Lyme disease aseptic meningitis can present as normal pressure hydrocephalus (NPH) with dementia, confusion, and gait disturbance — leading doctors to miss the underlying infection. An 80-year-old man in Pennsylvania developed progressive weakness, confusion, nausea, and fatigue over several days. CSF studies showed aseptic meningitis, CT scan revealed dilated ventricles, and he tested positive for Lyme disease on day four of hospitalization. His case demonstrates that Lyme-induced meningitis can cause hydrocephalus mimicking primary dementia, and emphasizes why healthcare providers treating NPH patients should consider Lyme disease as a differential diagnosis, particularly in endemic areas.

Progressive Weakness and Confusion

An 80-year-old man was admitted to a hospital in Pennsylvania, an area endemic for Lyme disease, due to increased weakness and confusion. He had “several days of nausea with decreased appetite, generalized malaise, fatigue, and weakness,” according to the authors.

The presentation — progressive confusion, weakness, nausea, fatigue — in an elderly patient could suggest multiple conditions: stroke, metabolic derangement, infection, medication toxicity, or dementia. The subacute progression over several days pointed toward infection or metabolic cause rather than acute vascular event.

Aseptic Meningitis and Hydrocephalus

Cerebrospinal fluid (CSF) studies suggested aseptic meningitis. And a CT scan showed dilated ventricles. Treatment for normal pressure hydrocephalus relieved his symptoms.

Aseptic meningitis means inflammation of the meninges without bacterial infection on routine cultures. Causes include viral infection, autoimmune disease, and tick-borne infections including Lyme disease. The dilated ventricles on CT indicated hydrocephalus — abnormal accumulation of cerebrospinal fluid.

Normal pressure hydrocephalus (NPH) is a syndrome characterized by the triad of gait disturbance, urinary incontinence, and dementia, with dilated ventricles but normal opening pressure on lumbar puncture. The confusion and weakness fit this pattern.

Lyme Disease Diagnosis on Day Four

On the fourth day of hospitalization, the man tested positive for Lyme disease by Western blot on bands 23KD and 39KD.

“The patient was subsequently diagnosed with aseptic meningitis secondary to Lyme,” the authors state.

The Western blot bands 23 and 39 are specific for Borrelia burgdorferi. Band 23 is OspC (outer surface protein C), and band 39 is BmpA. These bands indicate active or recent Lyme infection, not old resolved disease.

Treatment and Partial Resolution

He was treated with IV and oral doxycycline. But his dementia did not completely resolve, “likely due to primary dementia or other condition.”

“In the case of our patient, infectious meningitis was suspected due to this patient reportedly having had fevers and leukocytosis. Additionally, Lyme disease is among the most common reportable infections in Pennsylvania,” the authors state.

The partial response to antibiotics — improvement but not complete resolution of cognitive symptoms — suggests two possibilities: (1) baseline dementia existed prior to Lyme infection, with acute worsening from meningitis, or (2) chronic Lyme-induced CNS damage wasn’t fully reversible despite treating active infection.

The NPH-Lyme Connection

“Healthcare providers treating patients with NPH should consider Lyme disease as a differential diagnosis because of the multiple reported cases of NPH secondary to Lyme disease.”

This is a critical clinical teaching point. Normal pressure hydrocephalus in the elderly is often assumed to be idiopathic (age-related). But when NPH occurs with meningeal inflammation, infection should be investigated. Lyme disease can cause communicating hydrocephalus through meningeal inflammation obstructing CSF reabsorption.

Why Lyme Disease Causes Hydrocephalus

Lyme disease aseptic meningitis causes hydrocephalus through inflammation of the arachnoid villi — the structures that reabsorb cerebrospinal fluid from the subarachnoid space into venous sinuses. When inflammation blocks CSF reabsorption, fluid accumulates in the ventricles, causing hydrocephalus.

The mechanisms include:

• Meningeal inflammation: Spirochetal invasion causes inflammatory exudate
• Arachnoid villi obstruction: Inflammation impairs CSF drainage
• Increased CSF protein: Proteinaceous material clogs drainage pathways
• Chronic inflammation: Fibrosis and adhesions from prolonged infection

Unlike bacterial meningitis where CSF pressure is typically elevated, Lyme meningitis can cause hydrocephalus with normal opening pressure — hence “normal pressure hydrocephalus.”

Dementia or Infection?

The incomplete resolution of dementia raises important questions about Lyme disease and cognitive decline in the elderly. Was this:

Scenario 1: Pre-existing dementia (Alzheimer’s, vascular) + acute Lyme meningitis causing delirium superimposed on baseline cognitive impairment?

