Three-dimensional relationships of the optic radiation

This study examined the relationship of the optic radiation to the landmarks important in temporal lobe surgery. The optic radiation was dissected by applying Klingler's fiber dissection technique to 20 formalin-fixed human hemispheres. The dissections were performed with the operating microscope and imaged in three-dimensional photographs. Several measures quantified the relationship of the radiation to reliable surgical landmarks. In all specimens, the anterior loop of the radiation extended to the anterior tip of the roof of the temporal horn. The anterior edge of the optic radiation was located an average of 25 mm (range, 22-30 mm) behind the temporal pole. The optic radiation extended an average of 5 mm (range, 3-6 mm) anterior to the hippocampus head and 22 mm (range, 20-25 mm) anterior to the anterior edge of the lateral geniculate body. The optic radiation also extended an average of 2 mm (range, 1-3 mm) anterior to the tip of the temporal horn. The relationships of the optic radiation to important surgical landmarks are discussed. The optic radiation reached the anterior tip of the temporal horn. Resections that extend through the roof of the temporal horn more than 3 cm behind the temporal pole cross the anterior loop of the optic radiation.