1.
Klinical fnftomy, physiology of the external ear
2.
Otologyc examination
3.
Klinical anatomy, physiology and examination of the vestibular system
The ear consists of
three parts—the external, the middle and the
internal
- External Ear
Fig. i. Anatomy of the External,
Middle and Internal Ear (Semi-Schematic View)
(1) Pinna; (2) external auditory meatus; (3) tympanic
membrane; (4) tympanic
cavity; (5) malleus; (6) incus; (7) stapes; (8) Eustachian tube; (9)
vestibule; (10)
semicircular
canals; (11) cochlea; (12) auditory (acoustic) nerve
The shell-shaped pinna (Fig.
2) is composed of a skin-covered cartilaginous
lamella whose posterior surface is evenly convex and smooth, while its anterior
surface is concave, with semilunar folds and
hollows between them. The skin on the
anterior surface of the pinna adheres directly to the perichondrium; on the posterior surface, however, it may form folds owing to the presence of a small layer of loose cellular tissue. The free anteroexternal margin of the pinna is known as the helix; towards the bottom the pinna gradually turns into the lobe devoid of cartilage and consisting of well-developed fat and cellular tissue with a small number of vessels and nerves. The small protuberance of cartilage projecting over the external auditory meatus is named the tragus. In front of the helix and
parallel to it is a ridge known as the an
thelix, with the antitragus at
its posterior end.
The external auditory meatus extends
from the funnel-shaped hollow {cavum conchae) on
the outer surface of the pinna to the tympanic
membrane or drum. It is a canal directed horizontally
inwards and a little forward. Its average length
from the tragus top to the drum edge is
The external auditory meatus is curved in the horizontal and frontal planes. The
cartilaginous and bony đîă- tions of the meatus form an obtuse angle opening forward and downwards. Therefore, when examining the drum, the pinna must be pulled backwards and upwards, in order to straighten out the meatus. The oval lumen of the external auditory meatus has a longitudinal diameter of
In the newborn, there is neither bony auditory meatus, nor mastoid process, and in place of the former there is a bony ring or annulus, which is deficient in a small upper section, and is directly connected with the membra-nocartilaginous auditory meatus. The inner border of the annulus has a bony furrow (sulcus) into which the tympanic membrane is
inserted. In the bone-free upper part, the drum is directly attached to the lower edge of the squamosa, the so-called notch of Rivinus. By the end of the third year the external auditory
meatus is fully developed.
The external ear is supplied with
blood by branches of the external carotid
artery. It is innervated, in addition to the trigeminal branches, by the auricular nerve (ramus auricularis n. vagi) ramified in the
posterior wall of the auditory meatus. Mechanical irritation of the latter
wall, as in wax removal, often causes reflex cough. The
lymph from the walls of the auditory meatus drains into the nearest lymph nodes located in front of the auricle, on the mastoid process, and under the
inferior wall of the auditory meatus. Inflammations
in the external auditory meatus are often accompanied
by swelling and pain in these lymph nodes.
Tympanic
Membrane
The tympanic membrane (Fig. 3,
coloured Table I, Fig. 1) or drum is a thin
semi-transparent elliptical disc situated between
the external and middle ear. It is 9.5-10 mmX X
8.5-
facing forward and upwards and directly attached to the incisure in the squamosa
known as the notch of Rivinus (incisura Rivini) is lax, and is called
the pars flaccida or Shrapnell's membrane. The drum consists of three layers: an outer or epidermal layer
continuous with that of the auditory meatus, a middle layer of radiating and
circular connective tissue fibres, and an
inner layer of mucosa continuous with the mucous membrane of the tympanic cavity. Shrapnell's membrane or pars flaccida consists only of two layers and lacks the middle stratum of fibrous tissue.
In early childhood, the drum is
comparatively thick owing to the presence of a loose submucous layer. It grows compact with time and in old age becomes quite thin.
The drum is placed obliquely and
not perpendicularly to the long axis of the auditory meatus, so that it faces forward, downwards and inwards. In the newborns
and breast-fed babies, the drum is
almost horizontal.
Examination of the drum through the
auditory meatus reveals a funnel-shaped
concavity in its centre with an eminence called the umbo in its deepest place. The handle of the malleus embedded in the fibrous layer of the drum starts from the umbo and goes
forward and upwards to end above in a tiny knob
the size of a pin-head—the short process. The two
folds stretching anteriorly and posteriorly from the short process separate the upper lax membrana flaccida from the lower taut membrana tensa.
