Disease description.
Hemifacial spasm (HFS), also known as facial muscle twitching, presents as involuntary twitching of one side of the face. The twitching is paroxysmal and irregular, with varying degrees, and can be aggravated by fatigue, stress and voluntary movements. The onset of the twitching mostly starts from the orbicularis oculi muscle and then involves the whole face. The disease tends to occur after middle age and is commonly seen in women.
The initial symptom of facial myospasm is eyelid jumping, which is also known as “left eye jumping for money, right eye jumping for disaster”, so it usually does not attract people’s attention, but after a period of time, it develops into facial myospasm, even to the corners of the mouth, and in serious cases, even to the neck. Facial muscle spasm can be divided into two types, one is primary facial muscle spasm, one is secondary facial muscle spasm, that is, facial muscle spasm produced by the sequelae of facial paralysis. The two types can be distinguished from each other by their symptoms. In primary facial myospasm, the spasm can occur even at rest, and the spasm is relieved after a few minutes and is not controlled; in facial myospasm produced by the sequelae of facial palsy, the spasm is produced only when blinking and raising the eyebrows.
Disease Etiology
Vascular factors
In 1875, Schulitze et al. reported a case of HFS in which a “cherry” sized basilar artery aneurysm was found at autopsy in the facial nerve. It is now known that approximately 80% to 90% of HFS is due to vascular compression of the facial nerve exiting the brainstem region. Clinical data indicate that the anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) are the main vascular factors causing HFS, while the superior cerebellar artery (SCA) is less common. In addition, the superior labyrinthine artery and other large arterial variants such as vertebral artery and basilar artery may also compress the facial nerve, resulting in HFS.
It was thought that HFS was due to pulsatile compression of the artery, but recent studies have shown that a single venous vessel can also cause HFS when it compresses the facial nerve, and both of these vessels can compress the facial nerve at the same time, which affects the prognosis of HFS surgery to a certain extent.
Non-vascular factors
Non-vascular occupying lesions in the pontocerebellar angle (CPA), such as granulomas, tumors, and cysts, can also cause HFS, possibly due to.
(i) displacement of normal vessels due to the occupancy. singh et al. reported a case of a CPA epidermoid cyst that displaced the AICA and compressed the facial nerve resulting in HFS;
(ii) Direct compression of the facial nerve by the occupancy;
(3) The influence of the abnormal blood vessels of the occupancy itself such as arteriovenous malformation, meningioma, and aneurysm. In young patients, localized arachnoid thickening may be one of the main causes of HFS, while some congenital disorders such as Arnold-Chiari malformation and congenital arachnoid cyst may cause HFS. and congenital arachnoid cysts may occasionally cause HFS.
Other factors
The presence of compression in the region of the facial nerve out of the brainstem is the main cause of HFS, and most authors have observed during pontocerebellar horn surgery that the presence of vascular compression in regions other than the facial nerve out of the brainstem does not produce HFS, whereas Kuroki et al. observed in an animal model that demyelinating lesions of the facial nerve in regions other than the facial nerve out of the brainstem can show electromyographic changes similar to those of HFS. The presence of compression factors in areas other than the brainstem region of the facial nerve may lead to HFS, which needs to be further investigated.
Genetic factors
In addition, HFS can also be seen in systemic diseases such as multiple sclerosis. Only a few cases of familial HFS have been reported so far, and the mechanism is not known; it is presumed to be genetically related.
Clinical manifestations of primary facial myasthenia gravis mostly develop after middle age, more often in women. The twitching of the corners of the mouth is the most noticeable, and in severe cases, it may even involve the ipsilateral vastus cervicis muscle, but the frontalis muscle is less frequently involved. The degree of twitching varies, and it is paroxysmal, rapid and irregular twitching. The initial twitch is light and lasts for only a few seconds, and then gradually grows for several minutes or longer, while the interval is gradually shortened and the twitches gradually increase in frequency. In severe cases, the convulsions are tonic, causing the ipsilateral eyes to be unable to open, the corners of the mouth to be skewed to the ipsilateral side, and the inability to speak, often aggravated by fatigue, nervousness, and voluntary movements, but cannot imitate or control their onset by themselves.
The patient feels distracted and unable to work or study, which seriously affects the patient’s physical and mental health. Most of the convulsions stop after sleep. Bilateral lateral muscle spasms are rarely seen. If there is, it often starts on both sides successively, and most of the convulsions stop on one side and then the other side seizes again, and the convulsions are light on one side and light on the other side, but the simultaneous onset and convulsions on both sides have not been reported. A few patients have mild facial pain during convulsions, and some cases may be accompanied by ipsilateral headache and tinnitus.
Pathogenesis
It is becoming accepted that most patients with facial myoclonus are suffering from vascular compression of the cerebellopontine angle. The abnormal arterial vascular compression is within 5 mm of the facial nerve root. The facial nerve is repeatedly stimulated by arterial pulsation, resulting in compression of nerve fibers, atrophy and degeneration of the myelin sheath at the site of compression, and short-circuiting of action currents in the efferent and afferent nerve fibers. As the transneurons degenerate, the center loses its ability to integrate excitation, and when the electrical excitation is superimposed to a certain degree, a burst of downward transmission occurs, causing facial muscle spasm. Compression of vessels is common in the anterior inferior cerebellar artery, posterior inferior cerebellar artery, multiple vascular loops (complex), vertebral arteries, unnamed arteries and veins.
