Acute And Chronic Meningitis Health Article

Streptococcus pneumoniae , an encapsulated Gram-positive diplococcus, causes a severe form of bacterial meningitis that often leaves neurologic sequelae in survivors and is fatal in up to 30% of patients. The organism can affect all age groups and causes the most severe disease in the very young and the very old. There are over 90 serotypes identified among pneumococcal isolates, but a few serotypes predominate as the causes of meningitis. Different serotypes cause invasive disease in children (14, 6, 18, 19, 23, 4, 9) and in adults (1, 3, 4, 7, 8, 9, 12, 14). ^{19, 20} A group B streptococcus ( Strep. agalactiae ) is a pathogen of the neonatal period and often causes a devastating sepsis and meningitis. It colonizes the birth canal of women, from where it is transmitted to the child. The colonized newborn can develop group B streptococcal disease of early onset (developing at less than 7 days of age; median 1 day) or late onset (developing later than 7 days of age). Early-onset disease presents as a sepsis-like disease with a very high mortality rate; late-onset disease presents primarily as meningitis. ²¹ Group B streptococci are also increasingly found as cause of meningitis in older patients, particularly those who have chronic underlying diseases. ²² Listeria monocytogenes is a Gram-positive rod that causes meningitis preferentially in neonates, in adults who have underlying conditions such as alcoholism and on long-term treatment with corticosteroids, and in pregnant women. There is often an encephalitic component to presentation, with early mental status alterations, neurologic deficits and seizures. ²³

Staphylococci rarely cause meningitis, except in the setting of intraventricular shunts, or as a consequence of staphylococcal bacteremia in patients who have endocarditis, intravascular devices or suppurative foci. ²⁴ Streptococci (other than Strep. pneumoniae ), enterococci and Gram-positive anaerobes are rare causes of bacterial meningitis.

Haemophilus influenzae is a Gram-negative coccobacillus that is serotyped based on its capsule. Of the six encapsulated serotypes (a–f), type b causes almost all cases of invasive disease, including meningitis. Haemophilus influenzae meningitis is a disease of young children. ²⁵

Neisseria meningitidis , a Gram-negative diplococcus, is mainly responsible for bacterial meningitis in young adults; it causes both sporadic cases and epidemics. The organism is transmitted from person to person by droplets, a form of transmission favored by crowded conditions. ¹³

Enterobacteriaceae (e.g. Escherichia coli , Klebsiella spp. and Serrati a spp.) cause meningitis in neonates and in patients undergoing neurosurgical procedures.

Pseudomonas aeruginosa can cause meningitis in neutropenic patients and in patients after neurosurgery. ²¹

Viruses are the most common cause of aseptic meningitis (see Table 22.3). ⁵ Enteroviruses account for more than 80% of cases in which the cause is identified. Enteroviruses that cause meningitis include Coxsackie viruses A and B, echovirus and poliovirus. Enteroviruses are transmitted by the fecal-oral route and are spread through close contact in households and day care centers. Affected groups include infants, young children and those looking after them. Mumps, a paramyxovirus, is spread by respiratory droplets and is usually seen in the late winter and early spring. Neurologic complications range from encephalitis to meningitis. Young children are most commonly affected, and boys are more often affected than girls by a ratio of between 2 to 1 and 5 to 1. Mumps meningitis follows mumps parotitis, and there is often no salivary gland involvement at the time of presentation of aseptic meningitis. ⁵

Lymphochoriomeningitis virus is an arenavirus spread by contact with rodent urine or feces. The disease was most prevalent in young adults and in impoverished populations, but the virus has become a rare cause of meningitis. Patients present with the typical symptoms of acute meningitis. After an initial improvement, some patients relapse into a second phase of meningitis, which is believed to be immune-mediated. ²⁶

Patients infected with arboviruses (St Louis encephalitis virus, Western equine encephalitis virus, California encephalitis virus and Eastern equine encephalitis virus) usually present with symptoms of encephalitis rather than meningitis. However, a minority of patients have meningitis, with a paucity of symptoms suggestive of encephalitis.

Many of the herpesviruses cause neurologic complications, including aseptic meningitis. Primary genital herpes caused by herpes simplex virus type 2 is the most common cause. Aseptic meningitis is much less likely to complicate recurrent outbreaks of herpes. Herpes aseptic meningitis is a benign and self-limited illness that must be distinguished from herpes encephalitis, which is a serious illness that often has devastating neurologic consequences and often causes death. ²⁷

Varicella-zoster virus, cytomegalovirus and Epstein-Barr virus can also cause aseptic meningitis. HIV-1 has been identified as a cause of aseptic meningitis. Seroconversion of HIV-1 often causes a mononucleosis-like illness with fever, malaise, rash, myalgias and arthralgias, and this is sometimes associated with aseptic meningitis. ²⁸ Other less important viral etiologies of aseptic meningitis include adenovirus, measles and rubella.

