Infection of the mastoid process, a protrusion of the temporal bone of the skill, is known as mastoiditis. One of the most common causes is a result of a middle ear infection (otitis media) which spreads to the skull bone if left untreated or is severe. Most of these infections are bacterial in nature and can be effectively treated with antibiotics. However, if the desired results cannot be achieved then surgery may be necessary. The most commonly performed procedures in the treatment of mastoiditis are myringotomy and mastoidectomy.
Myringotomy for Mastoiditis
Myringotomy is a minor surgical procedure performed by cutting into the tympanic membrane (eardrum) to allow pus to drain out. The incision is usually semilunar in shape. The procedure is usually performed under general anesthesia in children while it may be done under local or general anesthesia in adults. The pus that has accumulated in the middle ear is drained through the incision and a small tube is placed through the incision. The patient is usually discharged on the same day.
Post-operatively the ear discharge should be mopped clean daily. Water should not be allowed to enter the ear for at least one week. The incision heals naturally without any sutures and the tube falls out with in a period of 12 to 18 months. Complications of myringotomy include injury to the middle ear bones, profuse bleeding from injury to the jugular bulb, and introduction new infection to the middle ear.
Mastoidectomy is surgical removal of the diseased and destroyed portions of the mastoid process. The indications for mastoidectomy in connection with mastoid bone infection include :
- acute mastoiditis which is not responding to the medication
- the presence of a cholesteatoma
- other complications of mastoiditis
- occult mastoiditis in the children
- chronic middle ear infection with persistent ear discharge
Mastoidectomy is also done in other situations like complicated middle ear infections, tumours like acoustic neuroma and in procedures related to cochlear implantation.
A thorough examination of the external ear, the auditory canal, the eardrum, and the middle ear is carried out before the procedure. The assessment of the facial nerve functioning and hearing is usually performed before the procedure. The hair behind the affected ear is shaved when the patient is prepared for the surgery.
The surgery can be done under local anesthesia or general anesthesia. The surgery is usually done using a post-auricular or retroauricular approach in which the skin incision for mastoidectomy is usually made about 1 centimeter behind the ear by pulling the external ear anteriorly. The diseased mastoid air cells and any cholesteotoma present are drilled and removed using burrs during the surgery.
Types of mastoidectomy
Canal wall down mastoidectomy is a type of mastoidectomy in which the back (posterior) wall of the external ear canal is removed. The removal of the back wall combines the ear canal and the mastoid process to form a single cavity. In severe cases the ear drum and the bones of the middle ear are also removed. This is also called radical mastoidectomy.
A canal wall down mastoidectomy in which the ear drum and the middle ear bones are not removed or in situations where it is reconstructed is called a modified radical mastoidectomy. The canal wall down mastoidectomy has several disadvantages like the requirement of frequent ear canal cleanings, the restriction on exposure of ear to water and the hearing loss.
Mastoidectomy is associated with complications like hearing loss, weakness of face (facial nerve injury), tinnitus, vertigo, bleeding, abnormalities in taste sensation, residual cholesteatoma, persistent ear discharge and recurrence of the infection.
Mastoid Infection Complications
Mastoiditis can potentially lead to life threatening complications due to the close proximity to vital structures. Even death can occur from the complications of mastoiditis and the children are at a greater risk of developing serious complications. The complications include :
- Abscess formation at different locations due to the spread of infection to the neighbouring tissues.
- Postauricular abscess refers to pus formation over the mastoid process. The pinna of the ear will be displaced forwards, outwards and downwards.
- Zygomatic abscess is spread of pus to the zygomatic air spaces of the zygoma bone. The swelling appears in front of the pinna of ear and may be associated with the edema of eyelids.
- Bezold abscess is tracking down of the pus from mastoid antrum to the upper part of the neck, either near the sternocleidomastoid muscle, angle of the jaw, near the carotid blood vessels or into the spaces on the either sides of pharynx. Patients present with fever, pain, swelling in the neck and with head tilt (torticollis).
- Citelli’s abscess is spread of pus from the posterior part of mastoid bone towards the occipital bone.Extradural abscess: Extradural abscess is collection of pus between the duramater (outermost membranous layer covering the brain) and the skull.
- Subdural abscess is the collection of pus between the duramater and the arachnoid mater (inner membranous layer covering the brain).
- Brain abscess is characterized by the collection of pus within the brain. The patients with brain abscess can present with fever, chills and rigors, motor and sensory disturbances, altered state of consciousness, visual, speech and auditory disturbances, ataxia and seizures.
- Parapharyngeal and retropharyngeal abscess
- Inflammation of labyrinths
- Facial nerve paralysis
- Hearing loss which may be conductive type of deafness initially may later become sensoryneural type with the involvement of 8th cranial nerve as part of disease progression.
- Petrositis results from the spread of inflammation to the pertrous part of temporal bone. It characterised by the classical triad of ear discharge, deep seated pain behind the eye balls and paralysis of the lateral rectus muscle of the eye due to involvement of the 6th cranial nerve.
- Thromobphlebitis of lateral sinus which is the inflammation of the lateral venous sinus and associated thrombus formation is characterised by very severe headache, fever with chills and rigor, edema of posterior end of mastoid process and anemia.
- Hydrocephalus can result from progressive inflammation of the lateral sinus and is characterised by obstruction to the absorption of CSF at the arachnoid villi and hence there will be disproportionate increase in the CSF pressure, edema of the optic disc (papilledema) and nystagmus.