Trigeminal neuralgia is one of the most common neurological diseases of the brain, mainly manifested by recurrent paroxysmal severe pain in the distribution area of the trigeminal nerve on one side of the face, with an incidence rate of 52.2/100,000 in China, slightly more in women than in men, and the incidence rate can increase with age. It occurs mostly in middle-aged and elderly people, and the right side is more than the left side.
The disease is characterized by severe pain with sudden onset and stop in the area of trigeminal nerve distribution in the head and face.
Trigeminal neuralgia is an intermittent pain, with lightning-like, knife-like or burning pain, which is intense and unbearable; the pain is periodic, often without warning, and stops suddenly after a few seconds to a few minutes. Trigger points are often located on the upper lip, nose, gums, corners of the mouth, tongue, eyebrows, etc. Light touch or stimulation of trigger points can trigger painful episodes; talking, washing face or brushing teeth, or even breeze can trigger painful episodes; patients often suddenly stop talking, eating and other activities during episodes, and the painful side can show spasms, i.e. “painful spasms”.
At the beginning of the disease, the number of episodes is small, and the interval is long, ranging from several minutes to several hours, but with the development of the disease, the episodes are gradually more frequent, the interval is gradually shortened, and the pain is gradually increased and intense. In severe cases, patients may feel painful and unbearable. Neurological examination is often free of abnormal signs.
Trigeminal neuralgia can be divided into two categories: primary (symptomatic) trigeminal neuralgia and secondary trigeminal neuralgia, of which primary trigeminal neuralgia is more common. Primary trigeminal neuralgia refers to those with clinical symptoms, but no organic lesions related to the onset of the disease are found by applying various examinations. Secondary trigeminal neuralgia has clinical symptoms, while clinical and imaging examinations can reveal organic diseases such as tumor, inflammation, vascular malformation, etc. Secondary trigeminal neuralgia usually has no trigger point, the triggering factors are not obvious, the pain is often persistent, and some patients can be found with other manifestations of the primary disease. CT, MRI and nasopharyngeal biopsy of the brain are helpful for diagnosis.
The etiology and pathogenesis of trigeminal neuralgia have not yet been clearly established, and various theories cannot perfectly explain its clinical symptoms. At present, most scholars tend to believe that the primary site of trigeminal neuralgia is in the peripheral rather than the central nervous system.
This theory has been greatly enriched and developed since Dandy (1929) proposed the mechanism of peripheral nerve compression and (1967) first applied microvascular decompression to treat trigeminal neuralgia with good results. The peripheral nerve compression mechanism suggests that the majority of trigeminal neuralgia is due to vascular compression of the sensory roots of the trigeminal nerve into the pontine area. Clinical observations have also revealed that the vast majority of patients with trigeminal neuralgia have arterial or venous compression at the trigeminal nerve root. The strongest support for this theory is the efficacy of trigeminal nerve microvascular decompression, with a recent cure rate of over 90%. In cases without vascular compression, compression of intra-neural microvessels that are difficult to see with the naked eye and atrophy of the trigeminal nerve roots and focal arachnoid thickening are considered as possible etiologies occurring in this region.
The REZ, located at the junction of the central and peripheral nerves, lacks protection from glial cells and lacks fibrous connections with surrounding tissues, which is the most vulnerable cause of involvement in this area. In addition to vascular compression, multiple sclerosis, benign and malignant tumors in the REZ region, arteriovenous malformations, posterior cranial recess malformations, focal cerebral infarction, and osteomyelitis of the jaw due to odontogenic infection can also lead to trigeminal neuralgia.
Common diseases that are easily confused with trigeminal neuralgia are as follows.
