Cervical myelography and posterior fossa examinations with amipaque: use of magnification and subtraction.

Metrizamide (Amipaque) was introduced via a modified C1--C2 puncture with the patient in the oblique position to study the cervical spine and posterior fossa. Biplane magnification and subtraction were employed. Results were excellent and reproducible. Subtraction is needed to evaluate the cerebellopontine angles, where both sides can be examined using a single puncture.