Can Lyme Disease Mimic Dementia? A Case of Reversible Cognitive Decline

Lyme disease can sometimes mimic dementia
Confusion, hallucinations, and behavioral changes may be reversible
Prompt diagnosis and antibiotic treatment can improve outcomes

Lyme disease can occasionally mimic dementia, presenting with cognitive decline, confusion, hallucinations, and behavioral changes. Although Alzheimer’s disease and other neurodegenerative disorders are far more common causes of progressive memory loss, clinicians should also consider potentially reversible conditions—particularly when symptoms develop rapidly or are accompanied by other signs of infection.

Although uncommon, recognizing this possibility is important because Lyme disease is a potentially treatable cause of dementia-like symptoms in the appropriate clinical setting.

Clinical perspective: Before specializing in Lyme disease, I served as Director of a Dementia Center and worked in geriatrics. One of the first steps in evaluating cognitive decline is to consider reversible causes. While most dementia is not reversible, treatable conditions—including infections such as Lyme disease in appropriate clinical settings—should be considered when the presentation is atypical or rapidly progressive.

Why Lyme disease may be mistaken for dementia

Neurologic Lyme disease may affect memory, attention, executive function, mood, and behavior. Some patients develop confusion, hallucinations, personality changes, or difficulty performing everyday tasks. While these symptoms do not necessarily indicate dementia, they can resemble Alzheimer’s disease or other neurodegenerative disorders, particularly in older adults.

Most older adults with dementia have Alzheimer’s disease or another neurodegenerative disorder rather than Lyme disease. However, rapidly progressive cognitive decline, confusion, hallucinations, migratory joint pain, elevated inflammatory markers, or a history of tick exposure should prompt clinicians to consider potentially reversible causes, including Lyme disease.

The diagnosis becomes especially challenging when cognitive symptoms develop in someone with pre-existing mild memory impairment. In these situations, a sudden decline or rapid change in behavior should prompt a careful evaluation rather than an immediate assumption of progressive dementia.

Can Lyme disease cause confusion?

Yes. Neurologic Lyme disease can occasionally cause acute confusion, delirium, hallucinations, and behavioral changes. When confusion develops rapidly—especially in conjunction with joint pain, elevated inflammatory markers, or a history of tick exposure—clinicians should evaluate for potentially reversible causes before concluding that a patient has irreversible dementia.

The following case illustrates how Lyme disease initially mimicked dementia but improved substantially after appropriate antibiotic treatment.

The authors describe the case of a 75-year-old man who was referred to an Alzheimer’s Disease Care Unit after rapidly developing symptoms initially thought to represent dementia. Subsequent testing confirmed Lyme disease.

The man reportedly had only mild memory loss but was admitted because of hallucinations, confusion, and aggressive behavior.

Two weeks earlier, he had been diagnosed with “cognitive impairment, deficit of memory, and poor capacity of criticism compatible with degenerative disease,” the authors explain.

Antipsychotic medications did not alleviate his symptoms, and he was referred to the Alzheimer’s unit. Upon admission, he exhibited delusions, hallucinations, aggressive behavior, urinary incontinence, and insomnia.

“He started presenting with hallucinations and aggressive behavior, requiring antipsychotic therapy and physical restraints to reduce the risk of self-injury.”

One month before the onset of his neuropsychiatric symptoms, the man developed knee pain that later migrated to other joints. He also recalled a tick bite approximately six months earlier.

According to his wife, he had experienced mild memory impairment over several years but had never demonstrated confusion, aggression, hallucinations, or significant behavioral changes at home.

A CT scan was unremarkable, but laboratory testing revealed elevated inflammatory markers.

“Cognitive impairment is usually seen as a condition destined to worsen and end in dementia, but a significant proportion of cases can be reversible.”

Because inflammatory markers remained elevated, the patient initially received empiric ceftriaxone for approximately one week without substantial improvement.

Given his history of migratory knee pain, clinicians pursued Lyme disease testing, which returned positive.

“Antibiotic treatment was initiated with intravenous ceftriaxone (2 g twice daily for 21 days),” the authors write, followed by doxycycline. Low-dose prednisone was prescribed to relieve persistent arthritis symptoms.

He briefly required an antipsychotic medication to control hallucinations, but it was later discontinued.

Following treatment for Lyme disease, the patient’s hallucinations, confusion, behavioral changes, and functional decline improved substantially. However, memory loss and executive dysfunction persisted, suggesting that underlying cognitive impairment may have coexisted with Lyme disease.

Frequently Asked Questions

Can Lyme disease mimic dementia?

Yes. In uncommon cases, neurologic Lyme disease may cause confusion, memory problems, hallucinations, behavioral changes, and cognitive decline that resemble dementia. A thorough medical evaluation is important because some causes of cognitive decline may be reversible.

Can Lyme disease cause confusion?

Yes. Lyme disease affecting the nervous system may cause confusion or delirium in some patients. Sudden or rapidly progressive confusion, particularly when accompanied by joint pain, elevated inflammatory markers, or a history of tick exposure, warrants prompt medical evaluation.

Can Lyme disease cause hallucinations?

Although uncommon, hallucinations and other neuropsychiatric symptoms have been reported in patients with neurologic Lyme disease. These symptoms should prompt evaluation for infectious, inflammatory, metabolic, and other reversible causes.

Can Lyme disease cause memory loss?

Some patients with Lyme disease report memory difficulties, slowed thinking, or problems with concentration. Persistent or progressive memory loss requires a comprehensive evaluation because many neurologic and medical conditions can produce similar symptoms.

Can Lyme disease be mistaken for Alzheimer’s disease?

Yes. Lyme disease may occasionally mimic Alzheimer’s disease or other dementias because both can involve memory loss and cognitive impairment. However, rapidly progressive confusion, hallucinations, behavioral changes, inflammatory findings, or a history of tick exposure should prompt evaluation for potentially reversible conditions before concluding that a patient has a neurodegenerative disorder.

Clinical Takeaway

This case highlights the importance of considering reversible causes of cognitive decline before concluding that an older adult has irreversible dementia. While Alzheimer’s disease remains the most common cause of progressive cognitive impairment, Lyme disease and other infections should be considered when confusion, hallucinations, behavioral changes, or rapid deterioration occur in the appropriate clinical setting.

Prompt recognition of Lyme disease may prevent unnecessary dementia diagnoses and substantially improve neuropsychiatric symptoms in appropriately selected patients.

Related Articles

Lyme Disease Misdiagnosis: Why It Happens
80-Year-Old Woman With Lyme Encephalopathy Instead of Dementia
Neurological Lyme Disease Symptoms and Brain Effects

---

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