Middle
Ear
The middle ear comprises the tympanic
cavity, the mastoid process with its
cellular system and the Eustachian tube
(Fig. 4), all directly interconnected.
The tympanic cavity is a small chamber, about 1 cu cm !n size,
lying in the depth of the temporal bone, between the tympanic membrane and the internal ear. In front, through the Eustachian tube, the
tympanic cavity communicates with the
nasopharynx; behind, through the entrance }nto
the mastoid antrum (aditus ad antrum.
Fig. 4. Section
Showing Middle Ear 1) Eustachian tube; (2) tympanic cavity; (3) antrum; (4) mastoid cells
The tympanic cavity, similar to the cells of the mastoid process, contains air
coming through the Eustachian tube.
It is customary to divide the
tympanic cavity into three parts: the middle and
biggest part, mesotympanum, corresponding
to the pars tensa of the drum; the upper part, epitympanum,
lying above the former and also known as the epitympanic recess or attic; the lower part, hypotym-panum, lying below the drum level.
The tympanic cavity has six walls.
The roof of the tympanic
cavity is a thin plate of bone separating the
tympanic cavity from the middle cranial fossa
where the temporal lobe is situated. This plate often has congenital fissures through which vessels pass from the middle cranial fossa. These anatomical features may account for the meningeal symptoms
frequently observed in young children with
acute otitis media.
The inferior wall or floor
of the tympanic cavity is separated from the
jugular bulb by a fairly thick bony plate. Bone
fissures in this wall are rarely found.
The Eustachian tube begins with an opening in the anterior wall separating
the tympanic cavity from the internal
carotid canal.
An opening in the upper part of
the posterior wall leads to the mastoid
antrum (aditus ad antrum mastoideum).
The internal wall separates the tympanic cavity from the internal ear. It is marked by a gentle eminence, the *
promontory
(promontorium), corresponding to the
basalturn of the cochlea. Above
and behind the
promontoryis an oval window or the fenestra vestibuli which leadsinto the vestibule and is closed by the foot plate of the stapes. Behind and below the promontory in a niche is a round window or the fenestra cochlea which leads intothe cochlea, and is filled with a thin membrane, the secon dary ympanic membrane.
On the internal wall above the
oval window is a bony torus—the horizontal
part of the facial nerve canal. On reaching the
entrance to the antrum, the facial nerve
canal turns downwards to form a descending knee,
then passes behind the posterior wall of the auditory meatus and through the stylomastoid foramen
to the base of the skull. The walls of this bony
canal may be eroded; in such cases, the middle
ear mucosa may come through fissures into direct contact with the sheath of the facial nerve. This sometimes causes the development of facial paresis and paralysis in suppurative
otitis media. Somewhat behind and above
the facial nerve canal, on the inner wall of the
aditus ad antrum, lies the peak of the
horizontal semicircular canal the clear contour of which
serves for orientation in operations on the middle ear.
The external wall of the tympanic
cavity is formed by the tympanic membrane, and above
the drum—by the external bony wall of the
epitympanic recess or attic.
The tympanic cavity contains the
three auditory ossicles—the malleus, the incus and
the stapes (Fig. 5)—which are interconnected
by joints and ligaments to form a continuous and
rather flexible chain between the drum and the
oval window. The handle of the malleus is woven, as it were, into the
fibrous layer of the tympanic membrane, and
the foot plate of the stapes is fixed in the oval window by means of an annular ligament. The incus
lies between the malleus and the stapes. The whole system is kept in place by ligaments fastening the malleus
and incus to the walls of the tympanic cavity.
The tympanic muscles. There are two muscles in
the tympanic cavity: (1) The tensor
tympani muscle which stretches the
tympanic membrane. It lies in the bony canal above the Eustachian tube, and
is attached to the handle of the
malleus. (2) The stapedius muscle
which arises from the posterior wall
of the tympanic cavity and is
attached to the head of the stapes by a slender tendon. The tensor tympani is innervated by a branch of
the trigeminal nerve, and
the stapedius muscle by a branch of the facial nerve.
The Eustachian or auditory tube which is about
The mastoid process located just behind the external auditory meatus is a bony structure
protruding downwards with the sternocleidomastoid muscle attached to it. In young children, the mastoid process
is not fully developed and represents a bony
tubercle behind the osseous tympanic ring.
