The main area to focus on when considering causes of facial numbness is the trigeminal nerves. These nerves will be affected in a number of ways which will result in decreased sensation to the side of the face involved. It's important to note that facial muscle control is not affected as the facial nerves, which are structures independent of the trigeminal nerves, supply muscle control to the face.
The trigeminal nerves are cranial nerves that originate from the brain stem and come around the face on either side to supply sensation to this area. The nerves divides into 3 main branches:
- The ophthalmic branch - the area of the forehead, eyes and top of the nose are supplied with sensation by this nerve.
- The maxillary branch - the area between the nose and including the upper jaw are supplied with sensation by this nerve.
- The mandibular branch - the area of the lower jaw and up to and including the temporal areas of the head are supplied with sensation by this nerve.
Causes of facial numbness
We shall now focus on the different mechanisms that can affect the trigeminal nerves in the face and how these situations would present in patients.
- Stroke and TIA (transient ischemic attack)- when blood flow to the brain is interrupted, the part of the brain which handles facial sensation is affected and numbness can occur. More severe symptoms such as power loss or paralysis dominate these issues though.
- Nerve injury - the above mentioned areas of the trigeminal nerves can be affected by direct trauma to those branches or compression of those branches due to prolonged pressure on them such as can occur when sleeping in an awkward position. These situations tends to resolve on their own when the pressure is relieved or when swelling of the nerves reduce.
- Peripheral neuropathy - nerve dysfunction can be caused by conditions such as diabetes, vitamin B6 deficiency, lead poisoning and excessive alcohol intake. Other causes of this condition may also include electrolytes imbalances of sodium, potassium or calcium.
- Migraines - during the aural or prodromal phase of this condition, that is to say during the time when associated symptoms occur, facial numbness can be one of the symptoms.
- Brain and nerve tumours - compression by these tumours can affect the function of the trigeminal nerves.
- Shingles - this is a blister-type rash caused by the herpes zoster virus which stays dormant in nerve cells and is then activated to result in an acute infection. During the prodromal phase, which occurs before blisters erupt, pain and decreased sensation can occur due to the virus affecting the nerves.
- Hypothyroidism - decreased thyroid functions can result in the trigeminal nerves being affected.
- Psychogenic/somatoform conditions - major depression, emotion and physical stressors as well as generalized anxiety and panic attacks can lead to facial numbness.
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