Timing is everything in corticospinal tract recovery after stroke.

results imply some transient retention of the toxinsecreting stem cells. Unfortunately, the investigators were unable to detect viable stem cells in the resection cavity after 72 hours by bioluminescence. Many potential agents against glioblastoma will be challenged by drug stability and poor blood-brain barrier permeability. Using neural stem cells to secrete tailored tumorspecific toxins or other biological agents within the resection cavity in direct contact with residual tumor may help overcome these obstacles. Although there are significant barriers to the clinical use of either autologous or nonautologous neural stem cells for the treatment of glioblastoma, Stuckey and colleagues present important in vivo evidence of the feasibility of engineering neural stem cells to secrete targeted cytotoxins that affect tumor progression. Alexander J. Gamble, DO* John A. Boockvar, MD*‡ *Feinstein Institute for Medical Research Manhasset, New York ‡Lenox Hill Hospital New York, New York