The upper border of the process is
the temporal line (linea temporalis), a bony torus which is a backward extension of the zygomatic process.
The floor of the middle cranial fossa usually
lies on a level with this line.
The anterior wall of the mastoid process is the posterior bony wall of the external auditory meatus.
Behind the spot where the superior wall of
the auditory meatus merges with the posterior wall, there is a small bony peak or the suprameatal spine (spina supra meatum) lying above the external auditory meatus. Behind
the spine there is a smooth depression, the mastoid fossa (fossa mastoidea). The suprameatal spine and the temporal line are important landmarks in surgical operations; the mastoid antrum (antrum
mastoideum) lies on the projection of the mastoid fossa (fossa mastoidea) in the
depth of the mastoid process.
The internal wall of the mastoid process abuts upon the
labyrinth, and more posteriorly is bordered by the post-cranial fossa. On the
surface facing the post-cranial fossa there
is a rather wide S-shaped groove, the sigmoid sulcus, containing part of the sigmoid sinus of the dura mater.
The central part of the mastoid process
is the antrum lying just behind the epitympanic recess. The antrum communicates with the tympanic
cavity and the air-filled cells of the mastoid process. The superior wall or roof of
the antrum separates it from the middle cranial fossa.
The following types of structure are to be found
in the mastoid process: the pneumatic or
large-celled, the diploic and the compact or "sclerotic". In the case
of pneumatic structures, the cavity of the mastoid process is divided by thin bony partitions into a lattice of larger and smaller cells. The diploic structure
has tiny cells resembling a diploetic bone;
the most frequent is the mixed form of mastoid structure where
smaller cells are to be found alongside bigger
ones. In compact structures the bone is indurated and the
cells are very few; this structure frequently occurs
as a result of chronic suppurative otitis media.
-The walls of the tympanic
cavity, antrum and mastoid cells are lined with a continuous thin mucosa
devoid of mucous glands. The mucous
membrane of the Eustachian tube and of
the adjoining part of the
tympanic cavity
floor is covered with ciliated columnar epithelium; the mucosa of the cartilaginous
part of the Eustachian tube contains mucous glands which are absent in the mucosa of the other parts
of the middle ear.
The middle ear is supplied with
blood mainly by branches of the external
carotid artery. Venous blood drainage from the middle
ear is maintained by the veins of the dura mater,
the venous sinuses and the venous plexuses round the carotid artery. Lymph
drainage is carried out in two ways: (1) through the
lymphatic vessels of the Eustachian tube to the retropharyngeal lymph
nodes and further to the deep cervical
glands; (2) through the lymphatic vessels across the
tympanic cavity to the lymphatic ducts of the external auditory meatus and
the lymph nodes in front of and behind the auricle.
The nerve supply of the middle ear is through branches of the glossopharyngeal, facial and sympathetic nerves.
Internal Ear or Labyrinth
The internal ear consists of
membranous and bony labyrinths, the latter
surrounding the former like a capsule. The
membranous labyrinth is filled with fluid known as endolymph, while around it and separating it from the bony shell is the spinal fluid known as perilymph.
The bony labyrinth is made up of
the vestibule, three semicircular canals
and the cochlea (Fig. 6).
The vestibule (vestibulum) lies
in the centre of the bony labyrinth on whose external wall is the oval window;
on the opposite, internal wall, there are two recesses for the two membranous sacs of the vestibule.
The front sac known as the saccule (sacculus) communicates with the membranous cochlea lying before the vestibule, while the rear sac or utricle (utriculus) is connected with the three membranous semicircular canals passing behind and above the vestibule. The intercommunicating sacs of the vestibule contain the statokinetic
receptors or maculae acusticae, otolithic organs made up of a highly-differentiated specific neuroepithelium covered with a membrane containing granules of carbonate and phosphorate of lime, i.e. the otoliths.
Fig. 6. Bony Labyrinth on Right
Side
(1; frontal semicircular canal; (?) ampulla of frontal semicircular
canal; (3) apex of cochlea; (4) medial turn
of cochlea; (5) apical turn of cochlea; (6) basal turn of cochlea; (7) round window; (8) oval window; (9) ampulla of
sagittal semicircular canal; (10) sagittal
semicircular canal; (11), (12) crura; (13)
ampulla of horizontal semicircular canal; crus commune
of frontal and sagittal semicircular canals
The semicircular canals are set at
right angles to each other and represent
the three planes of space. They are three in number: the external or
horizontal, the superior or frontal, and the
posterior or sagittal. One end of each canal
opens out into a larger space known as ampulla, the other
end is even. The frontal and sagittal canals have a
common even stem (crus commune).
