What is Trigeminal Neuropathy?
Trigeminal neuropathy refers to the condition where the trigeminal nerve, also known as the fifth cranial nerve, doesn’t function properly. This tends to result in numbing sensations, sometimes coupled with odd feelings classified as paresthesias, weakness while chewing, or even pain. The nerve can be affected anywhere from its source in the brain, branching out to the facial region. This condition could have known causes like injuries, tumors, autoimmune or demyelinating diseases, sometimes its cause remains unknown.
Sometimes, trigeminal neuropathy might be the first sign of an underlying tumor or a resurgence from a known cancerous process. Conditions like multiple sclerosis, brain tumors known as gliomas, and brain strokes are often reported to cause this neuropathy. Other causes include compression of the nerve due to blood vessels, tumors known as schwannomas or meningiomas.
Trigeminal neuropathy can cause pain in the region of the face that the trigeminal nerve has its branches. The pain is often relentless, and it feels like a burn or a squeeze, often bundled with heightened sensitivity to pain or cold temperatures. It’s really important to exclude other underlying dangerous conditions like cancer, blood vessel abnormalities, and autoimmune diseases.
It should be noted that trigeminal neuropathy and trigeminal neuralgia are separate conditions. Trigeminal neuralgia causes sudden, electric shock-like pain, but it doesn’t result in sensory or motor weakness. This neuralgia condition could be due to compression of the nerve because of blood vessels, known as classic trigeminal neuralgia. However, it could also be secondary caused by conditions like multiple sclerosis, blood vessel anomalies, or autoimmune diseases.
The trigeminal nerve is the biggest cranial nerve and comprises both sensory and motor sections. This nerve’s path can be split into four segments: brainstem, Meckel’s cave/cavernous sinus, and outside of the brain.
The brainstem contains three main nerve structures for sensory functions and one structure for motor function. These help in tasks like receiving sensory information from the muscles of the head and neck, and sending signals for processing located in the brainstem. It is also responsible for the sensations of touch, pain, and temperature that we feel in the lower face including the teeth and tongue, and helps with chewing movements.
The trigeminal nerve, after it leaves the brainstem, travels through a region near the brain called the prepontine cistern, and Meckel’s cave. The nerve then branches out into three parts that cover different areas of the face; one covering the region around the eyes (known as V1), one for the maxillary region (V2), and one for the mandibular region (V3).
The trigeminal nerve functions vary and include providing sensation to most of the face starting from the middle of the head to the lower chin, including the eye and outer ear, and the front 2/3rds of the tongue. The motor branches help in controlling the facial muscles involved in chewing. The nerve also plays a role in the control of some aspects of the sympathetic nervous system, which is involved in the body’s response to stress and danger, and the parasympathetic system, which controls the rest and digestion activities, including saliva production in certain glands.
What Causes Trigeminal Neuropathy?
Trigeminal neuropathy is a condition where the trigeminal nerve, which is responsible for sensation in your face, is damaged. This can have a variety of causes that range from minor to potentially life-threatening.
The most common cause is trauma, accounting for up to 40% of cases. This can occur accidentally, such as from a fall, or due to medical procedures like dental work. This trauma often results in damage to nerves in your mouth and lower face, which can lead to loss of sensation in these areas.
Another cause can be tumors, which can compress the nerve from either inside or outside of the skull, or spread along the nerve pathway. If you’re experiencing numbness in your lower lip and chin, this could be a sign of a serious condition, and you should seek medical advice immediately.
Blood vessels abnormalities, hemorrhages (bleeding), or disruptions in blood flow can also cause this condition and the symptoms can differ based on the location of the issue.
There are several diseases that can cause trigeminal neuropathy, with the most common being connective tissue disorder, scleroderma, progressive systemic sclerosis, and Sjögren’s syndrome. These conditions are often associated with painful nerve sensations, and a loss of sensation can occur in either one or both sides of your face.
Infections are not commonly associated with this condition, but they are still an important possible cause. In developing countries, leprosy is a significant cause of this condition. Other infections, like herpes simplex and the varicella-zoster virus, can also result in this condition.
There are other, less common conditions that can cause trigeminal neuropathy, with some of these being birth defects such as skull abnormalities, Arnold Chiari malformations, Moebius syndrome, and a lack of sensation in the face present at birth. Other rare causes include complications from sickle cell anemia, amyloidosis, and exposure to certain toxins.
