Many of us have experienced symptoms of COVID either first hand or from someone we know. Many, if not everyone, have had discussions like "well...it started out with a sore throat, then fever, then fatigue" or "I just felt a little off and then was fine" or "it wiped me out for days and I still can't smell or taste my food". But, if you thought symptoms of COVID were limited to:
Loss of taste or smell
Nausea or vomiting, and
Well, think again. Now we can add dizziness to that list. Symptoms can include:
A sensation of you or the world around you spinning (vertigo)
Feeling of unsteadiness or off-balance (disequilibrium)
A swaying or rocking sensation like you're on a boat
Light-headedness or sensation of floating
I realize this news comes at a time when people may be tired of hearing anything related to the C-word, or at a time when there is increased fear about a highly contagious new variant, but as a vestibular therapist who treats dizziness or if you experience a new onset of dizziness, it's an important differential when understanding the source of your symptoms. So here we will explore the evidence of post-COVID dizziness.
But I though COVID was a respiratory condition???
It is! Coronaviruses primarily affect the lining of the respiratory system, or epithelial tissue. They do this by attaching to a specific receptor on epithelial cells, angiotensin converting enzyme-2 (ACE-2). Once the virus attaches to this receptor it is then internalized by the cell and the virus' RNA then translates, replicates, and releases itself back into circulation in search of more ACE-2 receptors. ACE-2 receptors can be found in various body systems including the respiratory tract, lungs, kidneys, small intestine...and yes, you guessed it, the brain!
It is estimated that approximately 36% of patients hospitalized due to COVID-19 present with neurological symptoms including headache, dizziness, confusion, reduced consciousness, loss of taste or smell, muscle problems, stroke and seizures (1-2,6). It is also noted that neurological symptoms occur early on in the disease process and may be a sign of future disease progression, as well as another post-marker of when to test for COVID (1-3). Systematic reviews approximate headache and dizziness being the most common neurological symptoms, with dizziness ranging from an 8-13% prevalence (1,2). So we know the virus can attach and invade cells of the brain, but how does it affect the vestibular system specifically? The research is still inconclusive on the exact pathophysiology of the effects of COVID on the vestibular system. However, with what we know of how this virus impacts cells, neurons, and blood vessels, researchers have deduced a few possible mechanisms.
Initially, probably the most widely-known neurological symptoms were sudden loss of taste and/or smell. Our sensation of taste and smell arise from cranial nerves in the brainstem (the lowermost part of the brain). There are the olfactory nerve (smell) and the facial and glossopharyngeal nerves (taste). Just as COVID can affect these cranial nerves, it isn't surprising that is could affect the vestibularcocholear nerve, the cranial nerve responsible for spatial awareness/balance and hearing. When this nerve becomes inflamed by a viral infection, we can experience symptoms of dizziness and/or hearing loss. This is precisely what happens when someone experiences a condition known as vestibular neuritis or labyrinthitis, -itis meaning inflammation of the vestibular nerve or the labyrinth (vestibulocochlear organs). In fact, one of the very first reports of post-COVID dizziness mimicked vestibular neuritis/labyrinthitis when a women presented to the emergency department with a sudden onset of severe vertigo, imbalance, nausea, and vomiting (4). She was treated with steroids and vestibular therapy, as is normal for vestibular neuritis and was asymptomatic within a couple of weeks.
Decreased blood flow
Inflammation also sets off a cascade of events that can have significant downstream consequences. During periods of increased inflammation, your body produces a blood clotting promotor called thrombin. Say you have a cut or a wound, inflammation initiates blood coagulation via thrombin, your blood clots, and your cut or wound can stop bleeding and begin to heal. However, you do not want your blood to clot too much or you run the risk of getting clots in places you don't want, namely your lungs (pulmonary embolism) or your brain (ischemic stroke). For this reason, the body controls the levels of thrombin with anti-coagulating factors, such as anti-thrombin II. During COVID, these anti-coagulating factors can get impaired, and therefor the concentration of coagulating factors becomes higher than anti-coagulating factors, putting you at risk for blood clots (5). As mentioned, these clots can get into the brain, cutting off blood supply to parts of the brain that control our vestibular system, such as the aforementioned brainstem and cerebellum (my favorite part of the brain!). Clots can also cut off blood to the vestibular system itself in our inner ear. Keep in mind, the incidence of this is quite low with systematic reviews reporting anywhere from 1.5-2.5% of patients hospitalized with COVID (1,2,6).
