The sensitivity and specificity of high-resolution imaging in evaluating perineural spread of adenoid cystic carcinoma to the skull base

Objective: To evaluate the sensitivity and specificity of computed tomography (CT) and magnetic resonance imaging (MRI) in detecting perineural spread (PNS) of adenoid cystic carcinoma of the head and neck to the skull base. Design: Adenoid cystic carcinoma of the head and neck frequently exhibits PNS across the skull base. Failure to detect PNS before treatment can have significant negative consequences on the planning and outcome of therapy. High-resolution CT, MRI, or both are used to evaluate the presence of PNS; however, their accuracy in detecting perineural involvement has not yet been determined. Patients: Twenty-six consecutive patients with adenoid cystic carcinoma, who were treated with cranial base resection, were included in this study. The surgical resection specimens of all patients were thoroughly examined by 1 pathologist for the presence of PNS along cranial nerves or their named branches. A total of 38 nerves were examined, and PNS was defined as the presence of tumor in the perineural or endoneural space. The results of the preoperative imaging studies (CT and/or MRI) were then reviewed retrospectively by 1 head and neck radiologist, who was unaware of the pathology report. Radiological evidence of PNS was considered to be present on CT, MRI, or both if nerves showed evidence of thickening (regardless of enhancement), contrast enhancement (regardless of size), or widening of their bony foramina or canals. Results: Histopathologic evidence of PNS was present in 25 (66%) of 38 named nerves. The sensitivity and specificity of CT in detecting PNS were 88% and 89%, respectively. Magnetic resonance imaging had a higher sensitivity (100%) and specificity (85%). Conclusions: Perineural spread across the skull base is a frequent occurrence in patients with adenoid cystic carcinoma of the head and neck. Magnetic resonance imaging has a higher sensitivity and specificity than CT in detecting PNS along the base of the skull.