"Facial paralysis caused by air conditioning?" Doctors remind: The truth is...

As summer approaches, the temperature is getting higher and higher recently, and many people like to sleep with the air conditioner on. However, since many people find that their faces are paralyzed after getting up in the morning, they intuitively think that it is caused by the air conditioner and fan at night. So is the facial paralysis really caused by fans and air conditioners?

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There is nothing wrong with the idea of ​​looking for causes based on the chronological order, but be careful of a "logical trap" - the chronological order does not equal the causal relationship.

Let me first say the conclusion: whether you use a fan or air conditioner, your face can feel cool or even cold, but it will not cause facial paralysis.

Causes facial paralysis

The real culprit

The most commonly discussed facial paralysis has a professional name, called "idiopathic facial nerve palsy", also known as "Bell palsy", which is the most common type of facial paralysis. As the name suggests, this is a problem with the facial nerve. Patients with facial paralysis not only have their mouths tilted to one side, but also have air leaking from the corners of their mouths when they inflate, one eye cannot close, and when they look up, the forehead wrinkles on one side disappear or become lighter.

You should know that the facial nerve is not lying on the surface of the face. It is located very deep. The deepest starting point is in the brain stem, and then it runs in a bony canal. The shallowest branches are also buried in the muscles and glands, and are generally difficult to be injured.

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If it's not the wind, then what's the cause? So far, research has found that there are two possible causes: one is infection, and the other is "non-infection".

In terms of infection, reactivation of the herpes simplex virus is considered the most common cause [1]. Most people who experience facial paralysis also experience infection. The herpes simplex virus is a virus that particularly "likes to bully" nerves (a neurotropic virus). PCR-DNA testing has found that after the virus is reactivated, it will spread along the axons of the nerves (similar to wires), causing inflammation and demyelination (like destroying the insulating material outside the wire). In addition to the herpes simplex virus, many other viruses can also attack the facial nerve through various pathways. For example, the most familiar influenza virus is also a "suspected culprit" [2].

As for “non-infectious” causes, the main causes are compression and ischemia, which are concentrated in pregnant women. The risk of facial paralysis in pregnant women is three times higher than usual, especially in the last three months of pregnancy and the first week after delivery [3]. The reason may be related to “fluid retention” during this stage, because too much “water” may cause nerve compression.

In addition, pregnancy also puts the body in a "hypercoagulable state", which makes it easy for blood clots to form in the small blood vessels that nourish the nerves. The nerves do not receive enough blood supply and are then damaged [4]. (By the way, due to this hypercoagulable state, postpartum mothers should move around early instead of locking themselves in bed to "nourish blood clots.")

If you find yourself paralyzed

What to do?

Once you find that you have facial paralysis, the first thing you should do is go to the hospital and go directly to the neurology clinic. The reason why I emphasize this sentence is that you need to rule out central facial paralysis with the help of a doctor, such as stroke. If the final diagnosis is "idiopathic facial nerve palsy", you don't have to worry too much.

Because about 70% of people will recover spontaneously within the next 3 to 6 months[5]. If oral glucocorticoids are taken early, the complete recovery rate will be further improved to 80%~85%[6]. However, in reality, there is still a proportion of people who have not fully recovered or have mild sequelae even after half a year. This is more common in people who have very severe facial paralysis at the beginning, or are over 40 years old, have diabetes or hypertension that is not well controlled[7].

Therefore, combined with the best evidence in the world, the most recommended treatment plan is: take "prednisone" 40~60mg/day (dose adjusted according to body weight) within 3 days of symptom onset (7 days at the latest), and use it for 7 consecutive days. Considering the gastrointestinal side effects of glucocorticoids, some doctors will use stomach protection drugs at the same time, such as prazole. During medication, you also need to pay attention to blood potassium, blood sodium, blood pressure, and blood sugar. For specific situations, you must follow the doctor's instructions and never take the medicine on your own.

Summarize:

If you find that the corners of your mouth are crooked and there is air leakage when you inflate, it is basically facial paralysis. However, facial paralysis has nothing to do with air conditioning or blowing hair. The most likely causes are viral infection and edema compression. After discovering facial paralysis, the next step is to see a neurologist. After excluding central facial paralysis, the most common one is idiopathic facial nerve paralysis.

Don’t panic if you encounter this kind of facial paralysis, because about 70% of people will fully recover within 6 months even if they do nothing. Early oral hormones can increase the possibility of recovery to 80%, and oral hormones are currently the best evidence and most recommended treatment method.

References

[1]Schirm J, Mulkens PS. Bell's palsy and herpes simplex virus. APMIS. 1997 Nov;105(11):815-23. doi: 10.1111/j.1699-0463.1997.tb05089.x. PMID: 9393551.

[2]Gupta S, Jawanda MK, Taneja N, Taneja T. A systematic review of Bell's Palsy as the only major neurological manifestation in COVID-19 patients. J Clin Neurosci. 2021 Aug;90:284-292. doi: 10.1016/j.jocn.2021.06.016. Epub 2021 Jun 21. PMID: 34275565.

[3]Hilsinger RL Jr, Adour KK, Doty HE. Idiopathic facial paralysis, pregnancy, and the menstrual cycle. Ann Otol Rhinol Laryngol. 1975 Jul-Aug;84(4 Pt 1):433-42. doi: 10.1177/000348947508400402. PMID: 168802.

[4]Sax TW, Rosenbaum RB. Neuromuscular disorders in pregnancy. Muscle Nerve. 2006 Nov;34(5):559-71. doi: 10.1002/mus.20661. PMID: 16969835.

[5]Peitersen E. The natural history of Bell's palsy. Am J Otol. 1982 Oct;4(2):107-11. PMID: 7148998.

[6]Yoo MC, Soh Y, Chon J, Lee JH, Jung J, Kim SS, You MW, Byun JY, Kim SH, Yeo SG. Evaluation of Factors Associated With Favorable Outcomes in Adults With Bell Palsy. JAMA Otolaryngol Head Neck Surg. 2020 Mar 1;146(3):256-263. doi: 10.1001/jamaoto.2019.4312. PMID: 31971554; PMCID: PMC6990801.

[7]UpToDate: Bell's palsy: Treatment and prognosis in adults.

Author: Yu Zhouwei, attending physician of neurology, author of "Sleep Formula"

Reviewer: Gui Yaxing Director of the Department of Neurology, Shanghai First People's Hospital, Shanghai Jiao Tong University