Overview
Hemifacial spasm, also known as facial muscle twitching or facial muscle spasm, is a paroxysmal, irregular involuntary twitching, spasmodic or tonic attack of one side of the facial muscles. Neurologic examination is unremarkable except for mild facial paralysis. The onset can be at any age and can occur in children, but is more common in middle-aged women. Idiopathic cases are common, or are temporary or permanent sequelae of idiopathic facial nerve palsy.
Etiology
The cause of the disease is unknown, and the abnormal nerve impulses may be the result of pathologic stimulation of certain areas of the facial nerve pathway. These stimuli may arise from atherosclerotic dilatation of the vertebrobasilar system or from compression by aneurysms.In 1967, Jannette suggested that microvascular compression of the facial nerve root was the main cause of the disease, and that if the microvessels were retracted, the facial spasm could be relieved. Compression by the posterior inferior cerebellar artery or its branches accounted for 60%, and compression by the anterior inferior cerebellar artery and branches of the vertebral artery each accounted for 20% to 30%. Other causes are less than 1%, such as tumor of the cerebellar pontine angle, inflammation, demyelinating degeneration after facial neuritis, and venous compression. Some researchers believe that facial twitching may be caused by a “short circuit” between the proprioceptive afferent fibers and efferent fibers, resulting in the formation of abnormal peripheral reflexes.
Symptoms
Most patients with primary hemifacial spasms develop the disease after middle age, with a higher incidence in women. In the early stage of the disease, there are paroxysmal involuntary twitching of the orbicularis oculi muscle on one side of the face, which gradually and slowly extends to the other facial muscles on one side of the face, and the twitching of the muscles of the corners of the mouth is the most noticeable, and in severe cases, it may even involve the broad cervical muscles on the same side, but the frontalis muscle is less frequently involved. The degree of twitching varies, and the twitching is paroxysmal, rapid and irregular. At first, the convulsions are mild, lasting only a few seconds, and then gradually prolonged up to several minutes or longer, while the interval time is gradually shortened, and the convulsions are gradually aggravated frequently. In severe cases, it is tonic, resulting in the inability to open the eye on the same side, the corner of the mouth is skewed to the same side, and the inability to speak. It is often exacerbated by fatigue, nervousness, emotional excitement, and voluntary movement, but cannot mimic or control its attacks on its own. A convulsion can be as short as a few seconds or as long as more than ten minutes, and the length of the intervals is variable. The patient feels distracted and is unable to work or study, which seriously affects the patient’s physical and mental health. Most of the convulsions stop after sleeping. Bilateral facial spasms are rare. If there is, it is often the two sides of the successive onset of the disease, more than one side of the convulsions to stop, the other side of the seizure, and convulsions on one side of the light side of the other side of the heavier, bilateral simultaneous onset of convulsions at the same time has not been reported. In a few patients, the convulsions were accompanied by mild facial pain, and in some cases, headache and tinnitus on the same side.
The intensity of spasm was graded according to Cohen et al. (i) Grade 0 No spasm; (ii) Grade 1 External stimuli cause increased transient eye movements or mild facial muscle tremors; (iii) Grade 2 Spontaneous mild tremors of eyelids and facial muscles without functional disorders; (iv) Grade 3 Obvious spasm with mild functional disorders; (v) Grade 4 Severe spasm and functional disorders, e.g., the patient is unable to read a book due to the inability to keep his eyes open continuously, and he has difficulty in walking alone. Neurologic examination shows no positive signs other than paroxysmal twitching of the facial muscles. A few patients may be accompanied by mild paralysis of the affected facial muscles in the late stages of the disease.
Examination
There are no abnormalities.
Electromyography shows muscle fiber tremor and muscle bundle tremor waves. They are characterized by: (i) paroxysmal high-frequency pulses (150-400 per second); (ii) rhythmic or irregular repetitive emission of pulse clusters of 5-20 pulses per second, with each emission consisting of 2-12 pulses; (iii) the pulses are synchronized in all ipsilateral muscles of different facial muscles; and (iv) reversed stimulation of the facial nerve induces the typical pulse clusters.
Magnetic resonance imaging (MRI) in some patients reveals variable vascular compression at the facial nerve root.
Diagnosis
Based on the clinical features of the disease, paroxysmal, one-sided facial muscle twitching without other positive neurologic signs, the diagnosis is not difficult.
