Attention! Please do not confuse the diagnosis "trigeminal neuralgia" described in this article with the diagnoses of "trigeminal neuropathy" and "facial nerve neuropathy".
Trigeminal neuralgia is a chronic root disease, the main symptom of which is paroxysmal pain in the innervation zone of one, two, or all branches of this nerve. Pain in trigeminal neuralgia often reaches a pronounced degree.
Often, during an attack of pain in trigeminal neuralgia, vegetative symptoms are observed on the diseased side of the face in the form of sweating, redness, swelling, lacrimation, and increased salivation. Sometimes with trigeminal neuralgia, painful convulsive twitching of the facial muscles occurs with its clonic contraction.
In the intervals between attacks of trigeminal neuralgia, pain is absent or mild. Irritation of a certain zone when talking or eating food, according to the anatomical direction of the branches of the trigeminal nerve, provokes an attack of pain, so the patient is wary of causing irritation of this zone.
In those cases of trigeminal neuralgia, when it is possible to identify a pathological process localized in the brain, cranial cavity, extracranially in the tissues adjacent to the nerve or in the nerve itself and causing irritation of the nerve, they speak of the symptomatic form of trigeminal neuralgia.
The symptomatic form of trigeminal neuralgia is a manifestation of a tumor of intracranial localization, an inflammatory process of the paranasal sinuses, diseases of the teeth and jaws.
However, the so-called idiopathic (essential) form of trigeminal neuralgia is most often observed, in which sometimes an inflammatory etiology of the disease can be assumed, but most often the etiological factor cannot be identified.
Treatment of trigeminal neuralgia
With symptomatic trigeminal neuralgia, it is necessary to strive to eliminate the underlying disease. In unclear cases of trigeminal neuralgia, or if there is reason to believe the inflammatory nature of the disease, first resort to drug and physiotherapy.
Surgical methods for treating trigeminal neuralgia are aimed at interrupting the conduction of the nerve trunk and can be divided into two groups: extracranial and intracranial.
Extra-cranial access to the Gasser's ganglion
Extracranial methods of surgical treatment of trigeminal neuralgia include transection (neurotomy) or twisting of the peripheral branches of the trigeminal nerve and their alcoholization.
Trigeminal neurotomy (transection of the peripheral branches) is an easily performed operation that stops the pain associated with trigeminal neuralgia. However, after neurotomy of the trigeminal nerve, relatively rapid regeneration of the nerve is often observed, with the restoration of sensitivity and recurrence of pain attacks.
The best results in trigeminal neuralgia are given by a nerve twisting operation called neuroexeresis, in which a 2-4 cm long section of the peripheral branch is excised. However, after this operation, nerve twisting (neuroexeresis) usually regenerates after 6-12 months, and pains return.
To prevent the regeneration of the trigeminal nerve, after the operation of neurexeresis, they resort to filling the openings of the bone canals through which the branches of the nerve pass, with the help of wooden, bone, metal narrow pins, muscle, wax, paraffin, etc., but this does not lead to persistent recovery and after a certain time relapses of pain often occur.
To access the branches of the first branch of the trigeminal nerve, an incision is made in the medial supraorbital region. To detect the infraorbital nerve (a branch of the second branch of the trigeminal nerve), there is an extraoral approach by cutting the soft tissues in the medial region under the lower edge of the orbit, while avoiding injury to the branch of the facial nerve that innervates the lower eyelid. With an intraoral approach, an incision is made to the bone slightly below the transitional fold from the canine to the first molar, and after delamination with the mucous membrane, together with the periosteum, the nerve is exposed and isolated, which is captured by Pean's forceps, its peripheral end is cut off, and the central one is slowly twisted out of the infraorbital bone canal until it comes off.
With nerve dissection of the mental nerve (a branch of the third branch of the trigeminal nerve) by the intraoral route, an incision is made from the canine to the first molar, 0.5-0.75 cm below the gingival margin, i.e. slightly above the chin hole.
Most neurosurgeons have a negative attitude towards the operations of cutting or twisting the peripheral branches for trigeminal neuralgia and prefer a simpler and often very effective therapeutic measure in the form of alcoholization of the nerve trunk, which has become widespread.
