Lyme Disease or Dementia? A Case of Reversible Cognitive Decline
Cognitive decline may not always be dementia
Behavioral changes and hallucinations can occur in Lyme neuroborreliosis
Some dementia-like symptoms may improve with antibiotic treatment
Lyme disease or dementia? In some cases, symptoms that resemble dementia — such as confusion, hallucinations, and behavioral changes — may be linked to an underlying infection rather than neurodegeneration.
A 75-year-old man with suspected dementia was referred to an Alzheimer’s Disease Care Unit but later tested positive for Lyme disease.
He initially presented with mild memory loss but was admitted due to hallucinations, confusion, and aggressive behavior — symptoms that had developed rapidly over a short period.
Two weeks earlier, he had been diagnosed with cognitive impairment compatible with degenerative disease.
When Symptoms Don’t Fit Typical Dementia
Antipsychotic medications did not alleviate his symptoms, and he was referred to an Alzheimer’s unit.
On admission, he exhibited:
- Delusions and hallucinations
- Aggressive behavior requiring antipsychotic therapy and physical restraints
- Urinary incontinence
- Insomnia
These symptoms developed rapidly — an important distinction from typical neurodegenerative dementia, which generally progresses gradually over months to years.
Clues Suggesting an Underlying Infection
One month before his neuropsychiatric symptoms began, the patient developed knee pain that migrated to other joints.
He also reported a tick bite approximately six months earlier.
According to his wife, he had only mild memory issues previously — no confusion, aggression, or behavioral changes.
A CT scan was negative, but blood tests showed elevated inflammatory markers.
This combination of joint symptoms, inflammation, rapid cognitive decline, and tick exposure history raised concern for an infectious cause rather than primary neurodegeneration.
Diagnosis: Lyme Disease
Because of the joint symptoms, Lyme disease testing was performed and returned positive.
Antibiotic treatment was initiated with intravenous ceftriaxone, followed by oral doxycycline.
A low-dose steroid was used to manage arthritis symptoms, and antipsychotic medication was eventually discontinued.
Response to Treatment
Most of the patient’s symptoms improved following treatment for Lyme disease.
However, some deficits persisted — including memory loss and executive dysfunction — suggesting that while some effects may be reversible, others may take longer to recover or remain partially persistent.
This pattern is consistent with findings described in post-treatment Lyme disease syndrome (PTLDS), where cognitive symptoms may persist even after antibiotic therapy.
Can Lyme Disease Cause Dementia-Like Symptoms?
Some patients with Lyme neuroborreliosis report cognitive symptoms including memory loss, slowed processing, confusion, difficulty concentrating, personality changes, or hallucinations.
Rapid onset, fluctuating symptoms, systemic inflammation, joint pain, and neurologic findings may help distinguish Lyme disease from more typical neurodegenerative dementia.
Researchers continue to study the relationship between Lyme disease, neuroinflammation, cognitive decline, and reversible neurologic dysfunction.
Learn more about Lyme disease and dementia.
Why This Case Matters
The authors emphasized that sudden cognitive decline — especially with behavioral changes — should prompt evaluation for infections including Lyme disease, inflammatory conditions, and other neurologic disorders.
The authors specifically noted the importance for geriatricians that old age and progressive cognitive decline do not always indicate dementia. When acute cognitive symptoms appear in a previously functional older adult, an inflammatory or infectious cause should be considered before a degenerative diagnosis is assumed.
Cognitive impairment is often assumed to be progressive, but a subset of cases may be partially reversible when an underlying treatable cause is identified.
This case adds to a growing body of literature describing dementia-like presentations associated with Lyme neuroborreliosis.
In a separate case, an 80-year-old man initially diagnosed with Alzheimer’s disease improved significantly after intravenous ceftriaxone for Lyme neuroborreliosis. See the full case: Lyme disease mistaken for dementia: when confusion is reversible.
For a broader overview of cognitive complications in Lyme disease, see Lyme encephalopathy symptoms and complications.
Frequently Asked Questions
Can Lyme disease cause symptoms that look like dementia?
Yes. Lyme neuroborreliosis can cause confusion, hallucinations, behavioral changes, memory loss, and cognitive decline that may resemble dementia.
Can Lyme disease cause memory loss?
Some patients with neurologic Lyme disease report memory difficulties, slowed processing, brain fog, and concentration problems.
Can Lyme disease dementia be reversible?
In some cases, dementia-like symptoms associated with Lyme disease may improve after antibiotic treatment, particularly when diagnosis occurs before permanent neurologic injury develops.
How can clinicians distinguish Lyme disease from dementia?
Rapid onset, fluctuating symptoms, systemic inflammation, joint pain, tick exposure history, and poor response to standard dementia treatment may raise concern for Lyme disease.
Can Lyme disease be mistaken for Alzheimer’s disease?
Yes. Some reported Lyme neuroborreliosis cases were initially diagnosed as Alzheimer’s disease or other neurodegenerative conditions before further evaluation identified infection.
Clinical Takeaway
Lyme disease can present with symptoms that closely mimic dementia, including hallucinations, confusion, aggression, memory loss, and rapid cognitive decline.
When symptoms appear suddenly, fluctuate, or occur alongside systemic findings such as joint pain or inflammation, clinicians should broaden the differential diagnosis to include infectious and inflammatory causes.
A missed diagnosis of Lyme neuroborreliosis may allow a potentially reversible cause of cognitive decline to progress untreated.
Related Articles
These related articles explore neurologic Lyme disease, memory loss, encephalopathy, delayed diagnosis, and cognitive complications.
Delayed Lyme disease diagnosis
Lyme disease symptoms guide
Post-treatment Lyme disease syndrome (PTLDS)
Lyme disease coinfections
Lyme disease misdiagnosis
References
- Sanchini C, Papia C, Cutaia C, Poloni TE, Cesari M. A case of reversible dementia? Dementia vs delirium in Lyme disease. Ann Geriatr Med Res. 2023;27(1):80-82.
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
