Trigeminal neuralgia occurs in middle-aged and elderly people and is a brief, recurrent, severe pain in the distribution of the facial trigeminal nerve that lasts for a few seconds or minutes. The intervals between attacks are the same as those of normal people. It is often triggered by talking, brushing teeth, washing face or eating. Patients with trigeminal neuralgia often dare not wipe their faces or brush their teeth, dare not speak much, and even affect normal eating, thus seriously affecting their quality of life.
I. Pathogenesis
Trigeminal neuralgia can be divided into two types: secondary and primary. Secondary trigeminal neuralgia refers to facial pain caused by a clear cause, such as tumor or other compression or stimulation of the trigeminal nerve. For secondary trigeminal neuralgia, treatment is based on the principle of removing tumors and other causes. The more recognized pathogenesis of primary trigeminal neuralgia is caused by microvascular compression of the sensory roots of the trigeminal nerve into the brainstem segment, i.e. the theory of microvascular compression of the nerve roots.
Jannetta pointed out that the nearest 5-10 mm of the trigeminal nerve into the brainstem is the migratory zone, where the sheath formation is often incomplete and is particularly sensitive to the pulsatile and transverse compression of adjacent vessels. Kerr (1967) found that patients with primary trigeminal neuralgia have “pseudosynaptic” formation between nerve fibers at the root of the trigeminal nerve, and some adjacent upstream or downstream non-painful stimuli are transmitted through the “pseudosynaptic” to form pain sensation.
Diagnosis
Typical symptoms of trigeminal neuralgia include.
(1) Paroxysmal, “lightning-like” pain in the trigeminal nerve distribution area on one side of the face;
(2) This typical pain occurs when the trigger area is stimulated;
(3) It has periods of remission and exacerbation;
(4) The pain is usually more intense in the morning, but does not occur during sleep;
(5) Experimental treatment with adequate amounts of carbamazepine can reduce the pain.
Imaging should be performed in every case of “facial pain”. A cranial MRI is the first choice. A cranial MRI should include a conventional MRI and a skull base TOF enhancement scan. Conventional MRI can clarify the presence of pontocerebellar horn tumors and other disorders that cause secondary trigeminal neuralgia. The cranial base book TOF enhancement scan can indicate whether there is close contact of blood vessels in the trigeminal nerve root on the painful side, which can provide valuable information for the choice of treatment (whether to perform microvascular decompression).
III. Treatment
The treatment of primary trigeminal neuralgia includes medication (mainly carbamazepine), percutaneous trigeminal nerve root destruction methods (percutaneous radiofrequency ablation nerve root dissection, glycerol nerve root block, balloon compression), gamma knife irradiation, microvascular decompression, etc. The principle of primary trigeminal neuralgia treatment generally chooses drug treatment first. If the effect of drug treatment becomes poor or serious complications occur and drug treatment cannot be continued: if the cardiopulmonary function is acceptable and life expectancy is still long, microvascular decompression is generally chosen; if there is a major disease that cannot tolerate general anesthesia or advanced age (life expectancy is not long), percutaneous trigeminal nerve root destruction method or gamma knife treatment can be chosen.
1, drug treatment (mainly carbamazepine).
Carbamazepine (Deloitte) is the drug of choice for the treatment of trigeminal neuralgia. The initial dose is 200mg/day for the average adult, increasing by 200-300mg daily until the pain is relieved (extreme dose of 1200mg daily). The classical dose for pain control is 800-1200 mg/day. early dose-related side effects can be minimized by gradually increasing to therapeutic doses. Because carbamazepine induces its breakdown by liver enzymes, it may be necessary to increase the dose of carbamazepine after a few weeks of treatment.
Side effects of carbamazepine treatment: Early dose-related side effects include drowsiness, dizziness, nausea, and nystagmus. 5-10% of patients develop rash, erythema multiforme, and even the rare exfoliative dermatitis. Other side effects include aplastic anemia, hepatotoxicity, hyponatremia, and congestive heart failure. Therefore, routine blood and liver and kidney function tests should be performed regularly (every 2-3 months).
Other common drugs used to treat trigeminal neuralgia include oxcarbazepine, baclofen, etc.
Percutaneous trigeminal nerve root destruction methods (percutaneous radiofrequency ablation nerve root dissection, glycerol nerve root block, balloon compression)
In a group of 1600 patients who underwent 2138 radiofrequency ablation treatments, the immediate pain relief rate was 97%, but the pain relief rate was only 58% in single-treatment patients at the 5-year follow-up. Complications included decreased corneal reflexes (6%), weakness or paralysis of the occlusal muscles (4%), sensory dullness (1%), painful sensory loss (1%), and several other rare complications.
