Osaki MH, Osaki TH, Osaki T, Gameiro G, Belfort Jr R, Marie SKN. Orbicularis oculi morphological alterations in affected and non-affected sides in hemifacial spasm. J Neuroophthalmol. 2020;40(2):193-197.
Hemifacial spasm (HFS) is a condition characterized by involuntary spasms of the muscles innervated by the ipsilateral facial nerve. Most cases are unilateral, and although the non-affected side appears to be clinically normal, it is not known if this side can be considered normal regarding histopathological findings. Our study objectively evaluated and compared orbicularis oculi muscle samples of non-previous botulinum toxin-treated HFS and control patients using a digital image software (Image J). When compared to normal controls, endomysial and perimysial connective tissue areas were significantly increased (p= 0. 015) on the affected side, suggesting that HFS is associated with chronic alterations, leading to muscle degeneration. Cell density was observed to be significantly reduced on the affected (p=0.028) and also on the non-affected side (p= 0.003), when compared to normal controls, although clinically, there were no signs or symptoms of increased muscular contraction on the non-affected side in any of the HFS patients studied. Our findings suggest that some type of muscle homeostasis disturbance may be present in both sides, however, on the non-affected side, it would not be substantial enough to lead to muscle degeneration, as observed on the affected side. Additional immunohistochemical studies evaluating metabolic, degenerative, and regenerative alterations are already being conducted by our group and may add relevant contributions to the better understanding of this condition.