deafness and tinnitus. If the
affection comes on early in life, the prognosis is extremely poor from the
hearing point of view.
MENIERE’S DISEASE
Meniere's disease is characterized by deafness and tinnitus as well as by
vertigo, loss of balance, nausea and vomiting, and thus involves both the
cochlear and vestibular components of the inner ear.
PATHOLOGY. The most consistent histological finding in Meniere's disease is a
dilatation of the endolymphatic compartment of the inner ear. The aetiology of
this endolymphatic hydrops is unclear, but its presence infers an abnormality of
endolymph formation or absorption. Local ischaemia has been put forward by many
as a cause, thus prompting the widespread use of vasodilators. Another proposed
aetiology is that there is faulty absorption of endolymph by the endolymphatic
sac, and this has been given some support by the results of surgery on this
structure. Other causes which have been put forward at one time or another
include allergy, focal infection, biochemical disturbance, vitamin deficiency,
endocrine disturbances and viral infections.
CLINICAL FEATURES. The outstanding features are vertigo, vomiting, tinnitus and
deafness. The onset of the vertigo is often sudden, usually without warning and
may render the patient completely helpless within seconds of the onset. If
support is not at hand the patient may fall and injure himself. Vomiting may
accompany the dizziness or may follow it. There is frequently a feeling of
tension in the head or tinnitus during the attack and this passes off
afterwards. Similarly deafness may occur during an attack, the patient only
often noticing it when the incapacitating vertigo is settling. In the early
stages of the disease the hearing may return to normal after attacks, but if the
condition progresses and attacks recur deafness becomes established and more
severe. Between attacks clinical and cochlear examination may be completely
negative and the diagnosis may have to be assumed after a careful consideration
of the history. The typical attack may be modified in that instead of
vertiginous episodes there may be a constant sense of imbalance with occasional
exacerbations and periodic increases in the hearing loss with slight nausea
only. Fullness or pressure in the ear and suboccipital headaches are not
uncommon features. During a severe attack sweating, bradycardia and diarrhoea
may occur, probably as a result of vagal stimulation.
If the patient is seen during an attack he is completely disorientated, and
unable to stand or do anything for himself. He will usually lie down as still as
possible as any movement exacerbates the vertigo. Nystagmus is present but its
direction is not indicative of the side of origin of the symptoms. If the
patient is seen just after an acute attack has settled there will be
sensorineural deafness often associated with distortion of sounds.
DIAGNOSIS. Meniere's disease must be differentiated from other causes of
sensorineural deafness and tinnitus. The diseases most likely to give rise to
problems in differentiation are acoustic neuroma, labyrinthitis and,
occasionally, intracranial disease and syphilis.
Examination in Meniere's disease usually reveals normal intact tympanic
membranes with a negative fistula test. The patient is neurologically normal
apart from a sensorineural hearing loss, usually detectable by tuning-fork
tests. Audiometry will show a sensorineural hearing loss, except in early cases.
The hearing loss is frequently of a low tone or flat type but any pattern may
occur. Speech audiometry usually is in keeping with the pure-tone audiogram.
Recruitment is frequently present, impedance audiometry is normal and there is
no tone decay. In early cases the hearing loss is fluctuant, improving between
attacks and this is a useful finding at follow-up audiometry. In more advanced
cases there may be a persistent moderate or severe sensorineural loss.
Vestibular tests may be normal in the early case between attacks, but later a
canal paresis or hypofunction is found on the affected side. Radiography of the
mastoids will be normal as should be views of the internal auditory meatus.
In advanced Meniere's disease the acute symptoms frequently disappear, leaving
an imbalance which may be constant or may recur at intervals without nausea. An
anxiety state is quite commonly observed in those patients who have had several
disabling acute attacks. The occurrence of associated migraine is not unknown.
Lermoyez syndrome may be a variant of the disease. It consists of a progressive
loss of balance over days or weeks with increasing deafness and headache which
terminates with a paroxysm of vertigo, to be followed by immediate improvement
in the hearing and other symptoms.
TREATMENT. This is initially medical but a number of patients may benefit from a
surgical procedure.
