What Is an Internal Tremor? Causes and Treatment

An internal tremor is a shaking or vibrating sensation felt deep inside the body, even though no movement is visible to an outside observer. People describe it as a buzzing motor running beneath the skin, a quivering in the chest or limbs, or a whole-body vibration that only they can feel. The sensation has been documented across several neurological conditions, and it has gained renewed attention since the COVID-19 pandemic brought a wave of patients reporting it for the first time. Despite being a recognized symptom in research, internal tremors remain poorly understood, frequently dismissed, and difficult to treat.

What Internal Tremors Actually Feel Like

Researchers define internal tremor as a feeling of tremor in the extremities or trunk without actual movement being present.¹ That clinical description barely captures what patients report. In a qualitative study that analyzed hundreds of emails and social media accounts from people experiencing the symptom, descriptions ranged widely: some felt it as a fine, rapid vibration concentrated in the hands or feet; others described a deep shuddering in the chest, abdomen, or spine that came in waves.² Some people feel it all day. Others notice it primarily upon waking from a nap or a short sleep, describing a racing sensation paired with shakiness, “as if there is a fast motor running inside me,” that subsides after sitting still for a few minutes.²

The intensity varies. Some find it mildly annoying; others find it profoundly disruptive to sleep, work, and daily functioning. What nearly everyone shares is the frustration of experiencing a vivid physical sensation that no instrument or observer can detect.

Neurological Conditions Where Internal Tremors Are Common

Internal tremors are not exclusive to one disease. A study that surveyed patients with Parkinson’s disease, multiple sclerosis, and essential tremor found that all three groups reported internal tremors at high rates: roughly a third of Parkinson’s patients, about 36% of those with multiple sclerosis, and over half of people with essential tremor described experiencing them.¹ The fact that essential tremor had the highest prevalence is worth noting, since many people assume internal tremors are primarily a Parkinson’s symptom.

In Parkinson’s disease specifically, a larger investigation found that more than 30% of patients reported internal tremor. Nearly all of those patients also reported external, visible tremor as one of their most bothersome symptoms, which suggests a relationship between the two. The odds of experiencing internal tremor were roughly three times higher in women than in men after adjusting for disease severity and anxiety.³ That sex difference is striking and has not been fully explained, though it parallels other conditions where women report more sensory symptoms than men at equivalent disease stages.

In multiple sclerosis, internal tremors may relate to the way the disease disrupts nerve signaling through demyelination. In essential tremor, where the nervous system generates involuntary oscillations, the high rate of internal tremors hints that the brain’s tremor circuits can fire at levels too subtle to produce visible shaking but strong enough for the person to feel. Across all three conditions, internal tremor was linked both to the presence of visible tremor and to higher levels of perceived anxiety.¹

Long COVID and the Surge in Internal Tremor Reports

Before 2020, internal tremors were discussed almost exclusively in neurology clinics. The pandemic changed that. Among a sample of people with long COVID, 37% reported experiencing “internal tremors, or buzzing/vibration” as a symptom of their ongoing illness.⁴ The typical long COVID patient reporting this symptom was in their mid-forties, and about three-quarters were women. These were not people with pre-existing neurological conditions. They developed the sensation after a SARS-CoV-2 infection, often weeks to months later.

Researchers have proposed that post-COVID internal tremors may be linked to dysautonomia, a dysfunction of the autonomic nervous system that regulates heart rate, blood pressure, and other involuntary processes, as well as small fiber neuropathy, where the smallest nerve fibers in the skin and organs become damaged.⁵ Both conditions have been documented in long COVID patients independently, and either could plausibly generate a sensation of internal vibration without producing visible movement. The dysautonomia connection is especially interesting because it links internal tremors to other symptoms long COVID patients commonly report, including racing heartbeat, dizziness on standing, and blood-pressure instability.

The sheer volume of people newly experiencing internal tremors after COVID has done something that decades of neurology research did not: it forced the symptom into broader medical awareness. Patient communities, particularly through groups like Survivor Corps, have been central to documenting and characterizing the experience.²

Other Medical Causes

Beyond the conditions most commonly studied, several other medical problems can produce sensations that patients describe as internal tremors or vibrations.

