The varieties of junctional scotoma: 17 cases, a review, and a taxonomy

The hemi-decussation at the optic chiasm creates the potential for crossed and uncrossed fibers to be affected in isolation or in various combinations of nerve, chiasm and tract, with patterns that reflect the retinotopic arrangement of axons. We present seventeen cases that illustrate the field defects that can result and review the literature to create a taxonomy of junctional visual field defects. The complete junction defect is blindness in one eye and loss of the entire temporal field of the other. The classic junctional scotoma combines optic neuropathy in one eye with upper temporal hemifield loss in the other, and is often a sign of ventral compression. The less frequent atypical junctional scotoma involves the lower temporal hemifield and has a higher frequency of dorsal compression or non-compressive pathology. There are the monocular defects in the temporal ('junctional scotoma of Traquair') or nasal hemifield, the latter of which is rarely if ever due to a pituitary adenoma. Highly asymmetric bitemporal defects with or without a central scotoma and the paradoxical junctional scotoma occur by extension of the lesion causing the junctional scotoma of Traquair. The posterior junction defect results from combined damage to the optic chiasm and optic tract. Recognizing these various patterns is important clinically as junctional defects have the same localizing significance as bitemporal defects and are being encountered more often. In addition the probability of certain types of pathology varies with the type of junctional defect.