Lyme Disease or Dementia? A Case of Reversible Cognitive Decline
Cognitive decline may not always be dementia — in some cases the cause is infection.
Behavioral changes, hallucinations, and confusion can be features of Lyme neuroborreliosis.
Some cases of dementia-like illness may be reversible with appropriate 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 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 — 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.
Why This Case Matters
The authors emphasize 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 progressing cognitive decline do not always indicate dementia. When acute cognitive symptoms appear in a previously functional older adult, an inflammatory or infectious cause including Lyme disease should be considered before a degenerative diagnosis is assumed.
Cognitive impairment is usually assumed to be progressive, but a significant proportion of cases may be reversible when an underlying treatable cause is identified.
Not all dementia-like presentations are neurodegenerative.
This case adds to a growing body of evidence. In a separate case, an 80-year-old man initially diagnosed with Alzheimer’s disease recovered 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.
For a comprehensive overview of the Lyme disease and dementia overlap — including additional clinical cases and what the research shows — see Lyme Disease and Dementia: When Cognitive Decline Has Another Cause.
Frequently Asked Questions
Can Lyme disease cause symptoms that look like dementia?
Yes. Lyme neuroborreliosis can cause confusion, hallucinations, behavioral changes, and memory loss that closely resemble dementia — particularly when onset is rapid.
How can clinicians distinguish Lyme disease from dementia?
Key clues include rapid onset, systemic symptoms such as joint pain or inflammation, history of tick exposure, and failure to respond to standard dementia or psychiatric treatment. Lyme serology and spinal fluid analysis may help clarify the diagnosis.
Can Lyme-related cognitive decline be reversed?
In some cases, yes. This case demonstrates that hallucinations, confusion, and behavioral changes attributed to dementia improved significantly following antibiotic treatment for Lyme disease.
What symptoms should prompt evaluation for Lyme disease in an older adult?
Rapid-onset cognitive decline, behavioral changes, joint symptoms, elevated inflammatory markers, and a history of tick exposure — particularly when standard dementia treatment fails to produce improvement.
Clinical Takeaway
Lyme disease can present with symptoms that closely mimic dementia — including hallucinations, confusion, aggression, and rapid cognitive decline. When symptoms appear suddenly, fluctuate, or are accompanied by systemic findings such as joint pain or inflammation, clinicians should broaden the differential diagnosis to include infectious causes.
A missed diagnosis of Lyme disease in a patient with apparent dementia may mean a treatable cause of cognitive decline goes unrecognized — and a potentially reversible condition becomes permanent.
Related Articles
- Lyme Disease and Dementia: When Cognitive Decline Has Another Cause
- Lyme Disease Mistaken for Dementia: When Confusion Is Reversible
- Lyme Encephalopathy Symptoms and Complications
- Is It Dementia or Lyme Disease? When Neurologic Symptoms Are Misdiagnosed
- Neurologic Lyme Disease
- 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
