Primary trigeminal neuralgia is a neurological disorder characterized by recurrent electric shock-like or pins-and-needles, brief and severe pain in one or more branches of the facial trigeminal nerve. The pain attacks are unpredictable and last from a few seconds to a few minutes each time, or tens of minutes to several hours. About 80% of patients first consult a dentist because they think they have a toothache. It is more common in middle-aged and elderly people, and most of them are unilateral. It is reported that the annual incidence of primary trigeminal neuralgia is about 12.6/100,000 people, the average age of onset is 51.5 years, and the ratio of men to women is about 1:2.5. I. Trigeminal nerve application anatomy The trigeminal nerve is a mixed nerve, containing both somatic sensory and specific visceral motor fibers. The motor root of trigeminal nerve is thin, located in the anterior medial side of the sensory root, and exits the skull together with the mandibular branch of trigeminal nerve through the foramen ovale, which is distributed to the masticatory muscles and so on. The cytomes of somatosensory fibers are concentrated in the trigeminal ganglion (semilunar ganglion), which is located at the trigeminal ganglion pressure trace at the tip of the temporal bone rock, closer to the foramen ovale, which provides an anatomical basis for puncturing the semilunar ganglion of the trigeminal nerve for the treatment of trigeminal neuralgia. The trigeminal meningeal ganglion is wrapped by two layers of dura mater, and its peripheral protrusions form three large branches of the trigeminal nerve called the ophthalmic, maxillary and mandibular nerves, which are distributed in the skin of the face, the mucosa of the eyes, the mouth, the nasal cavity, the paranasal sinuses and the teeth, and the meninges, and conduct a variety of sensations such as pain, temperature and touch. In the posterior cranial fossa, the trigeminal nerve root is closely related to the blood vessels of the cerebellum and brainstem. If the blood vessels cause mechanical compression of the trigeminal nerve root, it can cause trigeminal neuralgia, which provides the anatomical basis for trigeminal nerve root microvascular decompression. Inside the trigeminal nerve root, the sensory root fibers are arranged to be distributed from the inside up to the outside in order, while the motor root is located in the sensory root fibers are distributed from the inside up to the outside down in order, and the motor root is located in the anterior superior internal side of the sensory root, which in turn provides an anatomical basis for selectively cutting the sensory root of the trigeminal nerve to treat trigeminal neuralgia. Primary trigeminal neuralgia refers to those who do not have positive neurological signs, and there is no obvious organic or functional lesion related to the pathogenesis by applying various examinations. The pathogenesis of primary trigeminal neuralgia is still unclear, and many theories exist, such as seizure theory, microvascular compression theory, neurodegeneration theory, bony compression theory, etc. In 1967, Jennetta et al. proposed that more than 90% of the pontocerebral entrance of the sensory roots of trigeminal nerve had distorted vessels across the compression, and treated with apparent microvascular decompression to achieve better results. This theory has led to a major step forward in the understanding of the etiology and treatment of trigeminal neuralgia. Recent studies have shown that more than 95% of the causes of primary trigeminal neuralgia are due to vascular compression; the compressed small arteries include the superior cerebellar artery, anterior inferior cerebellar artery, posterior inferior cerebellar artery, basilar artery, rock vein and vertebral artery or a combination of these vessels. Clinical manifestations Most commonly seen in middle-aged and elderly people, more often in women. The pain is confined to the sensory innervation area of the trigeminal nerve, with the 2nd and 3rd branches being the most common. Most of the pain is unilateral, but very few patients can have trigeminal neuralgia on both sides successively or simultaneously. The pain is briefly electric shock-like, knife-like or tear-like, and stops abruptly for a few seconds to one to two minutes each time. The pain is most pronounced in the cheeks, upper and lower jaws and tongue, and can be triggered by light touch on the nose, cheeks and tongue, called trigger point. Washing the face and brushing the teeth can easily trigger the 2nd painful attack, and chewing, yawning and speaking can trigger the 3rd attack. Severe cases are accompanied by reflex twitching of the ipsilateral facial muscles, called painful twitching, which may be accompanied by facial redness, high skin temperature, conjunctival congestion and tearing. The course of the disease can be cyclic, with each episode lasting several days, weeks or months and remission periods of several days to years. There are fewer episodes at the beginning of the disease and longer intervals. As the disease progresses, the intervals are gradually shortened. Neurological examination is usually without positive signs. There are no obvious lesions related to the onset of the disease on various examinations. Diagnosis Primary trigeminal neuralgia is not difficult to diagnose according to the location, nature and trigger point of pain, and there are no positive neurological signs, no obvious lesions related to the onset of the disease in various examinations, and combined with the age of onset of the disease. However, it should be differentiated from the following diseases before diagnosis: 1, secondary trigeminal neuralgia: primary or metastatic skull base tumor, multiple sclerosis, etc. can appear trigeminal neuralgia, showing persistent facial pain and hyperalgesia, retarded corneal reflex, etc., often combined with other cerebral nerve palsy. 