Unilateral vocal cord paralysis causes contralateral false-positive positron emission tomography scans of the larynx

Positron emission tomography (PET) is used in the management of head and neck cancers. It identifies tissue with increased metabolic activity and is not specific for malignancy. A false-positive PET scan of the larynx is associated with vocal cord paralysis. We reviewed PET scan reports of patients with lung cancer from 1998 to 2001 to identify patients with increased 18-fluoro-2-deoxyglucose uptake in the larynx without a known history of head and neck cancer and then correlated this increased uptake with laryngoscopic findings. There were 17 patients who had a positive PET finding in the larynx. Fifteen of those had a false-positive PET scan in the larynx. All had contralateral vocal cord paralysis. Two patients were noted to have head and neck cancer. We conclude that vocal cord paralysis can cause a false-positive PET scan on the contralateral side of the larynx due to overactivity of laryngeal muscles that compensate for the paralyzed cord.