Group 1 n=28 BOTOX - 300U Group 2 n=28 Placebo BOTOX (saline) All study subjects will receive one injection cycle (BOTOX 300U or Placebo) at Visit 2 (Treatment, Day 0) as per Supplement III. The study duration is approximately 61 weeks and consists of a Pre-Treatment Evaluation, a Treatment/Randomization Visit (Visit 2, Day 0), Telephone Follow-ups at 1, 3 and 4 weeks post-treatment, and Follow-up Visits at 6, 24 and 36 weeks (Visits 3 to 5). At Week 36, subjects will be offered open-label BOTOX 300U and will be followed for an additional 6 months, returning for evaluations at Weeks 48 and 60.