Olfactory dysfunction in patients with head trauma
R. L. Doty, D. M. Yousem, L. T. Pham, A. A. Kreshak, R. Geckle and W. W. Lee
Department of Otorhinolaryngology-Head and Neck Surgery, University of Pennsylvania Medical Center, Philadelphia, USA.
BACKGROUND: The ability to smell is commonly altered by head trauma (HT).
However, the nature, prevalence, prognosis, and etiology of such
alterations are poorly understood. OBJECTIVES: To quantitatively determine
the degree of olfactory function in patients with HT-related chemosensory
complaints and to examine the influences of age, sex, HT severity, time
since HT, and other variables on such function. Also, to use quantitative
magnetic resonance imaging (MRI) to establish whether and to what degree
damage to the olfactory bulbs and tracts, frontal lobes, and temporal lobes
occurs. PATIENTS AND METHODS: Two hundred sixty-eight patients with HT from
the University of Pennsylvania Smell and Taste Center, Philadelphia, were
administered a quantitative odor identification test, a depression
inventory, and a medical history questionnaire; 66 were retested after
individual test-retest periods ranging from 1 month to 13 years. The volume
of olfactory-related brain structures was determined in 15 patients and 15
controls using MRI. RESULTS: One hundred seventy-nine patients (66.8%) had
anosmia, 55 (20.5%) had microsmia, and 34 (12.7%) had normosmia. Frontal
impacts produced less dysfunction than back or side impacts. Of the 66
retested patients, 24 (36%) improved slightly, 30 (45%) had no change, and
12 (18%) worsened; only 3 patients, none of whom initially had anosmia,
regained normal olfactory function. Trauma severity was related to
olfactory test scores in patients with microsmia. Parosmia prevalence
decreased from 41.1% to 15.4% over an 8-year posttrauma period. Olfactory
bulb and tract volumes of male, but not female, patients with HT were
greatly reduced relative to volumes of controls. CONCLUSIONS: Patients
complaining of HT-related olfactory dysfunction typically have anosmia and
rarely regain normal olfactory ability, parosmia prevalence decreases over
time in such patients, and damage to olfaction-related brain structures can
be observed in most such patients using an appropriate MRI protocol.
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