Medical treatment. Many cases can be controlled by antihistamine labyrinthine
sedatives such as prochlorperazine maleate (Novamine), cinnarizine (Stugeron) or
promethazine theoclate (Pipolphen). Because many of these patients are anxious
they may be helped by tranquillizers. Vasodilators are used. Betahistine
hydrochloride (Mycrozer) appears to be the most useful recent addition to the
medical armamentarium and is routinely prescribed for most patients by a number
of people. It is a histamine analogue and is thought to work by causing local
vasodilatation and thus reducing the vertigo with occasional hearing improvement
and relief of tinnitus. Attempts to reduce the labyrinthine hydrops by fluid and
salt restriction and diuretics is widely practised and is probably worth while
in cases uncontrolled by other methods. Medical treatment controls the condition
in over two-thirds of patients.
During the acute attack sedation is essential and vomiting may necessitate
intramuscular administration of a labyrinthine sedative. Other drugs useful in
the acute attacks are chlorpromazine hydrochloride (Aminazine), atropine,
suprastine, natrii bicarbonas.
Surgical treatment. Decompression of the endolymphatic sac is gaining in
popularity as a method of reducing the vertigo, with some hope of reduction of
tinnitus and preservation and occasionally improvement in hearing. It is now
being done earlier in cases uncontrolled by medical treatment where there is
still useful hearing in the affected ear. Vestibular neurectomy has been
advocated. It relieves the vertigo but the hearing continues to diminish and it
is an intracranial procedure. In the persistently vertiginous patient where
there is no useful hearing in the affected ear surgical destruction of the
labyrinth may have to be considered. This, however, is a last resort and should
be used as such because a number of patients develop bilateral disease.
Selective destruction of the vestibular labyrinth with preservation of hearing
may be achieved by applying ultrasound to the affected lateral semicircular
canal.
PROGNOSIS. This depends upon the response to the various forms of treatment. If
treatment does not control the attacks the outlook is bad for the affected ear.
At the same time, remission occurs so frequently that it is difficult to be
precise in prognosis after one attack. The disease may be bilateral in up to 40%
of cases and therefore conservatism is essential.
SENSORINEURAL DEAFNESS
The term "sensorineural deafness" is used when the cause of the deafness is in
the cochlea or in the auditory nerve. The term "sensory deafness" is sometimes
used when the lesion is in the cochlea, and "neural" or "retrocochlear deafness"
may be used when the lesion is in the auditory nerve. Sensorineural deafness may
be so slight that the patient is quite unaware that he has a hearing loss, or it
may be so severe that there is no useful hearing at all. The majority of cases,
of course, fall in between these two extremes. When a patient presents
complaining of deafness it should be possible, without any real difficulty, to
make a diagnosis of conductive or sensorineural deafness if the some methods of
investigation are followed. Whether the lesion is in the cochlea or the auditory
nerve can usually be determined by a series of audiometric tests. In general,
the presence of recruitment means that the lesion is in the cochlea, and if
recruitment is absent the lesion is likely to be in the auditory nerve. Lesions
in either site will reduce the discrimination for speech but the loss of
discrimination will be relatively more marked in neural lesions. In most cases a
final pathological diagnosis can be made by careful history taking and clinical
examination, paying particular attention to associated symptoms and signs.
DEAFNESS DUE TO TRAUMA
PENETRATING INJURIES OF THE TEMPORAL BONE
These injuries may be caused by bullets or other missiles but are more commonly
caused by sharp implements such as knitting needles or hairgrips which pass
through the external auditory meatus, perforate the tympanic membrane and
penetrate the inner ear. The resulting deafness is usually complete but may be
overshadowed by the severe vertigo, nausea and vomiting that occur. The facial
nerve may also be damaged.
BLAST INJURY
Sensorineural deafness resulting from blast is maximal immediately after the
explosion. The tympanic membrane may or may not be ruptured but this does not
appear to influence the degree of sensorineural deafness. There is a natural
tendency to spontaneous improvement and the improvement is initially rapid,
particularly during the first 48 hours, but there may still be some improvement
for up to 6 months. The deafness is usually accompanied by tinnitus.
Head injuries which cause concussion without radiological evidence of skull
fracture may cause deafness due to haemorrhage into the middle ear or into the
cochlea. It must be remembered, however, that fractures of the temporal bone may
be very difficult to demonstrate radiologically.