The jynpulla of each membranous
canal contains a ridge. the crista ampullaris, which is a receptor, i.e. a nerve ending consisting ot a highly-differentiated neuroepithelium or hair and supporting cells.
The free surface of the hair cells
is covered with hairs which respond to the
slightest displacement or pressure of the
endolymph.
The receptors of the vestibule and
semicircular canals are the peripheral nerve endings
of the vestibular analysor.
Fig. 7. Organ of Corti (Schematic View)
(1) basilar membrane:
(2) tectorial membrane; (3), (4) hair
cells; (5) supporting cells; (6) nerve
fibres reaching hair cells
cate at the apex of the cochlea through a small opening known as the helicotrema Both channels
are filled with perilymph. ''
The scala vestibuli
communicates with the
vestibule, j while the scala tympani borders on
the tympanic cavity < through the round
window covered by the secondary tympanic membrane.
The scala vestibuli of the cochlea contains the thin Rei sner's membrane which
extends from the
osseous spirn lamina to cut off a small membranous canal of trianguli> section filled with endolymph and known as the cochles duct or ductus cochlearis.
The organ of Corti (Fig. 7.), a
complex receptive stru ture of the auditory
analyzor, rests on the basilar membrai (membrana basilaris), the lower wall of the ductus cochleii ris. The basilar membrane
is
an arrangement of elastu fibres of different lengths strung from the edge of the bony spiral lamina to the opposite, outer wall of the cochlea.
The organ of Corti has a very complex histological
structure containing hair cells and
supporting cells. The sensory cells covered
with hairs are situated in small groups between
the supporting cells. The cells are covered with a membrane called the tectorial membrane
(membrana tec-toria). The sensory hair cells are surrounded by a network of cochlear nerve
branches leading to the spiral ganglion of
the auditory nerve in the bony spiral lamina and further by intricate routes to the brain cortex.
PHYSIOLOGY OF THE ĹAR
The ear is one of the sense organs
by which man communicates with the outer world.
I.P. Pavlov's theory of the sense
organs presents them as analyzors, each
making up a single system of the following
components: (1) the peripheral part or receptors, i.e.
nerve endings adapted to respond to certain types of stimulation;
(2) nerve conductors to convey the impulse from the receptor; (3) a central
department in the brain cortex for a thorough
analysis of all stimuli and their transformation into sensations.
The ear performs two functions, the
first is hearing, and the other is
orientation in space and maintenance of equilibrium.
Auditory Function
The auditory function of the ear
consists in the conduction of sounds
through the external and middle ears.or cranial
bones"and their reception by the spiral organ of Corti, the receptor of the auditory analyzor. The external and middle ears make up the sound-conducting apparatus, whereas the internal ear, specifically, the organ of Corti, belongs to the sound-perceiving apparatus.
The auricle in man is of lesser
importance than in animals, and yet there is
no doubt that it plays a certain role in collecting
sounds and determining their direction.
The external auditory meatus conducts sound waves from the outer medium to the tympanic membrane. The mea-tal diameter has nothing to do with hearing acuity. Its atresia, however, as well as
its complete obstruction, as occurs in earwax impaction, hinders the passage of sound waves and considerably impairs the hearing.
Sound waves striking
the tympanic membrane
set it to vibration. The drum being onnected to the
handleof the malleus, these vibrations are transmitted
to the ossicular chain; and the foot
plate of the stapes, closing the oval window of the
labyrinth, rocks in and out of the oval window
according to the phase of sound vibrations. The vibration of the foot plate of the stapes in the oval window sets up vibrations in the perilymph. These
vibrations are transmitted to the basilar membrane and the organ of Corti which it supports.
The vibration of the basilar membrane causes the hair cells of the spiral organ of Corti to get in touch with the overhanging tectorial membrane. At
the same time, the mechanical energy of vibrations changes into the physiological process of nervous excitation which is conveyed to the most delicate receptors of the auditory nerve to be passed further to its nuclei in the medulla oblongata and through appropriate
canals to the cortical auditory centres in the temporal brain lobes where nervous impulses are interpreted as sounds heard.
The internal ear performs the most
important functions of the ear, because it is here
that sound perception takes place.
