There are several possible causes of facial numbness, also known as hypesthesia. Most of these causes can be traced to a problem in or affecting the trigeminal nerve.
It is one of twelve cranial nerves and is one of the most widely distributed nerves in the head. The cranial nerves can be categorized as two main nerve types: those that control motor responses such as blinking, chewing, or eye muscle movement, and those that respond to the sensations of taste, smell, hearing, and touch.
Numbness is an absence of the sense of touch. The trigeminal nerve, which as the name implies has three branches, controls both the sense of touch in areas in the face as well as the motor function associated with chewing. Damage to this nerve could, therefore, make chewing difficult, if not impossible, which would be a condition of paralysis. Some sufferers of face numbness also experience numb lips. Or it could create either a “pins and needles” sensation or a loss of feeling in parts of the face. Of the twelve facial nerves, it is usually considered number 5.
Several of the more well-known facial nerves are the oculomotor nerve (number 3), which controls the external muscles of the eye, the olfactory nerve (number 1), which relays the sense of smell to the brain, and the auditory nerve (number 8), which controls balance and hearing. The facial nerve (number 7) does not relay a sense of touch. It controls the muscles used in facial expressions and should not be confused with the trigeminal nerve, despite its name.
It becomes apparent that if several of these nerves are damaged, a number of different symptoms might be experienced. That is, of course, a somewhat unlikely event. Damage to the cranial nerves in the central nervous system would most likely cause a combination of numbness or paralysis in various parts of the body. Facial numbness in itself would usually be traced back to the trigeminal nerve and that nerve alone. Damage to the facial nerve or a dysfunction of that nerve, such as can be the case with Bell’s palsy, can cause paralysis of the facial muscles but seldom results in numbness.
The Anatomy of the Nerve
It was mentioned earlier that this nerve has three branches. If only one branch is affected, only one part of the face will experience numbness, pain, or some other nerve-related condition. In almost all cases, only one side of the face will be affected because there are two of them, one branching out from each sides of the central nervous system.
The upper branch is called the ophthalmic branch. This branch supplies sensation to the forehead, most of the scalp, and parts of the front of the face. The middle, or maxillary, branch services the cheek, the top lip, the upper jaw and gums, and the side of the nose. The lower, or mandibular, branch supplies sensation to the lower lip, jaw, teeth, and gums. One of the more unusual types of numbness in the facial area affects only the chin, in which case it is the mandibular branch that has been adversely affected by some condition.
There are approximately 12 primary causes of facial numbness plus the catch-all idiopathic cause where the face can become numb but the cause or causes remain unknown. Some of these causes will result in temporary numbness, some will cause a permanent loss of sensation, and still others can result in alternating periods of numbness or partial numbness together with periods during which normal sensations are felt.
Primary Causes of Facial Numbness
Hypothyroidism is a condition in which the thyroid gland is under-active and consequently fails to produce an adequate number of certain hormones required by the body. Hypothyroidism upsets the chemical balance the body is constantly attempting to maintain. Over time, hypothyroidism can lead to a number of adverse health conditions. There are many different symptoms that can be experienced by someone who has a hypothyroid condition, numbness to the face or other parts of the body being only one of them. Many different organs can be affected by hypothyroidism so it should come as no surprise that the nervous system could be affected as well. Numbness does not necessarily indicate hypothyroidism, but there have been cases where hypothyroidism has been found to be either a primary or a contributing factor to the numbness. The numbness itself has also been diagnosed as being a symptom of the condition.
Shingles is caused by the varicella-zoster virus.
It generally affects only adults and only those who have been infected with the chickenpox virus during their youth. If shingles does strike, it normally strikes only once, although in about 1 out of every 20 cases people will experience shingles more than once. Shingles typically appears on a part of the body and on one side of the body only. Its symptoms are usually present at or near the surface of the skin, but the condition can occur anywhere in the body, in rare cases even affecting vital organs. Shingles can occur in the face – facial shingles – and can cause nerve damage which usually tends to be temporary. The symptoms can be facial pain or numbness, either of which can last for several months if the trigeminal nerve has been affected. Shingles can be treated with medications to lessen the symptoms until the condition goes away on its own.
3) Trigeminal Neuralgia
Trigeminal neuralgia, or TN, often occurs when a blood vessel exerts too much pressure on the trigeminal nerve where it exits the brain stem. This pressure, which can be constant or off-and-on, tends to wear away the protective sheath that surrounds the nerve. TN can also be caused by a tumor and is sometimes one of the side effects brought about by multiple sclerosis. The primary symptom of TN is pain, which is often sharp and can eventually become debilitating. Numbness can also at times be a major symptom, a symptom which, while disconcerting, can be a great deal more bearable than pain.
Numbness experienced in the face or along one side of the body is one of the lesser known symptoms of a stroke. Stroke symptoms are usually thought of as facial drooping, weakness in an arm, slurring speech and sometimes the development of a sudden limp. When numbness occurs in the face as a result of a stroke, it can represent a somewhat dangerous condition. This is not because the numbness itself presents a danger, but because the symptom does not tend to be associated with having a stroke and when a person suffers a stroke time is of the essence. As is the case with other parts of the body following a stroke, only one side of the body is usually affected. In this case, only one half of the face or a part of one half of the face is apt to go numb. Since a stroke affects the brain, however, it is likely the entire trigeminal nerve will be affected and either the entire right side or left side of the face, but not both sides, will suddenly go numb. In many cases the type of stroke involved is called a lacunar stroke. This is a stroke that occurs deep in the brain and typically only affects sensations and not movements.
