Microvasculardecompression (MVD) has been introduced for 40 years. It is the most effective treatment for facial spasm, trigeminal neuralgia and glossopharyngeal neuralgia because of its small trauma, good safety, high cure rate and low complication rate, especially because it can completely preserve the function of blood vessels and nerves. MVD is a functional neurosurgery, and although there are risks of anesthesia and craniotomy, unlike cerebrovascular disease or brain tumor surgery, patients and their families have high expectations for the safety and results of the surgery. Therefore, the operator must have some microsurgical experience and ability, understand MVD surgery and have some knowledge of these diseases in order to perform this surgery.
Despite the high cure rate and safety of microvascular decompression, there is still a certain rate of complications and mortality. Kalkanis et al. summarized and analyzed 1590 patients who underwent MVD in 305 hospitals throughout the United States from 1996 to 2000. Oiwa et al. reported a 15.7% incidence of sensorineural deafness after MVD for facial myasthenia, and Lovely et al. analyzed 21 groups of 2095 patients with facial myasthenia who underwent MVD in the international literature, with a complication rate of 7.7-8.1%. Samii 2002 reported 143 procedures with complications including hearing impairment (15.9%), vertigo (9.6%), facial weakness (2.7%), and cerebrospinal fluid leakage (4.8%). Intracranial hemorrhage and brainstem infarction were the leading causes of death. Surgical complications include hearing impairment, facial palsy, facial numbness, hoarseness, dysphagia, diplopia, tinnitus, ataxia, cerebrospinal fluid leakage, intracranial infection, and intracranial hematoma. The incidence of surgical complications is clearly related to the experience and operation of the operator, and intraoperative vascular and nerve injury is the main cause of complications.
Therefore, obtaining a 100% cure rate and avoiding complications is the goal of workers in this field. Clinical practice proves that mastering proficient microsurgical skills and local anatomical knowledge, correctly performing local exposure, identification of responsible vessels, selection and placement of cushions, determination of treatment effect and prevention of surgical complications in microvascular decompression surgery are the keys to ensure successful surgery.
I. Cerebral contusion injury
Intracranial cerebral contusion is a more common complication after MVD surgery and has a higher incidence.
II. Intracranial hemorrhage or hematoma
Intracranial hemorrhage or hematoma is the most serious complication after MVD surgery, its incidence is low but most dangerous, and it is one of the main causes of death or disability of patients, so we should avoid such complications as much as possible.
Facial palsy and facial numbness
According to domestic and foreign literature, the incidence of temporary facial palsy after facial nerve decompression is 4~18%, and the incidence of permanent facial palsy is 0.9~6.0%, all of which are peripheral facial palsy. The facial palsy that appears immediately after surgery is mostly caused by direct damage to the facial nerve, and recovery is more difficult, while delayed facial palsy (appearing after 3 days after surgery) can all recover spontaneously. lovely et al. reported that the incidence of delayed facial palsy after facial nerve root MVD was 3%, mostly occurring 7-16 d (average 12 d) after surgery, the cause of occurrence is unknown, and all can recover spontaneously.
IV. Hearing impairment
Hearing disorders such as tinnitus (mostly high-pitched tinnitus) and deafness caused by auditory nerve injury after microvascular decompression surgery are more common and serious complications after HFS surgery, and are the main clinical problems at present.
V. Cerebrospinal fluid leakage
It is one of the common complications after MVD surgery and can cause serious central nervous system infection with serious consequences, and its incidence is 1.85~7.6%.
VI. Herpes of the mouth and lips
The more common complication of microvascular decompression for trigeminal neuralgia. MVD surgery can change or affect the conduction of the trigeminal nerve meniscus, which may be one of the reasons why the surgery is effective, but it is also easy to activate the herpes simplex virus (HSV) latent in the meniscus, and the nerve is damaged during surgery, which leads to the decrease of resistance, and the above reasons can cause perilabial herpes on the affected side.
