[1] Mid Atlantic Brain & Spine Inst, Annandale, VA USA
[2] George Washington Univ, Med Ctr, Washington, DC 20037 USA
[3] Univ British Columbia, Vancouver Hosp Hlth Sci Ctr, Vancouver, BC V5Z 1M9, Canada
[4] Casa Sollievo Sofferenza Hosp, Ist Ric & Cura Carattere Sci, Dept Neurosurg, San Giovanni Rotondo, Italy