Internal tremors, vibrations pester people with long COVID

Individuals with long COVID may experience internal tremors and vibrations, which can signal a worse health status compared with others without these symptoms, a study has shown.

“Individuals with long COVID symptoms of internal tremors may experience a particularly severe phenotype of long COVID,” the researchers said. “Clinicians should be aware of internal tremors and vibrations as a long COVID symptom.”

A total of 423 adults with long COVID (median age 46 years, 74 percent female, 87 percent non-Hispanic White) between 12 May 2022 and 1 June 2023 were surveyed. The exposure variables were internal tremors and vibration, while outcome variables included demographic characteristics, prepandemic comorbidities, new-onset conditions, other symptoms, and quality of life.

Of the participants, 158 (37 percent) had “internal tremors, or buzzing/vibration” as a long COVID symptom. [Am J Med 2025;138:1010-1018.E14]

Adults with and without internal tremors reported similar prepandemic comorbidities. However, those with internal tremors had worse health as measured by the Euro-QoL visual analogue scale (median: 40 vs 50 points; p=0.007), as well as higher rates of new-onset mast cell disorders (11 percent vs 2.6 percent; p=0.008) and neurologic conditions (22 percent vs 8.3 percent; p=0.004).

Previous findings

Only four prior studies have examined people with internal tremors. Recent studies involving large cohorts of adults with long COVID reported no symptoms of internal tremors. [Acta Neurol Scand 2001;104:312-315; Mov Disord 1996;11:3-7; J Neurol Sci 1997;150:S315; JAMA 2023;329:1934-1946]

“Our findings are consistent with and extend prior findings by showing that compared with others with long COVID, participants with internal tremors had worse quality of life and had significantly higher rates of neurologic symptoms,” the researchers said.

Dysautonomia

People with internal tremors had higher rates of new-onset dysautonomia, with statistical significance before but not after correction. The mechanism driving this disorder had possible associations with organ-selective sympathetic denervation. However, the pathophysiologic links among dysautonomia, long COVID, and internal tremors have not been established. [Compr Physiol 2014;4:805-826]

“Our findings add nuance to the hypothesized associations between myalgic encephalomyelitis/chronic fatigue syndrome [ME/CFS] and long COVID, which are often discussed together due to overlapping symptomatology and infectious etiopathogenesis,” the researchers said. [Medicina (Kaunas) 2021;57:418; J Transl Med 2022;20:429; Nat Med 2022;28:911-923]

More than 70 percent of participants in the current study reported excessive fatigue or exercise intolerance, but these symptoms of ME/CFS did not show a significant association with internal tremors.

“Our findings are consistent with prior observations of long COVID as a heterogeneous condition with many phenotypes, which may be driven by several mechanisms,” the researchers said. [Nat Med 2023;29:226-235; Ann Med 2022;54:1473-1487]

Movement

Internal tremors are characterized by a sensation of movement at any location inside the body and may occur either with or without visible external movement or muscle spasms. These differ from the known definition of tremors as “externally visible involuntary, rhythmic, oscillatory movement of a body part.” [BMJ Open 2023;13:e077389; Parkinsonism Relat Disord 2015;21:1145-1147]

“Until recently, internal tremors were mostly described in Parkinson's disease and essential tremor and not described in long COVID,” the researchers said. [Neurology 1995;45:565-568; Med Health R I 2009;92:262; Mov Disord 1996;11:3-7]

“Further research is needed to clarify the pathophysiology of internal tremors and vibrations and identify potential treatment targets,” they noted.