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Stephen McNutt, Bryan Costin, Thomas Plesec, Natta Sakolsatayadorn, Tal Rubinstein, George Trichonas, Jennifer McBride, Julian Perry; Anatomical and Histologic Evaluation of the Frontalis Muscle in Non-Preserved, Fresh-Frozen Cadavers. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3042.
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To characterize the macroscopic and microscopic structure of the frontalis muscle in fresh-frozen cadavers, and specifically the frontalis dehiscence.
Three fresh-frozen cadavers were marked in preparation for removal of tissue from the forehead for microscopic evaluation. Three blocks of tissue were removed at inferior, middle, and superior locations of the forehead. Dimensions of tissue blocks were 5mm x 3cm in height and width, respectively, with depth from skin to frontal periosteum. The first block of tissue was removed 1cm superior to a horizontal line drawn through the right and left supraorbital notches. The second block was subsequently removed starting 1cm above the superior aspect of the first block and the third block removed in similar fashion 1cm from the superior aspect of the second block (Fig.1). All blocks were marked with suture to define laterality and were submitted to pathology in formalin. Dissection was subsequently performed to expose the frontalis muscle. Inferior incisions were made at the upper eyelids with lateral incisions made lateral to the temporal fossa so as not to disturb the frontalis muscle during reflection and removal of skin.
The level of frontalis dehiscence was measured at 2 cm and 3 cm in two of the three cadavers. The third cadaver was Cushingoid due to high-dose steroids and lacked macroscopically identifiable frontalis muscle. Microscopic evaluation showed a lack of muscle fibers in the midline of tissue blocks. A microscopic area of “dehiscence,” or lack of muscle units, in all three cadavers was found, which corresponded to the level of dehiscence in the two macroscopically identifiable regions of dehiscence.
Dehiscence of the frontalis muscle observed macroscopically during gross dissection of fresh-frozen cadaveric specimens correlates with areas devoid of muscle fiber by microscopic evaluation of these same tissue samples. Clinical implications of these findings include administration of neurotoxin in the forehead, as administration in the midline forehead may not be efficacious.
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