Walsh & Hoyt: Topical Diagnosis of Optic Tract Lesions

Although lesions of the optic tracts are infrequently recognized, they are of great importance because they represent the first region beyond the optic chiasm where lesions produce a homonymous field defect. Common causes are tumor, vascular processes, demyelinating disease, and trauma. In his series of 100 consecutive homonymous hemianopias, Smith found only 3 that he attributed to a lesion of the optic tract. His criteria were extreme incongruity, a negative optokinetic response, a Behrs pupil (inequality of the pupils with the larger pupil on the side of the hemianopia), and evidence of neurologic disease in neighboring structures. Fujino et al. reported 16 patients with lesions referable to the optic tract among their 140 patients with homonymous hemianopia. The causes were vascular in five, tumor in four, and miscellaneous in seven. Savino et al. examined 21 patients who were thought to have lesions of the optic tract. The etiologies were primarily tumors, although one patient had demyelinating disease and two patients had suffered trauma.