Causes of facial pain

Facial pain is one of the most challenging entities for physicians and healthcare providers. This is mostly due to a wide range of etiologies (causes) for facial pain. These include those that are neurological (e.g. trigeminal neuralgia, trigeminal autonomic cephalalgia), dental (e.g. temporomandibular joint disorders, tooth/gum issues), sinus and nose related, and those that are related to rheumatologic/autoimmune disorders. 

The trigeminal nerve

Nerve supply of the face comes from the trigeminal nerve which is one of twelve cranial nerves in the human body. Trigeminal nerve starts from the brain and after it exits the brain, as the name indicates, is composed of three (tri) main divisions. Each division branches out to multiple small nerves as shown in the picture: Those branches supply the sensation to different parts of the face, mouth, tongue, nose, and sinuses. Any damage, injury or disease that affects trigeminal nerve, anywhere from its origin in the brain, to smallest branches on the face, can cause facial pain.

Getting the correct diagnosis

It is important that physicians take every patient’s complaint of facial pain seriously. This includes gathering a thorough history plus examination of head, teeth, eyes, noses, throat, and even neck, since any of these structures can contribute to facial pain. Due to this heterogeneity of causes, patients with facial pain often need to consult with multiple providers in order to get the correct diagnosis and proper treatment. With an incorrect diagnosis and treatments, patients are very likely to experience a more intensified pain and discomfort.

Medical causes of facial pain

Although most of the time, injury to the trigeminal nerve is due to trauma – like dental procedures, or compression of nerves by blood vessels or tumor, occasional medical disorders that affect the trigeminal nerve can be a source of the facial pain. Medical causes of trigeminal nerve injury are still not very known nor studied. In general, any pain that happens due to an injury to a nerve is referred to as a “neuropathic pain.” This definition is broad and covers over 100 conditions. 

Trigeminal neuropathic pain that is not TN

When the injury to the trigeminal nerve happens in the brain due to compression by blood vessels, it is known as trigeminal neuralgia which has very classic symptoms. The most challenging cases of trigeminal “neuropathic pain” involve patients with facial (trigeminal) pain who do not have classical trigeminal neuralgia. Most of these patients are labeled as having “atypical facial pain” or “atypical trigeminal neuralgia.” In practice, it reveals that some of these patients might have a “systemic medical disorder” which involves the trigeminal nerve, causing facial and trigeminal pain. 

Diseases and disorders

Among systemic medical causes, “inflammatory and autoimmune diseases” seem to be the most common disorders that can involve trigeminal nerves. Some of the autoimmune diseases such as Sjögren syndrome, scleroderma, lupus, and undifferentiated connective tissue disorder, can attack the trigeminal nerve and cause facial pain, sometimes similar to trigeminal neuralgia. We refer to this group of patients as “inflammatory trigeminal neuropathy” or “autoimmune trigeminal neuropathic pain.” 

It is critical to differentiate these groups from classical trigeminal neuralgia because the classical trigeminal neuralgia is treated with surgery called microvascular decompression that has shown to be the most effective treatment. If the two groups are not well differentiated and they are treated by performing the surgery, not only won’t the surgery make a difference, but it also might make the pain even worse and intractable to treatments. 

Sjogren syndrome

Two autoimmune disorders that most likely affect the trigeminal nerve are Sjögren syndrome and scleroderma: Sjögren’s syndrome is a chronic systemic autoimmune disease and like most autoimmune disorders it is more common in women. It is one the more prevalent autoimmune disorders which, since it’s symptoms sometimes are mild, it might not even be diagnosed. The main target of Sjögren’s syndrome is exocrine glands, which causes dryness of the main mucosal surfaces and therefore dry eyes and dry mouth are the key features of this syndrome.

If Sjögren’s syndrome does not affect any other organs, it might not even be diagnosed just based on dry eyes or dry mouth symptoms since these symptoms are nonspecific and common in the general population. However, in Sjögren’s syndrome, a variety of systemic manifestations may occur, including fatigue, musculoskeletal symptoms, cutaneous lesions and internal organ and neurological involvement. Based on some reports, up to 70% of Sjögren’s patients may suffer from neurological manifestations. “Neuropathy” is a classic neurological manifestation of Sjögren’s syndrome, therefore trigeminal nerve involvement could happen as part of neurological manifestation of Sjögren’s patients. In fact, trigeminal nerve is the most common cranial nerve that can be involved in Sjögren’s syndrome. As a result, in patients who have trigeminal neuropathy due to Sjögren’s syndrome, with no other cranial nerve involvement, facial and trigeminal pain will be the only major symptoms of the Sjögren’s syndrome since dry eyes or dry mouth symptoms could be mild.