VII. Intracranial infection
It mostly occurs 3~4 days after surgery, manifesting as increased headache, increased body temperature (mostly fever in the afternoon) and neck resistance, increased leukocyte count in lumbar cerebrospinal fluid, often accompanied by decreased sugar due to the consumption of glucose for bacterial metabolism, and inverted ratio of mononuclear and multinuclear leukocytes. When the body temperature is higher than 39℃, physical cooling should be given, while antipyretic drugs can be used, if necessary, intravenous hydrocortisone, supplemented with appropriate amount of sedative drugs, close observation of the patient’s consciousness, pupillary changes, strengthen dietary care and basic care, strict aseptic operation during the operation is the key to avoid postoperative infection. After strengthening antimicrobial treatment (intrathecal injection if necessary), all can be controlled.
VIII. Diplopia (abducens nerve palsy)
In adductor nerve palsy, diplopia can occur due to intraocular strabismus on the side of the palsy. Because the abducens nerve is the longest intracranial nerve in the brain, it is vulnerable to injury. The cause of the injury is mainly due to the strain on the abducens nerve or the irritation of blood cerebrospinal fluid after the release of cerebrospinal fluid in large quantities during surgery. Such complications can be treated with vasodilators, neurotrophic drugs, B vitamins and hormones with certain effect.
IX. Posterior group cranial nerve injury
The cause of this operation is the pontocerebellar horn, which is not sufficiently exposed and over-stretched nerve or direct injury is caused. It often occurs when the posterior cranial fossa is narrow, the local anatomy is complicated, and the surgical operation is complicated resulting in a long operation time. It is inevitable to touch or pull the posterior cranial nerve during MVD surgery, so there is more or less possibility to damage the posterior cranial nerve. The clinical manifestations are dyspnea, hoarseness, dysphagia, choking and coughing. Generally, these symptoms are mild and do not require special treatment. If it affects the daily life, a gastric tube should be placed, and symptomatic treatment such as simple swallowing training can gradually heal. To reduce the occurrence of this complication, familiarity with local anatomy, skillful and gentle microsurgical operation, avoiding overstretching of the nerve, and minimizing the operation time are required.
X. Hypocranial pressure syndrome
It is the most common complication after MVD. The reason is that a large amount of cerebrospinal fluid is released in order to fully expose the surgical field during surgery, and the stimulation of anesthesia and intracranial residual blood and ooze leads to the reduction of cerebrospinal fluid secretion, which causes different degrees of hypocranial pressure symptoms. The main symptoms are headache, dizziness and non-jet vomiting, which can be aggravated when raising the head or changing the position (especially in elderly patients with cerebral atrophy), and can be relieved after lowering the head.
After this complication, the patient should be placed in a flat position with the head tilted to the healthy side, and avoid getting out of bed for 3 days after surgery. At the same time, sufficient fluid should be supplemented to prevent or correct the symptoms of intracranial hypotension, so as to facilitate early recovery and prevent the occurrence of intracranial hemorrhage. In addition, it should be distinguished from intracranial hypertension, do not use hypertonic saline and dehydrating agents, and generally recover in 2~3d. For those who vomit frequently, keep the respiratory tract unobstructed and remove secretions and vomit from the oral and nasal cavities in time.
XI. Vertigo
A small number of patients will have more serious vertigo and unstable walking after surgery, which will disappear gradually within 1~2 weeks.
XII. Delayedresolution of symptoms
Defined as the persistence of postoperative myospasm for more than 1 week after microvascular decompression. The incidence of delayedresolution of symptoms after surgery is higher in patients with a longer history (more than 5 years) and vertebral artery involvement in compression. The reason for this may be that regeneration of local demyelinating lesions of the facial nerve and repair of ultrastructural pathological changes in motor neurons take time. In addition, the narrow posterior cranial fossa and insufficient free displacement of the thick vessels, which still partially transmit pressure through the pad cotton to the facial nerve root, may also be a cause. Those who experience delayed healing may resolve on their own within six months postoperatively, with the vast majority of them resolving within 3-6 weeks postoperatively.