1. toothache: trigeminal neuralgia is often misdiagnosed as toothache. There are cases in which healthy teeth are extracted or even all teeth are extracted but still ineffective to attract attention. The pain caused by dental disease is persistent, mostly confined to the gum area, with local caries or other lesions, and the diagnosis can be confirmed by X-ray and dental examination;
2.Migraine: The pain area is beyond the trigeminal nerve, and there are mostly visual aura before the attack, such as blurred vision and dark spots, which may be accompanied by vomiting. The pain is persistent and prolonged, often from half a day to 1-2 days;
3, trigeminal neuritis: short history, pain is persistent, trigeminal nerve distribution area sensory hypersensitivity or hypoesthesia, may be accompanied by motor disorders. Neuropathy mostly develops after a cold or paranasal sinusitis, etc;
4, paranasal sinusitis: such as frontal sinusitis, maxillary sinusitis, etc., for local persistent pain, may be accompanied by fever, nasal congestion, thick runny nose and local pressure pain, etc.;
5, glaucoma: easily confused with trigeminal nerve branch 1 pain, persistent pain, no radiation, vomiting, accompanied by congestion of the conjunctiva, shallow anterior chamber and increased intraocular pressure, etc;
6.Temporomandibular arthritis: the pain is limited to the temporomandibular joint cavity, persistent, with pressure pain at the joint site, accompanied by joint movement disorder, and the pain is closely related to the jaw movement, and X-ray and specialist examination are feasible to assist in the diagnosis;
7, cerebellopontine angle tumor: the nature of pain can be the same as trigeminal neuralgia or atypical. Mostly seen in young people, they have hyperalgesia in trigeminal nerve distribution area and can gradually produce other symptoms and signs in cerebellopontine horn of cerebellum. Cholesteatoma is more common, followed by meningioma and auditory nerve sheath tumor, the latter two with other cerebral nerve involvement. Ataxia and increased intracranial pressure are more obvious, CT and MRI examination can help to confirm the diagnosis;
8.Tumor invasion of skull base: most common is nasopharyngeal carcinoma, often accompanied by epistaxis and nasal congestion, which can invade most brain nerves, accompanied by enlarged cervical lymph nodes. Specialized examination of nasopharynx, biopsy, skull base X-ray, CT and MRI examination can assist in diagnosis;
9.Glottopharyngeal neuralgia: It is easily confused with trigeminal nerve branch 3 pain. The sites of glottopharyngeal neuralgia are different, such as 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 1% cocaine;
10.Trigeminal nerve hemianopsia tumor: ganglion cell tumor, chordoma, meningioma of the fossa mai, etc., may have persistent pain, and the patient has obvious trigeminal nerve sensory and motor disorders. There may be bone destruction and other changes on skull base X-ray;
11.Facial neuralgia: Mostly seen in young people, the pain extends 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 is persistent, up to several hours, not related to the movement, not afraid of touch, can be bilateral pain, heavier at night.
The treatment of trigeminal neuralgia includes both conservative treatment and surgical treatment. The following three drugs are commonly used to treat trigeminal neuralgia.
① Carbamazepine: It is a conventional drug for the treatment of trigeminal neuralgia and is effective for pain relief in most patients with initial onset, but about 1/3 of patients cannot tolerate its side effects such as drowsiness, vertigo and digestive discomfort. It is worth noting that although the incidence of allergic reactions to carbamazepine is not high, once it occurs, it is very serious, therefore, please read the instruction manual carefully before taking the drug, pay attention to the occurrence of side effects during the drug, and stop the drug in time if there is any discomfort;
②Oxcarbazepine: a new drug used in clinical practice in recent years, is a derivative of carbamazepine, the same effect as carbamazepine, but with fewer side effects;
Phenytoin sodium: less effective than carbamazepine and oxcarbazepine.
The surgical treatment of trigeminal neuralgia is known as microvascular decompression, which was first proposed by Professor Jannetta in 1967 and gradually accepted by everyone because of its good effect on the treatment of trigeminal neuralgia. With the development of microsurgical techniques and minimally invasive concepts, the surgical safety of microvascular decompression has been greatly improved, and it has now become the first choice for surgical treatment of trigeminal neuralgia. The method of microvascular decompression is: under general anesthesia, an incision of about 4 cm in length is made behind the affected ear and within the hairline.
The trigeminal nerve travel area is explored by microscopic access to the pontocerebellar angle, and all possible compressive vessels and arachnoid cords are “released” and isolated from the nerve root with Teflon pads. Once the responsible vessels were isolated, the source of irritation was eliminated. A diagram of the nerve after decompression is shown below.
The vast majority of patients have immediate postoperative pain disappearance and retain normal facial sensation and function without compromising quality of life.
What kind of patients with trigeminal neuralgia are suitable for microvascular decompression?
Theoretically, as long as patients diagnosed with primary trigeminal neuralgia, who are not effectively treated with medication or who cannot tolerate the side effects of medication, and if there are no contraindications to general anesthesia surgery, microvascular decompression is feasible for the treatment of trigeminal neuralgia. With the current technology, the safety of microvascular decompression surgery operation is already high for an experienced neurosurgeon. However, for patients of advanced age or with underlying diseases, the risk of surgical anesthesia is relatively high due to the potential risk of other organ functions in the body, and surgery is not recommended, and medication or gamma knife treatment can be chosen as appropriate.