Normal variations in size and neoplastic changes of skull foramina

Operability of head and neck cancers is usually limited by extension to the base of the skull. Intracranial extension occurs by tumor growth along the perineurium of cranial nerves and along blood vessels or by direct bone erosion. Skull involvement usually is determined by radiologic evidence of destruction or enlargement of skull foramina. Of particular importance to the head and neck surgeon are those foramina that serve as possible conduits for intracranial extension of cancers of the maxillary and ethmoid sinuses, nasopharynx, palate, and face. Not infrequently disparity in size from the contralateral foramina, or absence of a particular foramina, will be interpreted as substantial evidence of intracranial tumor extension. The purpose of this study was to determine within individuals the normal diameter variations between pairs of the foramen ovale, foramen rotundum, pterygoid canal, and infraorbital canal. One hundred fifty tomograms of the anterior skull area were studied and classified into tumor and non‐tumor groups. The frequency of nonvisualization and the range of normal size of each foramina were recorded.