Scenario 2: Lyme-induced dementia from chronic neuroborreliosis, with treatment initiated too late to fully reverse CNS damage?

Scenario 3: Inadequate treatment duration for chronic CNS infection requiring extended antibiotics?

The authors favor Scenario 1 (“primary dementia or other condition”), but without baseline cognitive assessment before infection, this remains uncertain. Many patients labeled with “dementia” in the elderly actually have reversible causes including infection, metabolic disorders, or medication effects.

Authors’ Conclusions

“Lyme disease … can present with multiple complications, including arthritis, heart rhythm defects, facial nerve palsy, impaired memory, and meningitis. Hence, Lyme disease should be considered as part of the differential etiology of meningitis.”

Clinical Perspective

This case highlights several important issues in elderly patients with neurologic Lyme disease. First, the presentation as progressive confusion and weakness is nonspecific in geriatric patients. These symptoms could represent stroke, medication toxicity, urinary tract infection, metabolic derangement, or dozens of other conditions. Without high clinical suspicion for Lyme in endemic areas, the diagnosis would be missed.

Second, the finding of aseptic meningitis should immediately prompt Lyme testing in endemic regions. Aseptic meningitis in adults has a limited differential: viral (enterovirus, HSV, VZV), autoimmune (sarcoidosis, Behçet’s), medication-induced, or tick-borne (Lyme, Powassan). In Pennsylvania, Lyme is the most common cause.

Third, the normal pressure hydrocephalus complicating meningitis is an important teaching point. NPH typically presents with the classic triad of gait disturbance (“magnetic gait”), urinary incontinence, and dementia (“wet, wobbly, and wacky”). When NPH develops in the setting of meningitis, this indicates communicating hydrocephalus from impaired CSF reabsorption.

Fourth, the partial response to treatment is frustrating but realistic. Not all Lyme-related cognitive dysfunction is fully reversible, particularly in elderly patients who may have concurrent age-related cognitive decline. However, partial improvement validates that infection contributed to symptoms even if complete resolution didn’t occur.

Fifth, the diagnostic delay — four days of hospitalization before Lyme testing — represents standard practice in many hospitals. Lyme disease isn’t on the initial differential for “confusion and weakness” in elderly patients. But in endemic areas, it should be tested early rather than after other workups are unrevealing.

Finally, the authors’ recommendation that NPH patients be evaluated for Lyme disease is important. When elderly patients present with new-onset hydrocephalus, infection should be investigated before assuming idiopathic age-related NPH. Treating underlying Lyme infection may prevent progression or even reverse hydrocephalus, avoiding the need for ventriculoperitoneal shunt placement.

Frequently Asked Questions

Can Lyme disease cause aseptic meningitis?

Yes. Lyme disease aseptic meningitis occurs when spirochetes invade the meninges causing inflammation without bacterial growth on routine cultures. CSF shows elevated lymphocytes and protein, similar to viral meningitis.

What is normal pressure hydrocephalus?

Normal pressure hydrocephalus (NPH) is a syndrome of gait disturbance, urinary incontinence, and dementia with dilated ventricles but normal CSF opening pressure. Lyme meningitis can cause NPH by obstructing CSF reabsorption through meningeal inflammation.

Can Lyme disease cause dementia symptoms?

Yes. Lyme-related cognitive dysfunction can mimic dementia with memory impairment, confusion, and processing difficulties. Some symptoms are reversible with antibiotics; others may represent permanent damage from chronic infection.

Why didn’t his dementia fully resolve with treatment?

Incomplete resolution may indicate: (1) pre-existing dementia worsened by acute infection, (2) permanent CNS damage from chronic Lyme, or (3) inadequate treatment duration. In elderly patients, distinguishing Lyme-induced from age-related cognitive decline is challenging.

Should all NPH patients be tested for Lyme disease?

In endemic areas, yes. When hydrocephalus develops with meningeal inflammation, infection including Lyme disease should be investigated. Treating underlying infection may prevent progression or reverse hydrocephalus without need for shunt placement.

What Lyme bands were positive in this patient?

Western blot bands 23 and 39 were positive. Band 23 (OspC) and band 39 (BmpA) are specific for Borrelia burgdorferi, indicating active or recent infection rather than old resolved disease.

Is Lyme disease common in Pennsylvania?

Yes. Pennsylvania consistently reports among the highest Lyme disease cases in the United States. The authors note Lyme is “among the most common reportable infections in Pennsylvania,” making it essential to consider in patients with unexplained neurologic symptoms.