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Can Lyme Disease Cause Brain Fog? Could Cytokines Play a Role?

Brain fog can affect memory, concentration, and processing speed
Inflammatory cytokines may contribute to cognitive symptoms
The role of neuroinflammation remains under investigation

Lyme disease brain fog may include difficulty concentrating, slowed thinking, word-finding problems, confusion, and short-term memory lapses. These cognitive symptoms can interfere with work, school, conversations, and everyday activities.

Although brain fog is commonly reported, it may arise from several overlapping mechanisms rather than a single cause. Researchers have examined direct nervous system involvement, persistent immune activation, inflammatory cytokines, autonomic dysfunction, sleep disruption, and other factors. These symptoms may also occur as part of a broader pattern of persistent Lyme disease symptoms.

Research involving patients with COVID-19 has raised an important question: Could inflammatory cytokines also contribute to brain fog in some patients with Lyme disease?

COVID-19 brain fog provides new clues

Because researchers cannot easily measure inflammation inside the brain during routine clinical care, studies of other illnesses associated with brain fog may provide useful clues.

In their article, published in the journal Cancer Cell,¹ Remsik and colleagues studied 13 hospitalized patients with COVID-19 who developed neurologic symptoms.

The authors described COVID-19 brain fog as a condition characterized by confusion, headaches, and short-term memory loss. More severe neurologic symptoms, including psychosis and seizures, were also reported in some patients.

The researchers expected to find evidence of COVID-19 infection in the cerebrospinal fluid (CSF). However, they did not detect the virus in the CSF samples they examined.

Instead, Remsik and colleagues found elevated inflammatory cytokines in the cerebrospinal fluid of patients with neurologic symptoms. According to the authors, these patients had persistent inflammation and high cytokine levels that appeared to help explain their symptoms.

“These increased CSF cytokines are likely the result of both increased blood barrier permeability and local production by cells in the CNS,” the authors write.

What are cytokines?

Cytokines are signaling proteins used by the immune system to coordinate inflammation and responses to infection. They can help the body fight pathogens, but excessive or persistent cytokine activity may also contribute to tissue inflammation and neurologic symptoms.

The term “cytokine storm” generally describes an intense and potentially dangerous systemic inflammatory response. In Lyme disease, it may be more accurate to discuss persistent immune activation, inflammatory cytokines, or neuroinflammation rather than assume that every patient experiences a true cytokine storm.

Could cytokines contribute to Lyme disease brain fog?

Experimental studies and clinical observations have raised the possibility that Lyme disease may affect the central nervous system directly in some patients, while immune activation may contribute to symptoms in others.

Some researchers have proposed that Borrelia burgdorferi, the bacterium that causes Lyme disease, may cross the blood-brain barrier in certain patients. Others have examined whether the immune response to infection may continue to affect the nervous system even when organisms are not detected in cerebrospinal fluid.

Dr. Robert Bransfield proposed that persistent immune activation and inflammatory cytokines may contribute to neuropsychiatric symptoms in some patients with chronic Lyme and other tick-borne diseases.²

The findings reported by Remsik and colleagues do not prove that cytokines cause Lyme disease brain fog. However, they provide biologic support for the broader hypothesis that immune activation and inflammation within or around the central nervous system may contribute to cognitive symptoms.

What else may contribute to brain fog in Lyme disease?

Brain fog is unlikely to have one explanation in every patient. Several overlapping factors may contribute, including:

• Neurologic involvement from Lyme disease
• Persistent immune activation or neuroinflammation
• Autonomic dysfunction or orthostatic intolerance
• Sleep disruption
• Fatigue and post-exertional symptom flares
• Pain, headaches, anxiety, or depression
• Medication side effects
• Other tick-borne infections or unrelated medical conditions

Clinicians should also consider coinfections such as Babesia, Anaplasma, or Ehrlichia when evaluating persistent cognitive symptoms. These infections may contribute to fatigue, neurologic complaints, or delayed recovery in selected patients.

More than one mechanism may be present in the same patient. A careful clinical evaluation is important before attributing cognitive symptoms to inflammation alone.

Can Lyme disease brain fog improve?

Brain fog may improve when the underlying contributors are identified and addressed. Treatment may include appropriate antibiotic therapy when active Lyme disease is present, evaluation for other tick-borne infections when clinically indicated, and management of sleep problems, autonomic dysfunction, pain, or other conditions that can worsen cognition.

Recovery is not always immediate or linear. Some patients notice gradual improvement in concentration, memory, and mental stamina over weeks or months, while others continue to experience fluctuating symptoms. In some cases, recovery from Lyme disease may continue after treatment ends.

There is not currently enough evidence to recommend treating cytokine levels directly as a standard therapy for Lyme disease brain fog. Additional research is needed to determine which inflammatory pathways are clinically important and whether targeting those pathways improves patient outcomes.

Frequently Asked Questions

Can Lyme disease cause brain fog?

Yes. Patients with Lyme disease may report difficulty concentrating, slowed thinking, word-finding problems, confusion, and short-term memory difficulties. These symptoms may result from neurologic involvement, immune activation, sleep disruption, autonomic dysfunction, coinfections, or several overlapping factors.

Can inflammation cause brain fog?

Inflammation may contribute to brain fog in some illnesses. Research involving COVID-19 patients found elevated inflammatory cytokines in cerebrospinal fluid despite no detectable virus in the CSF. Whether similar inflammatory mechanisms occur in Lyme disease requires additional study.

Does Lyme disease cause a cytokine storm?

A severe systemic cytokine storm has not been established as the usual explanation for Lyme disease brain fog. Persistent immune activation, altered cytokine activity, or neuroinflammation may be more appropriate terms when discussing possible inflammatory mechanisms in Lyme disease.

Can Lyme disease brain fog occur without meningitis?

Yes. Patients may report cognitive slowing, memory problems, or difficulty concentrating without clear evidence of meningitis or abnormalities in cerebrospinal fluid. Brain fog may reflect several overlapping neurologic, inflammatory, autonomic, sleep-related, or metabolic factors.

How is Lyme disease brain fog treated?

Treatment depends on the underlying cause. Patients may require evaluation for active Lyme disease, other tick-borne infections, autonomic dysfunction, sleep disorders, medication effects, and other medical conditions. Treatment and recovery should be individualized.

Clinical Takeaway

The COVID-19 study does not prove that inflammatory cytokines cause brain fog in Lyme disease. However, it adds support to the hypothesis that immune activation and neuroinflammation may contribute to cognitive symptoms in some patients.

Brain fog in Lyme disease is likely multifactorial, with infection, immune activation, autonomic dysfunction, sleep disturbance, and coinfections potentially contributing in different patients.

Further research is needed to determine how cytokines, infection, and other mechanisms interact in patients with Lyme disease brain fog.

Related Articles

Learn more about cognitive, neurologic, and autonomic symptoms associated with Lyme disease:

Brain fog in COVID-19 and Lyme disease patients
Autonomic dysfunction and Lyme disease
Lyme disease symptoms guide

References

1. Remsik J, Wilcox JA, Babady NE, et al. Inflammatory Leptomeningeal Cytokines Mediate COVID-19 Neurologic Symptoms in Cancer Patients. Cancer Cell. 2021;39(2):276-283.e3.
2. Bransfield RC. The psychoimmunology of Lyme/tick-borne diseases and its association with neuropsychiatric symptoms. Open Neurol J. 2012;6:88-93.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention