The base view in vertebral angiography. An aid in the diagnosis of extraaxial cerebellopontine angle tumors.

Though the advent of computed tomography has improved the detection of posterior fossa lesions, there are times when it can not be used to differentiate between an intra- and extraaxial lesion, particularly when the mass is anteriorly located. Base view angiography can be used to make this distinction, accurately localize the lesion, and demonstrate involvement or compression of vital adjoining structures.