Chronic meningitis is an irritation and inflammation of the Meninges with sub-acute onset and persisting cerebrospinal fluid (CSF) abnormalities / pleocytosis in the CSF lasting for at least 4 weeks. Compared to acute viral or bacterial meningitis, chronic meningitis is unquestionably less common. Consciousness impairment, epileptic seizures, neurological signs and symptoms, are all indicators of meningoencephalitis and encephalitis and even the formation of granulomas and/or abscesses that may progress over time. Pathogenic agents invade directly the Meninges, perivascular spaces or brain tissue or they elicit an allergic inflammatory reaction towards the invading agent leading to diffuse inflammatory response of the Meninges or the brain parenchyma. Moreover, chemical substances or the drugs elicit inflammatory responses in the Meninges through exposure. The infectious agents causing chronic meningitis including viruses (e.g., Lymphocytic Choriomeningitis, Mumps, Herpes Zoster, Arboviruses, Echoviruses etc), bacteria, (e.g., Mycobacterium Tuberculosis, Treponema Pallidum, Borrelia spp, Brucella spp etc), fungi (e.g., Cryptococcus Neoformans, Coccidioides species, Histoplasma species, Pseudallescheria Boydii etc), protozoa (e.g., Trypanosoma-brucei-species, Trypanosoma Cruzi etc) and even helminths (e.g., Cysticercus Cellulosae, Angiostrongylus species, Gnathostoma Spinigerum etc). There a many non-infectious reasons that can cause chronic meningitis. These causes may include meningeosis carcinomatosa, meningeosis lymphomatosa/primary CNS lymphoma, Bechet disease, sarcoidosis, Wegener granulomatosis, Sjögren syndrome, Vogt-Koyanagi-Harada syndrome, Migraine with CSF pleocytosis, Foreign body in CNS etc.
Neurologically, a patient presents with an insidious onset of headache, mild neck-stiffness, low grade fever and even development of hydrocephalus. Pleocytosis in the cerebrospinal fluid is required to meet the criteria for this diagnosis. A very thorough medical history, a precise physical and electrophysiological examination of the nervous system, neuroimaging, and laboratory tests are all required for the diagnosis of a patient with persistent meningitis. In Europe, tuberculosis meningitis, chronic inflammation of the Meninges caused by a parameningeal infectious focus, and meningeosis carcinomatosa are the most significant infectious and non-infectious causes of chronic meningitis in an immunocompetent patient. The most frequent causes in immunocompetent hosts in individuals with a history of travel to tropical regions are tuberculous meningitis, syphilis, and cysticercosis. The diagnostic range is wide in patients with immunocompromised state, with the most frequent causes being Cryptococcus neoformans, Mycobacterium tuberculosis, Cytomegalovirus, Toxoplasma gondii, Candida spp., and Acanthamoeba. Fungal infections, in particular, are more common in immunocompromised people. An individual exposed to bird excrement may get invasive cryptococcosis as a result of Cryptococcus neoformans, var. gattii, especially in tropical areas. Inhalation of dust or soil containing spores of Coccidioides immitis, Histoplasma spp., Blastomyces spp., Paracoccidioides spp., and Sporothrix schenckii in Central and South America and some regions of Africa may result in systemic mycosis, which eventually spreads to the central nervous system (CNS).
The need for neuroimaging, extracerebral sonography, computed tomography, and clinical examinations goes beyond just taking a patient's medical history. To design the biopsy of the Meninges or brain parenchyma, imaging of the intracranial structures is crucial , allowing the neurosurgeon to select the optimal location. Extracerebral invasive diagnostic techniques, such as potential biopsies of lymph nodes, skin, mucous membranes, muscle, liver, peripheral nerves, and bone marrow, should be considered before thinking about an intracranial biopsy. An extensive yet focused multidisciplinary assessment of a patient with persistent meningitis is required before making a decision on invasive bioptic procedures. A chronic infection of the CNS can be caused by a variety of Candida species. Neonates (premature infants), neutropenic patients, patients with diabetes mellitus, patients receiving long-term corticosteroid therapy, and intensive care patients with long-term central venous lines, external ventricular drains, and long-term broad spectrum antibiotic therapy are at particular risk to develop an invasive Candida infection of the nervous system. In order to control the disease's progression, antimicrobial chemotherapeutic approaches may be employed. Treatment of elevated intracranial pressure, external ventricular drainage, osmotic therapy, and a focus on anti-inflammatory therapies in the case of autoimmune illnesses are examples of adjunctive therapeutic techniques.
Reference:
Helbok, R., Broessner, G., Pfausler, B., & Schmutzhard, E. (2009). Chronic meningitis. Journal of neurology, 256(2), 168–175. https://doi.org/10.1007/s00415-009-0122-0
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