When Lyme Disease Mimics a Brain Tumor

Welcome to another Inside Lyme Podcast. I am your host Dr. Daniel Cameron. I find that the best way to get to know Lyme disease is through reviewing actual cases. In this episode, I’ll be discussing a case involving a 9-year-old boy with pseudotumor cerebri involving the brain due to Lyme disease.

Ezequiel and colleagues first described this case in the British Medical Journal Case Reports in 2017.

Pseudotumor cerebri means “false brain tumor” because its symptoms are similar to those caused by brain tumors. It’s also known as idiopathic intracranial hypertension.

Symptoms Mimic Brain Tumor

The boy was admitted to the hospital with “daily pulsatile frontotemporal headache, pallor, photophobia and phonophobia, without night awakening, vomiting or visual changes,” the authors write. Photophobia is sensitivity to light. Phonophobia is fear or aversion to sound.

The doctors found papilledema, which is swelling of the optic disc, but no neck pain. A CT scan of the patient’s head was normal. He had an increased opening pressure in his spinal tap. In other words, the fluid removed from his spinal tap was under higher pressure.

The boy was diagnosed with pseudotumor cerebri. Pseudotumor cerebri is a condition caused by elevated cerebrospinal fluid pressure in the brain. Symptoms can mimic a brain tumor, but in fact are due to intracranial pressure in the head.

He was prescribed acetazolamide while undergoing further evaluation. Acetazolamide is a diuretic and carbonic anhydrase inhibitor medication that is used to reduce eye pressure and intracranial pressure.

Extensive Testing for Infectious Causes

The boy was tested for a wide range of bacterial and viral infections, all of which were negative.

He lived in Portugal and because he had visited the countryside prior to developing symptoms, he was tested for Lyme disease. A Western blot and spinal tap revealed he was positive.

This finding illustrates an important principle: in non-endemic areas, Lyme disease may not be considered initially despite being the underlying cause.

Treatment for Neuroborreliosis

The boy was diagnosed with Lyme disease involving his brain and treated with a 21-day course of intravenous ceftriaxone. He recovered completely.

The authors point out, “CSF [cerebrospinal fluid] changes are not common, so in their presence, it is compulsory to investigate an infectious origin, as happened in this case, as the intracranial hypertension might be the only symptom of a central nervous system infection.”

Furthermore, “Borrelia infections should be actively investigated in children with central nervous system disease even in non-endemic areas.”

Why Pseudotumor Cerebri Matters in Lyme Disease

Pseudotumor cerebri as a manifestation of Lyme disease is uncommon but well-documented. When it occurs, it may be the only neurologic finding—no meningeal signs, no focal deficits, no obvious indication of infection beyond elevated intracranial pressure.

This creates diagnostic challenges. Pseudotumor cerebri has many potential causes, including medications, vitamin A excess, obesity, and idiopathic cases where no cause is identified. Infectious etiologies like Lyme disease may not be immediately considered.

The case demonstrates why infectious workup should be part of the evaluation for pseudotumor cerebri, particularly in children with recent outdoor exposure in areas where tick-borne illness occurs.

Geographic Considerations in Diagnosis

The boy lived in Portugal, which the authors describe as a “non-endemic area.” However, he had visited the countryside before developing symptoms.

This highlights how geographic assumptions can delay diagnosis. Clinicians may not consider Lyme disease in areas perceived as non-endemic, even when patients have exposure histories that warrant testing.

The case argues for broader consideration of tick-borne illness in children with unexplained neurologic symptoms, regardless of local endemic status.

Frequently Asked Questions

What is pseudotumor cerebri?
Pseudotumor cerebri, also called idiopathic intracranial hypertension, is elevated cerebrospinal fluid pressure in the brain without a mass lesion. Symptoms mimic brain tumors—headache, visual changes, papilledema—but imaging shows no tumor.

Can Lyme disease cause pseudotumor cerebri?
Yes, though uncommon. Lyme disease can cause elevated intracranial pressure presenting as pseudotumor cerebri. In some cases, this may be the only neurologic manifestation.

How is pseudotumor cerebri from Lyme disease diagnosed?
Diagnosis requires high clinical suspicion. Lumbar puncture demonstrates elevated opening pressure. Lyme serology from blood and cerebrospinal fluid confirms infection. Imaging rules out mass lesions.

Why wasn’t Lyme disease considered immediately?
The patient lived in an area considered non-endemic. Initial testing focused on more common causes. Only after negative bacterial and viral tests—and consideration of his countryside exposure—was Lyme disease tested.

How effective was treatment?
The boy recovered completely after 21 days of intravenous ceftriaxone. This response confirms the diagnosis and demonstrates that pseudotumor cerebri from Lyme disease is reversible with appropriate antibiotic therapy.

Clinical Takeaway

This case demonstrates that Lyme disease can present with pseudotumor cerebri as the sole neurologic manifestation. A 9-year-old boy developed daily headaches, photophobia, phonophobia, and papilledema—classic signs of elevated intracranial pressure. Imaging was normal. Lumbar puncture showed increased opening pressure. The clinical picture suggested pseudotumor cerebri, but extensive infectious workup was appropriately pursued. Only after testing for common bacterial and viral infections came back negative—and after considering his countryside exposure—was Lyme disease diagnosed through positive Western blot and cerebrospinal fluid testing. The authors emphasize that cerebrospinal fluid changes are uncommon in pseudotumor cerebri, making infectious investigation mandatory when present. More importantly, they argue that Borrelia infections should be actively investigated in children with central nervous system disease even in non-endemic areas. This challenges the geographic assumptions that often delay diagnosis. The boy’s complete recovery after 21 days of intravenous ceftriaxone confirms both the diagnosis and the treatment approach. Pseudotumor cerebri from Lyme disease is reversible when recognized and treated appropriately. But recognition requires clinical suspicion that transcends endemic boundaries.