external and middle ear

Otorhinolaryngology

Lec: 15
Objectives
1-Describe types of otitis externa
2-describe impacted ear wax
3- describe anatomy of middle ear

Otitis Externa Malignans (Malignant otitis externa):

Definition: A pseudomonas infection (occasionally caused by S. aureus), not infrequently fatal, occurring in elderly diabetic patients and in immuno-suppressed patients (patients with AIDS, leukemia, on steroids or chemotherapy, renal failure).

Pathology: The infection starts in the meatus usually at the junction of bony and cartilaginous portions, there is necrotic cartilage and granulations of the junction of bony and cartilaginous meatus. The infection may:
Spread to adjacent bone causing osteitis or osteomyelitis.
Spread to stylomastoid foramen → facial n. paralysis.
Spread to region of jugular foremen → paralysis of IX, X, XI, XII cranial nerves.
Spread to petrous apex → paralysis of V and VI cranial nerves.
Intracranial spread causing meningitis and sigmoid sinus thrombosis.

Clinical features:

Severe aural pain.
Purulent discharge.
Granulation tissue in the floor of the meatus.
Cranial nerves paralysis including V, VI, VII, IX, X, XI and XII cranial nerves.


Investigations:
Fasting blood sugar.
Ear swab for C/S.
CT scan and MRI to show bone destruction and spread of infection.

Treatment: Must be combined both medical and surgical:

1-Medical:
Control the diabetes.
Antibiotic oral ciprofloxacin 1.5 g/day for 3 months; Topical anti-pseudomonas e.g. ciprofloxacin or gentamicin drops.
Analgesia.
2-Surgical :
Removal of granulations

Prognosis: Early Treatment is essential because the condition may be fatal.

Eczematous otitis externa:
Definition: Allergic dermatitis of skin of the external ear.
Aetiology:
General: inhalation and food allergy.
Local: known as contact dermatitis e.g. local antibiotic like neomycin, allergy to infective organisms like bacteria or fungal infection.


Clinical features:
Itching;
Redness;
Oedema;
Vesicles →
Serous discharge.

Treatment:

Remove the allergic cause;
Cleaning of ear canal;
Topical steroid cream;
Systemic antihistamine to the relieve itching;
Treatment of secondary infection (when present).

Seborrhoeic Dermatitis:

Definition: A greasy, scaling and crusting condition of skin of external ear.
Aetiology: may be due to:
Abnormal quality and quantity of sebum and wax;
Pityrosporum.

Clinical features: Greasy yellow scales affect the scalp, postauricular sulcus, below ear lobule and ear canal.
Treatment:
Cleaning of ear canal (aural toilet);
Washing the scalp with selenium sulphide and ketoconazole containing shampoos;
Salicylic acid and sulphur 2% cream.


Neurodermatitis:
It is psychosomatic condition characterized by irritation. Constant scratching may cause lichenification of skin and introduce secondary bacterial infection.

Treatment:

Bandage the ear to prevent scratching;
Topical steroid to relieve irritation;
Treatment of secondary infection;
Treatment of underlying psychological disturbances.

General Principles in Treatment of Otitis Externa

1- Advise the patients to avoid getting water in the ear e.g. by using protective ear mounds.
2- Cleaning of ear canal by suction or mopping (NEVER USE SYRINGING)
3- Duration of treatment in otitis externa is at least for one week after resolution because of tendency to recurrence particularly in otomycosis.

Keratosis Obturans:

A keratotic mass of desquamating squamous epithelium is found in the bony portion of external auditory meatus due to faulty migration of squamous epithelium from the outer surface of tympanic membrane and the adjacent canal wall. It may be associated with bronchiectasis and sinusitis.

Clinically there are:

Conductive deafness;
Pain due to bone erosion;



The mass appear pearly white and glistening.
Treatment:
Removal of the keratotic mass (may be under general anaesthesia);
Regular follow-up because recurrence is expected and may be prevented by using sodium bicarbonate ear drops or by using salicylic acid 2% in alcohol.

Wax (cerumen):

Wax is a mixture of the secretions of the ceruminous glands, pilosebaceous glands and desquamated epithelium. These glands are situated only in the skin of the cartilaginous portion of the canal. Normally the wax is excelled outward from the canal (aided by jaw movements). There are two phenotypes of wax:
1-Wet phenotype: It is moist honey-colored (in Caucasians and Negroes).
2-Dry phenotype: It is brittle grey (In Mongoloid races).

Impacted Wax: Impacted wax may be due to:

Excessive wax formation;
Retention by stiff hairs;
Canal stenosis.

Clinical features:

Conductive deafness (main feature);
Tinnitus;
Earache;
Vertigo;
Reflex cough through stimulation of auricular branch of vagus n.