Some bacterial infections can cause an aseptic meningitis syndrome. ²⁹ Patients who have bacterial meningitis and who have been partially treated with antibiotics may have symptoms of meningitis with a CSF profile very similar to that of aseptic viral meningitis. Parameningeal bacterial foci (e.g. brain abscesses and epidural abscesses) can be associated with culture-negative meningitis, usually with a predominantly granulocytic CSF pleocytosis. Symptoms of meningitis are generally mild or absent.

Bacterial endocarditis can cause a cerebritis, which is characterized by vasculitis of the small cerebral vessels; it can also be associated with aseptic meningitis.

Spirochetes commonly cause brain infections with meningeal inflammation and a CSF profile similar to that of viral meningitis. Secondary syphilis rarely (in about 1% of all cases) causes acute, aseptic meningitis that can be associated with hydrocephalus, cranial nerve palsies and encephalitic changes.

Aseptic meningitis is also a manifestation of early Lyme disease and is frequently associated with cranial and peripheral neuropathies. ³⁰

Both the early and second phase of leptospirosis can cause an aseptic meningitis. ³¹ The CSF shows a moderate lymphocytic pleocytosis and is sterile. The meningitis resolves without specific therapy over the course of a few weeks. Rickettsiae, including Coxiella burnetii and Ehrlichia spp., can cause an aseptic meningitis with lymphocytic pleocytosis and elevated protein concentrations as part of the meningoencephalitis that characterizes infections by these intracellular pathogens.

Naegleria fowleri , and rarely Acanthamoeba spp., can cause an acute meningoencephalitis that occurs most commonly in children and young adults and resembles bacterial meningitis with signs indicating severe brain involvement. The organism is acquired by swimming in fresh water. The CSF shows a polymorphonuclear pleocytosis with increased protein and decreased glucose concentrations, many erythrocytes and a negative Gram stain. A fresh, warm sample of CSF should be examined microscopically for evidence of motile amebae. The disease is fatal in more than 95% of cases. ³²

Neurosurgery involving the posterior fossa can result in aseptic meningitis ('posterior fossa syndrome'). Signs of meningitis appear rapidly, but patients often do not look very ill. The CSF shows a polymorphonuclear pleocytosis with elevated protein and low glucose mimicking bacterial meningitis, but cultures remain negative. The syndrome is diagnosed after excluding infectious causes (particularly bacteria) and is treated with high doses of corticosteroids for several days.

Other noninfectious diseases causing aseptic meningitis include carcinomatous meningitis, sarcoidosis, systemic lupus erythematosus and Behçet's disease. Many drugs have been linked to aseptic meningitis, most importantly trimethoprim-sulfamethoxazole (cotrimoxazole), nonsteroidal anti-inflammatory drugs and OKT3, an antibody directed against T cells. ³³ Mollaret's meningitis is a recurrent lymphocytic meningitis, usually seen in young women. The cause is unknown but is thought by some to be related to herpes simplex virus. ³⁴ The episodes are benign and self-limiting, the prognosis is good.

Worldwide, tuberculous meningitis, which results from the rupture of a tubercle into the adjacent subarachnoid space, is the most important cause of chronic meningitis. The presentation is typical for chronic meningitis — slowly progressive headache and signs of meningeal irritation, followed by cranial nerve involvement, other neurologic deficits and progressive mental status changes over a period of weeks. Tuberculous meningitis may be a consequence of either primary infection or reactivation of disease. The diagnosis can be confirmed by a positive CSF culture; however, M. tuberculosis is recovered from the CSF in only 38–88% of cases. A moderate lymphocytic pleocytosis is most common. The glucose can be very low; the protein is often very high. Cerebrospinal fluid smears for acidfast bacilli are positive in only a minority of cases (10–20%). Skin tests for delayed hypersensitivity to tuberculin are frequently negative in tuberculous meningitis, whether resulting from primary infection or reactivated disease. ¹⁸

Chronic meningitis is an unusual complication of brucellosis. Symptoms of the meningitis tend to progress over an extended period of months to years. The diagnosis should be entertained when there is a history of exposure to farm animals or consumption of undercooked meats or unpasteurized dairy products from endemic areas. ³⁵