2. Toothache: The disease is easily misdiagnosed as toothache in the early stage, but toothache is usually persistent and dull, limited to the gum area, and may be aggravated by eating cold or hot food. Local examination of the teeth and X-ray examination can help to differentiate. 3.Glottopharyngeal neuralgia: a severe episodic pain confined to the distribution area of the glottopharyngeal nerve, quite similar in nature to trigeminal neuralgia, located in the tonsils, root of the tongue, pharynx and deep part of the ear canal, lasting from a few seconds to a minute each time, often triggered by swallowing, speaking, yawning and coughing. The painful trigger points can be found in the throat, tongue root and tonsillar fossa. Bupivacaine applied to the affected tonsils and pharynx can temporarily stop the attack. 4.Pterygopalatine neuralgia: a kind of rare facial neuralgia, which is also cut-like, burning-like or drill-like pain, distributed in the posterior part of the nasal root, zygomatic area, maxilla, palate and gingival area, often involving the ipsilateral orbit, with pain radiating to the frontal, temporal, occipital and ear areas, without trigger points. The nasal mucosa on the diseased side is congested, nasal congestion, and lacrimation during the attack, which can occur several to dozens of times a day and last for several minutes to several hours each time. 5.Sinusitis: persistent dull pain in the sinus area, local pressure, fever, runny nose, increased blood leukocytes and other inflammatory manifestations, nasal examination and X-ray can confirm the diagnosis. 6.Atypical facial pain: the pain site is vague and indefinite, deep or diffuse, not easy to locate, mainly located in the lower part of one side, but also can be bilateral, no tenderness point. Emotion is the only factor that aggravates the pain, and is seen in patients with depression, hypochondria and personality disorders. Temporomandibular joint dysfunction syndrome: This syndrome is mainly characterized by restricted mouth opening, pain in the joint and surrounding muscles during mouth opening and chewing, and joint popping. There is usually no spontaneous pain, and there may be pressure pain in the joint and muscle area. V. Treatment The treatment of primary trigeminal neuralgia is roughly divided into medication, surgery and so on. The effect of drug treatment tends to diminish after one year, and peripheral nerve block is effective in the short term. Therefore, for patients with unsatisfactory results of drug treatment, surgical treatment such as trigeminal ganglion disruption and microvascular decompression can be considered. There is still a debate on which method to use, but in terms of treatment effectiveness, microvascular decompression is generally considered the best, followed by percutaneous trigeminal ganglion dissection. Microvascular decompression can relieve patients’ pain more permanently and completely without causing facial numbness, especially paralysis of the ophthalmic branch of the trigeminal nerve. 1.Medication:Medication is usually chosen as the first choice and will have beneficial effects for most patients initially. As time goes on, the effect of all drugs gradually decreases, and side effects of drugs gradually appear, such as drowsiness, mental depression, granulocyte decline, drug-related hepatitis, exfoliative dermatitis, etc. Common drugs are carbamazepine, phenytoin sodium, lamotrigine, pimozide. 2.Closure therapy: a method of injecting chemical drugs (such as anhydrous alcohol, anhydrous glycerin, botulinum toxin type A, etc.) into the affected peripheral branches of the trigeminal nerve, nerve trunk or hemianopsia, blocking the conduction function of the nerve and causing the loss of sensation in the area it innervates, so as to achieve the purpose of pain relief. This method is effective, simple, with few adverse effects and postoperative complications. It is clinically suitable for people who are old and weak, unwilling to accept surgical treatment or have contraindications to surgery. The selection of injection site should follow the principle of superficial to deep, from far to near, that is, from the peripheral branch of the trigeminal nerve, the nerve trunk at the base of the skull to the semilunar ganglion in the order. 3.Surgical treatment:Drug treatment is preferred for primary trigeminal neuralgia, but there are still some patients with ineffective application of drug therapy, allergy, or dizziness, ataxia, impaired liver and kidney function, and even complications such as aplastic anemia and granulocyte deficiency. Therefore, surgical treatment is a good choice for such patients, and surgical treatment of primary trigeminal neuralgia has all achieved good results. Surgical methods include radiofrequency thermocoagulation, percutaneous puncture microballoon compression, selective trigeminal sensory root dissection and trigeminal nerve root microvascular decompression. Trigeminal nerve root microvascular decompression is currently the surgical treatment of choice for primary trigeminal neuralgia, providing patients with long-term pain relief. The procedure uses a careful microscopic examination of the entire length of the trigeminal nerve, focusing on the entry into the brainstem, and if the responsible vessels are found, they are opened with Teflon cotton pads to keep the vessels away from the nerve and brainstem. This method is suitable for patients with primary trigeminal neuralgia who have failed conservative treatment, patients with bilateral trigeminal neuralgia, and those who do not want to accept the legacy of facial numbness from severing sensory nerve roots. This method maximizes the function of the trigeminal nerve and produces less permanent neurological dysfunction. Since this method requires craniotomy, there are certain surgical risks. With the development of neuroendoscopic applications, microvascular decompression of trigeminal nerve roots performed under neuroendoscopy has led to further development of microvascular decompression of trigeminal nerve roots toward better results and less trauma.