Perineural spread of cancer to the skull base

Perineural spread, is a well recognized but poorly understand phenomenon that has been described in mucosal and cutaneous cancer of the head and neck. Perineural spread can be a portal of entry for head and neck cancer to the central nervous system. This usually occurs through the foramina at the cranial base. Failure to detect perineural involvement prior to treatment can have significant consequences on the outcome of oncologic therapy. High resolution imaging including CT and MRI is important in this respect, although an optimum modality with a high degree of sensitivity and specificity is still lacking. This study evaluates the sensitivity and specificity of CT and MRI in detecting perineural spread in head and neck cancer/skull base tumors. The surgical specimens of 26 patients were thoroughly examined by one pathologist for the presence of perineural spread in large named nerves. A total of 37 nerves were examined and perineural spread was detected in 24 (65%). The pre-operative imaging studies (CT/MRI) were then reviewed retrospectively by one head and neck radiologist who was unaware of the pathology report. Radiological evidence of perineural spread was considered to be present if there was widening of bony foramina on CT and/or enhancement of named nerves on MRJ. The sensitivity and specificity of CT scans in detecting perineural spread is 87% and 89% respectively. MRI had a higher sensitivity ( 100%) and specificity (92%).