Otitis externa is an inflammatory condition, usually self-limiting, of the external auditory canal(EAC). It is commonly seen in primary care because it affects all age group. Summertime increase in incidence are due to water exposure in swimming and related activities. Otitis externa can be either diffuse or circumscribed, acute or chronic, or can have eczematous feature. Rarely, it can progress to necrotizing or malignant otitis externa in diabetics or other immunocompromised patient, leading to serious illness, cranial nerve palsies, or even death. Risk factors include trauma to external auditory canal, swimming or moisture exposure, use of hearing aid, and predisposing skin disorders, such as eczema, seborrhea, or psoriasis.
I. Clinical presentation
Symptoms
The most frequently described symptoms are itching, purulent discharge, otalgia, plugging of the ear, mild hearing loss , ear fullness, and tinnitus.
Signs
On examination, there is pinnal tenderness, an erythematous and edematous external auditory canal, and a discharge. Pinnal eczema is often present.
II Diagnosis
Acute otitis externa
It is usually infectious in origin, with Staphylococcus aureus or Pseudomonas aeruginosa being the most common isolates. Fungi, such as Aspergillus, Candida and other, have also been implicated. Anaerobes may also play a role. Culture in acute otitis should be reserved for therapeutic failure because most cases response to the first line therapy. Non infectious causes such as contact dermatitis, eczema, psoriasis, or trauma should be sought.
Chronic otitis
Chronic otitis is defined by symptoms lasting longer than 2 month. Similar etiologies to acute otitis are seen, but chronic otitis may be due to failure to diagnose and treat the correct pathogen initially. Predisposing factor remain important to consider.
Necrotizing or "malignant" external otitis !
This is a rare but important infection seen most commonly in elderly diabetics. Sever ear pain and systemic signs and symptoms may be present along with cranial nerve palsies. If not detected early and treated aggressively, this condition may progress to skull base osteomyelitis with possible erosion to the CNS. Pseudomonas is the most common pathogen.