Differential diagnosis
This disease needs to be differentiated from the following diseases:
1. Secondary facial muscle spasm
Cerebellar pontine horn tumor or inflammation, pontine tumor, brainstem encephalitis, medullary cavernous disease, motor neuron disease, craniocerebral injury can appear facial muscle twitching, but often accompanied by other cerebral nerves or pyramidal fasciculus damage manifestations, such as the same side of the facial pain and facial hyperalgesia, hearing impairment, the contralateral side or limb muscle strength, etc., and the facial muscle twitching is only one of the symptoms, so it is not difficult to differentiate.
2. Epilepsy
Facial muscle limited convulsions may also be partial motor epilepsy, but its convulsions are larger in amplitude, and tend to involve the neck, upper limbs or even lateral limbs, or the typical Jackson seizure which spreads sequentially according to the motor areas of the cerebral cortex. Epileptic wave emission is seen on EEG. Brain CT or MRI may have positive findings. Epilepsy limited to facial muscle twitching is rare.
3. Hysterical blepharospasm
It is common in middle-aged or older female patients, mostly bilateral, and limited to the spasm of eyelid muscles only, while the facial muscles in the lower part of the face are not involved. It can be accompanied by other hysterical symptoms, and its occurrence and disappearance are related to suggestion.
4. Habitual facial muscle spasm
Commonly found in children and young adults, it is a short-lived contraction of the eyelids or facial muscles, often bilateral, and can be temporarily controlled by the will. The onset of habitual facial muscle twitch is related to mental factors. The electromyogram and electroencephalogram are normal, and the muscle contraction waves on the electromyogram are the same as those produced during active movement during convulsions.
5. Trigeminal neuralgia
Trigeminal neuralgia is a paroxysmal, transient, severe pain in the face, which may be accompanied by facial muscle twitching when the pain is severe. Although the primary facial muscle twitch develops to severe, the twitch time is longer can also cause facial pain, but its pain degree is not as intense as trigeminal neuralgia.
6. Chorea and tardive dyskinesia
There may be involuntary twitching of facial muscles, but they are bilateral and accompanied by similar involuntary movements of limbs.
7. Meige syndrome
Blepharospasm-oromandibular dystonia syndrome. It is more common in elderly women, manifesting as bilateral blepharospasm, accompanied by dystonia of the orofacial, facial, mandibular and cervical muscles.
Complications
The disease progresses slowly and worsens gradually, and generally does not resolve spontaneously. If left untreated, some patients experience paralysis of the affected facial muscles and the convulsions stop in the later stages of the disease. Hearing loss, facial paralysis and cerebrospinal fluid leakage may occur in some patients undergoing microvascular decompression surgery. In order to prevent the complications of microvascular decompression surgery, firstly, attention should be paid to the surgical position, avoiding sitting or semi-sitting position to prevent a large amount of air from entering the vein and causing air embolism in multiple organs. The surgeon should strengthen the training of basic surgical skills, open the mastoid airspace to be closed in time, skillfully use the suction device and adjust the pressure, carefully identify the form of vascular compression in the area of the facial nerve out of the brainstem, and avoid blindly electrocoagulating, separating, or cutting off the blood vessels. The application of brainstem auditory evoked potentials, direct potentials of the auditory nerve, and electromyography of the facial nerve during surgery will significantly reduce the occurrence of complications.
Treatment
The first choice of treatment for this disease is medication, but due to the poor effect of medication, microvascular decompression surgery is now the main treatment method, and botulinum toxin injection of facial nerve branches is also more commonly used.
1.General treatment
(1) Drug therapy Carbamazepine, baclofen and other kinds of sedative, stabilizing and antiepileptic drugs, such as gabapentin, phenytoin sodium, phenobarbital, diazepam, nitrazepam, clonazepam, etc., are more effective for patients with less severe symptoms, while patients with more severe symptoms can only be reduced.
(2) Physiotherapy or acupuncture The application of direct current calcium iontophoresis, infrared therapy or stratospheric electrical stimulation can reduce symptoms, but not cure.
(3) microvascular decompression surgery Indications: ① drug, acupuncture, physical therapy and other treatments are ineffective; ② CT and (or) MRI can not be excluded from secondary facial muscle spasm; ③ to exclude Bell facial muscle paralysis or facial nerve trauma after facial muscle spasm.
2.Surgical method
Anesthesia: Same as trigeminal microvascular decompression.
(1) Position Same as trigeminal nerve microvascular decompression.
(2) Incision and bone window The incision and bone window are basically the same as that of trigeminal nerve microvascular decompression, but the bone window is slightly lower and larger. In addition to revealing the beginning of the sigmoid sinus, it should also be closer to the base of the posterior cranial fossa.
