What is Neurolisteriosis?
Neurolisteriosis is a central nervous system infection caused by Listeria monocytogenes, a foodborne bacterium that shows particular tropism for the brain and meninges, presenting most commonly as meningitis, brainstem encephalitis (rhombencephalitis), cerebritis, or rarely myelitis. 1, 2, 3
Clinical Presentations
Neurolisteriosis manifests in several distinct patterns:
- Acute meningitis is the most common presentation, characterized by fever, headache, altered mental status, and neck stiffness 2, 3
- Rhombencephalitis (brainstem encephalitis) presents with cranial nerve palsies, autonomic dysfunction, myoclonus, and can mimic facial neuritis in early stages 4, 5
- Cerebritis appears as focal brain parenchymal infection with ring-enhancing lesions on MRI 3, 5
- Myelitis is exceptionally rare but documented, presenting as acute spinal cord inflammation 6
A critical diagnostic pitfall is that neurolisteriosis can present with a "locked-in syndrome" pattern due to brainstem involvement 4. The brainstem syndrome may include lower cranial nerve involvement, respiratory drive disturbance, and autonomic dysfunction 4.
High-Risk Populations
While classically associated with immunocompromise, neurolisteriosis occurs across diverse populations:
- Elderly patients over 50 years have significantly increased risk 1, 2
- Immunocompromised individuals including those with HIV, cancer, organ transplant recipients, and patients on prolonged corticosteroids or immunosuppressive therapy 2, 7
- Pregnant women have 10-17 times higher risk of invasive listeriosis 2
- Patients with chronic liver disease, including cirrhosis or hemochromatosis 2
- Healthy adults can develop neurolisteriosis, particularly in regions with poor sanitary conditions and inadequate food manufacturing controls 3, 5, 8
Diagnostic Characteristics
The cerebrospinal fluid (CSF) findings in neurolisteriosis are notably variable and can be misleading:
- CSF may show lymphocytic predominance in up to 50-70% of cases, mimicking viral meningitis 7
- Normal or near-normal CSF cell counts can occur, particularly in brainstem encephalitis presentations 9, 6
- Normal glucose (glycorrachia) is present in approximately half of cases 3
- CSF can be turbid or slightly turbid with elevated protein 3
Brain MRI may reveal microabscesses in the brainstem, ring-enhancing foci, or gadolinium enhancement of basal meninges 4, 3, 5.
Critical Treatment Considerations
The most dangerous pitfall is initiating empiric therapy with only a third-generation cephalosporin, as Listeria monocytogenes is naturally resistant to all cephalosporins. 1, 2
- Ampicillin or amoxicillin 2 g IV every 4 hours must be added to empiric regimens for patients over 50 years or those with any immunocompromising condition 1
- Treatment duration is minimum 21 days for confirmed neurolisteriosis 1
- Dexamethasone should be discontinued immediately if Listeria is identified, as its use has been associated with increased mortality in neurolisteriosis 1
- Antibiotics must be initiated within 1 hour of hospital presentation for suspected bacterial meningitis 1, 7
For penicillin-allergic patients, trimethoprim-sulfamethoxazole or meropenem are acceptable alternatives 1.
Prognosis and Outcomes
The prognosis depends critically on early recognition and appropriate antibiotic therapy 9. Even with treatment, neurolisteriosis can result in prolonged recovery requiring months of intensive care, with some patients requiring long-term mechanical ventilation support 5. However, with prompt ampicillin-based therapy, good outcomes are achievable 3, 6.