Direct L5 dorsal root ganglion (DRG) application of sodium fluorescein results in very limited spread to the ipsilateral DRGs. When sodium fluorescein was applied onto the L5 DRG at 25 to 30 μl and the intensity of fluorescein epifluorescence was assessed 30 min later, we noted a lack of labelling in the L3 DRG (A). Although there was some epifluorescence detected in the ipsilateral L4 DRG (B), substantially higher level of labelling was noted in the L5 DRG (C). Importantly, there was no spillage into the corresponding segment of the spinal cord (D) shown as the complete absence of epifluorescence (image magnification of all tissue slices was ×5).