By definition, the duration of signs, symptoms and inflammation in chronic meningitis last longer than 4 weeks.
Chronic meningitis due to infectious causes are more common in those who are immunosuppressed, including those with HIV infection or in children who are malnourished.
Also, some of the infectious agents that cause chronic infectious meningitis such as mycobacterium tuberculosis, many fungal species and viruses are difficult to isolate from the cerebrospinal fluid (the fluid surrounding the brain and spinal cord) making diagnosis challenging.
Some of the possible symptoms of chronic meningitis (due to any cause) include headache, nausea and vomiting, fever, and visual impairment.
[6][2] Other signs associated with chronic meningitis include altered mental status or confusion, and papillary edema (swelling of the optic disc).
Worldwide, HIV and AIDS (which are characterized by immunosuppression) are major risk factors for the development of chronic infectious meningitis.
[3] Diabetes, recent ear surgery or neurosurgery, and the presence of a ventriculoperitoneal shunt are other risk factors for the development of chronic infectious meningitis.
These fungi include coccidioidomycosis, histoplasmosis, blastomycosis, aspergillus and cryptococcus gattii (which may also cause chronic meningitis in those with normal immune function).
These droplets are then inhaled to the lungs where the mycobacterium tuberculosis is phagocytosed by macrophages as part of the Th1-helper T cell response and a granuloma forms.
[5] Chronic meningitis is defined by signs and symptoms being present longer than four weeks and includes pleocytosis, or the presence of inflammatory cells in the cerebrospinal fluid.
[2] Nucleic acid amplification or PCR of the cerebrospinal fluid may also assist in identifying a causative organism.
[2] Metagenomic sequencing has been used to detect a wide variety of genetic material in a sample (rather than testing for specific predetermined organisms with PCR) of the cerebrospinal fluid and aids in the identification of infectious causes of chronic meningitis that are difficult to isolate by conventional methods.
[2] Anti-fungal empirical therapy is also commonly employed due to fungi's ubiquitous presence and ability to cause opportunistic infections in those who are immunosuppressed.
[4] The World Health Organization recommends a screen and treat approach to diagnose cryptococcal meningitis in those with HIV.
Those who screen positive for serum cryptococcal antigen should undergo a lumbar puncture followed by treatment if the cerebrospinal fluid contains cryptococcus.
Those who cannot undergo a lumbar puncture but screen positive for cryptococcal antigen in the serum should be presumptively treated.
[3][2] Diuretics such as furosemide or acetazolamide, osmotic agents such as mannitol, external ventricular drainage, or ventriculoperitoneal shunts may also be used in tuberculosis meningitis to control intracranial pressure.
In children who developed tuberculosis meningitis, those who had the BCG vaccine had milder symptoms and were less likely to die from the disease.
[4] In those who survive tuberculosis meningitis, 30% have longstanding neurological impairments including seizures, weakness, deafness, blindness, intellectual disability.