Treatment:
Syringing with water at body temperature used to remove soft wax.
Suction is the safest way to remove wax when there is history of tympanic membrane perforation. Suction used to remove soft, not hard wax.
Removal with ring probe, hook and forceps when there is hard wax.
Ceruminolytics like sodium bicarbonate can be used to soften the wax.

Syringing is used to remove soft wax, when the wax is hard it can be softened by instillation of sodium tricarbonate ear drop 5% for 2-3 days before syringing every 2 hours, then syringing is done.

Procedure of syringing

The pinna is pulled upwards, outward, and backwards to straighten the meatus. Normal saline at 37°C is used as the irrigating solution. A special syringe made of stainless steel is used for syringing. The stream of irrigating solution should be directed onto the roof or posterior wall of the meatus so that it passes around the wax plug forcing it outwards by pressure from behind. Syringing directly onto the mass of wax will tend to impact the wax more deeply and may cause tympanic membrane perforation. Pain, vertigo and tinge of blood in the fluid coming out of the meatus are features of tympanic membrane perforation and when it occurs we should stop the procedure.

Contra-indications of syringing:

Presence of tympanic membrane perforation or history of tympanic membrane perforation.
Previous ear surgery.
Presence of middle ear disease.
An only hearing ear.
History of otitis externa following previous syringing.
Young children.
Non-occlusive ear wax.


Risks of ear syringing:
Failure to remove the wax;
Development of otitis externa;
Tympanic membrane perforation;
Trauma to external auditory canal;
Pain;
Vertigo;
Damage to ossicles and inner ear (rare).

Foreign Bodies in the Ear

Aetiology:
Through external auditory meatus e.g. child putting a stone in the external auditory canal.
Penetrating trauma.
Surgery e.g. grommet (ventilation tube put through myringotomy in the tympanic membrane) after extrusion from the tympanic membrane may lodge in the external auditory canal and sometimes it may be missed in the middle ear.

Site of foreign bodies: Usually the foreign body is found just lateral to the constriction of the junction of cartilaginous and bony portions of external auditory canal, sometimes the foreign bodies may pass through the constriction to deep bony portion of the canal or ever through the tympanic membrane into the middle ear or even to inner ear.

Types of foreign bodies:

1-Inanimate:
Organic e.g. piece of paper, vegetable foreign bodies,
Inorganic: e.g. metallic foreign bodies, plastic foreign bodies.
2-Animate foreign bodies e.g. insects enter the external auditory canal.


Pathology:
Inorganic foreign body does not cause much inflammation, while organic foreign bodies causing inflammation and infection with oedema of the ear canal and discharge.
Alkaline button batteries causing extensive liquefactive necrosis and needs urgent removal.
In the external auditory canal, foreign body may cause trauma of the skin of the canal, infection of the skin of the canal i.e. otitis externa.
Foreign body may cause tympanic membrane perforation. In the middle ear may cause dislocation or fracture of ossicles and secondary infection of middle ear i.e. otitis media. Foreign body causing ossicular dislocation and displacement of stapes → rupture of oval window membrane → leakage of perilymph from inner ear (inner ear damage) → sensori-neural deafness, vertigo and tinnitus. Labyrinthitis which is infection of the inner ear occurs as a result of foreign body.

Clinical features: More common in young children

1-Asymptomatic
2-Symptomatic → includes:
Otalgia
Bleeding
Deafness
Vertigo
O/E → the foreign body will usually be seen in the external auditory canal.

Treatment:

Removal of foreign bodies and the methods include:
A strong magnet → for ferrous foreign bodies.
Suction → for vegetable foreign bodies.
Syringing → can be used to remove insects "the insect can be killed before syringing by spirit drops into the meatus".
Syringing should not be used to remove vegetable foreign bodies because they swell on-syringing causing more impaction.
Hook or probe → for round foreign bodies. The probe is passed above and beyond the foreign body and then withdrawn outward.
Forceps → to remove foreign bodies which are not rounded.
Post-aural incision → sometimes needed to remove foreign bodies that cannot be removed by the above methods.


Surgical Anatomy of Middle Ear Cleft:
The middle ear cleft consists of:
Tympanic cavity.
Eustachian tube.
Mastoid antrum and mastoid air cell system.

1-Tympanic cavity:

It is biconcave disc-shaped cavity within temporal bone. The tympanic cavity is thought of as a box with 4 walls, a roof and a floor.






A-The lateral wall of tympanic cavity: The tympanic membrane forms the central portion of the lateral wall, above and below the tympanic membrane, the lateral wall is formed by bone. Tympanic membrane is pearly grey in colour, oval in shape and lies obliquely. Tympanic membrane consists of 3 layers:
Outer epithelial layer.
Middle fibrous layer.
Inner mucosal layer.