A break in the conduction of the nerve trunk with persistent anesthesia of the area in trigeminal neuralgia is achieved by chemical blockade of the nerve by intraneural injection of 1-2 ml of 80% alcohol with novocaine. Blockade with trigeminal neuralgia with the use of alcohol with novocaine is most often performed on an outpatient basis and does not give complications.
When the needle is inserted into the nerve trunk of the trigeminal nerve, first, 1-2 ml of 2% novocaine solution is injected. A few minutes after, by the nature of the conduction anesthesia, they are convinced of the correct position of the needle, alcoholization of the trigeminal nerve is performed.
With neuralgia of the second branch of the trigeminal nerve, this injection, depending on the localization of the trigger zone, can be done through the infraorbital, incisal, large palatine, and zygomatic-facial foramen. With neuralgia of the third branch of the trigeminal nerve, depending on the location of the pain, the injection is either done through the chin opening, or they resort to mandibular, lingual, or buccal anesthesia.
The best results of alcohol blockade are observed with neuralgia of the second and third branches of the trigeminal nerve. Often, the period of absence of pain in trigeminal neuralgia lasts 0.5-1 year or more. After this pain-free period, repeated alcoholization of the trigeminal nerve is indicated. Alcoholization with neuralgia of the first branch of the trigeminal nerve in most cases is ineffective.
In severe forms of trigeminal neuralgia, after unsuccessful attempts at drug and physiotherapeutic treatment, extracranial novocaine and alcohol blockades, sometimes undertaken transections and exeresis of the peripheral branches, indications for intracranial operations arise.
Injections of various substances into the gasser node or the intracranial sections of the branches of the trigeminal nerve, or coagulation of the gasser node by puncture access through the skin of the face with a needle passing through the foramen ovale with trigeminal neuralgia, have become quite widespread.
The introduction of novocaine or alcohol directly into the gasser knot with trigeminal neuralgia often gives a good result, and when the pain returns, a second injection is made. However, this method is associated with the risk of damage to adjacent brain formations, since the injected alcohol spreads into the cranial cavity.
Even after a safely injected alcohol into the gasser knot, adhesions can form in its circumference, which, if necessary, an intracranial operation is a cause of great difficulties for the neurosurgeon.
Deep injections of alcohol into the trunks of the second and third branches of the trigeminal nerve in the area of the round and oval foramen have been used by some surgeons, but exact hitting the trunks requires thorough preliminary training on corpses and even in experienced hands due to the individual characteristics of the skull skeleton sometimes turns out to be impossible.
To achieve hydrothermal destruction of the sensitive root of the trigeminal nerve, percutaneous puncture of the foramen ovale is used (using the principle of stereotaxic neurosurgery). After passing the needle under X-ray control into the cranial cavity to the sensitive root of the trigeminal nerve, its thermal destruction is performed by injecting hot water in a small dose into the trigeminal cistern of the Meckel's sinus.
Electrocoagulation of the Gasser node using a needle inserted through the foramen ovale was applied back in 1931 by Kirshner using a specially designed apparatus. In 1936, this author reported that when 250 patients with trigeminal neuralgia were treated by this method, relapses of pain occurred only in 4% of cases. Schmechel (1951) reported the results of electrocoagulation of the gasser node according to Kirchner in 118 patients: in half of the patients with trigeminal neuralgia, the pain disappeared after single electrocoagulation, in the rest, it was possible to achieve success after repeated or repeated use of the method.
Heness (1957) recommends using electrocoagulation of the gasser's node for trigeminal neuralgia in elderly patients: for 229 coagulations performed in 171 patients, 62.5% showed recovery, 15.8% improved, and there was not a single death. Only 25 patients with trigeminal neuralgia had to undergo intracranial surgery.
The idea of removing the Gasser's ganglion in severe neuralgia of the trigeminal nerve was implemented by Rose (1890), who, after resecting the upper jaw, penetrated the foramen ovale at the base of the skull and scraped out the Gasser's ganglion in parts. The method did not become widespread due to its difficulty and non-radical nature.