Normal hearing depends on the
normal condition of the apparatus for sound
perception and conduction.
The tension of the drum and the ossicular chain necessary
for normal sound conduction is maintained by the combined
action of the tympanic muscles. For normal vibration
the tympanic membrane requires a constant equilibrium
between air pressure in the middle ear cavity and in the outer air, that is on both sides of the drum. This is maintained by the passage of air through the Eustachian tube during swallowing.
Disturbance of air supply to the middle ear through the
Eustachian tube causes air in the middle ear to be sucked in and the drum to be indrawn, which is followed by deterioration of hearing. The normal condition of the sound-conducting apparatus is extremely important for the transmission of low tones to the labyrinth, that is, sounds with a low frequency of vibrations per second.
There are two ways of conducting sound waves to
the labyrinth: air conduction (through the external
auditory meatus, the tympanic membrane and the chain of ossicles) and bone conduction (directly through the cranial
bones and the stapes).
High tones, i.e. sounds of a high
vibration frequency per second, are easily conducted
to the labyrinth not only through the tympanic
membrane and the ossicular chain, but through the cranial bones and the stapes as well.
Man can hear external sounds with
a frequency of 16 to 20,000 cycles per second,,
The human ear can differentiate between
sounds of different pitch, intensity and timbre.
There are a number of theories which seek to
explain the essence of hearing and the ability of
the ear to differentiate between sounds. The oldest and most widespread among
them is the resonance theory advanced by Helmholtz in 1863 and based on the physical phenomenon of sympathetic vibration. According to this theory the fibres of the basilar membrane
vibrate in unison with sounds, similar to the action of
strings in certain musical instruments, such
as the piano or the harp. The short, thin and tighter fibres of the basilar membrane which lie in the basal turn of
the cochlea vibrate in unison, i.e. resonate when stimulated by a high tone,
whereas the longer, thicker and less taut
fibres in the apical turn of the cochlea resonate
in response to low tones.
There are a number of serious
objections to the resonance theory as it
oversimplifies the essence of hearing as a physiological process by describing it from the mechanical aspect alone, and fails to give a picture of the physiological properties of the auditory analyzor as a whole. It should be noted, however, that the localization of perception of high and low tones in the basal and apical cochlear turns
respectively, on which the resonance theory is based, has been confirmed by experiments and clinical observations.
In opposition to the resonance
theory so-called telephonic theory of hearing
asserts that the basilar membrane vibrates all over like a telephone membrane. It denies any analysis of sound being made in the peripheral receptor contained in the cochlea. This concept has been disproved by clinical practice and experimental research.
The first to prove beyond doubt that sounds of
different pitch are perceived in different
parts of the cochlea wasL.A. Andreyev by
experiments with conditioned reflexes made in I.P.
Pavlov's laboratory. The experiments were made on dogs which developed conditioned reflexes of salivation to tones of low, moderate and high frequency. After the reflex had been firmly established, the cochlea on one side was completely destroyed, and the animal retained its conditioned reflex. This was followed by a selective destruction of different parts of the cochlea.
Destruction of the cochlear apex with a thin drill caused disappearance of the conditioned reflex to low-pitched sounds, whereas destruction of the cochlear
base was followed by disappearance of the
reflex to high-pitched sounds. These experiments have
proved that an injury to the apical turn of the cochlea
causes loss of low tone perception, whereas an injury to the basal turn of the
cochlea is accompanied by loss of high tone
perception.
Thus, according to the teachings
of I.P. Pavlov and his followers, the
peripheral receptor of the auditory analyzor makes
a primary analysis of sound by converting the latter's
mechanical energy into the physiological process of nervous excitation. This, in turn, is conveyed through nerve canals to appropriate centres in the brain cortex where the nerve impulses are finally interpreted as sounds heard. I.P. Pavlov's teaching gives a clear idea of the functions of each part of the auditory analysor, thus presenting the latter's entire activity as a single physiological process.
The faculty of locating the origin
of sounds, the so-called ototopia depends
upon binaural hearing. It is largely lost in people with unilateral hearing, who have to turn their heads in various directions to locate the origin of sound. People with two healthy ears can easily determine the direction of sounds without turning their heads.
The ability to find the direction
of sounds is a function of the central
nervous system. If a sound comes from one side,
it arrives at the ear on the other side with an insignificant delay of 0.0006 sec.
This delay makes it possible to
'determine the direction of sound.
