Table of Contents
Primary Category
Neurocritical Care
P-Category
Secondary Category
Neuroinfectious
S-Category
Authors:
Contents
Introduction
- Central nervous system (CNS) infections are uncommon amongst the immunocompetent population
- A state of immuno-incompetency increases susceptibility of the CNS to infection
- CNS infections incur serious burden on the morbidity and mortality of cancer patients
- Evolving drug resistance, prolonged prophylactic antimicrobial use and intense chemotherapeutic regimes have given rise to a patient group vulnerable to atypical infections e.g progressive multifocal leukoencephalopathy (PML)
- CNS infections in the immunocompromised are, more often than not, medical emergencies
Defining Immunosuppression
Immunosuppression is defined as decreased ability of the body to mount an immune response in order to ward off disease or infection; it is determined by the interaction of several factors, these include:
- Age (extremes of age)
- Baseline disease : autoimmune disease, inflammatory disease, cancer
- Comorbidities : diabetes mellitus, uremia, cirrhosis, COPD, etc.
- Underlying immunodeficiencies : HIV, splenectomy, pregnancy, B-Lymphocyte/Immunoglobulin deficiency, T-Lymphocyte depletion, Neutropenia
- Previous therapies : immunosuppressive therapy, biological treatments, antimicrobial therapy, chemotherapy
- Compromise of mucocutaneous barrier : burns, indwelling catheters, surgery
- Immunomodulating viruses : CMV, HHV-6, EBV, HBV, HCV, HIV, RsV
Epidemiology
The most common opportunistic organisms for CNS infections are:
- Aspergillus fumigatus
- Cryptococcus neoformans
- Cytomegalovirus
- Epstein-Barr virus
- Listeria monocytogenes
- Mycobacterium tuberculosis
- Toxoplasma gondii
- Human immunodeficiency virus
Patients susceptible to opportunistic CNS infections
- Patients with HIV
- 40-60% of patients with HIV develop neurological complications
- patients may present with a normal neurologic examination
- Patients undergoing solid organ transplant (SOT)
- up to one-thirds of patients undergoing SOT will develop neurological complications
- Patients undergoing chemotherapy
- Patients with hematologic disorders
- including stem cell transplantation
- 15% of patients undergoing allo-HSCT develop CNS infection
Clinical presentation
- The clinical picture and prognosis of CNS infections in the immunocompromised host differ from patients with an immunocompetent status
- Immunosuppression leads to an altered and lessened immune response, leading to less obvious symptomatology
- Absence of typical symptoms such as fever or meningism
- Corticosteroids blunt the immune response
- Steroid therapy also reduces contrast enhancement on imaging
- Presence of multiple concurrent infections
- Heightened response to pathogens rarely seen in immunocompetent patients
Table 1 : Drugs associated with risk of specific CNS infections
Drug | CNS infection |
I. Drugs approved for neurological conditions | . |
Alemtuzumab | VZV, HSV, TB, PML, CMV, Listeria, Nocardia |
Dimethyl fumarate | PML, VZV |
Eculizumab | Neisseria meningitidis |
Fingolimod | VZV, HSV, PML, Cryptococcus, Listeria |
Natalizumab | PML VZV, HSV |
Ocrelizumab | VZV, HSV, PML* |
Teriflunomide | PML, TB |
Corticosteroids (prednisone, methylprednisolone, dexamethasone) | PML, VZV, PJP, Candida |
II. Drugs used off label for neurological conditions | ㅤ |
Azathioprine | PML, CMV, EBV-associated PCNSL |
Cyclophosphamide | PML, sepsis, bacterial infections (urine, lung) |
Ibrutinib | Aspergillus, PML |
Infliximab | VZV, TB, PML, demyelinating lesions ➔ MS |
Methotrexate | Toxoplasmosis, EBV-associated lymphoproliferative disorder |
Mycophenolate mofetil | PML, PCNSL |
Rituximab** | Toxoplasmosis, enterovirus, Babesia, WNV, CMV, VZV, Cryptococcus, PJP, Powassan virus, PML |
III. Drugs associated with CNS infections with no primary neurological indication | ㅤ |
Adalimumab (also certolizumab, etanercept) | PML |
Brentuximab | PML |
Cyclosporine/tacrolimus | ㅤ |
Fludarabine | PML, VZV, HSV, Listeria, Cryptococcus |
Leflunomide | PML, TB |
Ruxolitinib | PML, toxoplasmosis |
*PML associated with ocrelizumab to date only seen in patients previously on natalizumab or dimethyl fumarate
**Rituximab associated with reactivation of hepatitis B virus and the unusual severity of infections with Babesia and WNV
Table modified from : Pruitt AA. Central Nervous System Infections in Immunocompromised Patients. Curr Neurol Neurosci Rep. 2021;21(7):37. Published 2021 May 26. doi:10.1007/s11910-021-01119-w
Table 2 : Parasitic CNS infections in immunosuppressed hosts
Parasite | Associated condition | Neuroimaging finding | Recommended testing | Note |
Schistosoma species | HIV
Bone marrow & liver transplant | Solitary or multiple hyperdense lesions | Serology, Stool, Urine, CSF | Larvae are detectable in esophageal and peritoneal fluid |
Strongyloides stercoralis | HIV