FRACTURES OF THE TEMPORAL BONE
A longitudinal fracture of the temporal bone is the more common type. The
fracture begins in the squamous temporal bone and extends along the roof of the
bony external auditory meatus, often with rupture of the tympanic membrane. The
fracture line crosses the roof of the middle ear to pass into the petrous
temporal bone. It then runs anterior to the labyrinthine capsule, through the
carotid canal and ends near the foramen lacerum or foramen spinosum. In
longitudinal fractures the labyrinthine capsule is rarely ruptured and
sensorineural deafness, when it occurs, is due to labyrinthine concussion.
Transverse fractures cross the petrous bone at right angles to its long axis, so
that the fracture may pass through the vestibule of the inner ear. The resulting
sensorineural deafness is severe or complete and there is very severe rotatory
vertigo. The facial nerve is damaged in about 50% of these fractures.
NOISE-INDUCED DEAFNESS
It has long been recognized that constant exposure to loud noise will cause
sensorineural deafness and it is well known that boiler-makers, coopers and
workers in noisy factories will become deaf if their exposure to noise is
prolonged. Workers in many occupations run the risk of noise-induced deafness
where they are exposed to loud machinery noise, power drills or saws, to engine
noise, riveting machines, drop forges, etc.
Traumatic exposure to noise may also occur in sports such as shooting, and it
may occur in recreation, particularly with the introduction of very high
amplification in the entertainment world. The first effect of exposure to
excessive noise is a temporary loss of hearing maximal at 4 to 6 kHz. The
deafness is accompanied by tinnitus. This effect is only temporary and is known
as temporary threshold shift. If the exposure to excessive noise is repeated and
prolonged, a permanent hearing loss may occur. This permanent loss is due to
damage to the hair cells of the organ of Corti and is not reversible. With
further exposure to noise the deafness will inevitably increase, but no further
increase in the deafness will result if there is no further exposure to
traumatic noise. Initially the maximum hearing loss is at 3, 4 or 6 kHz, but as
the deafness increases the trough at one frequency disappears and a smooth
high-tone loss results. Eventually the low tones are affected as well. With most
industrial noises both ears are affected symmetrically, although occasionally
there will be unequal exposure to noise.
Apart from temporary threshold shift, noise-induced deafness is permanent and
will not be helped by treatment. A proportion of patients will be helped by a
hearing aid, although many find that a hearing aid gives poor discrimination. It
follows, therefore, that prevention is more important than the management of the
deafened worker.
DEAFNESS DUE TO VIRUSES
Mumps can cause sudden sensorineural deafness which is usually unilateral. The
deafness is generally severe or total and comes on about the fourth or fifth day
of the disease. The deafness is occasionally accompanied by vertigo. The hearing
loss is permanent. Other viruses which may cause deafness are measles, chicken
pox, zoster, rubella or poliomyelitis. Influenza type A or B may cause
sensorineural deafness and this may be accompanied by myringitis bullosa
haemorrhagica.
PRESBYACUSIS
The term "presbyacusis" is used to describe hearing loss resulting from
degenerative changes of ageing. In sensory presbyacusis there is high-tone
hearing loss associated with atrophy of the organ of Corti commencing at the
basal end of the cochlea. In neural presbyacusis there is a loss of neural
elements. This produces no consistent audiometric pattern of loss, but there is
marked loss of speech discrimination out of proportion to the pure-tone loss.
Degeneration of the stria vascularis produces a flat type of audiometric loss
but with good speech discrimination. The hearing may also be affected by
alteration in the conduction along a defective basilar membrane. These types of
presbyacusis may occur as distinct entities or may occur in combination. The
hearing loss is symmetrical in the two ears and progression is usually slow. The
deafness may become evident at any time beyond the third decade, but patients do
not usually become concerned about their deafness until the speech range is
affected. Characteristically old people complain of difficulty in understanding
speech, even though the speech appears to be loud enough. They also have
difficulty in hearing in the presence of background noise so that they find
group conversations difficult to follow. The difficulty in understanding speech
is due to the inability to hear higher frequencies which means that consonant
sounds, which carry most of the meaning of speech, cannot be heard properly.
Recruitment of hearing also adds to the distortion. Loss of the neural elements
may result in very poor discrimination of speech. These difficulties are made
worse by lack of concentration associated with the slowing down of mental
processes.
