Long-term follow-up of olfactory loss secondary to head trauma and upper respiratory tract infection.

OBJECTIVE: To determine the extent to which olfactory function can improve after loss induced by head trauma or a previous upper respiratory tract infection (URI) and the time for this improvement for more effective patient counseling.
DESIGN: Patients initially evaluated at the University of Cincinnati (Ohio) Taste and Smell Center were reevaluated for olfactory loss with the University of Pennsylvania (Philadelphia) Smell Identification Test 1 to 5 years after initial testing. Changes in score on this test were used to indicate improvement in sensory function. Subjective information on olfactory ability and olfactory symptoms was also collected.
SETTING: University-based tertiary care center. PATIENTS AND OTHER PARTICIPANTS: Forty-one patients with olfactory loss induced by head trauma (20) or previous URI (21).
RESULTS: Seven (35%) of 20 patients with head trauma improved on the smell test by 4 points or more. Fourteen of 21 (67%) patients with a previous URI had improved scores of this magnitude or more. A statistically significant correlation was noted between the amounts of improvement and length of follow-up for URI patients. Thirteen of these patients also reported improved olfactory function.
CONCLUSION: These findings for patients with head trauma are consistent with other reports of recovery of (or improvement in) olfactory function after trauma-induced loss. For patients with previous URI, these data indicate that improvement in olfactory function occurs, but the improvement may take several years.