Sometimes, if no cause can be found after extensive evaluation, this condition is labeled as idiopathic. The symptoms can last for several years, but about half of patients named with an idiopathic cause will recover over time without treatment. However, it’s important to continue regular check-ups, as this condition can be the first symptom of a serious underlying health problem.
Lastly, Raeder paratrigeminal syndrome is a rare but important type of trigeminal neuropathy to recognize and diagnose. It causes particular symptoms like partial eyelid droop and less pupil size on one side of the face, along with a headache or facial pain. It’s crucial to get checked, as various causes, like aneurysm, trauma, tumor or inflammation can produce this syndrome.
Risk Factors and Frequency for Trigeminal Neuropathy
Figuring out how many people have trigeminal neuropathy (a nerve-related condition in the face) can be difficult. There was one study that asked 535 mouth and jaw surgeons in California about their experiences with this condition. They reported that during their careers, 94.5% had seen injuries to the inferior alveolar nerve (a nerve in the lower jaw) and 53% had seen injuries to the lingual nerve (a nerve in the tongue).
Signs and Symptoms of Trigeminal Neuropathy
Patients with a condition called Trigeminal Neuropathy (TNO) often experience a range of symptoms affecting the skin and vision, along with certain motor manifestations. They may also experience a specific kind of pain associated with this condition.
The skin symptoms can include:
- Hypoesthesia – a partial loss of sensation
- Anesthesia – a complete loss of sensation
- Hyperesthesia – abnormal discomfort, such as burning or itching
When the first division of the trigeminal nerve (V1) is affected, patients often experience prominent visual symptoms due to this nerve’s involvement in providing sensory input to specific parts of the eye. These symptoms can include corneal scratches and loss of vision.
Patients can also present with motor symptoms, like spasms of the chewing muscles, weakness, or lockjaw. There could be an unusual reflex in the jaw as well. Doctors must carefully examine these patients to check for issues with other cranial nerves, particularly nerves VI, VII, and VIII. If multiple nerves are involved, it could indicate the presence of a tumor.
The pain experienced with Trigeminal Neuropathy differs from that of Trigeminal Neuralgia. While the latter is quick, sharp, shock-like pain without sensory loss or weakness, the former is a constant pain in areas served by one or more divisions of the trigeminal nerve. This pain can be accompanied by changes in sensation, heightened sensitivity to touch, and enhanced response to cold.
There are three main types of trigeminal neuropathic pain:
- Pain from a herpes zoster infection
- Post-herpetic neuralgia (PHN)
- Post-traumatic trigeminal neuropathic pain
Motor symptoms could also include a decrease in the strength of the chewing muscles, which may impact eating, drinking, and speaking.
Testing for Trigeminal Neuropathy
Diagnosing conditions that affect the trigeminal nerve, which is a nerve responsible for sensation in the face and motor functions such as biting and chewing, can sometimes be complicated. Symptoms alone can often lead to inaccurate conclusions. To accurately pinpoint the issue, doctors need a collection of medical investigations, which can include blood tests, fluid analysis from your brain and spine (also known as cerebrospinal fluid or CSF), and detailed imaging scans of the entire pathway of the trigeminal nerve.
Blood and CSF tests help check for possible infections caused by viruses or bacteria like herpes, syphilis, or leprosy, as well as inflammation-related conditions like multiple sclerosis, connective tissue disorders, Sjögren’s syndrome (an autoimmune disease that affects your saliva and tear glands), and sarcoidosis (a disease that causes inflammatory cells to form in various organs). These tests become particularly useful if there are other symptoms suggesting a person may have an autoimmune or rheumatologic disorder. The doctor might check for certain markers in your blood linked to these conditions, such as immunoglobulin, complement, and various antibodies.
If the exam results and symptoms highly suggest Sjögren’s syndrome, a small sample of tissue may be taken from your salivary glands (called a biopsy) for further examination.
To look for possible abnormalities or lesions in areas such as your sinuses, base of the skull, pontocerebellar angle (the area where the brainstem connects with the cerebellum), brainstem, or the cerebral cortex (the brain’s outermost layer), a complete radiological assessment is needed. This involves several types of imaging scans like X-rays, CT scans, and MRIs, with different areas being focused on depending on the modality.