Secondary syphilis may cause chronic meningitis. The disease is slowly progressive, and generally symptoms have been present for more than 1 month before presentation. Cranial nerve palsies are common; the facial and acoustic nerves are the most frequently affected. Diagnosis is based on a positive Venereal Disease Research Laboratory (VDRL) test in CSF. ³⁶

The diagnosis of meningitis associated with Lyme disease, caused by Borrelia burgdorferi , should be considered in patients who live or have travelled through endemic regions, particularly those with a history of a tick bite or erythema chronicum migrans. Meningitis may persist for weeks and may be associated with cranial nerve palsies and peripheral neuropathies. ³⁰ Syphilis, other spirochetal diseases and collagen vascular diseases may result in a false-positive Lyme serology.

Presentations of chronic meningitis caused by Cryptococcus neoformans , an encapsulated, ubiquitous fungus, range from a subacute meningoencephalitis to fever of unknown origin. People at highest risk are those with defects in cellular immunity such as occurs in AIDS, hematologic malignancies and prolonged use of high-dose corticosteroids, even though a significant number of patients with cryptococcal meningitis in the pre-AIDS era had no identifiable immune defect. The CSF shows a moderate lymphocytic pleocytosis, but in patients who have AIDS, inflammation may be virtually absent. Cryptococcal antigen latex agglutination is positive in more than 90% of cases, whereas microscopy of India ink preparations to visualize the yeast in CSF is less sensitive. ³⁷

Coccidioides immitis grows in the dry sandy soils of the southwest USA, and Central and South America. Acute infection is acquired by inhalation of the spores, and meningitis develops within a few months. There are few distinguishing features of the disease; some patients who have generalized disease have erythema nodosum; hydrocephalus is a common complication. Cerebrospinal fluid eosinophilia in patients who have lived or traveled though endemic regions should alert the clinician to the possibility of Coccidioides meningitis. Complement-fixing antibodies are present in the CSF in 75–95% of cases, and CSF cultures are positive in more than 50%. ³⁸

Histoplasma meningitis is a rare complication of histoplasmosis. The diagnosis should be considered in patients who live or have traveled through endemic regions — the Ohio River Valley of the USA, the Caribbean and South America. Cerebrospinal fluid cultures are positive in 27–65% of cases. Blood should be cultured and a buffy coat of the blood should be examined for the presence of the fungus. Histoplasma polysaccharide antigen is found in the urine, blood or CSF in 61% of patients and in an even higher proportion of patients who have AIDS.

Candida meningitis is rare and is most commonly a result of disseminated infection or placement of a ventricular shunt. Risk factors for candidemia are the prolonged use of antibiotics or corticosteroids, hyperalimentation, neutropenia, abdominal surgery, intravenous drug use and intravenous catheterization. Neonates are particularly prone to disseminated infection. Cerebrospinal fluid cultures are diagnostic.

Neurocysticercosis is endemic in Mexico, South America and Asia. Infection is acquired by eating food contaminated with eggs of Taenia solium . Seizures are the most common manifestation. Intraventricular and basilar cysts (racemose cysticercosis) may present with signs of obstructive hydrocephalus. The CSF shows a lymphocytic pleocytosis with eosinophils. Computed tomography (CT) scans of the head show multiple calcified lesions. Serology of blood and CSF may provide support for the diagnosis.

Angiostrongylus cantonensis , the rat lung worm, is most prevalent in Asia and the Pacific Islands and is acquired by the ingestion of raw or inadequately cooked shellfish or snails. Symptoms are typical of chronic meningitis, and rash with pruritus is also common. Infection results in peripheral eosinophilia and chronic eosinophilic meningitis, which resolves spontaneously within 2 months. There is no effective therapy.

Other less common causes of infectious chronic meningitis are organisms that usually cause abscesses, which may leak into the subarachnoid space to cause chronic meningitis. These conditions include blastomycosis, paracoccidioidomycosis, phaeohyphomycoses, mucormycosis, actinomycosis, nocardiosis and toxoplasmosis. Less common fungi causing this syndrome include Sporothrix schenckii , chromoblastomycoses and Aspergillus spp.

Meningeal carcinomatosis may cause a chronic meningitis that is difficult to distinguish from infectious causes. Neurosarcoidosis is an uncommon complication of sarcoidosis. Basilar inflammation is a prominent feature, resulting in cranial nerve palsies. The CSF shows a lymphocytic pleocytosis and usually a normal glucose. Less common noninfectious causes include systematic lupus erythematosus granulomatous angiitis, Behçet's disease and Vogt-Koyanagi-Harada syndrome.