As part of the Master Scientific Illustration program I wrote a thesis on facial expression. The final part of the thesis was all about the neurology of the face. For this I started with the anatomy of the nerve the makes facial expression happen: the facial nerve.
After illustrating the general anatomy of the facial nerve, I wanted to show a few neurological conditions that have an effect on facial expression: central paralysis, peripheral paralysis and hemifacial spasms.
The infographic shows the difference between the disorders by showing where and what happens in the anatomy of the motor circuit. If someone’s half of the face is completely paralyzed, you are dealing with a peripheral paralysis. If there is still movement possible in the forehead and around the eye, you are dealing with a central paralysis. Hemifacial spasms are spasms that typically start in the lower eyelid, and eventually spread across the entire half of the face.
With a central paralysis the lesion is localized somewhere above the facial motor nucleus. The lesion causes a paralysis of the contralateral side of the face. There is still movement possible in the forehead and around the eye.
With a peripheral paralysis the lesion is localized somewhere below the facial motor nucleus. The lesion causes a paralysis of the entire half of the afflicted (ipsilateral) side of the face.
Hemifacial spasms are characterized by irregular, involuntary muscle contractions (spasms) in one half (hemi) of the face. These spasms are caused by the compression of the facial nerve as it comes out of the brain stem.