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Olfactory impairment may indicate traumatic brain injury

Abnormal olfactory performance could be predictive of traumatic brain injuries prior to neuroimaging, according to a recently publish study in Neurology.

“The presence of measureable abnormalities with central olfactory dysfunction provides added value to the practicing physician for preclinical detection of intracranial injury, and accordingly, subsequent disease-modifying early interventions. When considering whether to order advanced neuroimaging, a functional disturbance with central olfactory impairment should be regarded as an important tool to inform the decision process,” Air Force Col. Michael S. Xydakis, MD, MS, from otorhinolaryngology/head and neck surgery at Walter Reed National Military Medical Center, Bethesda, and colleagues wrote.

Michael S. Xydakis

Researchers evaluated 231 polytrauma inpatients – U.S. service members acutely injured during combat in either Iraq or Afghanistan (TBI Group) and a demographically comparable blast-injured control group – requiring immediate evacuation to Washington, D.C. for care. Patients’ olfactometric scores were compared with their contemporaneous neuroimaging findings and clinical diagnoses of traumatic brain injury (TBI).

Results indicated that olfactometric scores were better predictors of abnormal neuroimaging than chance alone (area under the curve = 0.78; 95% CI, 0.7-0.87). In all troops with mild TBI and controls, normosmia was present. Compared with injuries in other brain regions, patients displaying radiographic evidence of frontal lobe injuries were 3 times more likely to have olfactory impairment (RR = 3; 95% CI, 0.98-9.14).

All patients that were available for follow-up showed normalized olfactory scores.

Researchers noted that while there is limited sensitivity in quantitative identification of olfactometry for TBI injuries, the high specificity as a marker for detection of acute structural neuropathology from trauma should be considered.

“Getting a CT scan in a combat zone is often the equivalent distance of placing a soldier in a helicopter in Washington, D.C., and sending them to Boston. It requires a significant investment in personnel and aviation resources; not to mention flying over hostile terrain. Using abnormalities with the sensory systems has opened up an entirely new avenue of investigation for diagnosing brain injuries,” Xydakis said in a press release. – by Casey Hower

Disclosure: The researchers report no relevant financial disclosures.