Temporal access to the Gasser's ganglion
Hartley (1882) and Kruse (1882) described intracranial access to the Gasser's ganglion with the aim of removing it in trigeminal neuralgia. After osteoplastic trepanation of the temporal bone scales, detachment of the dura mater from the base of the middle cranial fossa, and elevation of the temporal lobe, it is possible to obtain ample access to the Gasser's ganglion. However, extirpation of the Gasser's ganglion, which gives a satisfactory result in terms of getting rid of pain, is a difficult and dangerous intervention, especially in view of the thinness of the wall of the cavernous sinus, immediately adjacent to the node, and is no longer used at present.
This operation was replaced by a less traumatic, more easily performed, and no less effective operation of cutting the sensitive root behind the Gasser's ganglion, which was first successfully performed by Spiller and Frazier (1901).
This operation was proposed after experiments on dogs showed that after transection of the dorsal root of the trigeminal nerve, there were no signs of fiber regeneration. The essence of this operation is that after the formation of a small trepanation window in the temporal region, the dura mater is lifted from the base of the skull and the Gasser's ganglion is reached. After opening the Meckel capsule, the sensitive part of the trigeminal nerve root is cut behind the node, leaving its motor part intact.
This operation is still the safest and most reliable of all surgical methods for treating trigeminal neuralgia. Frazier found that from three parts of the Gasser's ganglion, three groups of fibers separate from each other enter the retrogasseral sensitive root, respectively, to the three peripheral branches of the trigeminal nerve; while the bundles of fibers run more or less in parallel, and only a few of them anastomoses.
Among the various improvements in temporal radicotomy for trigeminal neuralgia, the main one is the preservation of the motor root and partial transection of the sensory root, i.e. preservation of the first branch in the absence of its involvement in the pathological process in order to prevent neuroparalytic keratitis. If after total transection of the root of the trigeminal nerve, neuroparalytic keratitis, which in some cases ends with the death of the eye, occurs in 16.7%, then after partial transection of the root, it is observed in 4.4% of patients.
Suboccipital access to the Gasser's ganglion
The transection of the sensitive branch of the trigeminal nerve root directly at the pons of varoli from the side of the posterior cranial fossa was first successfully performed by Dandy (1925), who emphasized the advantages of this approach over the temporal one.
When the root of the trigeminal nerve is crossed at the pons, pain sensitivity is turned off, but in most cases, tactile sensitivity is preserved, which eliminates the unpleasant sensations of numbness on the side of the operation, which are often observed with temporal access.
The neurosurgeon Dandy had good results with this operation. Having by 1921, the experience of 200 operations of dissection of the root with neuralgia of the trigeminal nerve by the occipital path, he reported that the last series of 150 operations were not a single fatal outcome. However, the materials of other authors published later show that when approaching from the side of the posterior cranial fossa, a higher mortality rate is observed (3-5%) compared to the temporal approach (0.8-1.9%).
Relapses of pain after retrogasseral transection of the trigeminal nerve root, according to different authors, range from 5-18%. Often (according to different authors, in 10-20% of cases) in patients who have undergone the Spiller-Frazier operation for trigeminal neuralgia, paresthesias appear in the anesthetized area of the face, sometimes reaching a painful degree.
Considering that with the temporal extradural approach to perform retrogasseral radicotomy, a number of complications are observed associated with damage to the gasser node, superficial large petrosal nerve, oculomotor nerves, tympanic cavity, middle meningeal artery, an intradural approach technique was proposed for retrogasseral transection of the trigeminal nerve root, the above education. After opening the dura mater and raising the temporal lobe of the brain, the Meckel cavity is opened and the sensitive root is transected. In this way, 51 patients were operated on with fairly good results, but with two deaths.
In the literature, cases of neuralgia of the third branch of the trigeminal nerve in patients with epidermoids located in the cerebellar pontine angle have been described. This allowed Taarnhoy to suggest that, although under normal conditions, due to the anatomical location of the sensitive root of the trigeminal nerve, compression is impossible, however, even with the development of minor changes of a vascular or inflammatory nature in the membranes of the brain, compression of a part of the root in the narrow canal formed by the dura mater can occur in the area of the sharp upper edge of the stony bone.
