Effects of head injury on olfaction and taste.

Traumatic events such as motor vehicle accidents, falls, or assaults can lead to dysfunction in olfaction or gustation. Mechanisms of posttraumatic olfactory dysfunction include direct injury to the sinonasal tract or olfactory epithelium, shearing effect on olfactory fibers at the cribriform plate, or brain contusion or intraparenchymal hemorrhage. Posttraumatic gustatory dysfunction is rare, but may occur as a result of direct injury to the tongue, injury to cranial nerves VII or IX, or brain contusion or hemorrhage. Evaluation of head-injured patients presenting with olfactory or gustatory complaints should include a thorough history, including assessment for pre-and posttraumatic chemosensory dysfunction and potential mechanisms of injury, complete head and neck examination including nasal endoscopy and cranial nerve testing, and focused radiographic imaging, usually CT of the sinuses and skull base. Formal olfactory and gustatory testing may be performed using various techniques, although in cases potentially involving litigation, methodologies able to detect malingering should be used. Treatable causes of chemosensory disturbance, most notably conductive olfactory losses caused by chronic rhinosinusitis or nasal obstruction, should be ruled out. In the event of neurosensory deficits, recovery may occur up to 12 to 18 months after the traumatic event. All patients should be counseled regarding the risks of their chemosensory deficits, and given suggestions for appropriate compensatory strategies.