Hemifacial spasm a facial dyskinesia, that has close resemblance to other similar disorders. Clinical presentation and evaluation of the underlying causes are crucial for accurate diagnosis and successful treatment.
The clinical presentation of hemifacial spasm features unilateral, nonpainful, involuntary facial movements of muscles innervated by the facial nerve. Certain stressors such as fatigue and anxiety may trigger these movements. Even activities like speaking, reading or coughing can precipitate spasms. These ipsilateral symptoms are clonic or tonic and progressive. These symptoms can also occur during sleep . Bilateral spasms are very rare.
Hemifacial spasms resemble myoclonic jerks. These movements are usually progressive and involve other facial muscles similarly to how segmental myoclonus involves other body parts. At initial onset, these intermittent spasms occur in the orbicularis oculi muscle causing twitching of the eyelids, which in turn results in closure of the eyes. This slowly progresses to the other ipsilateral muscles of the face. After a gradual period, the spasms cause contraction of all unilateral muscles. While initially intermittent, it progresses to a continuous synchronized fashion.
In more severe cases, platysma muscle contractions consequently leads to pulling and drooping of the mouth to the ipsilateral side. As the disorder progresses, additional facial muscles become involved  . In certain cases, patients have reported clicking sound in the ear secondary to the stapedius muscle contraction. Other cases have presented with vision impairment due to the contraction of orbicularis muscle .
Primary and secondary forms may differ in presentation . One study investigated the differences and concluded that primary type usually affects the periocular muscle initially followed by lower facial muscles, while the latter affects upper and lower facial muscles simultaneously .
Clinically, it is important to identify the underlying cause if there is one. As discussed above, examples include compression or injury of the facial nerve due to aberrant blood vessels or pathologies such as a tumor or stroke, respectively. Patients usually are self aware especially in social environment. This in turn can cause anxiety and stress. The quality of life of those affected with hemifacial spasms is usually decreased.
To diagnose accurately, a thorough review of the signs and symptoms, medical history and physical exam are important. Diagnostic tests include blink reflex testing and electromyography (EMG).
A diagnostic result on the blink reflex test is spread and variable synkinesis, which does not occur in other craniofacial dyskinesia or seizures. This test consists of stimulating one branch of the facial nerve to trigger a response in another branch. Synkinesis is the voluntary movement of one muscle triggering the involuntary movement of another one. A diagnostic finding on EMG is high frequency, intermittent discharges which are analogous to facial movements.
MRI can aid in identifying a compressive lesion or any pathology (ie. tumors) in the cerebellopontine angle. T2 images are beneficial on detecting vascular compression. Cerebral angiography isnot useful for diagnostic purposes but important prior to microvascular decompression surgery.
There are several different treatments for hemifacial spasm.
Botulinum toxin or botox is the treatment of choice for many patients. This drug is injected under guidance of EMG. It is injected in the upper eyelids. This achieves a good response particularly for patient who suffer from persistent contractions. Results are seen approximately 3 to 5 days after administration of the toxin and theeffects last for 6 months usually. This works by paralysis of the muscles innervated by facial nerve. It is a good treatment option for those who are poor surgical candidates. Side effects include asymmetrical look, also ptosis may develop temporarily.
Alternatively, patients may opt for non-botox treatments. Anticonvulsants such as carbamazepine and benzodiazepines are suitable for noncompressive lesions. The muscle relaxer baclofen can also be used. Overall, these medications are not effective.
Microvascular decompression surgery can be performed to treat compressive lesions, particularly in those who achieve inadequate alleviation of spasms with botox. Surgical decompression on the aberrant blood vessels compressing the facial nerve can result in very successful outcomes    . A study compared patients who receive botox before surgery versus those who did not. The results did not show differences in results and complications . A research study indicated that it is crucial to identify the correct vessels prior to surgery . As with all procedures, there are risks and therefore benefits and risks should be carefully weighed.
The prognosis is correlated to treatment. Botulinum toxin has a high success rate at 95% . Furthermore, quality of life improves in affected individuals , since the disorder can compromise quality of life and even be disabling. This drug is effective 3 to 5 days after injection and peaks with the first 2 weeks of treatment .
Some patients, particularly with compressive lesions, require surgery. 94% have had long term (>6 years) relief of symptoms post surgery. Recurrences have occurred after surgery but 86% of those were within 2 years of the procedure For patients with no symptoms 2 years post procedure, the chance of recurrence is 1% .
In summary, both botox and microvascular surgery can achieve excellent results. However, the latter provides a possible cure.
Most cases of hemifacial spasms are classified as primary hemifacial spasms . While previously considered idiopathic, this is attributed to compression of the facial nerve at its root exit in the cerobellarpontine angle.
All etiologies should be considered when evaluating the patient. One study reported the various possible causes. 62% of patients in this study were considered to be affected by the primary form. The secondary etiologies reported were Bell's palsy in 11% and injury to facial nerve in 6% of patients in the study. There were very few secondary to demyelination or cerebrovascular insults.
