Blast injury to the tympanic membrane.

On March 23, 2005, a large explosion at a petroleum refining facility in South Texas killed 15 individuals. An 18-year-old man who had been inside a shed approximately 100 yards from the blast sustained head trauma but survived. His right ear had been facing the direction of the explosion, and he incurred a penetrating injury just below the right angle of the mandible from flying debris. The trauma resulted in a delayed palsy of the mandibular division of the facial nerve.

The man presented to our office 1 week later complaining of a transient high-pitched tinnitus in the right ear. Examination of the right tympanic membrane revealed that some subepithelial blood vessels had ruptured and thrombosed (figure). Prominent vessels could be seen coursing along the handle of the malleus and the superior external auditory canal wall. Similar submucosal hemorrhages were noted outside the ear, primarily over the mucosa of the right lateral pharyngeal wall and the right soft palate. The left tympanic membrane and left pharyngeal wall were spared. Audiometric evaluation demonstrated an isolated 30-dB sensorineural heating loss at 4 kHz. The tinnitus resolved spontaneously over the ensuing few months.

[FIGURE OMITTED]

It can be hypothesized that the explosive wave of compression and rarefaction resulted in the rupture of the small blood vessels on the side facing the blast, but those on the other side were protected by the acoustic shadow of the skull. The blast did not rupture the tympanic membrane, but it appeared to have caused a permanent threshold shift at 4 kHz.

From the Department of Otolaryngology--Head and Neck Surgery, University of Texas Health Science Center at Houston.

Arun K. Gadre, MD