Acute mastoiditis

Acute mastoiditis is typically a disease of children, and may complicate neglected acute or chronic otitis media. It is rare where primary care is good. In babies, it occasionally presents as a swelling over the mastoid process.

If acute mastoiditis complicates acute otitis media (uncommon), the child continues to have fever, and his ear continues to discharge pus in increasing quantity through a perforation in his drum.

If acute mastoiditis complicates chronic otitis media, the patient has: (1) A dull nagging pain; this may either be a new pain, or an increase in an old pain. (2) Increasing discharge; he is so used to a discharge anyway, that he does not usually complain about this. (3) Increasing deafness. Chronic otitis media will already have made him deaf, and he may not notice that his deafness has been getting worse. (4) Tenderness over his mastoid process. (5) Sometimes, oedema of the skin over his mastoid process, due to underlying infection, giving it a ''velvety feel'. (6) A swelling in the posterosuperior wall of his meatus. (7) Anterior rotation of his pinna, so that his ear sticks out more on the affected side than on the normal one. This is a very characteristic sign, and should make you suspect the diagnosis, as you see him walking through the outpatient department; it can however also be caused by a swollen postauricular lymph node, by a meatal boil, or by cellulitis of his scalp.

Four operations are possible: (1) If pus has gathered under his periosteum you can simply open this and drain the pus. (2) You can open his mastoid cortex to allow pus to drain. (3) You can remove all the cortex overlying his mastoid antrum, and saucerize the opening, by removing some or all of the air cells of his mastoid (cortical mastoidectomy). Depending on how many air cells you open, this is potentially much more dangerous than simply opening his mastoid cortex[md]his dura, his sigmoid sinus, and his 7th nerve are all at risk. (4) If he has chronic mastoiditis, an expert can do a radical mastoidectomy.

Fig. 25-3 CORTICAL MASTOIDECTOMY. A, the incision behind a child's pinna, showing the approximate position of his antrum. B, the surface of his bone has been cleared. This diagram also shows the surface markings of his mastoid antrum, the area to be cleared, and the danger area where his lateral sinus is closest to the surface, and thus in the greatest danger of being injured. Gouge away from it towards his external auditory meatus. C, the surface of his temporal bone has been chipped away and the more superficial air cells cleared. Note that his cleaned out antrum is the deepest part of the wound. His lateral sinus is more at risk lower down.

ACUTE MASTOIDITIS X-RAYS are seldom necessary. Normal mastoids differ greatly in the number of air cells they contain, so compare both sides for differences in density and structure. The early sign is diffuse haziness of the cells. After about 2 weeks the bony septa between them break down.

If a mastoid is sclerotic and its air cells poorly developed, suspect that the mastoiditis is acute-on-chronic. This makes mastoidectomy less urgent, which is fortunate, because it is more difficult.

THE DIFFERENTIAL DIAGNOSIS includes inflammation of the postauricular node, a boil in the patient's external auditory canal, and inspissated wax in his ear.

Suggesting mastoiditis, no pain on pulling his ear. Pain on deep pressure over the upper part of his mastoid at 11 o'clock in relation to his right external auditory meatus. Don't test for tenderness over the tip of his mastoid. A profuse mucopurulent discharge, a swelling on the inner bony part of his meatus at 11 or 12 o'clock, marked middle ear (conductive) deafness, and cloudy mastoid air cells on the X-ray.

CAUTION ! The mastoid is always tender during the first few days of an attack of otitis media, before the drum has burst. Only diagnose acute mastoiditis, when tenderness and fever appear in a patient who has had a discharge for several weeks (mastoiditis is uncommon in acute otitis media).

Suggesting postauricular lymphadenitis and swelling of the tissues round it[md]some septic lesion on his scalp or neck, particularly infected ringworm or impetigo, or following lice in his scalp; his pinna may be pushed forwards; no discharge or deafness, a normal drum. Swollen lymph nodes are usually at 8 or 9 o'clock in relation to his right ear, whereas the swelling of mastoiditis is at maximal at about 11 o'clock.

Suggesting a boil (furuncle) in his external auditory meatus (25.3, rare in a child)[md]swelling in the outer cartilaginous part of his meatus, and his mastoid is not tender. His hearing is diminished if his meatus is blocked, but becomes normal if you are able to open it by pulling his pinna upwards and backwards. Pain on pulling his ear and on chewing, a history of other boils, thick scanty discharge. If you can see his drum, it is normal. If the boil is on the posterior wall of his meatus, his pinna may be pushed forwards. X-rays show a normal mastoid.

DRAINING THE PERIOSTEUM [s7]FOR ACUTE MASTOIDITIS If pus has already found its way to the surface of his mastoid, and is lying under his periosteum, there is no need to do a cortical mastoidectomy. Incise the skin and periosteum close behind his ear as in A, Fig. 25-3, but stop there. Insert a drain for a few days. If his infection does not resolve, deeper drainage or cortical mastoidectomy will be necessary.

