From the Research
In central facial palsy, the lower face is primarily affected while the upper face is relatively spared. This pattern occurs because the upper facial muscles receive bilateral cortical innervation (from both hemispheres of the brain), while the lower facial muscles receive only contralateral innervation (from the opposite hemisphere) 1. When a lesion occurs in the brain's motor cortex or along the corticobulbar tract above the facial nucleus in the pons, it disrupts signals to the contralateral lower face, causing weakness of the mouth and cheek on the side opposite to the brain lesion. The patient typically presents with drooping of the corner of the mouth, difficulty smiling symmetrically, and food collection in the affected cheek. The forehead and eye closure remain largely intact because these upper facial movements continue to receive innervation from the unaffected hemisphere.
Some key points to consider in central facial palsy include:
- The distinction between central and peripheral facial nerve palsy can be difficult but is very important for the workup and treatment 2
- Central facial palsy is commonly seen in stroke patients and serves as an important localizing sign in neurological examinations
- The use of quantitative ultrasonography of facial muscles can help to better characterize their status in patients with chronic facial palsy 3
- The assessment and rehabilitation interventions for central facial palsy in patients with acquired brain injury are still being researched and developed 4
It is essential to note that central facial palsy can be caused by various conditions, including stroke, tumors, and demyelinating lesions 2. A thorough diagnostic workup, including imaging studies and neurological examination, is necessary to determine the underlying cause of the condition. The affected area in central facial palsy is primarily the lower face, with the upper face being relatively spared, and this pattern is crucial for diagnosis and treatment 1.