'Doctor, my ear is blocked'--when to panic.

There are very few ear-related emergencies in ENT; however, when the eardrum appears normal, an innocuously sounding 'blocked ear' may just be one. The causes of a blocked ear may be divided into three broad categories: (i) arising from the ear (otological); (ii) arising from other adjacent head and neck structures (nonotological); and (iii) idiopathic.

Otological causes

Otological causes are described logically by following the anatomy of the ear from the external to the middle to the inner ear.

Anything that physically blocks or compromises the conduction of sound waves to the eardrum will cause a blocked sensation. Wax, a foreign body, squamous debris in the ear canal and swelling of the canal due to otitis externa are common causes. It is interesting that even what seems on inspection to be a minute amount of wax can induce this blockage. It is particularly the case when the wax lies on the inferior aspect of the canal or is in contact with the tympanic membrane. Ear drops that precipitate can form a visible membrane on the tympanic membrane and compromise its movement. Otitis externa is mainly due to mechanical trauma (finger or pen scratching) or chemical trauma (swimming--water). The significant pain and canal swelling with abundant discharge and squamous debris blocks the ear.

A perforation of the eardrum, barotrauma or haemotympanum due to trauma, sudden shock waves or inadequate equalisation often leads to a blocked ear. A further cause of a conductive hearing loss is ossicular chain disruption after trauma. Middle-ear fluid may be serous, mucoid, glue like or purulent in acute and chronic otitis media and even contain CSF (after trauma). These conditions lead to conductive hearing loss and are often treatable and reversible.

Nerve (sensorineural) hearing loss is a highly significant cause of a blocked ear sensation and it is vital to recognise it immediately when the onset is acute. This hearing loss, particularly in the low frequencies, is interpreted by the patient as either a blocked feeling, sensation of wax, or foreign body in the ear. Patients who develop sudden sensorineural hearing loss (SSNHL) which is caused by a viral inflammation of the cochlea are surprisingly well and have no associated symptoms such as pyrexia, rash, or dizziness. Herpes simplex type 1 is implicated. Otoscopy is absolutely unremarkable. A patient with a 'normal' examination is not commonly sent for an audiogram and only if tuning fork testing with the Rinne and Weber tests is used, will a diagnosis of hearing loss be made. Unfortunately this is not done by many doctors. The drum looks normal and commonly a diagnosis of eustachian tube dysfunction is made. Topical and systemic decongestants and even antibiotics are prescribed and sadly the diagnosis and opportunity for reversible treatment are missed. Herpes zoster is implicated in rare cases and typical zoster vesicles appear in the ear canal and on the eardrum. Nausea, vomiting and dizziness may be present only if the vestibular system is involved (complete labyrinthitis). This makes the diagnosis easier.

There is level 2 evidence of a good chance of recovery of the hearing loss if treatment for SSNHL is given within 24 hours and perhaps within 1 week of onset. If treatment is withheld, the hearing loss will be permanent in 50-60% of patients. High-dose corticosteroids (60-100 mg/ day) are used for 5-10 days. There is no good evidence that the addition of antiviral agents improves the outcome. However, when faced with the prospect of permanent deafness, many doctors will add antivirals for 5 days. Vascular aetiologies have been implicated but not proven. There is a range of therapeutic modalities available, none of which are evidence based. These include carbogen (combination of 95% oxygen and 5% carbon dioxide) to improve blood supply to the cochlea, vasodilators, haemodilution, anticoagulants, and homoeopathic and herbal remedies.

Ototoxic medications, e.g. chemotherapeutic agents (e.g. Cisplatin), antiinflammatories, and aminoglycoside antibiotics, will affect hearing. Rarer causes of SSNHL are tumours of the 8th cranial nerve (acoustic neuromas) and brain tumours.

Non-otological causes

It is essential to consider adjacent structures in the head and neck when the eardrum appears normal and no otological cause can be found. The temporomandibular joint (TMJ) lies immediately anterior and adjacent to the external ear canal and is separated by a thin bony wall and capsule. Inflammation in this joint is often referred to the ear, causing a 'blocked ear' sensation. Common causes are trauma to the jaw, malocclusion, new dentures, bruxism and excessive clenching, and recent extensive dental work with patient's jaw open for a lengthy time. The ligaments in the jaw joint are supplied by the same cranial nerve as that which supplies the two tiniest ligaments in the body, i.e. stapedial tendon and tensor tympani muscle. These two middle-ear tendons retract the eardrum and stapes to dampen sound and block loud noise. With TMJ ligament and tendon spasm, this can induce spasm in these two middle-ear tendons, leading to a blocked ear sensation. Impacted wisdom teeth and other related dental problems may refer to the ear. Oral and hypopharyngeal lesions can also refer to the ear.

Neck spasm, whiplash injury and recent cervical spine surgery can all cause a referred blocked feeling in the ipsilateral ear that should also be considered.

Summary

When the eardrum and otological examination appear normal and the patient is surprisingly well, you should have a high index of suspicion of a SSNHL. If you are unable to use tuning forks, urgently refer to an audiologist for a hearing test. You will have a very grateful and relieved patient if you confirm your early diagnosis and institute immediate treatment.

PETER FRIEDLAND, MB BCh, FCS (SA) (Otol), MMed (Otol), Diploma Financial Management

Associate Professor, Department ENT Head Neck and Skull Base Surgery, Sir Charles Gairdner Hospital and Ear Science Centre, School of Surgery, University of Western Australia, and Co-Director Research, Ear Science Institute of Australia

E-mail: [e-mail]