[1] Louisiana State Univ, Dept Anesthesiol, Dept Pharmacol Toxicol & Neurosci, Hlth Sci Ctr Shreveport, Shreveport, LA 71103 USA
[2] Louisiana State Univ, Sch Med, Hlth Sci Ctr, Shreveport, LA USA
[3] Univ Arkansas Med Sci, Little Rock, AR USA
[4] Amer Univ, Caribbean Sch Med, Sch Med, Preston, Lancs, England
[5] Creighton Univ, Mt View Headache & Spine Inst, Sch Med, Phoenix, AZ USA
[6] Louisiana State Univ, Dept Anesthesiol, Hlth Sci Ctr Shreveport, Shreveport, LA 71103 USA
[7] Louisiana State Univ, Hlth Sci Ctr Shreveport, Dept Neurol, 1501 Kings Highway, Shreveport, LA 71103 USA
[8] Univ New Mexico, Dept Pain Med, Albuquerque, NM 87137 USA