Trigeminal neuralgia is a chronic syndrome, a neuropathic disorder that manifests itself with excruciating pain crises in the areas of the face innervated by the fifth cranial nerve : forehead and eye, jaw down to the chin or to the upper part of the cheek.
The trigeminal nerve
The trigeminus, also called the fifth (V) cranial nerve, originates from the brain stem, at the base of the brain, and represents the largest nerve termination within the skull. The V pair of cranial nerves (one for each side of the face) transmits sensory stimuli to the brain and receives motor impulses from it. The trigeminal nerve is in fact made up of motor and sensitive fibers.
Three branches run from each trigeminal ganglion:
- Upper branch (ophthalmic nerve, V1) - innervates eye, forehead, scalp and frontal face;
- Medium branch (maxillary nerve, V2) - innervates cheek, side of the nose, jaw, upper lip, palate, teeth and gums;
- Lower branch (mandibular nerve, V3) - innervates mandible, lower, lower part of lip, mouth and tongue. It also stimulates the movement of the muscles involved in biting, chewing and swallowing (it is a mixed sensory and motor nerve).
Neuralgia can affect one or more branches of the trigeminal nerve. The maxillary branch is most frequently involved, while the ophthalmic branch is the least affected termination.
Types of trigeminal neuralgia
Trigeminal neuralgia can be divided into several categories, depending on the type of pain:
- Type 1 trigeminal neuralgia (TN1) represents the typical manifestation, characterized by excruciating and intermittent pain (it occurs only at certain times and is not constant). TN1, when no cause of origin can be identified, is called idiopathic ;
- Type 2 trigeminal neuralgia (TN2) is known as atypical trigeminal neuralgia. The pain is acute and constant and may present burning characteristics;
- Symptomatic trigeminal neuralgia (STN) is instead the consequence of an underlying pathological condition, such as multiple sclerosis.
To learn more: Symptoms Inflammation of the trigeminal nerve
The main symptom of trigeminal neuralgia is severe, lancinating pain that comes on suddenly and is located in specific areas of the face. The painful crisis almost always involves only one side of the face and can typically involve the jaw, upper jaw, cheek and less often the eye and forehead.
Trigeminal neuralgia can present with a "tingling" sensation or numbness in the face, which turns into a burning pain, extreme or similar to an electric shock. A crisis can last from a few seconds to two minutes, but can be repeated in rapid succession throughout the day. Some people experience a dull and constant pain even in the refractory periods, which separate the different episodes of acute trigeminal neuralgia. However, the symptoms may disappear completely and not recur for months or years.
Typical trigeminal neuralgia (TN1) usually has the following characteristics:
- The pain is sudden, intermittent, sharp and excruciating or similar to an electric shock.
- You can experience regular spasms of pain for days, weeks or months for each episode.
- Pain may affect a limited area of the face or may spread to neighboring areas.
- The frequency of crises increases over time. In severe cases, pain can occur hundreds of times a day.
- Pain attacks rarely occur during the night when the patient is sleeping.
A less common form of the disorder, the atypical trigeminal neuralgia (TN2) is characterized, instead, by a less intense but pulsating and continuous pain, or by a dull burning sensation. This manifestation sometimes occurs sporadically, can last a day or more and is associated with a slight but persistent pain between the attacks. This form of trigeminal neuralgia responds less positively to treatment than the type 1 form.
Even if the exact causes are not always known, neuralgia is often determined by the compression of the trigeminal nerve or by an underlying disease (in the latter case it is called secondary trigeminal neuralgia ). Trigeminal neuralgia can also be an effect of the normal aging process.
Compression of the trigeminal nerve. Evidence suggests that in 80-90% of cases, the cause of neuralgia is the contact between the nerve and a blood vessel that runs close to it. This proximity can create pressure on the trigeminal nerve near the point where it enters the brain stem (the lowest part of the brain that merges with the spinal cord); repeated compressions cause erosion of the protective coating around the nerve (ie the myelin sheath), altering the normal conduction of nerve impulses.
Structural causes. Other causes that can affect the trigeminal nerve are damage to the relative myelin sheath, determined by:
- Blood vessel abnormalities (such as an aneurysm);
- Cysts or tumor formations ;
- Diseases such as multiple sclerosis, a long-term condition that affects the central nervous system;
- Post-herpetic complications (Herpes Zoster infections).
Triggering factors and trigger zones
Spontaneous attacks of trigeminal neuralgia can be caused by a wide variety of daily movements or activities. Some patients are sensitive in some regions of the face, called trigger zones, which, if stimulated, can trigger a painful crisis; these areas are usually located near the nose, lips, eyes, ears or oral cavity. Therefore, the appearance of painful attacks can be avoided by avoiding, as far as possible, the stimulation of these triggers; it is actually a rather spontaneous defensive reaction, for which some patients try to avoid talking, eating, kissing or drinking. Other activities, such as shaving your beard, putting on makeup or brushing your teeth, can also trigger trigeminal neuralgia. For example, pain can be caused by exposure to the wind. If this is the case, the patient can avoid sitting near open windows or air conditioning sources and wear a scarf wrapped around the face on particularly windy days. Even a very hot or cold drink can trigger pain: using a straw to drink hot or cold drinks can help prevent the contact of the liquid with the painful areas of the mouth.
The diagnosis is generally based on the analysis of the patient's clinical history and the reported symptoms, and in addition to an objective examination, it also requires a thorough neurological examination.
The first diagnostic approach is based on the collection of information related to the symptoms reported by the patient, in particular on the description of the characteristics and the position of the pain . The objective examination allows to evaluate in which areas the painful crisis occurs: head, mouth, teeth, temporomandibular joint, etc. The neurological examination allows defining exactly which branches of the trigeminal nerve are involved. Before confirming the diagnosis of trigeminal neuralgia, further investigations allow the exclusion of other pathologies that can cause facial pain. Furthermore, these analyzes are important to distinguish the classic form of secondary-form trigeminal neuralgia caused by another condition (called symptomatic trigeminal neuralgia). If this second case is confirmed from the diagnostic point of view, then the treatment must focus on the underlying disease.
Other disorders, such as post-herpetic neuralgia and cluster headaches, can cause similar facial pain. Even trigeminal nerve injuries (resulting from a dental operation, stroke or facial trauma) can produce a neuropathic disorder characterized by a dull, burning and persistent pain. Because of the overlapping symptoms, and the variety of conditions that can cause facial pain, making the diagnosis is often difficult; nevertheless, finding the exact cause of neuralgia is essential to define the correct therapeutic approach.
Other conditions that must be excluded are:
- Multiple sclerosis;
- Infection or rupture of a tooth;
- Pain in the lower jaw;
- Temporal arteritis;
- Traumatic injury of a cranial nerve (post-traumatic neuralgia);
- Facial pain with no known cause (idiopathic).
Most patients undergo magnetic resonance imaging ( MRI ) to rule out a tumor or multiple sclerosis as a cause of pain. This scan can clearly show whether the trigeminal is compressed by a blood vessel, cyst or neoplastic formations. An angiography performed by magnetic resonance ( MRA ) can also contribute to more clearly defining the etiology of trigeminal neuralgia: nerve compression, aneurysm and any other anomaly or malformation along the course of the nerve termination.
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