(3) Exposure of the facial nerve After draining cerebrospinal fluid or dehydrating with 20% mannitol via lumbar puncture, the dura mater is cut. The facial nerve root should be exposed from the inferior cerebellar approach and the superior cerebellar approach (i.e., the trigeminal microvascular decompression approach) should not be used. The latter approach only exposes the cerebellopontine angle segment of the facial-auditory nerve and is prone to strain injury to the auditory nerve. The lower part of the lateral cerebellum is gently lifted up with a cerebral pressure plate, and one or two bridging veins are cut off after electrocoagulation with bipolar electrocoagulation forceps. The lateral horn of the medullary pool of the cerebellum was opened, the cerebrospinal fluid was aspirated, and the cerebellar pontine angle of the cerebellum was explored for any abnormality. Then the parasympathetic, vagus and glossopharyngeal nerves were identified, and the cerebellum was further elevated, and the arachnoid fasciculus between the cerebellum and the posterior group of cerebral nerves was cut off after electrocoagulation with bipolar electrocoagulation forceps. The choroid plexus of the lateral saphenous fossa of the fourth ventricle was revealed, and the cerebellar pompeii was lifted to reveal the brainstem and the facial auditory nerve. An automatic retractor is placed.
(4) Decompression of the facial nerve Usually the facial nerve is located anteromedially and the auditory nerve is located posterolaterally; the former is gray and the latter is yellowish. Almost all arterial compression occurs within 5 mm of the facial nerve exiting the brainstem, mostly the posterior inferior cerebellar artery, vertebral artery, anterior inferior cerebellar artery or its branches, and a few are veins. Mostly single-vessel compression, a few multiple-vessel compression. Since side-lying can change the relationship between the brain and blood vessels, any blood vessel 1 to 2 mm from the facial nerve root is considered to have compression on the nerve. In typical patients, the facial nerve is often compressed anteriorly and inferiorly, while in atypical patients it is compressed posteriorly or superiorly. The blood vessels are separated from the nerve with a mini-peeler, an absorbent gelatin sponge (gelatin sponge sheet) is inserted between the blood vessels and the nerve, and a polyester sheet is used to encircle the exocerebral segment of the facial nerve. If the vein is difficult to separate by compression, it can be cut off by electrocoagulation with bipolar electrocoagulation forceps. Care should be taken not to damage the penetrating branch of the blood vessel into the brainstem. Stop bleeding properly, close the dura mater tightly, and suture the muscle layer, subcutaneous tissue and skin in layers.
(5) Postoperative management Same as trigeminal microvascular decompression. The disappearance of postoperative facial muscle spasm is gradual. If the facial muscle spasm is still the same as before 30 days after surgery, another surgery is often needed to investigate.
3. Botulinum toxin injection
Botulinum toxin injection into the spastic muscle is gradually being widely used. The mechanism of treatment is to use botulinum toxin to block neuromuscular transmission, reduce the degree of facial muscle spasm, without affecting the normal nerve conduction.
(1) Injection method The facial nerve divides into terminal branches after passing through the parotid gland, and distributes in a fan shape to the facial expression muscles. Injections are made with a hypodermic needle into the subcutaneous tissue at or adjacent to these sites. The extent of injection can be selected according to the site of facial muscle spasm, and can be performed under electromyographic guidance if available.
(2) Efficacy The follow-up time reported so far is short, with early complete remission of 80% to 100%, but usually 12 to 16 weeks, the symptoms recur after the metabolism of botulinum toxin, and the injection needs to be repeated. Certain patients develop antibodies to botulinum toxin after injection, which can affect the efficacy of repeated botulinum toxin injections. Common complications include: facial paralysis, dry eyes, diplopia, dysphagia, etc. The probability of these complications is low for each injection, but after 3 years of cumulative injections, the incidence rate reaches 60% to 75%.
4. Ethanol injection method
Injecting different concentrations of anhydrous ethanol into the facial nerve trunk can temporarily interrupt the conduction function of the facial nerve and relieve the facial muscle twitching. Nerve conduction disorder behind the injection, facial muscle paralysis or incomplete paralysis immediately, this kind of facial muscle paralysis can be recovered in a few months. The efficacy of the treatment is maintained for a short period of time, most of the patients recur in about 6 months, and need to be injected again. This method is less used now.
5. Other surgical methods
Such as facial nerve trunk or branch amputation, can destroy the conduction function of the facial nerve, paralysis instead of convulsions, at present basically do not use.