There are several proposed mechanisms likely responsible . The chronic irritation of the facial nerve resulting in hyperexcitability of the the nucleus in one of them. This is explained in further detail in the pathophysiology chapter.
The prevalence of hemifacial spasms is 10 people per 100,000 population .
Gender: There is insufficient data, but one study reported that women were twice as likely to be affected than men. In addition, annual incidence in age adjusted statistical analysis was 0.81 per 100,000 population in women and 0.74 per 100,000 population in men.
Age: Idiopathic type onset of age is the 5th or 6th decade. Affected individuals in younger ages should raise suspicion to underlying disease such as multiple sclerosis.
Race: Race may likely be a factor since the condition is more common in northeastern Asians, but more epidemiological investigations are needed before conclusions could be drawn.
Epidemiological assessment of hemifacial spasms are inadequate overall and should be investigated further to achieve a better understanding.
The pathophysiology is complex and various theories are available. It is important to differentiate between the various etiologies to elucidate the pathophysiology of hemifacial spasms.
While the primary type was thought to be idiopathic, it is more likely due to aberrant blood vessels compressing the facial nerve at the root exit zone, at the site at which the nerve exits the brainstem. The likely vessel culprits are inferior posterior cerebellar artery (PICA) or the inferior anterior cerebellar artery (AICA).
A brief background about the structure of the facial nerve is helpful to understand the pathophysiology better. At the root exit zone, the facial nerve has an arachnoid membrane only, the epineurium is absent. There are no tissue septa either . These reasons contribute to why the nerve is vulnerable to compression in this region.
At the root of pathogenesis due to neurovascular compression are various proposed electrophysiological mechanisms. This disorder could be attributed to either of the mechanisms :
The older age onset of patients is likely related to arterial hypertension. These patients tend to exhibit vessels in the brainstem that undergo elongation and other changes throughout life. This eventually leads to contact between the nerve and artery resulting in compression and likely demyelination . This process contributes to the proposed mechanisms.
The secondary type is attributed to other pathologies that cause damage to any segment of the facial nerve. Tumors, arteriovenous malformations, and Paget disease comprise lesions that are compressive. Stroke, multiple sclerosis, and basilar meningitis are considered noncompressive lesions. These can elicit spasms .
There is no prevention for hemifacial spasms.
Hemifacial spasm is a craniofacial dyskinesia characterized by non painful, involuntary, intermittent, irregular tonic and clonic contractions. The causes of this disorder are either primary or secondary . The former was considered idiopathic, but is believed to be secondary to neurovascular compression of the facial nerve at the root entry zone in the brainstem. Secondary hemifacial spasm is due to etiologies that can cause damage to the facial nerve. Examples include multiple sclerosis, brainstem cardiovascular insults, or tumors. The clinical manifestations of both types differ. Careful consideration of the patient’s presentation and underlying causes is essential to determine treatment.
There are multiple treatment options for hemifacial spasms including botulinum toxin and microvascular decompression. Both are effective. It is important to assess the patient thoroughly and choose the appropriate treatment.
Hemifacial spasm is a disorder in which one side of the face has non painful, but involuntary intense contractions or spasms. These contractions may start in the eye region and spread to lower part of the the same side. These spasms are triggered by emotional distress or anxiety, or even mundane activities such as reading or talking. In some cases, the mouth may pull to the side. While it is not painful, the condition can affect the individual's life especially in social situations. It is thought that certain populations in Asia are more affected than Caucasians. It also tends to affect middle aged and elderly women more commonly than men.
The are different causes. In most cases, this is due to blood vessels compressing the facial nerve, the nerve that allows some of the facial muscles to move. Also there are other causes such as tumors, stroke, Bell's palsy, multiple sclerosis, and so forth.
To diagnose this disorder accurately, your doctor may refer you to a neurologist. A complete history and physical exam is necessary. Since there other disorders that have similar symptoms, it is crucial to differentiate this from the others. Your doctor will test a reflex on your face and perform electromyography (EMG) to make a confirmatory diagnosis. Also, your doctor will rule out other causes by performing an MRI or other imaging techniques.
Treatment consists of medication or surgery. The most effective medication is the botulinum toxin, or botox. This can be injected in top eyelid. Effects are seen in 3 to 5 days and last for about 6 months. The most common side effects of botox in this case is an asymmetrical look on the face and possible drooping of the eye. Antiseizure medications such as carbamazepine and benzodiazepines could be used in those who do not want botox. Another medication that can be used is baclofen, which is a muscle relaxer. These do not achieve good results such as those of botox or surgery.
Microvascular decompression is a surgical procedure that can be very effective and achieves a cure since it decompresses the pressure of the blood vessel. This is associated with side effects. Your doctor will explain the benefits and risks. Together you can make a decision.