For instance, a high-resolution CT scan of the brain, sinuses, and areas of the face like the jaw and cheeks is very effective in diagnosing tumors at the pontocerebellar angle. On the other hand, an MRI with a special dye (gadolinium) is considered the best way to view the course of the trigeminal nerve, especially for areas such as the pontocerebellar angle, the internal auditory canal, and the brainstem.
If the clinical examination suggests any issues with the mandibular nerve (a branch of the trigeminal nerve that controls jaw movement), the MRI should include the lower jaw area. Some special imaging modes (such as fat-suppressed images) can also be used to check for any spread of tumors along the nerve.
In some cases, the doctor might also request a CT angiogram or MR angiogram (imaging techniques that highlight the blood vessels) to check for abnormalities such as aneurysms or vascular malformations that could be pressing on the trigeminal nerve. Furthermore, they might also consider a CT or MR venogram (imaging techniques that focus on the veins) to evaluate the part of the trigeminal nerve that passes through a large vein at the base of the skull called the cavernous sinus.
Treatment Options for Trigeminal Neuropathy
Treatment for TNO, or idiopathic neuropathic orofacial pain, depends largely on what is causing the symptoms. One of the main goals of treatment, especially when pain is the most prominent symptom at first, is to reduce the pain by at least 30%. Treating this type of pain can be complex and often requires a several tactics.
For neuropathic pain, the first treatment option usually includes certain types of medication, such as tricyclic anti-depressants (TCAs), serotonin-norepinephrine reuptake inhibitors (SNRI), or gabapentinoids (like gabapentin and pregabalin). These medicines work by blocking or inhibiting certain chemicals in the brain and nerves that are associated with pain. Despite their effectiveness, they can have side effects, including drowsiness, dry mouth, dizziness, and in rare cases, more severe effects.
If first-line treatments are not sufficient, other options include topical lidocaine or capsaicin creams that are applied to the skin. These have the advantage of fewer overall side effects, but when used in the mouth, they can be less effective due to saliva. Opioids, a type of strong painkiller, are generally a third-choice option due to concerns about potential misuse and harmful effects.
The type of medication used will often be tailored to a patient’s individual health and personal preferences. It may be necessary to use a combination of medications from various classes. Among TCAs, nortriptyline is often preferred due to its lower sedative effects and fewer side effects compared to amitriptyline. As for SNRIs, duloxetine has been widely documented as effective in treating neuropathic pain.
If conventional treatments are not successful in managing pain, other therapies may be considered. These can include injections of botulinum toxin, nerve destruction procedures (neuroablation), cold therapy (cryotherapy), and nerve stimulation techniques (neuromodulation). These techniques have varying degrees of success.
Another important method of treating TNO is to address the root cause. For instance, if the pain is caused by an underlying condition, treating that condition could help to lessen the pain. If a tumor is affecting the trigeminal nerve, it might be surgically removed, and infections would be treated with antimicrobial medications. The herpes virus has been implicated in some cases of idiopathic TNO, and in these instances, antiviral treatment with acyclovir has shown some benefit. Steroids have also been tried with varying degrees of success.
Finally, the psychological aspects of dealing with chronic pain should not be overlooked. There is an increased chance of developing depression in patients dealing with chronic pain, which in turn, can actually worsen the symptoms of pain. Therefore, treating any concurrent depression is critical to effectively managing neuropathic pain. Therapies such as cognitive behavioral therapy (CBT) can be beneficial in helping patients cope with persistent pain and improve their quality of life.
What else can Trigeminal Neuropathy be?
When attempting to diagnose TNO, or Trigeminal Nociceptive Outflow (sharp facial pain), doctors need to be aware of several other conditions that might present with similar symptoms:
- Trigeminal Neuralgia: This causes severe, sudden pain that lasts from seconds to two minutes within the area serviced by the trigeminal nerve.
- Persistent Idiopathic Facial Pain: This is a condition where facial or oral pain occurs daily and lasts more than two hours a day for three months or longer.
- Central Neuropathic Pain: This is a type of pain related to underlying issues in the central nervous system like multiple sclerosis or post-stroke pain rather than the cranial nerve V.
