Facial nerve palsy. Diagnosis, differential diagnosis and treatment.
Facial nerve palsy is a condition that affects the movement of one side of the face due to damage or inflammation of the facial nerve (the 7th cranial nerve). The facial nerve controls the muscles of facial expression, as well as some functions of the eye, mouth, and ear. Facial nerve palsy can cause symptoms such as drooping of the eyelid, corner of the mouth, or cheek, inability to close the eye, smile, or frown, and loss of taste on the affected side. Facial nerve palsy can also affect hearing, balance, and tear and saliva production.
ETIOLOGY
There are many possible causes of facial nerve palsy, but the most common one is idiopathic, meaning that the exact cause is unknown. This type of facial nerve palsy is also called Bell’s palsy, and it is thought to be related to viral infections, such as herpes simplex or herpes zoster, that trigger an immune response that inflames the nerve. Other causes of facial nerve palsy include trauma, tumors, infections, autoimmune diseases, diabetes, Lyme disease, sarcoidosis, and stroke.
DIAGNOSIS
The diagnosis of facial nerve palsy is based on the history, physical examination, and sometimes additional tests, such as blood tests, imaging studies, or nerve conduction studies. To diagnose the type of facial paralysis, a physical examination and some tests can be performed, such as asking the patient to raise their eyebrows, close their eyes, smile, or show their teeth.
DIFFERENTIAL DIAGNOSIS OF FACIAL NERVE PALSY
The difference between peripheral and central facial paralysis is based on the location of the lesion or damage that affects the facial nerve. Peripheral facial paralysis occurs when the lesion is outside the brain, such as in the temporal bone, the parotid gland, or the facial muscles. Central facial paralysis occurs when the lesion is inside the brain, such as in the cerebral cortex, the brainstem, or the cerebellum.
Peripheral facial paralysis causes weakness or paralysis of the entire half of the face on the same side as the lesion, including the forehead, the eye, the mouth, and the cheek. Central facial paralysis causes weakness or paralysis of the lower half of the face on the opposite side of the lesion, sparing the forehead and the eye.
The reason for this difference is that the facial nerve has two types of fibers: upper motor neurons (UMN) and lower motor neurons (LMN). UMN fibers originate from the cerebral cortex and descend to the brainstem, where they cross over to the opposite side and synapse with LMN fibers. LMN fibers exit the brainstem and travel through the temporal bone, the parotid gland, and the facial muscles, where they innervate the muscles of facial expression.
A lesion in the UMN fibers affects the contralateral lower face, because the UMN fibers for the forehead cross over twice, once in the cortex and once in the brainstem, making them bilaterally innervated. A lesion in the LMN fibers affects the ipsilateral whole face, because the LMN fibers do not cross over after leaving the brainstem, making them unilaterally innervated.
TREATMENT
The treatment of facial nerve palsy depends on the cause and severity of the condition. For idiopathic facial nerve palsy, the main treatment is corticosteroids, which reduce inflammation and improve recovery. Other treatments may include antiviral drugs, eye drops, physical therapy, or surgery. The prognosis of facial nerve palsy varies depending on the cause and extent of nerve damage. Most cases of idiopathic facial nerve palsy recover spontaneously within 3 to 6 months, but some may have residual weakness, synkinesis (involuntary movements), or pain. Other causes of facial nerve palsy may have a poorer outcome, especially if the nerve is severed or compressed by a tumor.
EVOLUTION AND PROGNOSIS
The evolution of facial nerve palsy is influenced by several factors, such as the age, health, and immune status of the patient, the time of onset and diagnosis, the type and duration of treatment, and the presence of complications or comorbidities. Some patients may experience a complete recovery, while others may have permanent or recurrent facial nerve palsy. The quality of life and psychological well-being of the patient may also be affected by facial nerve palsy, as it can impair communication, social interaction, and self-esteem.
In conclusion, facial nerve palsy is a disorder that affects the movement and function of one side of the face due to damage or inflammation of the facial nerve. It can have various causes, symptoms, treatments, and outcomes, depending on the individual case. The most important things to remember are:
– Facial nerve palsy can affect the muscles of facial expression, as well as the eye, mouth, and ear on the affected side.
– The most common cause of facial nerve palsy is idiopathic, or Bell’s palsy, which is likely related to viral infections and immune reactions.
– The treatment of facial nerve palsy depends on the cause and severity, but corticosteroids are often used for idiopathic cases.
– The prognosis of facial nerve palsy varies, but most cases of idiopathic facial nerve palsy recover within 3 to 6 months, while other causes may have a poorer outcome.
– Facial nerve palsy can affect the quality of life and psychological well-being of the patient, so emotional support and counseling may be helpful.