Understanding of the disability of presbyacusis helps in the management. In
speaking to such patients, it is essential to speak slowly and distinctly rather
than simply to shout at them. Many can be helped by hearing aids but, again, the
poor discrimination with distortion may make it very difficult to get
satisfactory results.
OTOTOXICITY
It has long been recognized that quinine and the salicylates may cause deafness.
Fortunately this deafness is usually reversible when the drugs are stopped.
During the last 25 years many therapeutically valuable drugs have been
introduced which may cause a selective toxic action on the cochlea or vestibule.
The ototoxicity may be temporary or permanent.
AMINOGLYCOSIDES
The first antibiotic of this group which was shown to be ototoxic was
streptomycin, when used in the treatment of tuberculosis. In large and prolonged
doses it produced loss of vestibular function. This was well compensated in
young patients but older patients remained permanently unsteady.
Dihydrostreptomycin was introduced to overcome this effect but, in fact,
produced cochlear damage which was particularly distressing because the deafness
continued to progress even when the drug was withdrawn. Neomycin produces a
similar, but even more severe, effect because its excretion is often impaired by
nephrotoxic action on the renal tubules. Gentamicin, kanamycin, tobramycin
combine ototoxicity and nephrotoxicity. Most of these drugs are rarely used
systemically unless infection is dangerous to life. Where they are given
systemically the blood level should be monitored, particularly where there is
any possibility of renal failure. Even when applied locally or by mouth there is
some risk of absorption and ototoxicity.
Ototoxic effects may be caused by the diuretic drugs ethacrynic acid and
furosomide. Fortunately, in the case of ethacrynic acid, the deafness may be
reversible. Cytotoxic drugs such as the nitrogen mustards may be ototoxic, as
well as anthelmintics such as oil of chenopodium.
OTHER CAUSES OF SENSORINEURAL DEAFNESS
Other causes of sensorineural deafness are: perilymph fistula, surgical trauma,
suppurative labyrinthitis, syphilis, acoustic neurinoma.
SUDDEN IDIOPATHIC DEAFNESS
This term is used for deafness that comes on extremely suddenly so that the
patient is actually aware of the moment of the onset of the deafness. It can
also be applied when a patient wakes up in the morning and finds that he has
become deaf. The deafness may be accompanied by tinnitus and there is often
distortion of hearing and also a resonance effect so that sound of one frequency
produces a feeling of resonance in the ear. No other signs of ear disease are
discovered on investigation but, of course, conditions such as an acoustic
neurinoma or Meniere's disease must be excluded. On audiometric testing the most
usual type of audiogram is a low-tone loss similar to that seen in Meniere's
disease, but less often there are other audiometric patterns or even total loss
of hearing. In most cases there is quick recovery from the deafness within
hours, days or weeks, but if there is no recovery within 3 weeks it is unlikely
to take place spontaneously. This tendency to spontaneous recovery makes
assessment of treatment difficult, but there is evidence that the hearing may be
improved by treatment.
TREATMENT OF SENSORINEURAL DEAFNESS
1. Cause removal.
2. Vasodilators (Trental, Cavinton).
3. Inhibitors of cholinesterase (Galantamine, Proserine).
4. Vitamins (B1, B6, Nicotinic acid, Cocarboxylase, Ascorbinic acid).
5. Biogenic stimulators (Extract Aloe, Fibs, Humisol).
6. Specific antidotes (Unithiol, Natrii Thiosulfas) (for patient with toxic
deafness).
7. Electrophoresis of Vit. B1 or KI in the ear.
8. Oxygenotherapy (for patient with toxic deafness).
9. Hearing aid.
Fig. 1. Left auricule (lateral view).
1. Lobule. 2. Antitragus. 3. Tragus. 4. Cavum conchae. 5. Fossa
triangularis. 6. Helix. 7. Scapha. 8. Antihelix Lymph nodes: A.
Superficial cervical, B. Pre-auricular, C. Postauricular.
Fig. 3. Right tympanic membrane. Broken lines indicate medial relations.
1. Pars flaccida. 2. Pars tensa. 3. Cone of light. 4. Lateral process of
malleus. 5. Handle of malleus. 6. Umbo. 7. Anterior fold. 8.
Posterior Fold.
A. Head of maleus. B. Body of incus. C. Aditus. D. Long process of
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