Objectives: Our objectives were 3-fold: Assess the impact of the injection paradigms on muscle function and strength, assess the efficacy and safety over 10 years of repeated treatments every 3 months, identify risk factors maintaining chronicity in this unremitting migraine population.

Method: One hundred patients were injected with a Botox dilution ratio of 1:1 with a sterile 0.9 % saline solution, 50 patients with a 100u vial of Botox in one, 1cc tuberculin syringe, and 50 patients with a 200u vial of Botox in two-1cc tuberculin syringe during 10 years.

Results: The strength of the paracervical and first portion of the trapezius muscle was altered in 6% (100u) and 18% (155u) of subjects. The strength of the second portion of the trapezius muscle was altered in 2% (100u) and 10% (155u) of subjects.

Muscle function of the paracervical and first portion of the trapezius muscles was altered in 34% (100u) and 28% (155) of subjects. For the second portion of the trapezius, muscle 58% (100u) and 52% (155) of subjects. The efficacy of Botox was constantly maintained during the 10 years of treatment. 72% (100u), and 74% (155u) of subjects had less than 7migraine days /month (77% improvement). Early onset of migraine, comorbid emotional burden and chronic neck pain, should be considered as risk factors for the unremitting condition.

Conclusion: Muscle strength, and function alteration did not have an impact on esthetics of the face and on normal daily muscle function in both cohorts. In both cohorts, more than 70% of patients had more than 75% improvement in monthly migraine days. Depth of the toxin injection, diffusion and presence of adipose tissue (lean versus obese patients) may be responsible for muscle strength and function alteration.