Updated: Jan 5, 2022
Symptoms of Facial Paralysis & Bell's Palsy are almost same. Bell’s palsy is a type of facial paralysis happen due to dysfunction of 7th Cranial nerve. It is named after Sir Charles Bell [1774 to 1842], who was a Scottish surgeon, neurologist and anatomist. He is renowned for noting difference between motor and sensory nerves in the spinal cord.
What is the difference between Upper Motor Neurone and Lower Motor Neurone facial palsy?
If the forehead is not affected (i.e. the patient is able to raise fully the eyebrow on the affected side) then the facial palsy is likely to be an upper motor neuron (UMN) lesion. Paralysis which includes the forehead, such that the patient is unable to raise the affected eyebrow, is a lower motor neuron (LMN) lesion.
The facial nucleus is divided into two halves. The upper half of the nucleus receives innervation from not only the contralateral motor cortex but also from the ipsilateral motor cortex. But the lower half of the nucleus receives innervation only from the contralateral motor cortex.
Now, upper part of the face is supplied by upper part of the nucleus and lower part of the face is supplied by lower part of the nucleus.
So, in UMN facial play, contralateral paralysis of lower facial muscles is seen. This is because of the ipsilateral innervation. In this case, patient is unable to smile, unable to whistle, but can raise eyebrow.
In LMN facial palsy, there is ipsilateral paralysis of both upper and lower facial muscles. Clinical features are drooping of corner of mouth, loss of labial fold but typical features are inability to raise the eyebrows and close the eyelids properly.