Orientation of the body and its
individual parts in space is made possible by
co-operation of many receptors. Apart from eye-sight,
the location of the body and its parts is identified
through nerve endings lying in the skin, as
well as in the muscles, joints and tendons, which are called proprioceptors.
In addition to the above-mentioned
receptors, the cerebellum and, above all, the vestibular apparatus perform an important function in body orientation and in maintaining equilibrium at rest and in motion. The vestibular apparatus consists of
the vestibule containing the otolith system and the semicircular canals with their ampullae containing the nerve endings of the vestibular
analysor.
The accelerations imparted to the
body during its movement in space are
adequate or specific stimulants for the nerve endings of the vestibular analyzor.
Movements along a straight line cause displacement of the otoliths and stimulate
the receptors of the otolith, or statolith, structure contained
in the vestibular sacs. Angular or
rotatory motions are followed by
displacement of the endolymph in the semicircular
canals and stimulation of receptors in the ampullae.
Stimulation of the receptors of
the vestibular analyzor produces a number of reflex reactions which cause a change in the tonus of some muscle
bundles of the torso, extremities, neck and
eyes. This, in turn, causes the whole body to change position and maintain balance.
One of the unconditioned reflexes
observed in stimulation of the semicircular canals is
nystagmus which consists in a rhythmic movement of
the eyes in a certain direction and back, such
as lateral and vertical nystagmus. Nystagmus may
be observed in different positions of the eyeball,
for example, in gazing straight ahead and in an extremely
side-long glance. The observation of nystagmus !S
used to assess the reaction of a stimulated vestibular
apparatus.
The role of the vestibular apparatus
becomes particularly apparent during an acute
disturbance or cessation of *ts function, which
occurs in some diseases. The patients suffer from
severe static and dynamic disorders: they
are unable to stand, walk and sit; they cannot
co-ordinate their movements, develop
spontaneous nystagmus, etc. This is accompanied by vertigo, nausea and vomiting. Three
to four weeks later these symptoms subside due to compensation from the central systems. A more or less intensive reaction
of the vestibular apparatus to adequate, i.e. specific, stimulation depends on the state of
the central nervous system, its higher division, the brain cortex, in particular.
This examination begins with collection
of data on the case, followed by inspection
of the ear and a functional examination of hearing. In
a complex examination nose
and throat, the latter
two are always be dealt with.
A case history must include an
account of the symptoms as described by the patient,
and the circumstances under which the
illness began.
In gathering this information attention should be paid to (a) ear pain and its character; (b) pus discharge; (c) deterioration of hearing or total deafness; (d) tinnitus; (e) dizziness. It is equally important to find out whether the patient complains of headaches, chills, etc. Among the numerous causes of ear diseases the most frequent are inflammations in the nose and throat which produce acute otitis media. Therefore, it is important to know if the ear disease in question was preceded by influenza, acute rhinitis, etc. Then general details should be obtained, i.e. information about the general state of health, past diseases, infectious ones in particular, working and housing conditions, and other facts relating to the everyday life of the patient. Examination of the ear includes an external examination and palpation of the ear and the mastoid process,
as well as inspection of the external auditory meatus and the tympanic
membrane (otoscopy).
-
Otoscopy
Examination of the external
auditory meatus and the tympanic
membrane, as well as the tympanic cavity when the drum is absent, requires artificial lighting and a head mirror (Fig. 9) to reflect the light into the ear and the ear speculum (Fig. 10). The best source of illumination is a 50 to 60 W frosted bulb; the head mirror is a round slightly concave mirror 8 to
head, to the right and a little behind, as shown in Fig. 8. The head mirror is so fixed before the examiner's left eye that the eye, the mirror hole and the ear under examination are in one straight line.
Both eyes are used when making an
otoscopic examination, the left eye necessarily
peering through the mirror hole. Before
inserting the ear speculum, one should examine the meatal opening and measure its diameter. Little children are examined with the aid of an assistant who keeps the child's head firmly pressed to his breast with one hand, and holds its arms with the other. The legs of the child are pressed between the legs of the assistant.
The ear speculum with its dilated
part held between the thumb and the forefinger is
carefully introduced into the meatal opening
with a gentle rotation to a depth of 1 to
be given to the posterosuperior wall to detect possible thickenings and even considerable overhangings extending downwards and outwards.