Glycerine nerve root block results in less facial sensory abnormalities than radiofrequency ablation treatment, with an immediate postoperative pain relief rate of 80-90% and a median recurrence time of 16-36 months.
Balloon compression, in which balloon compression of the trigeminal nerve hallux valgus causes hallux valgus destruction, has a recent efficiency rate of 78-100%, with a median recurrence time of 3.5 years. 20% of patients have mild sensory dullness, and transient bite weakness may occur in most patients [4].
1, Gamma knife irradiation
Gamma radiation is focused on the brainstem entry area of the trigeminal nerve root, and a single high-dose irradiation destroys the nociceptive conduction pathway and blocks nociceptive transmission to achieve analgesia. The analgesic effect usually appears 1-8 weeks after treatment, and more than 60% of patients can have pain relief [5]. Gamma knife treatment of trigeminal neuralgia is more suitable for elderly patients and patients with systemic diseases that are not suitable for surgery. A few patients will have facial numbness after treatment, and if numbness occurs it usually disappears after a period of time.3.
3. Microvascular decompression
Microvascular decompression was first proposed and implemented by Professor Jannetta in 1967. The theory of trigeminal nerve root microvascular compression is the theoretical basis of microvascular decompression. Microvascular decompression is a radical treatment for the cause of trigeminal neuralgia.
The method of microvascular decompression is as follows: under general anesthesia, an incision is made behind the affected ear, within the hairline, and a cranial opening is made with a diameter of about 2-3 cm, followed by a microscopic operation: the trigeminal nerve root travel area is explored intracranially, the arachnoid membrane around the trigeminal nerve is fully released, all vessels that may produce compression on the trigeminal nerve root are separated, and Teflon pads are inserted between these vessels and the adjacent brainstem so that the responsible vessels ( The Teflon spacer is inserted between these vessels and the adjacent brainstem, isolating the responsible vessel (the vessel that is compressing the nerve and causing pain is called the “responsible vessel”) from the nerve root.
In the vast majority of patients, the pain disappears immediately after surgery, and normal facial sensation and function are preserved. Jannetta (1997) reported that in 1204 patients with primary trigeminal neuralgia who underwent microvascular decompression, one week after surgery, pain relief was 82% complete, 16% partial, and 2% ineffective. One year after surgery, pain relief was complete in 75% and partial relief in 9%. Ten years after surgery, pain relief was 64% complete and 4% partial [6]. Microvascular decompression has the characteristics of minimally invasive, high safety, significant effect and low recurrence and complication rate, especially it can completely preserve trigeminal nerve function, so microvascular decompression is the preferred treatment for primary trigeminal neuralgia with poor drug effect.
4. Identification of similar diseases
1.Dental pain: the pain caused by dental disease is persistent, mostly confined to the gingival area, with localized gingival swelling, and dental examination can confirm the diagnosis.
2. Secondary trigeminal neuralgia: its pain level is milder, and the duration of the pain attack is longer, or it is persistent pain with paroxysmal aggravation. There is usually no trigger point and the triggering factors are not obvious.
3.Temporomandibular arthritis: the pain is confined to the temporomandibular joint cavity, is persistent, there is pressure pain at the joint site, the joint movement is impaired, the pain is closely related to the jaw movement, X-ray and specialist examination are feasible to assist the diagnosis.
4.Glottopharyngeal neuralgia: The pain is located in the soft palate, tonsils, pharyngeal wall, tongue root and external auditory canal. The pain is induced by swallowing action. The pain can disappear after spraying the pharyngeal area with surface anesthetics such as 1% pantocaine or cocaine.
5.Paranasal sinusitis: such as frontal sinusitis, maxillary sinusitis, etc. The pain is limited and persistent, and there may be fever, nasal congestion, thick runny nose and local pressure pain.
6.Migraine: The pain area is beyond the range of trigeminal nerve, and there are mostly visual aura before the attack, such as blurred vision, which may be accompanied by vomiting. Pain attacks are long, often lasting from half a day to 1-2 days.
7, trigeminal neuritis: mostly after the onset of the flu or paranasal sinusitis, etc.. Short history, pain is persistent, trigeminal nerve distribution area sensory hypersensitivity or hypoesthesia, may be accompanied by motor disorders.
8, trigeminal nerve hemianopsia tumor (such as ganglion cell tumor, chordoma, meningioma of the fossa mai, etc.): there may be persistent pain, the patient trigeminal nerve sensory and motor impairment is obvious. Magnetic resonance can help to identify.
Facial neuralgia: Mostly seen in young people, the pain is beyond the trigeminal nerve and can extend to the back of the ear, the top of the head, the occipital neck, and even the shoulder. The pain can be persistent, up to several hours, not related to the movement, not afraid of touch, can be bilateral pain, and can be heavier at night.