1.Overview
Facial myoclonus is a recurrent paroxysmal, involuntary twitching of one or both facial muscles (orbicularis oculi, expression muscles, orbicularis oris), aggravated by emotion or tension, and in severe cases, difficulty in opening the eyes, distorted corners of the mouth, and twitching-like murmurs in the ears.
Typical facial spasm is a spasm that starts from the eyelid and gradually progresses downward to involve the lower facial muscles such as the cheek expression muscles, while atypical facial spasm is a spasm that starts from the lower facial muscles and gradually progresses upward to eventually involve the eyelid and frontal muscles. Atypical facial spasms are less common in clinical practice, and the vast majority are typical facial spasms.
Facial myospasm is more common in middle-aged and elderly people, with slightly more women than men, but there is a trend toward younger age of onset. Although most facial myospasms are located on one side, bilateral facial myospasms are not uncommon.
2.Diagnosis and differential diagnosis
(1) Diagnosis of facial myospasm The diagnosis of facial myospasm mainly depends on the characteristic clinical manifestations. For patients who lack characteristic clinical manifestations, they need to be clarified by auxiliary examinations, including electrophysiological examination, imaging examination, and carbamazepine treatment test.
Electrophysiological examinations include electromyography (EMG) and abnormal muscle response (AMR), or lateral spread response (LSR). In patients with facial spasm, EMG can record a high frequency of spontaneous potentials (up to 150 per second) and AMR is an abnormal electromyographic response specific to facial spasm, and a positive AMR supports the diagnosis of facial spasm.
Imaging studies include CT and MRI to identify intracranial lesions that may be causing the facial spasm, and 3D-TOF-MRA to help understand the distribution of blood vessels around the facial nerve. Patients with facial myasthenia are generally effective with carbamazepine treatment at the beginning of the disease (with a small number of patients experiencing ineffectiveness), so carbamazepine treatment trials are useful for diagnosis.
(2) Differential diagnosis of facial myospasm Facial myospasm needs to be differentiated from bilateral blepharospasm, Meijer syndrome, occlusal spasm, post-facial palsy and other facial dystonia disorders.
(1) Bilateral blepharospasm: This is characterized by recurrent episodes of involuntary eye closure of both eyelids, often at the same time, and the patient often shows difficulty in opening the eyes and reduced tears.
(2) Meijer syndrome: Patients often start with recurrent episodes of involuntary eye closure of the eyelids bilaterally, but with the prolongation of the disease, involuntary twitching of the muscles below the eye fissure will gradually appear, manifesting as involuntary abnormal movements of the face bilaterally, and with the aggravation of the disease, the scope of muscle spasm will gradually expand downward, even involving the muscles of the neck, limbs and trunk.
③ Bite muscle spasm: It is a spasm of unilateral or bilateral masticatory muscles, and patients may have different degrees of upper and lower jaw bite disorder, teeth grinding and mouth opening difficulties, and trigeminal nerve motor branch lesion is one of the possible causes.
(4) Posterior facial palsy: It is manifested by restricted movement of the ipsilateral facial expression muscles, involuntary twitching of the ipsilateral corners of the mouth as well as concomitant movement of the corners of the mouth and eyelids, which can be identified based on the exact history of facial palsy.
Preoperative evaluation
(1) Electrophysiological evaluation Pre-operative electrophysiological evaluation can help the differential diagnosis of facial spasm and objective understanding of the functional level of facial nerve and vestibular nerve, which should be actively carried out in hospitals with conditions.
(2) Imaging evaluation Patients with facial myasthenia must undergo imaging evaluation before undergoing microvascular decompression (MVD) surgery, preferably MRI, and cranial CT scan should be performed for patients who cannot undergo MRI.
The significance of MRI is to identify intracranial lesions that may be causing facial spasm, such as tumors, cerebral vascular malformations (AVMs), and skull base malformations. MRI is also important to identify the vessels that are in anatomical contact with the facial nerve and even to show the type and thickness of the vessels and the degree of compression of the facial nerve.
However, it must be pointed out that the vessels shown on MRI are not necessarily the real responsible vessels, and a negative 3D-TOF-MRA examination is not an absolute contraindication to MVD surgery, only that patients with a negative 3DTOF-MRA examination need to be chosen for MVD with more caution, and the patient needs to be rechecked for a definite diagnosis of facial spasm, and the results of electrophysiological evaluation should be referred to if necessary.
4.Treatment
(1) Drug treatment
The most commonly used medications for facial spasticity include carbamazepine (Deloitte), oxcarbazepine, and valium [23]. Alternative drugs include phenytoin sodium, clonidine, baclofen, topiramate, gabapentin, and haloperidol.
②Medication can reduce the symptoms of facial muscle twitching in some patients.
③Facial muscle spasm medication is often used in the early stage of onset, in those who cannot tolerate surgery or refuse surgery, and as an adjunctive treatment for those whose symptoms cannot be relieved after surgery. For patients with mild clinical symptoms, significant drug efficacy, and no adverse drug reactions, long-term application is possible.