It is possible to examine the ear
without the aid of artificial lighting only
in cases of a sufficiently wide and fairly
straight auditory meatus. To avoid
obstructing the light with his own head, the
doctor should be at some distance from the
patient, although ear details will not be
seen so clearly.
The normal drum is an oval disc of
a pearly grey colour on which the following landmarks are clearly visible (Fig.
3, coloured Table I, Fig. 1). A whitish-yellow
knob, the size of a pin-head, projecting
from the anterosuperior part of the drum is the short
process of the malleus. Two grey-isk-white
streaks extending backwards and forwards from
it are the anterior and posterior folds separating the anterosuperior part of the drum, the pars flaccida of Shrap-nell, from the lower tense part, the pars tensa. From the short process the handle of the malleus can be seen extending downwards and backwards. Its broader lower end terminates at the centre of the drum, the umbo.
At otoscopy, the light rays from the mirror form on the drum a brilliant cone-shaped
light reflex with the top pointed to the centre (umbo) and the base facing
the anteroinferior edge of the tympanic membrane.
For convenience, in describing
changes on the tympanic membrane, the-latter
is divided into four quadrants (Fig. 3) by an
imaginary line extending the malleus handle to the
edge of the drum and by an intersecting line drawn at right angles to the first through the centre of the umbo; thus forming
the anterosuperior, anteroinferior, posterosuperior
and posteroinferior quadrants. The drum is very closely connected with the tympanic cavity; therefore, it will reflect any existing morbid condition of the middle ear. Thus, a change in colour, for
instance, redness of the drum, indicates otitis media. Changes in location of the landmarks, the light cone in particular, manifest themselves in cases of drum retraction resulting from chronic diseases of
the middle ear.
The mobility of the drum may be tested by the use of a pneumatic speculum (Fig. 11). The dilated end of this speculum is hermetically sealed with a lens, and a tube branching from
its side is attached to a rubber bulb. To facilitate observance of drum mobility through the lens, the speculum is tightly fitted into the auditory meatus, the air being alternately
compressed and rarefied with the rubber bulb,
causing the drum to move in and out. At otoscopy the examination begins with the
healthy ear in order to compare it with its diseased counterpart.
Examination of the Auditory Function
Fig. 12. Noise-box |
The functional examination of hearing is made by means of whisper and conversation voice, tuning forks and audiometers. The whisper test should be carried out in a quiet room of
adequate size. Each ear is examined separately, while the other ear is closed with a finger tip. The patient turns the ear to be tested to the examiner so that he does not see the letter's face and cannot guess his words by watch- ing the lip movements. The whisper should always be of the same intensity obtained by breathing out effortlessly and using the residual air to call out words.
The normal ear can hear whispered speech with a
prevalence of low tones, i.e. consonants, labial and
palatal sounds, b, p, t, m, n, at a distance of 5 to
been compiled by V.I. Voyachek. The first group of words primarily contains low sounds heard at a distance of
By using this table one may roughly determine the nature of the ear disease. A poor perception of words of the first group (low tones) will indicate a defect in the sound-conducting apparatus, i.e. conduction deafness. Impaired hearing of words from the second group (high tones) will point to a lesion in the sound-perceiving apparatus, i.e. nerve deafness. If whispered speech is heard at a di- stance of 6 to
Other methods of excluding the
normal ear, such as rubbing the pinna with
the flat of the open hand or shaking the finger plugging the auditory canal are less
reliable.
Tuning fork tests. Hearing
acuity is determined by the whisper test
with comparative ease and quickness. But the differential diagnosis between the conduction and perception types of deafness, as well as a more accurate
determination of hearing acuity is
made by using tuning forks (Fig. 13).
The tuning fork produces a clear tone without overtones. The human ear can hear in a sound range of 16 to 20,000 cycles per sec. The highest and lowest
tones perceptible to the human ear
indicate the higher and lower limits
of hearing respectively. The tones heard between the upper and lower limits of hearing make up the so-called audible range or register. This range
decreases noticeably with age, mostly
due to reduction of the upper limit
of hearing. A set of tuning forks can be used to examine hearing acuity for
different tones, from 64 to 4,096 cycles
per sec, as well as to determine air and bone conduction. To estimate air conduction, a sounding
tuning fork is held near the meatal
opening. When bone conduction is being determined, a sounding tuning fork is
placed on the head or the mastoid process. In normal hearing air conduction is better than bone conduction. In
medical practice, bone and air conduction is examined only with two tuning forks, of the types C128 and
C'2i048. The following experiments
can help in a differential diagnosis between the conduction and
perception types of
deafness.
