18F-DOPA PET/CT unravels malignant paraganglioma mimicking temporomandibular joint disorder.

This report presents a 29-year-old patient with severe temporomandibular joint (TMJ) pain. Anamnesis and clinical examination led us to the diagnosis of TMJ disorder. He was also in control for a malignant paraganglioma originating from the right carotid body. After initial surgery 8.5 years ago and the removal of metastases 2 years ago he was deemed disease free. An (18)F-3,4-dihydroxyphenylalanine (DOPA) positron emission tomography (PET)/CT scan was obtained during follow-up 6 months before he was presented to our clinic. Suspicious of a connection between the actual pain and the tumour, we scrutinized these images. We found a tiny pathological tracer uptake in the right jugular foramen but no correlating finding in the matching CT. We repeated the DOPA PET/CT and found several metastases including the previously detected lesion. Further thin-slice CT and MRI showed a 5 mm paraganglioma located anteriorly to the jugular bulb within the jugular foramen. The lesion was in close relation to the Arnold's nerve, a branch of the vagus nerve which carries sensory information from the external tympanic membrane, external auditory canal and the external ear and explained the severe pain in our patient. He then underwent radiotherapy (45 Gy) during which the pain diminished considerably. In a variety of neuroendocrine tumours, including paraganglioma, DOPA PET/CT allows primary diagnosis, staging and restaging with a higher detection rate than conventional radiological imaging. Owing to low anatomical resolution however, high resolution contrast-enhanced CT and MRI are necessary to complete the investigations.