In patients with facial and trigeminal pain who do not have classic trigeminal neuralgia, presence of some nonspecific symptoms could suggest the possibility of Sjögren’s syndrome. These symptoms could be:

• Unexplained fatigue or tiredness

• Severe dry eyes that require treatment. Complaints that can happen due to dry eyes are broad and could be feelings of stinging, burning or itchy eyes, feeling of sand in the eyes, sore and swollen eyelids, discomfort when looking at light or even blurry vision. 

• Severe dry mouth which can present with tongue sticking to the roof of mouth, feeling that food stuck in the mouth or throat, specifically dry food even changes in how food tastes.

 • Frequent dental cavities despite keeping good dental hygiene 

• Dry skin or vaginal dryness

• Rashes (especially after being in the sun) 

• History of multiple unexplained miscarriages 

• Muscle and joint pain with stiffness and swelling 

These are the symptoms that are usually not asked about by physicians if patients present with facial and trigeminal pain. Therefore, patients need to be aware of this disease and pay attention to those nonspecific symptoms, particularly when they’re diagnosed as “atypical trigeminal neuralgia” or “atypical facial pain”.

Diagnosis of Sjögren’s syndrome is not always easy since the blood test that is for Sjögren’s could be negative in up to 40-50% of patients with this syndrome. Particularly in the patients who are in the beginning of the disease process and their body probably did not make enough antibody to be detected. Therefore, in patients with facial pain for whom there is a question of Sjögren’s syndrome as the reason for their trigeminal neuropathic pain, consultation with an expert physician in this field (usually rheumatologist) might help to clear the potential Sjögren diagnosis and lead to proper treatment. 

Scleroderma

Scleroderma has been described as a chronic autoimmune disorder which is much less common compared to Sjögren’s syndrome. However, since neurological and particularly trigeminal nerve involvement is one of the most common manifestations in this autoimmune disease, it’s worth to mention it as a potential differential diagnosis of facial pain.

Scleroderma like Sjögren’s syndrome is more common in women and in young to middle age, with peak onset in individuals aged 30-50 years. Patients with scleroderma, experience progressive skin tightness and induration, often preceded by swelling and puffiness The other important symptom that can be suggestive of scleroderma is “Raynaud’s phenomenon”. Raynaud’s phenomenon is pale to blue to red sequence of color changes of the fingers or toes, most commonly after exposure to cold. 

Raynaud’s is more characteristic of scleroderma but can be seen in other autoimmune disorders. Raynaud’s phenomenon that is not associated with systemic sclerosis or other autoimmune diseases is known as primary Raynaud phenomenon. It occurs in 5-15% of the general population. 

Beside skin manifestation, scleroderma, like Sjögren’s syndrome has lots of nonspecific symptoms including: 

• Gastrointestinal symptoms which can range from dyspepsia, bloating, reflux to difficulty swallowing 

• Respiratory symptoms like progressive shortness of breath, chest pain and dry persistent cough 

• Musculoskeletal symptoms like severe muscle pain and fatigue and even muscle weakness, joint pain with loss in joint range of motion

• Kidney involvement, which usually presents with early onset hypertension, usually resistant to regular treatment which sometimes can cause renal failure 

We need to keep in mind that since the symptoms in Sjögren’s syndrome and scleroderma as well as other autoimmune disorders that can attack trigeminal nerve are nonspecific, the entire clinical picture needs to be considered before suggesting these possibilities as the reason for facial pain. The most important factor is “age of the onset” of trigeminal pain. Since classical trigeminal neuralgia, which is the most well-known etiology for facial pain, never starts before the age of 40 and rarely before the age of 50. Patients with facial pain in that age group need to be aware of the possibility of autoimmune disorder as a differential. Particularly because it is noted that those age groups (between 20-50 years) are the most common age for autoimmune disorders.