Just as a viral infection can cause inflammation and dysfunction to the vestibulocochlear nerve, certain drugs can also damage this nerve. This is known as ototoxicity. Oto- meaning ear, and toxicity- meaning...well, I think you can guess what it means. Remember, when the vestibulocochlear nerve is damaged, you can get symptoms of hearing loss, tinnitus (or ringing in the ears), and dizziness or imbalance. Unfortunately, certain medications used to treat COVID, have also been known to have ototoxic capacities. Hydroxychloroquine, used to treat malaria, and currently being widely used to treat COVID can result in mild to complete, reversible and irreversible, hearing loss. Ivermectin is an anti-parasitic drug that, while not approved by the FDA for the treatment of COVID, has been used to treat COVID. While hydroxychloroquine primarily affects the cochlear (or hearing) part of the vestibulocochlear nerve, ivermectin primarily affects the vestibular (or balance) part of the nerve, resulting in dizziness and imbalance. Other drugs used to treat COVID with potential ototoxic effects include: azithromycin, lopinavir-ritonavir, and ribavirin (7).
Prolonged bed rest
If you are unfortunate to be hospitalized due to COVID, chances are you have been laying in a bed for days, possibly weeks or months. Prolonged bed rest is considered a risk factor for developing Benign Paroxysmal Positional Vertigo (BPPV). As an avid reader of my blog, I'm assuming you have a good understanding of BPPV:) But if not, feel free to catch yourself up!
A small study looked at eight patients hospitalized with COVID and reporting dizziness. All eight patients were found to have BPPV. The study postulates that this could be due to prolonged bed rest, viral inflammation of the vestibular nerve (as discussed above), certain medications, or forced positioning (8). This latter, known as "proning", is where patients are rolled onto their stomachs to help clear their lungs of fluid. It is thought that proning may contribute to dislodging the otoconia from the inner ear and thus causing BPPV.
Can Vestibular Rehabilitation Help?
We are still learning a lot about how COVID affects the vestibular system, and therefor treatment options. However, in the causes outlined above, vestibular rehabilitation can help significantly improve or completely resolve dizziness symptoms. Some causes such as BPPV can be resolved in as little as 1-2 visits; whereas, other causes such as inflammation, blood flow, and ototoxicity may take months. If you have recently had COVID and are experiencing symptoms of dizziness, let your primary healthcare provider know and seek out a qualified vestibular physical therapist.
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Pinzon RT, Wijaya VO, Buana RB, Al Jody A, Nunsio PN (2020) Neurologic characteristics in coronavirus disease 2019 (COVID- 19): A systematic review and meta-analysis. Front Neurol. 2020;565(11).
Montalvan V, Lee J, Bueso T, De Toledo J, Rivas K. Neurological manifestations of COVID-19 and other coronavirus infections: A systematic review. Clinical Neurology and Neurosurgery. 2020;194:105921.
Malayala S V, Raza A (June 30, 2020) A Case of COVID-19-Induced Vestibular Neuritis. Cureus 12(6): e8918.
Jose, RJ, Manuel, A. COVID-19 cytokine storm: the interplay between inflammation and coagulation. Lancet Respir Med. 2020 Jun;8(6):e46-e47.
Harapan BN, Yoo HJ. Neurological symptoms, manifestations, and complications associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease 19 (COVID-19). J Neurol. 2021;268(9):3059-3071.
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Picciotti PM, Passali GC, Sergi B, De Corso E. Benign Paroxysmal Positional Vertigo (BPPV) in COVID-19. Audiol Res. 2021 Aug 13;11(3):418-422.