Thyroid disorders are a well-established cause of tremor. Hyperthyroidism classically produces a fine, fast postural tremor in the hands, but the range of movement disturbances associated with thyroid dysfunction is broader than many people realize. A case report described a woman with Graves’ disease who presented with a disabling combination of myoclonus, choreic movements, and postural tremor, all of which resolved completely within three months once her thyroid levels were brought back to normal with medication and beta-blockers.⁶ While that case involved visible movements, the sensory overlap with internal tremors is plausible. Thyroid screening is one of the first things a doctor should check in someone reporting new-onset internal tremor, because if the thyroid is the cause, treatment can resolve the symptom entirely.

Postural tachycardia syndrome, or POTS, is another condition where internal tremor-like sensations arise. People with hyperadrenergic POTS, a subtype characterized by surges in adrenaline, often experience tremor while upright that can feel internal or barely visible. This has been documented in patients with hypermobile Ehlers-Danlos syndrome, a connective-tissue condition that frequently co-occurs with POTS.⁷ The mechanism makes intuitive sense: when your autonomic nervous system is dumping adrenaline inappropriately, you feel amped up and shaky from the inside, even when your hands look steady. If you experience internal tremors along with a racing pulse when standing, lightheadedness, or exercise intolerance, POTS is worth investigating.

Low blood sugar, medication side effects (especially from stimulants, certain antidepressants, and bronchodilators), caffeine excess, and alcohol withdrawal can all produce internal sensations of trembling as well. These tend to be episodic and tied to a recognizable trigger, which distinguishes them from the chronic, unexplained internal tremors that prompt people to seek medical evaluation.

Why Anxiety Keeps Coming Up

In nearly every study of internal tremors, anxiety appears as a significant associated factor. Among Parkinson’s patients, those who reported internal tremor were substantially more likely to report anxiety than those who did not, even after adjusting for how severe their disease was. Anxiety independently increased the odds of reporting internal tremor by about 70%.³ In the study comparing Parkinson’s, multiple sclerosis, and essential tremor patients, perceived anxiety levels were linked to internal tremor across all three diseases.¹

This does not mean internal tremors are “just anxiety.” The relationship is more complicated than that. Anxiety activates the sympathetic nervous system, releasing adrenaline and raising muscle tension, which can amplify real physiological signals. A person with subclinical tremor activity in the brain may only notice it when anxiety lowers the threshold at which the sensation becomes conscious. It is also worth considering the reverse: living with a persistent, unexplained physical sensation tends to produce anxiety. The causation likely runs in both directions, and separating the two is one of the hardest problems in this field.

For practical purposes, though, the connection matters because anxiety-reducing interventions sometimes help. If anxiety is contributing to or amplifying the sensation, addressing it may not cure the internal tremor but can make it less intrusive.

The Problem of Normal Test Results

One of the most consistently reported frustrations among people with internal tremors is that standard medical tests come back normal. Brain MRIs, CT scans, EKGs, echocardiograms, stress tests, pulmonary function tests, and extensive blood panels reveal nothing abnormal.² From the patient’s perspective, this is maddening: the sensation is vivid and constant, yet every objective measure says they are fine.

The reason is straightforward but unsatisfying. Standard diagnostic tools are designed to detect structural abnormalities, visible movement, or measurable electrical signals. Internal tremors, by definition, produce no visible motion and no signal strong enough for surface electromyography or standard neuroimaging to pick up. The problem may lie in altered sensory processing, in autonomic nerve signaling, or in subclinical oscillatory activity in the central nervous system that falls below the detection threshold of current instruments. Research into small fiber neuropathy testing in long COVID patients is beginning to offer a potential exception, since quantitative tests for small fiber function can sometimes reveal damage that conventional nerve conduction studies miss.⁵

For now, internal tremor remains largely a clinical diagnosis based on patient history. The normal test results do not mean nothing is wrong. They mean the available tools are not sensitive enough to detect what is happening.

Treatment Options and Their Limits

There is no established, evidence-based treatment specifically for internal tremors. This is partly because the symptom has not been studied with the same rigor as visible tremor, and partly because it cuts across so many different underlying conditions.

In Parkinson’s disease, the standard dopaminergic medications that help with visible tremor and stiffness do not reliably help with internal tremor. An early study found that antiparkinsonian medication failed to relieve internal tremor in about three-quarters of Parkinson’s patients who reported it.⁸ That disconnect is important: it suggests internal tremor in Parkinson’s may not arise from the same dopamine-depleted circuits that produce the classic resting tremor. It may instead involve sensory processing pathways or autonomic dysfunction that levodopa does not reach.