Grading of spasticity intensity as developed by Cohen et al.
Grade 0: no spasm ;
Grade 1: Increased transients or mild fluttering of facial muscles caused by external stimuli;
Grade 2: spontaneous mild tremors of eyelids and facial muscles without functional impairment;
Grade 3: pronounced spasticity and mild dysfunction;
Grade 4: severe spasm and dysfunction, e.g., the patient is unable to read and has difficulty walking alone because he cannot keep his eyes open. Neurological examination is not positive except for paroxysmal twitching of facial muscles. A small number of patients may have mild paralysis of the affected facial muscles in the late stage of the disease.
Care
Preoperative care
1) Preoperative preparation: In addition to the routine preoperative neurosurgical preparation, electroaudiometry and magnetic angiography (MRA) should be performed to carefully assess the frequency, intensity and duration of facial muscle spasms to provide a comparison for postoperative nursing observation.
2) Psychological care: Although HFS is not life-threatening, the involuntary facial appearance seriously hinders the social life and psychological health of patients, and even adversely affects the marriage and employment of some young patients. In addition to the prolonged course of the disease, the patient has been tossed around for medical treatment and has undergone repeated medication and even botulinum toxin injection treatment, which has left some patients in a state of high mental tension and emotional irritability for a long time, with doubts about the effect of surgery and a desire to talk, be understood and cared for. Therefore, after the patients were admitted, we listened patiently to their complaints while taking a detailed medical history, and gave them understanding, sympathy and comfort for their pain and discomfort caused by the disease, and guided them to vent their frustration. At the same time, we explained in detail the purpose, method, effect and postoperative precautions of the operation, so that the patient could enhance his confidence and be in the best condition for treatment.
Postoperative care
1) General care: 24h postoperative lying down with the pillow removed, closely observe any active bleeding and changes in vital signs, pupils, limb movement and language, the postoperative nurse should understand the intraoperative situation in detail to have a good idea, report any abnormality to the doctor in time and give corresponding treatment. Continuous low-flow oxygenation for 24h after surgery to prevent brain tissue edema around the incision. Pay attention to any symptoms of brainstem damage, observe any symptoms of increased intracranial pressure such as severe headache, frequent vomiting, slow pulse rate and elevated blood pressure, and be alert to the occurrence of secondary intracranial hemorrhage. Fasting water for 24h after surgery, followed by transition from liquid food to an easily digestible, high-calorie, high-vitamin, high-protein diet. If transient facial numbness occurs, the food should not be too hard, too cold or too hot to avoid damaging the oral mucosa.
2) Observation of the efficacy after surgery After the patient is awake, the frequency, intensity and duration of facial muscle spasms are promptly evaluated, and the time when the facial muscle spasms stop twitching is recorded. In patients with severe facial muscle spasm, the eye fissure on the affected side can be seen to be enlarged after surgery, which is due to the relaxation of the previously tense facial muscle after the cause of the disease is removed, not due to facial nerve injury, and is the first sign of successful surgery. Although the MVD surgery released the vascular compression, the regeneration and repair of facial nerve root myelin sheath and the stabilization of facial nerve motor nucleus excitability need time to complete, and the postoperative efficacy should be followed up for more than 6 months.
Facial spasm drug and surgical treatment process
Treatment method
Treatment details
Treatment indications
Drug treatment
Drugs such as Phenytoinum Natricum or Carbamazepine.
They may be effective in some mild cases.
Surgical treatment1
Facial nerve trunk compression and branch severance: Under local anesthesia, an incision is made under the stem mammary foramen, the nerve trunk is identified, and the nerve trunk is compressed with vascular forceps.
The force of compression should be controlled appropriately. In mild cases, recurrence will occur within a short period of time, and in severe cases, permanent facial paralysis will remain. If the distal branches are identified, the nerve branch responsible for the main spasm is identified under electrical stimulation and selectively cut, the effect is better than compression, but mild facial palsy still has to occur after surgery, and there is also recurrence after 1 to 2 years, which is rarely used now.
Surgical treatment 2
Facial nerve decompression: The mastoid is chiseled open under local anesthesia, and the horizontal vertical segment of the facial nerve is completely ground away with an electric drill, and the nerve sheath is cut longitudinally to decompress the nerve fibers.
The decompression procedure is complicated, especially the full segment decompression procedure is not only difficult but also dangerous. It is also debatable whether the so-called efficacy is due to the traumatic facial gods during surgery, not the effect of decompression.
Surgical treatment3
Combing of the vertical segment of the facial nerve: After grinding the vertical segment of the facial nerve canal, the vertical segment is dissected longitudinally by 1 cm with a fibrous knife and spaced with a silicone film.
The purpose is to cut the crossed nerve fibers to reduce abnormal impulse conduction. The disadvantage is that it is difficult to achieve the exact degree of neither obvious facial paralysis nor spasticity.
Surgical treatment 4
Microvascular decompression: Under general anesthesia, a straight incision is made in the hairline behind the ear, and the anatomical relationship between the facial auditory nerve and the surrounding blood vessels in the pontocerebellar angle is observed under a microscope. A Teflon spacer of the appropriate size is inserted. If the responsible vessel is clearly identified intraoperatively, the vessel that may be compressing the nerve is treated and decompression is performed.