Hemifacial spasm (HFS)
HFS is a common neurological disorder of the brain, which refers to recurrent paroxysmal, involuntary twitching of the facial muscles (orbicularis oculi, orbicularis oris) on one or both sides of the face, especially when emotional or stressful, and in severe cases, difficulty in opening the eyes, distortion of the corners of the mouth, and tinnitus. Typical facial spasm is a spasm that begins in the eyelids and progresses downward to the cheek muscles, while atypical facial spasm is a spasm that begins in the lower facial muscles and progresses upward to the eyelids and frontal muscles. Atypical facial spasms are less common clinically, and the vast majority are typical facial spasms.
Facial myospasm is more common in middle-aged and elderly people, more women than men, and there is a trend of younger age of onset. Although most facial myospasms are located on one side, bilateral facial myospasms are not uncommon.
Diagnosis and differential diagnosis
Diagnostic criteria The diagnosis of facial myasthenia gravis is mainly dependent 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 examination: including electromyography (EMG) and abnormal muscle response (AMR)
or lateral spread response (LSR) testing. In patients with facial spasm, EMG records a high frequency of spontaneous potentials (up to 150 per second), and AMR is a high frequency of spontaneous potentials (up to 150 per second).
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 myoclonus, and three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA)
It is also useful to understand the vascular distribution around the facial nerve. MRI is important to identify intracranial lesions that may be responsible for facial spasm, such as tumors, AVMs, and skull base deformities. MRI is also important to identify the vessels 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.
In particular, 3D-TOF-MRA has become a routine preoperative examination for MVD, and MRI imaging techniques based on it have evolved to show all vessels in anatomical relationship with the facial nerve in 360°.
However, it must be noted 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, but patients with a negative 3DTOF-MRA examination need to be selected for MVD with more caution, and the patient needs to be re-examined for a definitive diagnosis of facial myoclonus, with reference to electrophysiological evaluation if necessary.
Differential diagnosis Facial dystonia needs to be differentiated from facial dystonia disorders such as bilateral blepharospasm, Major’s syndrome, occlusal dystonia, and post-facial palsy.
(1) Bilateral blepharospasm: This is characterized by recurrent episodes of involuntary eye closure of both eyelids, often at the same time, and patients often have difficulty opening their eyes and reduced tearing.
(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. 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.
4. Treatment
1. Drug treatment
Commonly used medications for facial spasticity include carbamazepine (Dexedrine), oxcarbazepine, and valium. Alternative drugs are 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 effects such as liver and kidney function impairment, dizziness, drowsiness, leukopenia, ataxia, tremor, etc. may occur with drug therapy, and should be discontinued immediately if adverse drug reactions occur. In particular, there is a risk of exfoliative dermatitis with carbamazepine treatment, and severe exfoliative dermatitis can be life-threatening.
2. Botulinum toxin injection
Commonly used drugs: botulinum toxin type A for injection (botulinum toxin
A). It is mainly used in adult patients who cannot tolerate surgery, refuse surgery, fail surgery or relapse after surgery, or have ineffective drug treatment or drug allergy. It should be used with caution when there is a decrease in efficacy or serious adverse reactions. Allergic patients and those who are allergic to this product are prohibited to use it.
3. Microvascular decompression
According to the latest research progress, the cause of facial muscle spasm is mainly due to the compression of blood vessels around the facial nerve. The purpose of surgery is to separate the blood vessels at the root of the facial nerve, remove the compression, and fundamentally solve the cause of the disease.
Indications for surgery.
①Primary facial spasm is clearly diagnosed, and secondary lesions are excluded by cranial CT or MRI.
secondary lesions are excluded.
②Severe symptoms of facial myospasm, 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 who have relapsed after MVD surgery can be operated again.
⑤ Patients with ineffective postoperative MVD may be considered for early surgery if the first surgical decompression is considered inadequate and the postoperative AMR is positive.
If the test is positive, early reoperation can be considered.
The criteria for determining the efficacy of postoperative facial spasm are divided into four levels.
①excellent: complete disappearance of facial spasm symptoms.
(2) apparent remission (good): the symptoms of facial myospasm basically disappeared, only when the emotional tension and excitement, or specific facial movements only occasionally triggered, the patient subjective satisfaction, the above two levels are “effective”.
③Partial remission (fair): The symptoms of facial spasm are reduced, but still more frequent, and the patient is subjectively unsatisfied.
Ineffective (poor): no change in facial spasm symptoms, or even aggravated. For patients with ineffective and partial remission, it is recommended to retest the AMR, and if the AMR is positive, it is recommended to operate again as soon as possible; on the contrary, if the retest
On the contrary, if the AMR is negative, follow-up or adjuvant medication or botulinum toxin treatment is possible.
Postoperative complications and management
1. Cerebral nerve dysfunction
Cerebral nerve dysfunction is mainly facial palsy, tinnitus, hearing impairment, and in a few patients, facial numbness, hoarseness, choking on water, diplopia, etc. Acute cerebral neurological dysfunction occurs within 3 days after surgery, while delayed cerebral neurological dysfunction occurs after 3 days of surgery, and the majority of delayed cerebral neurological dysfunction occurs within 30 days after surgery. For example, more than 90% of delayed facial palsy occurs within 1 month after surgery, which may be related to surgical operation and postoperative cold secondary to viral infection. Therefore, it is recommended that care should be taken to keep the brain warm within 1 month after surgery to reduce the occurrence of delayed facial palsy.
2. Cerebellar and brainstem injury
MVD treatment for facial palsy has a 0.1% morbidity and mortality rate, mainly due to cerebellar and brainstem injury, including infarction or hemorrhage. The key to avoid cerebellar injury is to reduce the duration and intensity of straining.
3. Cerebrospinal fluid leakage
Tightly suturing the dura is the key to prevent cerebrospinal fluid leakage; for those whose dura cannot be tightly sutured, muscle fascia can be taken for repair, while applying biologic adhesive to completely patch the artificial dura with the dura; tightly closing the open air chamber with bone wax; strictly suturing the incision in accordance with the four layers of muscle, fascia, subcutaneous tissue, and skin, without leaving a dead space.
If cerebrospinal fluid nasal leakage occurs, immediately tell the patient to lie down with the pillow, tell the patient not to pick, dig or block the nostrils, keep the nostrils clean, observe the change of body temperature, and use antibiotics to prevent infection. If necessary, use dehydrating agent or lumbar pool drainage to reduce intracranial pressure. If the leak does not heal for a long time or recurs several times, repair of the leak is needed.
4. Low intracranial pressure syndrome
It may be caused by prolonged exposure of the surgical site, release of large amount of cerebrospinal fluid and reduced secretion of cerebrospinal fluid after surgery. It often manifests as headache, dizziness, nausea and non-jet vomiting, along with low blood pressure and accelerated pulse rate, and the symptoms can be relieved after lowering the head position. During surgery, the dura mater should be filled with saline when sutured to expel air. Take a flat position after surgery.
5. Other complications MVD
The operation should be strictly regulated to avoid complications such as infection, poor wound healing, balance disorder, incision pain, distal septal site hematoma, and vertebral artery injury. Some patients develop vertigo after surgery, most of them are found during postoperative activities, the symptoms vary in severity, the severe ones affect activities and can be gradually relieved, mostly within 1-2 weeks, a few patients can last for more than 1 month, but do not affect activities.