Predilection for cns
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Infections / Organisms with Predilection for the CNS
Certain pathogens across all categories - bacteria, viruses, fungi, and parasites - show a specific tropism or "predilection" for the central nervous system. Here is a systematic overview:
BACTERIA
Nocardia spp. (especially N. farcinica)
The CNS is involved in up to two-thirds of cases of disseminated nocardiosis. The vast majority present with one or more brain abscesses (ring-enhancing, multilobulated on MRI). N. farcinica in particular has a special predilection for CNS involvement. Meningitis is uncommon and usually results from spread from an adjacent brain abscess. - Harrison's Principles of Internal Medicine 22E, p. 1403
Listeria monocytogenes
Classic CNS pathogen - causes meningitis and rhombencephalitis (brainstem encephalitis), with particular predilection for the brainstem. Affects immunocompromised, elderly, neonates, and pregnant women.
Mycobacterium tuberculosis
Has a well-established CNS predilection via hematogenous spread - causes tuberculous meningitis (most common form of CNS TB), tuberculomas, and tuberculous abscesses.
Treponema pallidum
Syphilis has a well-known CNS predilection - neurosyphilis affects the meninges, blood vessels, and brain parenchyma (tabes dorsalis, general paresis).
VIRUSES
Herpes Simplex Virus (HSV-1 & HSV-2)
HSV-1 is the most common cause of sporadic viral encephalitis, with a characteristic predilection for the temporal lobes and limbic system. HSV-2 causes neonatal encephalitis and aseptic meningitis.
Rabies Virus
Classic neurotropic virus - spreads centripetally via peripheral nerves to reach the CNS, with a predilection for the limbic system, brainstem, and spinal cord.
Poliovirus
Predilection for anterior horn cells of the spinal cord (lower motor neurons), causing flaccid paralysis.
JC Virus (John Cunningham Virus)
Causes Progressive Multifocal Leukoencephalopathy (PML) - almost exclusively targets oligodendrocytes in the CNS white matter in immunocompromised patients.
West Nile Virus & Tick-borne Encephalitis Virus
These viruses have a predilection for the basal ganglia, thalami, and brainstem - as noted in Grainger & Allison's Diagnostic Radiology, which states "West Nile virus and tick-borne encephalitis have a predilection for the basal ganglia, thalami and brainstem."
HIV
Has tropism for CNS macrophages and microglia - causes HIV encephalopathy, HIV-associated neurocognitive disorder (HAND), and vacuolar myelopathy.
Enteroviruses (e.g., EV-A71, Coxsackievirus)
Predilection for brainstem (brainstem encephalitis), anterior horn cells, and meninges.
FUNGI
Cryptococcus neoformans / C. gattii
The paradigmatic fungus with CNS predilection - causes cryptococcal meningitis/meningoencephalitis. Has tropism for the CNS due to factors like the presence of catecholamines (dopamine) in the brain, which support its growth. Especially in HIV+ patients with low CD4 counts.
Melanized (Dematiaceous) Fungi
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Cladophialophora bantiana - the most common neurotropic melanized fungus; causes cerebral phaeohyphomycosis, often in immunocompetent hosts
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Approximately 50% of cerebral phaeohyphomycosis patients are immunocompetent
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These fungi are described as "neurotropic" - having a specific predilection for the CNS, resulting in localized lesions with black necrotic tissue
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Also: Rhinocladiella mackenziei (highly neurotropic, near-100% mortality)
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Scedosporium spp. - can cause CNS infection especially post near-drowning
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Lomentospora prolificans - disseminated CNS disease in immunocompromised
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Tietz Textbook of Laboratory Medicine 7e, p. 3443-3444
Mucorales (Rhinocerebral Mucormycosis)
Rhizopus spp. most common. Rhinocerebral form in uncontrolled diabetics - sinusitis spreads directly to the brain via angioinvasion.
PARASITES
Toxoplasma gondii
Has particular predilection for cells of the CNS (and lung, heart, lymphoid organs). Brain cysts form in gray matter. Reactivation in immunocompromised (HIV, transplant) causes Toxoplasmic Encephalitis (TE) - the most frequent CNS opportunistic infection in AIDS before cART. - Medical Microbiology 9e, p. 822
Taenia multiceps (Coenurosis)
The larval stage (coenurus) has a predilection for the CNS, causing space-occupying cystic lesions. T. multiceps - CNS; T. serialis - subcutaneous/muscular tissues.
Taenia solium (Neurocysticercosis)
The most common cause of acquired epilepsy worldwide in endemic regions. Cysticerci lodge in brain parenchyma, meninges, ventricles, and spinal cord.
Naegleria fowleri
Enters via cribriform plate, with predilection for the olfactory bulbs and frontal lobes - causes Primary Amebic Meningoencephalitis (PAM), rapidly fatal.
Trypanosoma brucei (African Sleeping Sickness)
Has predilection for CNS - enters the brain causing meningoencephalitis with characteristic sleep disturbances and neurological deterioration.
Quick Summary Table
| Category | Organism | CNS Manifestation |
|---|---|---|
| Bacteria | Nocardia farcinica | Brain abscess (ring-enhancing, multilobulated) |
| Bacteria | Listeria monocytogenes | Meningitis, rhombencephalitis |
| Bacteria | M. tuberculosis | TB meningitis, tuberculomas |
| Bacteria | T. pallidum | Neurosyphilis |
| Virus | HSV-1 | Temporal lobe encephalitis |
| Virus | Rabies | Limbic/brainstem encephalitis |
| Virus | Poliovirus | Anterior horn cell destruction |
| Virus | JC virus | PML (white matter) |
| Virus | West Nile / TBE | Basal ganglia, thalami, brainstem |
| Fungus | Cryptococcus | Meningoencephalitis |
| Fungus | C. bantiana | Cerebral phaeohyphomycosis |
| Fungus | Rhizopus | Rhinocerebral mucormycosis |
| Parasite | T. gondii | Toxoplasmic encephalitis (ring-enhancing lesions) |
| Parasite | T. solium | Neurocysticercosis |
| Parasite | T. multiceps | Coenurosis (cystic CNS lesions) |
| Parasite | N. fowleri | Primary amebic meningoencephalitis |
| Parasite | T. brucei | Sleeping sickness meningoencephalitis |
The common mechanisms of CNS predilection include: neurotropism (ability to infect neural cells), evasion of blood-brain barrier, survival in the immunologically privileged CNS microenvironment, and in some fungi, utilization of CNS-specific substrates (e.g., catecholamines for Cryptococcus).
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