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Central facial palsy (colloquially referred to as central seven) is a symptom or finding characterized by paralysis or paresis of the lower half of one side of the face.It usually results from damage to upper motor neurons of the facial nerve.
Branches of the facial nerve leaving the facial motor nucleus (FMN) for the muscles do so via both left and right posterior (dorsal) and anterior (ventral) routes. In other words, this means lower motor neurons of the facial nerve can leave either from the left anterior, left posterior, right anterior or right posterior facial motor nucleus.
The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue.
In patients with severe injury, progress is followed with nerve conduction studies. If nerve conduction studies show a large (>90%) change in nerve conduction, the nerve should be decompressed. The facial paralysis can follow immediately the trauma due to direct damage to the facial nerve, in such cases a surgical treatment may be attempted.
The upper motor neuron descends in the spinal cord to the level of the appropriate spinal nerve root. At this point, the upper motor neuron synapses with the lower motor neuron or interneurons within the ventral horn of the spinal cord, each of whose axons innervate a fiber of skeletal muscle. [1] [2]
Frequently, the diagnosis is based on clinical findings (i.e. LMN vs. UMN signs and symptoms, patterns of weakness), family history of MND, and a variation of tests, many of which are used to rule out disease mimics, which can manifest with identical symptoms. [15] [16]
Thus the facial artery can be used as an important landmark in locating the marginal mandibular nerve during surgical procedures. [2] Damage can cause paralysis of the three muscles it supplies, which can cause an asymmetrical smile due to lack of contraction of the depressor labii inferioris muscle . [ 3 ]
Facial synkinesis is a common sequela to Idiopathic Facial Nerve Paralysis, also called Bell's Palsy or Facial Palsy. [2] Bell's Palsy, which is thought to occur due to a viral reactivation which can lead (through unknown mechanisms) to diffuse axon demyelination and degeneration of the seventh cranial nerve, results in a hemifacial paralysis due to non-functionality of the nerve.