In 1952, Taarnhoy made a report, unexpected for neurosurgeons, that pain in trigeminal neuralgia disappears after a simple "decompression" of the gasser node, in which a wide dissection of the dura mater is performed over the gasser node and root. For this, it is also necessary to additionally expand the opening in the tentorium, through which the root passes from the posterior cranial fossa to the middle one. Out of 10 patients operated on with this method with trigeminal neuralgia, 7 pain disappeared, and in three the effect of the operation was incomplete.
In 1954, Taarnhoy made an additional report on the good results of his operation in 76 patients with trigeminal neuralgia. According to Love and Svayen (1954), Taarnhoy's operation was performed at the Mayo clinic on 100 patients. In this case, complete success immediately after the intervention was achieved in half of the cases of trigeminal neuralgia, but in 31 patients a relapse occurred within 1-22 months after the operation.
In the historical aspect, there is a general trend towards the movement of interventions for trigeminal neuralgia from the periphery to the center. Starting with resections of the peripheral branches, then proceeding to transection of the root (first directly behind the Gasser's ganglion, and then at its entrance to the pons varoli), surgeons then undertook transection of the bulbospinal tract of the trigeminal nerve. In 1931, the anatomist Koontz proposed to cut the descending tract of the trigeminal nerve in the medulla oblongata. In this case, one should expect that the pain will be extinguished while the sensitivity of the face and oral mucosa and the motor portion of the root are preserved. In 1936 N. Burdenko proved the possibility of crossing the pathways in the medulla oblongata of a person by performing a bulbotomy operation for hyperkinesis.
The operation of tractotomy for trigeminal neuralgia was first performed by Shokvist (1937) and consists in the intersection of the sensory tract of the trigeminal nerve on the lateral surface of the medulla oblongata. Near the inferior angle of the 4 ventricles, in the immediate vicinity of the nerve bundles 10, a tracheotomy is introduced to a depth of 2-3.5 mm and an incision is made 2.5-4 mm long.
According to summary statistics, covering 583 Shoquist tractotomies for trigeminal neuralgia, postoperative mortality is 1.5%. On 124 tractotomies, a large number of relapses (37%) was noted, which is 5 times higher than their number with retrogasseral root transection using the temporal approach. This circumstance forces us to restrainedly treat tractotomy for trigeminal neuralgia, which has limited indications.
This operation is indicated in those cases of neuralgia when the previously performed retrogasseral root transection was ineffective or a relapse of pain arose some time after it. Shokvist himself (1957) considered this operation to be more indicated for neuralgia of the first branch in young people (to avoid constant tactile anesthesia in later life), with "large" trigeminal neuralgia in combination with pain caused by multiple sclerosis, and contraindicated for neuralgia of the third branches, since in the area of its innervation anesthesia cannot be guaranteed.
According to Dalessio (1982), 25-50% of patients with trigeminal neuralgia stop responding to pain medication. Such patients with drug-resistant trigeminal neuralgia are forced to resort to surgery to relieve the suffering. According to Tatli (2008), different surgical methods for treating pain in trigeminal neuralgia have both advantages and limitations.
Microvascular decompression of the trigeminal nerve
Microvascular decompression of the trigeminal nerve in the area of its exit in the cerebellopontine angle is recognized today as the most long-lasting pain-relieving surgery for trigeminal neuralgia. The operation for microvascular decompression of the trigeminal nerve is performed through the retrosigmoidal access (behind the auricle). Thus, there are currently three main surgical approaches to the intracranial sections of the trigeminal system:
- Temporal approach to the root and gasser node in the middle cranial fossa
- The suboccipital approach through the posterior cranial fossa, in which transection of the sensitive part of the root or the descending tract of the trigeminal nerve can be performed
- Microvascular decompression of the trigeminal nerve in the region of its exit in the pons
Medication treatment of trigeminal neuralgia
It should be pointed out that as new effective medications are proposed, the indications for surgical treatment of trigeminal neuralgia in some patients are decreasing. In particular, a pronounced therapeutic effect in this disease of Tegretol, Lyrica, Suksilep can be noted.