18F-FDG PET, contrast CT and MRI to comprehensively diagnose and assess rare perineural spread of squamous cell carcinoma to the greater auricular nerve

We present a case of a 78-year-old male with a primary parotid squamous cell carcinoma which spread via the left facial, trigeminal and greater auricular nerves. The patient presented with left facial droop and paraesthesia. Initial MRI scans demonstrated involvement of the trigeminal and facial nerves with no sign of a primary lesion. Abnormal enhancement within the left parotid substance on FDG PET-CT demonstrated the primary malignancy which was confirmed on histology by core biopsy. There was also focal avidity along the course of the left greater auricular nerve consistent with perineural infiltration, extending from the posterior aspect of the parotid to the left cervical plexus at C2/C3. To our knowledge, this is the second case of squamous cell carcinoma perineural spread to the greater auricular nerve imaged on FDG PET-CT scanning. This case highlights the importance of multimodality imaging correlation in the workup of primary head and neck malignancies and associated perineural spread, which is essential in adjuvant radiation therapy planning to reduce local recurrence, improve prognosis and overall survival.