The diagnosis of acute otitis media is made via clinical means. Both visual otoscopy and pneumatic insufflation should be used to document this diagnosis. Tympanometry and/or acoustic reflectometry are not routinely required for the diagnosis of AOM.
Acute otitis media is frequently overdiagnosed in the pediatric population. The tympanic membranes may normally appear red secondary to a vigorously crying patient and be falsely diagnosed as AOM. A significant number of AOM cases will have an opaque, yellow appearing tympanic membrane rather than frank erythema. Careful visual otoscopy and gentle insufflation can help eliminate the problem of overdiagnosing AOM.
In addition to examination of the ears, the physical examination should document the absence of mastoid tenderness and nuchal rigidity.
The various tympanic membrane appearances in AOM are dependent upon several factors, most importantly, elapsed time since the onset of the infection. Isaacson has shown (with some rather beautiful photographs of his son's developing AOM) the progression of middle ear changes found in a treated case of acute otitis media. As might be expected, there are only minimal changes early in the course of the illness (slight vascular engorgement) four hours after onset of ear pain. Approximately eight hours into the illness, the tympanic membrane begins to show changes consistent with positive pressure (slight bulge) but remains normal to insufflation. 24 hours after onset of symptoms, vascular engorgement progresses and negative pressure (TM retracted) is noted. An effusion is present three days into the course of the illness and is essentially resolved by day six.