Long COVID Symptoms: Internal Tremors and Vibrations
Most people associate symptoms such as shaking or trembling movements with neuromuscular diseases, such as Parkinson’s disease—but now, some Long COVID patients have reported experiencing internal tremors and vibrations. These are described as movements or sensations inside the body, with or without visible external muscle movement—a symptom previously undiscovered in the complex pathology of the illness and quite rare in and of itself.
In a new study published in The American Journal of Medicine, led by Yale School of Medicine’s Harlan Krumholz, MD, Harold H. Hines Jr. Professor of Medicine (Cardiology), and Akiko Iwasaki, PhD, Sterling Professor of Immunobiology, the researchers sought to learn more by comparing Long COVID patients who have internal tremors and vibrations to Long COVID patients without these symptoms.
An understudied symptom
Back in 2021, a qualitative study by Dr. Krumholz collected emails and comments from patients with Long COVID experiencing internal tremors. "People around the world reached out to us and shared stories about their Long COVID symptoms, including internal tremors and vibrations, which they described as burdensome and, in some cases, quite debilitating,” says Tianna Zhou, MD, the first author of the paper and a recent graduate of Yale Medical School. “When we looked in the scientific literature, very few studies described internal tremors or vibrations in either Long COVID or other conditions. We wanted to shed light on a set of symptoms that are important to patients but understudied."
The severity of the tremors varies widely. In some patients, they affect the arms and legs, while others report feeling them throughout their body; the tremors can range from a slight vibration to a feeling of near paralysis and can occur at a frequency of every few hours all the way to a near constant basis. This study helped establish internal tremors as a prolonged and debilitating symptom in some Long COVID patients.
“Many patients with these symptoms have been dismissed, as this aspect of the syndrome has not been well described,” says Dr. Krumholz. “Others feel alone and wonder if they are the only ones experiencing it. This research informs the medical profession—and helps people with the condition know that they are not alone."
New findings on internal tremors
In the new study, Yale researchers compared demographic and socioeconomic characteristics of Long COVID patients with internal tremor symptoms, the effect of having other medical conditions prior to COVID-19, and the onset of new conditions. Of 423 Long COVID study participants, 37% described having internal tremors or vibrations.
Gender was the only statistically significant demographic factor that was identified—of the study group, 81% of female participants reported internal tremors as a symptom compared to 70% of male participants. Importantly, participants with internal tremors reported significantly worse Long COVID symptom severity and had higher rates of experiencing such additional wide-ranging symptoms as visual flashes of light, hair loss, tingling or numbness, chest pain, and ringing in the ears.
Participants with internal tremors reported higher rates of new-onset mast cell disorders, a group of diseases in which mast cells are abnormally active and typically cause symptoms such as itching, nausea, and abdominal pain. Participants also reported higher rates of new-onset neurological disorders and conditions, including seizures and dementia, as well as stress and anxiety disorders compared to Long COVID participants without internal tremors.
A possible treatment
Currently, low-dose naltrexone (LDN), a drug that has been used to treat chronic pain and discomfort in fibromyalgia and other rheumatological disorders, is sometimes used to relieve internal tremors and vibrations in Long COVID patients with varying levels of success. When administered in a daily dose of 1 to 5 mg, naltrexone is thought to reduce inflammation, release endorphins, and normalize cortisol levels to alleviate discomfort. At its usual dose—50 mg or greater—naltrexone is used to treat addiction.
In one study, 52 participants with Long COVID were treated with a two-month course of LDN. The researchers conducted a survey and found that the participants reported an improvement in Long COVID recovery, daily activity limitation, energy levels, pain levels, concentration levels, and sleep disturbance. The study concluded that LDN was safe to use in Long COVID patients but required additional randomized control trials to validate its therapeutic use.
“Just recognizing these symptoms is important to patients, but the real need is for targeted therapies," says Dr. Krumholz. “By deepening our understanding of the mechanisms of Long COVID, we aim to identify potential treatments that can alleviate the burden of this condition.” The Krumholz lab, in collaboration with Iwasaki and her lab, aims to continue advancing knowledge of Long COVID and hopes to develop targeted therapies for patients affected by Long COVID.
Kenny Cheng is an undergraduate majoring in molecular, cellular, and developmental biology at Yale University.
The last word from Lisa Sanders, MD:
Internal tremor was one of the first unusual symptoms I heard about from my patients when I started the Long COVID Care Center at Yale in January of 2023. My patient, a young man from New York City, described a strange shaking or vibration in his internal organs—the way you might feel when standing next to a rapidly spinning motor or when attending a concert where the subwoofer is turned all the way up and the sound of the bass seems to travel through the body. He found low-dose naltrexone useful for this disquieting symptom. Since then, I’ve seen many people who share this unusual symptom. Sometimes it’s reported as mild and annoying—as it was for that first patient I saw. For others, it can contribute to a cacophony of symptoms that make even getting out of bed daunting.
The recent observation by Zhou et al. (The American Journal of Medicine study mentioned above) that this tremor is often seen in those most dramatically and devastatingly affected by Long COVID has changed my approach to patients, and I now routinely ask about this specific symptom. I continue to try low-dose naltrexone but eagerly await studies to support the efficacy of this and other medications to treat these unusual tremors. As is said far too often with this disorder—more research is desperately needed.
Read other installments of Long COVID Dispatches here.
If you’d like to share your experience with Long COVID for possible use in this blog (under a pseudonym), write to us at: LongCovidDispatches@yale.edu. It may appear, space permitting, in a future post.
Information provided in Yale Medicine content is for general informational purposes only. It should never be used as a substitute for medical advice from your doctor or other qualified clinician. Always seek the individual advice of your health care provider for any questions you have regarding a medical condition.