The Weber test of
sound lateralisation (Fig. 14a). A C128 tuning fork is" sounded and placed on the vertex, and the patient is asked to say in which ear the sound is
heard best. In case of conduction
deafness, such as caused by earwax impaction in the auditory meatus or otitis
media, the sound will be best
heard in the diseased ear. In the event
of nerve deafness, the tuning fork will be best heard in the normal ear.
^" The Rinne tesi or
comparison between bone and air conduction (Fig.
14b). When_a sounding C3La8JLuningjfork applied to the mastoid process"
can no longer beTTeanT, it~is~hil(rto the_ear; it then appears Jhat_the_soiind is heard longer byair Conduction than by ~bone~conduction. normally for &1) to 90 sec compared~"to 45 sec in the casejii
Bone conduction. In such
circumstances^—the~^lnnltest is considered
positive (Rinne+); a positive Rinne is observed
in patients with normal hearing, as well as in those with
nerve deafness, jn conduction deafness the jiutalion of bone_conduction_inay_^e_gaual to thatof air conduction or~even~exceed~it^considerablY, in Iwhich_"caseTEiIIBinna test~Ts~coBsidered Taegative (Rinne —).
The Schwabach
test compares the duration of bone conduction
from the vertex or the mastoid process of
the patient with the normal bone conduction of the
examiner. In conduction deafness, bone
conduction is lengthened, whereas in nerve
deafness it is shortened.
The acuity of hearing for high
tones is determined with a G4
tuning fork of 2,048 cycles per sec. A certain high tone loss is noticeable in deafness due to old age and in nerve deafness.
A more accurate and quicker examination of hearing is made with a special instrument called the audiometerwhich
can be used to estimate hearing acuity within the entire
tone range important in the estimation of hearing.
Examination of tho
Vestibular Fiinrtinn
Examination of the vestibular function
is preceded by questioning and examining the
patient. Patients with vestibular
disturbances usually complain of giddiness, unstready gait, as well as occasional sickness and vomiting. Examination of the patient may reveal a nystagmus often associated with a functional vestibular disturbance.
Vestibular nystagmus may be
observed in a patient looking sideways and sometimes
in a patient staring straight ahead. Disorders in
co-ordination, static equilibrium and balance of walking
are also likely to
happen. Special clinical tests are used to examine the vestibular function. These tests are based on procedures for artificial
stimulation of the vestibular receptors to produce
nystagmus. There are three basic tests of this kind, the rotation, caloric and compression tests.
The rotation test involves
turning the patient's body around the vertical axis to cause endolymph
movements in the semicircular canals, which stimulate the receptors and produce
nystagmus. The patient is seated in a chair
(Fig. 15) which can be rotated horizontally and is revolved at a speed of 10 revolutions in 20 sec. This stirs up the endolymph in the semicircular canals.
When the chair is stopped abruptly after rotation to the right, the patient will have
leftward nystagmus; Fig. 15. Rotating Chair if the
procedure is reversed the
nystagmus will be in the opposite direction. So
that the nystagmus may be studied, the patient is
directed to look at the examiner's finger,
which is held at a distance of
In most people with normal vestibular sensitivity the duration of post-rotational nystagmus is, on the average, 30 to 35 sec. Among the disadvantages of this test is that rotation stimulates both labyrinths, though with unequal force.
The caloric test is based
on the phenomenon of endolymph movement in the
semicircular canals under the effect of cooling or heating by artificial means.
During this test each labyrinth is
examined separately. Each ear in turn is
syringed with water; a cold douche at 16° to 30
°G causes nystagmus to the side away from the ear being tested, whereas a warm douche at 38° to 41 °C causes nystagmus in the opposite
direction.
Absence of nystagmus in the
caloric test may indicate a loss
of vestibular sensitivity.
In case of dry perforation one
should abstain from the caloric test for fear
of provoking a relapse of suppurative otitis.
Some pathological conditions of
the labyrinth are likely to produce a
nystagmus caused by air compression or rarefaction in the auditory canal. This is known as the compression test. If there is a fistula
or a bone defect in a labyrinth wall (external
semicircular canal), the air compressed with a bulb
in the auditory meatus causes nystagmus towards the diseased ear, whereas aspiration produces nystagmus to the opposite side. This phenomenon is called the fistular
symptom.