(4) Adverse reactions such as impairment of liver and kidney function, dizziness, drowsiness, leukopenia, ataxia, tremor, etc., may occur with drug therapy and should be discontinued immediately. In particular, there is a risk of exfoliative dermatitis with carbamazepine treatment, and severe exfoliative dermatitis can be life-threatening.
(2) Botulinum toxin injection
(1) Commonly used drugs: Botulinum toxin A for injection. It is mainly used for adult patients who cannot tolerate surgery, refuse surgery, fail surgery or relapse after surgery, or have ineffective drug therapy or drug allergy. It should be used with caution in case of decreased efficacy or serious adverse reactions. Allergic persons and those who are allergic to this product are prohibited to use.
The upper and lower eyelid muscles are injected at 4 or 5 points on the medial and lateral sides of the upper and lower eyelid or on the temporal side of the lateral canthus. In case of facial or orofacial twitching, 3 injections are required in the middle, lower and cheek muscles. Depending on the condition, injections can also be given to the inner and outer brow or upper lip or lower jaw muscles. The starting volume is 2.5 U/0.1 ml per site.
Additional injections can be given to those with residual spasms after 1 week of injection, or the original amount or double the amount (5.0 U/0.1 ml) can be given to those with recurrence. However, the total dose should not be higher than 55 U in one injection and the total dose should not be higher than 200 U in one month.
(3) Efficacy: More than 90% of patients are effective for the initial injection of botulinum toxin, and the time for complete relief and significant improvement of spasticity after one injection is 1~8 months, mostly concentrated in 3~4 months, and the efficacy gradually decreases with the prolongation of the disease and the increase of the number of injections.
The interval between two treatments should not be less than 3 months. If the treatment fails or the efficacy gradually decreases after repeated injections, other treatment methods should be considered. Therefore, botulinum toxin injections cannot be used as a long-term treatment for facial muscle spasm. It should be noted that the effect after each injection is closely related to the selection of the injection site, the size of the injection dose and the skillfulness of the injection technique.
④ Adverse reactions: A small number of patients may experience transient symptomatic dry eye, exposure keratitis, lacrimation, photophobia, diplopia, ptosis, reduced transience, incomplete lid closure, and varying degrees of facial palsy, which will recover spontaneously within 3-8 weeks. Patients with repeated botulinum toxin injections will experience permanent eyelid weakness, shallow nasolabial folds, crookedness of the corners of the mouth, and facial stiffness.
(5) Precautions: Use with caution in patients with fever, acute infectious diseases, pregnant women and children under 12 years of age; aminoglycoside antibiotics are prohibited during the use of this product; 1:1000 epinephrine should be available for first aid in case of allergic reactions, and patients should be kept in the hospital for short-term observation after injection.
(3) Microvascular decompression is currently the most effective treatment for facial spasm.
Hospital and department should have the following conditions: ① Hospital should have an independent neurosurgery establishment. (2) Equipment (microscope) and instruments for microsurgery are available. ③ CT and MRI, conditional units should be equipped with neurophysiological monitoring equipment and personnel. ④ should be mastered by skilled microsurgery skills of senior neurosurgeons to complete.
Indications for surgery: ① The diagnosis of primary facial myospasm is clear, and secondary lesions are excluded by cranial CT or MRI. ②Severe symptoms of facial spasm, affecting daily life and work, and the patient’s strong desire for surgery. ③Patients treated with drugs or botulinum toxin should be operated actively in case of poor efficacy, ineffectiveness, drug allergy or toxic side effects.
④Patients with recurrence after MVD surgery can be operated again. ⑤ Patients with ineffective post-operative MVD may be considered for early reoperation if the first surgical decompression is considered inadequate and the post-operative AMR test is positive. Patients with no remission or even progressive worsening of symptoms may also be considered for reoperation.
Contraindications to surgery: ①The same contraindications as general craniotomy. ②Patients with severe hematologic disease or vital organ dysfunction (heart, lung, kidney or liver). (3) Caution should be exercised when choosing MVD surgery in elderly patients.
5.Efficacy evaluation
The criteria for determining the efficacy of facial spasm after surgery are divided into four levels.
①Cure (excellent): the symptoms of facial myospasm completely disappear.
②Obvious remission (good): Facial myospasm symptoms basically disappeared, only when emotional tension and excitement, or specific facial movements only occasionally induced, the patient subjective satisfaction, the above two levels are “effective”.
③Partial remission (fair): Facial spasm symptoms are reduced, but still more frequent, the patient is subjectively unsatisfied.
Ineffective (poor): no change in the symptoms of facial spasm, or even aggravated. For patients with ineffective and partial remission, it is recommended to retest AMR, and if AMR is positive, it is recommended to operate again as soon as possible; on the contrary, if AMR is negative, it can be followed up or assisted with medication or botulinum toxin treatment.
6.Complication control
Cerebral neurological dysfunction is mainly facial palsy, tinnitus, hearing impairment, and in a few patients, facial numbness, hoarseness, choking and coughing, diplopia, etc. Acute cerebral neurological dysfunction occurs within 3 days after surgery, while delayed cerebral neurological dysfunction occurs after 3 days of surgery, and most delayed cerebral neurological dysfunction occurs within 30 days after surgery.