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# Chronic bacterial meningoencephalitis: TB, syphilis, Lyme

- Lesion

Tuberculosis, syphilis and Lyme disease can smoulder in the brain for weeks or years, causing chronic meningitis, strokes and dementia.

Updated Nov 12, 2026

## Key points

- Tuberculous meningitis: basal exudate with granulomas, obliterative endarteritis causing infarcts, and hydrocephalus; CSF with lymphocytes, very high protein and low glucose.
- Tuberculoma: caseating granuloma acting as a mass; important in countries with high TB burden such as Colombia.
- Meningovascular neurosyphilis: endarteritis (Heubner arteritis) with plasma cells, causing strokes.
- Paretic neurosyphilis: spirochetes in the cortex, neuron loss, rod-shaped microglia and iron deposits; dementia and psychosis.
- Tabes dorsalis: loss of dorsal roots and dorsal columns: lost position sense, ataxia, lightning pains, Argyll Robertson pupils, Charcot joints.
- Lyme: lymphocytic meningitis, facial palsy, radiculitis; transmitted by Ixodes ticks.

## What it is

Some bacteria cause slow, granulomatous or chronic inflammation of the meninges and brain. Tuberculous meningitis forms a thick gelatinous exudate at the base of the brain that strangles arteries and blocks CSF flow; a tuberculoma is a caseating mass. Neurosyphilis, in the tertiary stage, affects meningeal vessels, the cortex (general paresis) or the dorsal columns (tabes dorsalis). Lyme neuroborreliosis gives lymphocytic meningitis and cranial nerve palsies, typically of the facial nerve.

## Structure

- TB meningitis gross: grey gelatinous exudate filling the basal cisterns, around the circle of Willis and cranial nerves.
- Neurosyphilis can also give gummas, rare necrotic granulomatous masses; congenital syphilis can involve the CNS.
- In HIV, neurosyphilis and tuberculous meningitis are more frequent and more aggressive.

## Chronic bacterial infections of the CNS

| Disease | Main lesion | Key microscopy | Typical consequence |
| --- | --- | --- | --- |
| [Tuberculous meningitis](https://durgical.com/en/conditions/tuberculosis/) | Basal gelatinous exudate | Caseating granulomas, endarteritis | Infarcts, hydrocephalus, cranial nerve palsies |
| [Tuberculoma](https://durgical.com/en/conditions/tuberculosis/) | Intraparenchymal mass | Caseation with epithelioid histiocytes and giant cells | Seizures, mass effect |
| [Meningovascular neurosyphilis](https://durgical.com/en/conditions/syphilis/) | Thickened meninges and arteries | Plasma cells, obliterative endarteritis | Strokes |
| [General paresis](https://durgical.com/en/conditions/syphilis/) | Cortical atrophy, frontal | Spirochetes, rod microglia, iron | Dementia, psychosis |
| [Tabes dorsalis](https://durgical.com/en/conditions/syphilis/) | Dorsal roots and columns | Axon and myelin loss | Sensory ataxia, lightning pains |
| [Lyme neuroborreliosis](https://durgical.com/en/conditions/lyme-disease/) | Meninges, cranial nerves, roots | Lymphocytes and plasma cells | Facial palsy, radiculitis |

## Clinical notes

- Tuberculous meningitis develops over weeks with headache, confusion, cranial nerve palsies and fever; delayed diagnosis leaves severe sequelae.
- Argyll Robertson pupils: small pupils that accommodate but do not react to light, classic of tabes.

## Memory aid

TB glues the base of the brain; syphilis strikes vessels, cortex or the back of the cord; Lyme bites the facial nerve.

## Test yourself

Think of the answer, then tap the question to see it.

## Why does tuberculous meningitis cause infarcts?

The basal exudate causes obliterative endarteritis of arteries crossing the subarachnoid space, which narrows and occludes them.

## Which part of the spinal cord is lost in tabes dorsalis?

The dorsal roots and dorsal columns, so position and vibration sense are lost and gait becomes ataxic.

## Which cranial nerve is classically affected by Lyme neuroborreliosis?

The facial nerve, sometimes on both sides.

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## Connections

## Related 5

- [Acute meningitis: pyogenic vs aseptic](https://durgical.com/en/general-pathology/acute-meningitis-pyogenic-vs-aseptic/)
- [HIV in the brain and PML](https://durgical.com/en/general-pathology/hiv-in-the-brain-and-pml/)
- [Granulomatous inflammation: caseating vs non-caseating, the causes to know](https://durgical.com/en/general-pathology/granulomatous-inflammation-caseating-vs-non-caseating-the-causes-to-know/)
- [Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous](https://durgical.com/en/general-pathology/patterns-of-necrosis-coagulative-liquefactive-caseous-fat-fibrinoid-gangrenous/)
- [Infectious vasculitis and aortitis](https://durgical.com/en/general-pathology/infectious-vasculitis-and-aortitis/)

## Related conditions 6

- [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/)
- [Syphilis](https://durgical.com/en/conditions/syphilis/)
- [Lyme disease](https://durgical.com/en/conditions/lyme-disease/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Congenital (TORCH) infections: syphilis, toxoplasmosis, CMV and Zika](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/)
- [Spinal tuberculosis (Pott disease)](https://durgical.com/en/conditions/spinal-tuberculosis/)

## Microorganisms 3

- [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/)
- [Treponema pallidum](https://durgical.com/en/microbiology/treponema-pallidum/)
- [Borrelia burgdorferi](https://durgical.com/en/microbiology/borrelia-burgdorferi/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Meningitis - tuberculous: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000650.htm) (MedlinePlus, US National Library of Medicine, 2026); [Neurosyphilis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000703.htm) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/chronic-bacterial-meningoencephalitis-tb-syphilis-lyme/