Hemifacial Spasm
Einstein Health Glossary
ICD 10 - G513
What is hemifacial spasm?
It is an involuntary muscle contraction of the muscles on one side of the face, innervated by the facial nerve. It causes tonic and/or clonic contractions, often mistaken for motor tics.
Types
The main type is idiopathic, meaning it has no defined cause. However, there are cases that occur after peripheral facial paralysis, which are secondary to vascular malformations and, in rare cases, tumors.
Causes
The exact cause is unknown. It is believed, for example, that the size of the cranial vault may be a risk factor, as smaller skulls (especially a smaller posterior fossa) could make the facial nerve more vulnerable to compression by vascular structures, such as loops of the posterior circulation.
These vascular loops, in turn, become more evident and excessively tortuous in patients with high blood pressure. It is no coincidence that hypertension is another known risk factor for the development of hemifacial spasm.
Symptoms
The main symptoms are involuntary facial movements, which can even interfere with vision—since the orbicularis oculi muscle, which closes the eyelids, may remain closed most of the time. It is important to note that this is the only involuntary movement that does not disappear during sleep.
Diagnosis
Diagnosis is essentially clinical, based on the correct assessment of the described signs and symptoms. The most qualified professional for this interpretation is a neurologist, who can distinguish the condition from others that also involuntarily affect body movements, particularly the face.
Differential diagnoses to be considered include: tics, blepharospasm, tardive dyskinesia, facial synkinesis, myokymia, among others. Complementary exams such as brain CT, MRI, and facial electroneuromyography are used only to evaluate other differential diagnoses.
Treatment
The standard treatment is the application of botulinum toxin type A. The procedure is relatively simple but requires a trained professional, usually a neurologist. Ideal amounts of the toxin are injected into different points of the hemiface to stop the involuntary facial movements. In general, applications are performed every 4 to 6 months, depending on the case.
The results of botulinum toxin application are superior to all forms of drug treatment. The most common side effects of botulinum toxin application to the face are related to unwanted paralysis of facial muscles, which can lead to drooping eyelids or facial asymmetries.
Again, with well-trained professionals, the risks are greatly reduced. In selected cases, surgeries using facial nerve decompression techniques may be performed.
Prevention
There is no way to prevent it. The most important thing today is to identify patients with this involuntary movement early and offer the standard treatment with botulinum toxin.