[1] Med Univ Plovdiv, Fac Med, Plovdiv, Bulgaria
[2] Univ Hosp St Ivan Rilski, Dept Neurol Surg, Sofia, Bulgaria
[3] Univ Multiprofile Hosp Act Treatment & Emergency M, Dept Gen & Clin Pathol, Sofia, Bulgaria
[4] Med Univ Plovdiv, Dept Anat Histol & Embryol, Plovdiv, Bulgaria
[5] Med Univ Sofia, Fac Med, Sofia, Bulgaria