DRAINING THE MASTOID CORTEX [s7]FOR ACUTE MASTOIDITIS If you cannot refer him and do not feel able to do a cortical mastoidectomy, be content with draining his mastoid cavity. This could be life-saving! Incise behind his ear, as described below, and open his periosteum[md]there may be pus under it. Then use a gouge to open the cortex of the bone for about 1 cm, and expose some of his mastoid air cells, which will be full of pus. Dress the wound as described below.

CORTICAL MASTOIDECTOMY [s7]FOR ACUTE MASTOIDITIS INDICATIONS. Acute mastoiditis. Draining the mastoid is not quite the urgent operation that it was in the days before antibiotics, so give them and try to refer him. If you cannot refer him, give him antibiotics for 2 to 4 days, and operate when his infection has settled a little. His mastoid must be drained soon, to reduce the risk of infection spreading to cause thrombophlebitis of his lateral sinus, or a brain abscess.

ANTIBIOTICS are necessary. The most suitable ones are likely to be chloramphenicol with metronidazole.

THE EQUIPMENT includes bone gouges and a mallet, a periosteal elevator, a self retaining retractor, a headlight and suction (both essential), curettes (preferably Collier and Morris), and bone wax (3.1) to control bleeding.

CAUTION ! Use a gouge; the angle of a chisel is more likely to enter his dura or his lateral sinus.

ANAESTHESIA. (1) Ketamine (A 8.1). (2) General anaesthesia (A 10.1).

INCISION. Shave the hair behind his ear. Lay him on his back, with his head on a sandbag, turned towards the other side. Put two towels under his head, and fold the upper one round it. Feel for the site of his suprameatal triangle, just inferior to the posterior end of his zygomatic process. Make a curved incision about 0.5 cm behind his pinna, and following the same curve. Start it just beyond his zygomatic process superiorly, and extend it just beyond the tip of his mastoid inferiorly.

CAUTION ! (1) Don't extend the incision beyond the tip of an infant's mastoid, because his facial nerve is very superficial just there, and you may cut it. There is no real mastoid tip in a baby; the incision must be high. (2) Don't include his temporalis muscle in the upper part of the incision, because it will bleed unnecessarily.

Deepen the incision down to the bone. You will see his temporalis muscle at the upper end of the wound, and his sternomastoid at the lower end. Use a periosteal elevator to raise them both, with his periosteum. Elevate his periosteum forwards, as far as the lateral end of his posterior bony meatal wall, backwards for a few millimetres, and upwards with his temporalis muscle, to the level of the upper attachment of his pinna. Expose a wide enough area of bone to identify the following three landmarks:

(1) Henle's spine, at the junction of the superior and posterior bony walls of the meatus. Define the edge of the canal carefully, and you will find this spine. It overlies the entrance to the mastoid antrum, which lies about 12 mm below the surface in an adult: follow the posterior meatal wall inwards to find it.

(2) The suprameatal ridge, which is a posterior prolongation of the zygomatic process, and marks the lower limit of the dura of his middle fossa.

(3) His antrum lies under a well-defined pitted triangle, the suprameatal (MacEwen's) triangle (C, Fig. 25-2) formed: (a) Superiorly by his suprameatal ridge (and the superior tangent of his external auditory meatus); (b) Anteriorly by an oblique tangential line across his posterior meatal wall at the spine of Henle; and (c) Posteriorly, by a vertical tangent to the posterior wall of his meatus.

Insert a self-retaining retractor to keep the flaps away from the field of operation, and to help control bleeding.

Remove the cortex of his mastoid with a gouge and hammer in the directions shown in E, Fig. 25-2. Remove chips of bone little by little. Chip forwards towards his external auditory meatus, away from the place where his lateral sinus is nearest the surface. If you chip too far backwards, you will enter it. Start working widely and shallowly with the largest gouge, and gradually deepen the cavity with smaller ones, until you reach his antrum. The bone usually changes colour as you reach it. You may have to chip away quite a lot of bone. If pus is working its way to the surface, his antrum will be easier to find.

CAUTION ! (1) As long as you keep below the superior tangent of his external auditory meatus, you will be safe. There is not always a very clear depression in the suprameatal triangle, but if you work into its centre behind Henle's spine, you will reach the antrum. (2) Remember that the antrum lies about 12 mm deep in a adult, but is only a few millimetres deep in an infant. (3) If you reach his dura, STOP! Don't remove any more bone, or you may damage it. If you do, you may cause meningitis, or uncontrollable bleeding from his lateral sinus. (4) Take special care not to damage the medial, or the anteromedial, wall of his antrum, because you may damage his lateral semicircular canal, or his facial nerve. (5) Remember that the tip of the long process of his incus is in the floor of the entrance to his antrum[nd]don't disturb it. (6) Preserve his posterior meatal wall, and don't dissect the skin from it.

As soon as you remove the cortex of his temporal bone, pus may flow from his mastoid air cells. Use swabs and a curette to carefully remove all pus, granulation tissue, and loose pieces of necrotic bone from his antrum and mastoid air cells. Chip and scrape away bone containing air cells, including his antrum, which is the deepest area to be cleaned.

Make the bony cavity saucer-shaped, so that the flaps will fall into it and obliterate it. Syringe it with warm saline, insert a corrugated drain, and start to shorten this after 48 hours.