Chronic meningitis

Chronic meningitis
Healthcare workers performing a lumbar puncture, obtaining a sample of the cerebrospinal fluid aids in the diagnosis of chronic meningitis
Specialty	Infectious disease, Microbiology, Neurology, Neurosurgery
Symptoms	Headache, lethargy, confusion, fever, nausea, vomiting, visual impairment
Complications	Cranial nerve palsies, ophthalmoplegia, seizures, ataxia, psychiatric disorders, hemiparesis, deafness, blindness, intellectual disability
Duration	Chronic, by definition lasting longer than 4 weeks. With some infections lasting many months
Causes	Microorganisms (bacteria and fungi), viruses, and non-infectious causes including cancer, medications, autoimmune disease or inflammatory conditions
Risk factors	HIV infection, diabetes, immunosuppression
Diagnostic method	Culture of microorganism from the cerebrospinal fluid (CSF), biopsy of tissue or CSF sample with staining of organism, molecular methods such as immunoassay (antigen or antibody assays), nucleic acid amplification, magnetic resonance imaging (MRI) of the brain
Prevention	Vaccination, BCG vaccine in tuberculosis meningitis[1]
Medication	Antibiotics, antifungals, antivirals in infectious causes
Prognosis	Poor

Chronic meningitis is a long-lasting inflammation of the membranes lining the brain and spinal cord (known as the meninges). By definition, the duration of signs, symptoms and inflammation in chronic meningitis last longer than 4 weeks.^[2] Infectious causes (due to bacteria, fungi and viruses) are a leading cause and the infectious organisms responsible for chronic meningitis are different than the organisms that cause acute infectious meningitis. Tuberculosis and the fungi cryptococcus are leading causes worldwide. 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. Chronic meningitis sometimes has a more insidious course than acute meningitis. 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. No cause is identified during initial evaluation in one third of cases.^[3] Magnetic resonance imaging (MRI) of the brain is more sensitive than computed tomography (CT scan) and may show radiological signs that suggest chronic meningitis, however no radiological signs are considered pathognomonic or characteristic. MRI is also normal in many cases further limiting its diagnostic utility.

Worldwide, tuberculosis meningitis is a leading cause of disability and death, with central nervous system tuberculosis (with tuberculosis meningitis being the most common type) occurring in 5-10% of all cases of extrapulmonary tuberculosis and 1% of all cases of tuberculosis overall.^[4] Cryptococcal meningitis is also a major cause of death and disability worldwide, especially in areas where HIV and AIDS are more common, accounting for more than 100,000 yearly deaths in Sub-Saharan Africa.^[3] Cryptococcal meningitis accounts for about 68% of meningitis cases in those with HIV and has a mortality rate of 10-25%, with delays in diagnosis and treatment being especially common and associated with a poor prognosis.^[5] The treatment for chronic infectious meningitis is directed at the underlying infectious agent.