5) Nerve Tumors
A neuroma is a growth or swelling affecting a nerve. Roughly half of all neuromas occur in the head or neck region, although facial neuromas are actually quite rare. They are so rare, in fact, that they are often misdiagnosed. When facial neuromas do occur, they are almost always benign. Nevertheless, a neuroma that places pressure on a nerve that is responsible for transmitting sensations to the brain can cause numbness to occur in the face. This depends, of course, on which branch of the nerve is affected.
6) Transient Ischemic Attack
A transient ischemic attack, or TIA, produces symptoms similar to that of a stroke except the symptoms, which can include numbness in one side of the face, tend to be temporary, usually lasting for only a few minutes and seldom longer than an hour. A TIA is in itself not particularly dangerous. The main danger behind this type of attack is that a person who has experienced one is usually at a much higher risk of experiencing a stroke later on. A TIA can, therefore, present an opportunity to take preventive measures to lessen the chance of experiencing a stroke at a later time. Common TIA symptoms are weakness in the muscles of the face, temporary paralysis of the facial muscles, or numbness. It is possible to experience more than one TIA and, should the symptoms last for 24 hours or more, it is usually considered a stroke. A TIA is different than the much more common ischemic stroke in that, while a blood clot in the brain is the major cause, the blockage is brief and does not cause permanent damage. These blood clots either move up from the heart or are caused by cholesterol buildup in an artery which can lead to the formation of a clot. A TIA is sometimes referred to as a “mini-stroke.”
7) Hemiplegic Migraine
A hemiplegic migraine is a somewhat rare type of migraine. It is a severe type of migraine with aura. When a hemiplegic migraine is experienced, the symptoms often mimic those of a stroke, with muscle weakness, paralysis, or a feeling of numbness occurring in one half of the body. Numbness can occur in an arm, a leg, or one side of the face. At times pain is experienced rather than numbness. Pain, weakness, or numbness is often accompanied by other symptoms of a migraine with aura condition. Hemiplegic migraines appear to be primarily genetic in origin. Three genes have been shown to have a definite linkage to the condition. Defects of mutations in one or more of these genes can result in a limiting of the body’s ability to make a certain protein needed for clear communication between nerve cells.
There are two types of trauma which can cause numbness. One of them, and perhaps the more obvious of the two, is injury where the trigeminal nerve or one of its branches has suffered some physical damage.
This could cause a number of different symptoms, but a loss of sensation is one of the more likely ones. The other type of trauma results from a branch of the nerve becoming compressed. This is akin to sleeping on one’s arm with the result that the arm “goes to sleep,” a somewhat uncomfortable condition usually consisting of an initial numbness followed by a “pins and needles” sensation. Sleeping in an awkward position is one of the leading causes of trauma to the nerve and can result in facial numbness that, while temporary, can sometimes last for several hours or even longer.
9) Numb Chin Syndrome
A special type of numbness involving a part of the face is a result of the numb chin syndrome, so-called because of several factors involved. The chin tends to be affected rather than other parts of the face because the nerve innervating the chin, the maxillary nerve, is the only part of the nerve affected. While the primary cause is trauma, other causes of this syndrome can be much more serious as they involve either tumors or cancers. Cancers are especially serious because they may have invaded the jaw bone, although there are many other cancers which can lead to this particular symptom.
10) Multiple Sclerosis
The fact that one of the symptoms of multiple sclerosis, or MS, is numbness felt in one or more parts of the face should not be too surprising in that MS is a disease that affects the brain, the spinal cord and, of course, the nervous system. Early stage symptoms of this disease have a tendency to come and go and do not always point to MS as the cause. Many of these symptoms, facial numbness being a case in point, can easily be caused by another condition or disorder. Numbness in one part of the body or another, and especially in the face, tends to be one of the first symptoms experienced by a person who has MS. This numbness can progress over time for several hours and even for several days before it subsides, only to return at some later time.
11) Peripheral Neuropathy
Peripheral neuropathy refers to disorders of the peripheral nerves. The term once commonly used for these disorders was neuritis. This tended to suggest the presence of a single type of disorder, but there are a host of different conditions, well over 100 at latest count, that can contribute to this disorder. Insofar as the face becoming involved is concerned, peripheral neuropathy is a kind of catch-all condition since there are so many nervous system disorders that could conceivably cause numbness on one side of the body, an arm, a little toe, or the face.
12) Focal Seizures
In general, seizures affect major parts of the brain. Focal seizures on the other hand affect only a small part of the brain. Symptoms of focal seizures, sometimes called partial seizures, often primarily involve the face, producing twitching, abnormal facial movements, or numbness. The causes of these seizures can be complex but are usually described simply as a “mixing up” of electrical signals in the brain. These seizures can be simple or complex in nature and typically last anywhere from just a few seconds to several minutes.
Sometimes numbness can come about as a result of depression, feelings of acute stress, or panic attacks. When one of these conditions is the case, the numbness is said to be the result of a psychogenic condition. Brain tumors can be yet another cause of these feelings of numbness.
In summary, the causes of facial numbness can be quite large in number, yet the condition is not all that common. In most all instances, only one side of the face or a part of one side of the face will be involved. These symptoms can be transitory, long-lasting, or repetitive. A feeling may, in some cases, be a temporary, one-time occurrence. At other times the numbness may be symptomatic of an underlying condition that can be quite serious. As is the case with many symptoms, the duration of the symptom, its severity, and whether or not it appears to be chronic will determine if medical attention or advice is needed. One of the greatest dangers lies in the condition known as a transient ischemic attack. It is not dangerous in itself but is often misdiagnosed, if diagnosed at all, and is an indication that the person affected is at a somewhat high risk of experiencing a genuine stroke later on.