When a treatable underlying cause exists, addressing it can resolve the symptom. Hyperthyroidism-related tremor responds to normalization of thyroid function.⁶ Medication-induced tremor resolves when the offending drug is changed. Anxiety-driven or anxiety-amplified tremor may respond to anxiolytic treatment, cognitive behavioral therapy, or stress-reduction techniques. POTS-related symptoms can improve with salt loading, compression garments, exercise reconditioning, and sometimes medications like fludrocortisone or midodrine. The treatment, in short, depends entirely on what is driving the symptom in a given person.

For people with internal tremors that remain unexplained or are not responsive to disease-specific treatment, the options are frustratingly limited. Beta-blockers are sometimes tried, since they can dampen the sympathetic nervous system activity that may contribute to the sensation. Some patients report subjective benefit from magnesium supplementation, though controlled evidence for this is thin. Mindfulness-based stress reduction and regular aerobic exercise have general evidence for improving autonomic regulation and may help reduce symptom burden. None of these approaches has been tested specifically for internal tremor in a randomized trial.

Why Getting Taken Seriously Is So Difficult

People with internal tremors frequently describe frustrating encounters with the healthcare system. In a qualitative study that surveyed individuals reporting the symptom after COVID-19, one of the seven major themes that emerged was “experience with medical establishment,” and it was not a positive one. Respondents described being told that nothing was wrong, that the symptom was psychological, or simply that their doctors did not know what to do.²

The pattern is not unique to long COVID. Parkinson’s patients have been reporting internal tremors for decades, and the symptom still does not appear on most standard rating scales used to assess the disease. If a symptom is not measured, it tends to be ignored in treatment planning. Multiple sclerosis and essential tremor are in similar positions: internal tremor is acknowledged in the research literature but rarely asked about in routine clinical visits.

Part of the problem is structural. Medicine is built around objective findings: lab values, imaging, measurable signs. A purely subjective sensation with no objective correlate falls into a gray area that the system handles poorly. Patients pick up on this. Many report that after extensive testing reveals nothing, the implicit message is that the problem is in their head. Researchers have pushed back on this framing, emphasizing that the symptom is real and reproducible across large cohorts, even if current technology cannot image or measure it.¹

When to Seek Evaluation

Internal tremors are worth bringing to a doctor’s attention, particularly if they are new, persistent, or worsening. While the symptom itself is not considered dangerous, it can be an early feature of conditions that benefit from timely diagnosis. Parkinson’s disease, thyroid disorders, multiple sclerosis, and POTS all have treatments that work better when started earlier. A basic workup typically includes thyroid function tests, a neurological exam, and sometimes an MRI of the brain and spine, depending on what other symptoms are present.

If you have been told that everything is normal but the sensation persists, asking about autonomic testing or small fiber neuropathy assessment may be worthwhile, particularly if you also experience dizziness on standing, abnormal sweating, or palpitations. A referral to a neurologist with experience in movement disorders or autonomic medicine can make a meaningful difference, since these specialists are more likely to recognize internal tremor as a legitimate symptom and to have a framework for investigating its cause. The evidence base remains thin, but the phenomenon is real, it is common across several well-studied diseases, and the growing body of post-COVID research is gradually pulling it out of the shadows.

1
PubMed. Internal tremor in Parkinson’s disease, multiple sclerosis, and essential tremor
2
PubMed Central. Characterisation of internal tremors and vibration symptoms
3
PubMed Central. Internal tremor in people with Parkinson’s Disease: Demographic characteristics and comorbid symptoms
4
PubMed Central. Internal Tremors and Vibrations in Long COVID: A Cross-Sectional Study
5
PubMed Central. Internal Tremor in Long COVID May Be a Symptom of Dysautonomia and Small Fiber Neuropathy
6
PubMed Central. Erratic movement disorders disclosing Graves’ disease and paralleling thyroid function but not autoantibody levels
7
ScienceDirect. Chapter 45 – Feeling shaky with palpitations: Hypertension, tachycardia, dizziness, and near syncope
8
PubMed. Internal tremor in patients with Parkinson’s disease