- Primary Stabbing Headache: This condition causes sharp, sudden pains that only last a few seconds and can happen in the areas covered by the trigeminal nerve.
- First Bite Syndrome: This is characterized by sudden facial pain triggered by the first bite of a meal but lessens with subsequent bites.
- Paroxysmal Hemicrania: This condition results in pain often located in the ophthalmic trigeminal region, lasting from minutes to under two hours. It is often accompanied by symptoms such as eye tearing, eye redness, stuffy nose, ptosis (drooping of the eyelid), facial swelling, and flushing.
- Short-lasting Unilateral Neuralgiform Headache Attacks: This is characterized by sudden, intense bursts of pain in any of the three divisions of the trigeminal nerve. It lasts a few seconds to minutes and often comes with symptoms like redness and tearing.
- Dental Pain: This condition causes continuous, aching pain that’s often triggered by actions like brushing teeth or chewing food.
Recognizing and considering these conditions is crucial for accurately diagnosing TNO.
What to expect with Trigeminal Neuropathy
The overall outcome depends on the underlying cause of the TNO, also known as Trigeminal Neuralgia. If a tumor such as a meningioma, which is a type of non-cancerous tumor that forms on the brain or spinal cord, is pressing on the trigeminal nerve, it can often be removed through surgery leading to a successful treatment.
A granulomatous lesion, which is an area of inflammation in tissue, may react positively to drugs that modulate the immune response.
Dealing with neuropathic pain, which is caused by damage or disease affecting nerves, can be quite challenging. If the root cause is a disorder of connective tissue, its recovery is generally unlikely. If the pain is due to cancer, the prognosis is normally poor.
It’s also quite possible that some patients dealing with neuropathic pain won’t find relief with commonly used drugs. In such cases, treatments like injections of Botulinum toxin (a type of drug that blocks nerve activity), nerve ablation (which involves removing or damaging the nerve to relieve pain), or neuromodulation (a treatment that alters the nerve activity through delivering electrical or pharmaceutical agents directly to a target area) are considered. These options are usually saved for those patients who haven’t found relief with standard treatments or continue to experience symptoms. However, the outcomes of these treatments often vary from patient to patient.
Possible Complications When Diagnosed with Trigeminal Neuropathy
Trigeminal neuropathy is a condition that could lead to several complications including:
- Neurotrophic keratitis: This condition makes patients prone to developing sores on the clear front surface of the eye (cornea). The aim of treatment is to shield the cornea and prevent vision loss.
- Trigeminal trophic syndrome: This is typically seen as skin sores and abnormal sensations, stemming from damage in the trigeminal nerve system. It’s usually caused by procedures that damage the trigeminal nerve, strokes in the medulla or pons of the brain, head and face surgeries, injuries, and shingles infections. Management revolves around easing symptoms, promoting skin recovery, and averting skin infections.
- Numb chin syndrome: This usually manifests as a decrease or total loss of sensation over the chin and lower lip. The most frequent cause is tooth removal procedures, especially of the molars. Other triggers include drug reactions (like from mefloquine or allopurinol), infections (Lyme disease, herpes, or syphilis), multiple sclerosis, giant cell arteritis, rheumatic disorders, sarcoidosis, and stroke in the thalamus. Numbness occurring in this area may indicate more severe conditions.
Preventing Trigeminal Neuropathy
Patients should be educated about the signs and symptoms of a condition known as trigeminal neuropathy, which could be a result of an underlying medical condition. Trigeminal neuropathy is a disorder affecting the trigeminal nerves in the face, leading to pain, numbness, or tingling. It’s important for patients to receive a thorough examination and regular check-ups to monitor the condition.
Even though family doctors can identify this condition, visiting a general neurologist – a doctor specializing in nervous system disorders – is often recommended. Neurologists can help discover the root cause of the problem. Even if the first examination by the neurologist doesn’t show any abnormalities, it is still advisable to stay in touch with them to rule out conditions such as an autoimmune or neoplastic disease, which are conditions that involve the immune system or the uncontrolled growth of cells, respectively.
If a cause of the condition that can be addressed surgically is identified, the patient will need to consult with a neurosurgeon or neurovascular surgeon. These are specialists who operate on the nervous system, including the brain and the blood vessels in the brain, to determine if a surgical procedure is required.