Tympanic membrane is divided by the anterior and posterior mallelar folds into part above the folds called pars flaccida, and part below the folds called pars tensa. The 3 layers of tympanic membrane are present in pars tensa but the middle fibrous layer is not present in pars flaccida. The circumference of pars tensa is thickened into fibro-cartilage called tympanic annulus which sits in a bony groove of tympanic bone called tympanic sulcus.
The edge of pars flaccida does not form tympanic annulus & there is no tympanic sulcus in the tympanic bone around the pars called notch of Rivinus. The anterior and posterior malleolar folds extend from the anterior and posterior ends of notch of Rivinus respectively to lateral process of malleus. The handle of malleus descends downwards and posteriorly between the inner mucosal and middle fibrous layers of tympanic membrane. The lowest point of the handle of malleus called Umbo, from the Umbo a cone of light extends downwards and forwards when the tympanic membrane is seen by otoscopy.
B-The roof of tympanic cavity (Tegmen tympani) is formed by petrous & small part of squamous temporal bone; it separates the tympanic cavity from middle cranial fossa.
C-The floor of tympanic cavity is formed by thin plate of bone separate the tympanic cavity from the jugular bulb.
D-The anterior wall of tympanic cavity: The lower part of anterior Wall is thin plate of bone separate the cavity from internal carotid artery, above it is the opening of Eustachian tube and above it is the canal for tensor tympani muscle.
E-The posterior wall of tympanic cavity: In its upper part has the aditus (irregular hole connects the tympanic cavity attic (tympanic cavity is divided into: 1. Upper part called attic; 2. Lower part called hypotympanum; & 3. Middle part called mesotympanum) to mastoid antrum. Below the aditus is a small depression called fossa incudis which houses the short process of incus and its ligament. Below fossa incudis a conical projection called pyramid which contains the stapedius muscle which is inserted into the stapes neck. The facial n. which passes in the medial wall of tympanic cavity posterior to oval window it bends at a second genu to run vertically through the posterior wall.
F-The medial wall of tympanic cavity: The medial wall separates the tympanic cavity from inner ear. The promontory is a rounded elevation occupying the central portion of the medial wall; it has small grooves on its surface for nerves of tympanic plexus. The promontory covers the basal coil of cochlea. Behind and above the promontory lies the oval window which is closed by stapes foot plate and it's an annular ligament and it separates the tympanic cavity from scala vestibuli of inner ear. Below and behind the oval window lies the round window which is closed by round window membrane and separates the tympanic cavity from scala tympani of inner ear.

The processus cochleariformis which is curved projection of bone lies in the anterior and superior part of the medial wall in front of point of entry of facial nerve from the inner ear to medial wall of tympanic cavity. The processus cochleariformis houses the tendon of tensor tympani (supplied by mandibular branch of Vth cranial and arise from the bony canal above the Eustachian tube) which then bends at right angle and passes laterally to be inserted into the medial aspect of the upper end of malleus handle.
The facial nerve passes in a bony canal from the inner ear to enter the medial wall of tympanic cavity just behind the processus cochleariformis and then bends posteriorly (1st genu) and passes above the promontory and oval window, at the posterior end of oval window it bends in a second genu to pass vertically in the posterior wall of tympanic cavity In the tympanic cavity the facial n. gives rise to chorda tympani nerve and nerve to stapedius muscle.
The epithelial lining of tympanic cavity is of columnar epithelium but it becomes cuboidal epithelium in postero-superior part of the cavity and finally becomes flattened, single layer epithelium in mastoid antrum.
The tympanic cavity contains 3 ossicles, 2 muscles and 2 nerves.


Ossicles
(1) Malleus (2) incus (3) stapes.
Malleus is the largest ossicle, consist of head, neck, lateral and anterior processes and handle. The handle descends between the inner mucosal and middle fibrous layers of tympanic membrane. The head has in its postero-medial surface a facet to articulate with the incus.



Incus has body, short and long processes. The body articulate with head of malleus, the short process projects from the body backwards and attached to fossa incudis by a ligament. The long process descends downwards and its tip directed medially (lenticular process) to articulate with head of stapes.
The stapes consist of head, neck, two crura and foot plate. The head articulates with lenticular process of incus, the foot plate lies in the oval window and attached to the bony margin by annular ligament.

Muscles

Stapedius muscle.
Tensor tympani muscle (described previously).

Nerves

Chorda tympani.
Tympanic plexus found on promontory and formed by tympanic branch of glossopharyngeal nerve and carotico tympanic nerves arise from sympathetic plexus around internal carotid artery. This plexus supply the mucosa of tympanic cavity, Eustachian tube and mastoid antrum.