Heart & kidney transplant | Brain abscess of mycotic aneurysm | Serology, Stool, CSF | ㅤ |
Taenia solium | HIV
Kidney tranplant | Calcified or ring-enhancing lesions; large cysts; scolex on MRI | Serology, CSF | ㅤ |
Toxoplasma Gondii | HIV
Bone marrow, heart, kidney, liver & lung transplant | Solitary or multiple ring enhancing lesions; edema. MRI more sensitive. | Serology, CSF | Trophozoites can be detected in biopsy tissue specimen |
Trypansoma Cruzi | HIV
Heart, kidney & liver transplant | Large solitary or multiple ring enhancing lesions with surrounding edema | Serology, CSF | ㅤ |
Table compiled and modified from : Walker M, Zunt JR. Parasitic central nervous system infections in immunocompromised hosts. Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America. 2005;40(7):1005-1015. doi:10.1086/428621
Table 3: CNS Prophylaxis
Condition | Prophylaxis Used |
HIV | Advised vaccinations, prompt management |
Solid organ transplant (SOT) | Advised vaccinations before surgery, regular monitoring |
Chemotherapy | Advised vaccinations before initiating therapy, regular monitoring |
Hematological disorders | Permissible vaccinations, regular monitoring |
ㅤ | ㅤ |
Vaccines recommended for immunocompromised patients
- Inactivated influenza vaccine
- Hepatitis A
- Hepatitis B
- Human Papilloma Virus
- DTaP
- Inactivated polio vaccine
- Meningococcal vaccine
- Pneumococcal vaccine
- Rabies
- Varicella-Zoster
- The best form of prophylaxis and/or prevention of CNS infection in the immunocompromised is regular monitoring, testing, imaging & prompt management
- Suspicion of CNS involvement necessitates immediate diagnostic procedures, including but not limited to :
- CT scan
- MRI scan
- PET scan
- Lumbar puncture/CSF analysis
- blood culture
- PCR assays
- Histopathological workup
- Brain biopsy
- Although specific diagnosis is crucial, literature suggests covering the following organisms
- Listeria (ampicillin),
- Cryptococcus (Amphotericin B and/or fluconazole),
- Herpes simplex virus (acyclovir or ganciclovir),
- other common bacterial pathogens (vancomycin/linezolid, ceftriaxone)
- broad spectrum management should be continued until a diagnosis is confirmed
- For HIV patients : intensify antiretroviral therapy and/or increase CNS penetration
- Always consider Mycobacterium tuberculosis in patients from developing countries and administer anti-tuberculous therapy (ATT)
- Immunosuppression management should be tailored to the needs of the patient
- Sudden reduction in steroid dosage may result in hydrocephalus
- Neurosurgical intervention may be required
Further reading
- Dougan C, Ormerod I. A Neurologist’s Approach to the Immunosuppressed Patient. Journal of Neurology, Neurosurgery & Psychiatry. 2004;75(suppl 1):i43-i49. doi:10.1136/jnnp.2003.035071
- Zunt JR. CENTRAL NERVOUS SYSTEM INFECTION DURING IMMUNOSUPPRESSION. Neurologic clinics. 2002;20(1):1-v. Accessed October 12, 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2695971/
- Pruitt AA. Central Nervous System Infections in Immunocompromised Patients. Current Neurology and Neuroscience Reports. 2021;21(7). doi:10.1007/s11910-021-01119-w
Bibliography
1. Rm L, De B, Ml R. Neurological manifestations of the acquired immunodeficiency syndrome (AIDS): experience at UCSF and review of the literature. Journal of neurosurgery. 1985;62(4). doi:10.3171/jns.1985.62.4.0475
2. Levin SN, Lyons JL. Infections of the Nervous System. The American Journal of Medicine. 2018;131(1):25-32. doi:10.1016/j.amjmed.2017.08.020
3. Castro I, Ruiz J, Tasias M, Montero M, Salavert M. Central nervous system infections in immunocompromised patients. Revista Española de Quimioterapia. 2018;31(Suppl 1):56-61. Accessed October 12, 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6459576/
4. Dougan C, Ormerod I. A Neurologist’s Approach to the Immunosuppressed Patient. Journal of Neurology, Neurosurgery & Psychiatry. 2004;75(suppl 1):i43-i49. doi:10.1136/jnnp.2003.035071
5. Wright AJ, Fishman JA. Central Nervous System Syndromes in Solid Organ Transplant Recipients. Clinical Infectious Diseases. 2014;59(7):1001-1011. doi:10.1093/cid/ciu428
6. Pruitt AA, Graus F, Rosenfeld MR. Neurological Complications of Transplantation. The Neurohospitalist. 2013;3(1):24-38. doi:10.1177/1941874412455338
7. Zunt JR. CENTRAL NERVOUS SYSTEM INFECTION DURING IMMUNOSUPPRESSION. Neurologic clinics. 2002;20(1):1-v. Accessed October 12, 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2695971/
8. Pruitt AA. Central Nervous System Infections in Immunocompromised Patients. Current Neurology and Neuroscience Reports. 2021;21(7). doi:10.1007/s11910-021-01119-w
9. Walker M, Zunt JR. Parasitic central nervous system infections in immunocompromised hosts. Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America. 2005;40(7):1005-1015. doi:10.1086/428621
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