Facial paralysis

GENERAL ASPECTS FACIAL PARALYSIS

Facial paralysis is an alteration of facial mobility that can be caused by injury to the motor pathways from their origin in the cerebral cortex to their exit to the muscles through the facial nerve.

A complete clinical history and neurological examination is important to identify certain aspects that allow differentiating the site of the lesion and orienting to the possible causes. They usually cause facial asymmetry due to the involvement of one side of the face, and according to their extension they can be differentiated:

1. Central facial paralysis (with origin within the central nervous system): usually there will be a unilateral paralysis exclusively of the lower part of the face, producing an asymmetry when smiling and difficulty in retaining food in the mouth.
2. Peripheral facial paralysis (with origin in the facial nerve): it will produce a unilateral paralysis of half of the face, producing an alteration of the lower and upper part of the face, with difficulty to move the mouth, raise the forehead and eyebrow, as well as to close the eye, which may cause a slow blinking or an incomplete closure of the eye (Bell’s sign) that may favor the existence of ocular erosions due to dryness and irritation.

In addition, peripheral lesions of the facial nerve may produce other symptoms related to other nerve fibers located on this nerve. Thus, in these cases a decrease in taste, an increased sensitivity to sounds and a decrease in tear secretion may be associated.

CENTRAL FACIAL PARALYSIS

• Acute

Cerebral stroke is the main cause of sudden central facial paralysis, either by interruption of cerebral blood flow (ischemic) or by rupture of blood vessels (hemorrhagic). It is often associated with other neurological symptoms such as impaired speech, weakness or sensory impairment on one side of the body.

Therefore, in case of a sudden facial paralysis of central aspect, it is necessary to urgently perform a cerebral and vascular imaging test of the intracranial arteries, with a computerized tomography or cranial magnetic resonance imaging and their respective angiographic studies. If the suspicion is confirmed, endovenous treatments such as fibrinolysis or mechanical thrombectomy may be considered if a large caliber artery is occluded.

• Progressive

It may be caused by expansive brain lesions such as a brain tumor or an intracranial inflammatory or infectious lesion. They are usually associated with other neurological symptoms such as those previously mentioned, as well as epileptic seizures.

After clinical assessment, a brain imaging should be performed, preferably a cranial brain MRI, and high-field studies with higher definition may be requested depending on the degree of suspicion. Surgical treatment could be considered in case of tumor pathology, as well as other antibiotics or immunomodulators according to the diagnosis.

PERIPHERAL FACIAL PARALYSIS

• Acute

Idiopathic Bell’s palsy is the most common cause of spontaneous peripheral facial paralysis, and is attributed to inflammation of the facial nerve, sometimes due to a viral agent. It may be associated with pain in the ear region, which when very intense or associated with vesicles is usually due to a herpes zoster infection (Ramsay-Hunt syndrome). Other causes are secondary to trauma (due to bone or facial injury and after ear or parotid surgery) or to the complication of acute otitis.

The diagnosis of idiopathic Bell’s palsy is clinical, with unilateral weakness of the upper and lower part of the face with onset within a few days, and may be associated with alterations in taste, hearing or lacrimal secretion. In typical cases with a good evolution, complementary tests are not usually necessary.

Treatment consists of a short course of oral corticosteroids (e.g. prednisone for one week) and in cases where there is suspicion of herpes zoster infection, antiviral drugs such as valacyclovir can be associated. The prognosis improves with this treatment, and targeted physiotherapy may help, and about 80% of patients show a significant improvement within six months. As sequelae, facial weakness may persist or abnormal involuntary movements may appear in the affected part (synkinesias or hemifacial spasm).

• Progressive

It may be caused by tumors in the nerve pathway, either by involvement or compression. It is advisable to perform an MRI of the internal auditory canal, assessing surgical treatment in case a tumor of the facial or acoustic nerve is found.

• Atypical

In cases with bilateral involvement of the face, with several recurrences or any other atypical findings, more rare causes should be considered. These include various infectious diseases (such as borrelia) or immune-mediated diseases such as Guillain Barré syndrome, sarcoidosis, Sjogren’s syndrome or Melkersson-Roshenthal syndrome.

For those patients with atypical data, apart from a cranial MRI, the rest of the studies should be individualized according to the clinical suspicion. If there is suspicion of neuroinfection or immune-mediated disease, a lumbar puncture should be performed to analyze the cerebrospinal fluid. In addition, detection of antibodies against borrelia, an electromyogram in Guillain Barré syndrome, or serum autoimmunity panel and body image studies in other systemic autoimmune diseases may be performed. Treatment of these pathologies includes antibiotic or immunomodulatory treatments (such as immunoglobulins or corticosteroids).

FREQUENT QUESTIONS

When to make a medical consultation for facial paralysis?

It should be consulted in any episode of facial paralysis, since it is convenient to differentiate the type of paralysis, since there are multiple causes that require different complementary tests and treatments that can modify the prognosis.

When to go to the emergency room for facial paralysis?

A hospital emergency department should be consulted when there is sudden unilateral involvement of the mouth (acute central facial paralysis) or when accompanied by other neurological symptoms (e.g. visual disturbances, slurred speech, loss of strength), seizures or general symptoms (e.g. fever, vomiting).