Pathogenesis

Drainage from the ear can originate from a variety of sources. It is convenient to categorize the pathogenesis of this disorder according to the etiology. By far, the most common cause of otorrhea is infectious in etiology. In this category, acute bacterial infections of the external and middle ear are very common causes of ear drainage. Fungal infections of the external ear can also be common in certain environments or after aggressive treatment of a bacterial infection. While ear drainage most often is caused by common external and middle-ear bacteria, immunocompromised individuals can manifest otorrhea from infectious agents not commonly present in patients with healthy immune systems. In these individuals, a diligent search for the causative agent is critical in achieving a satisfactory outcome. Associated with the infectious causes is tympanostomy tube drainage, which can occur in a significant percentage of individuals who undergo the procedure (1,2). After bacterial infections, the next most common pathogenesis of otorrhea is a group of disorders that we categorize as allergic dermatitis. Once again, the frequency of these disorders is dependent on the environment and patient population. While allergy has been implicated as a major cause of ear drainage, the link may be difficult to prove in individual patients. Irritants, however, show a clear relationship and can range from hairspray to over-aggressive digitalization (or Q-tipping) of the ear. Finally, there is a group of "other disorders" that is largely composed of systemic disorders that may manifest with otorrhea. The most well known, but certainly not the only disorder in this class, is Wegener's granulomatosis (Chapter 8). Diagnosis of these disorders is critical, since systemic complications may be associated and the ear drainage may be the first sign of a more serious systemic disorder.

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