Chronic Meningitis



Chronic Meningitis


Joseph R. Zunt

Kelly J. Baldwin



INTRODUCTION

Chronic meningitis is commonly defined as inflammation of the meninges, most often accompanied by a pleocytosis of greater than 5 white blood cells per microliter in the cerebrospinal fluid (CSF), that has persisted for at least 1 month without spontaneous resolution. Clinical presentation often includes headache, nausea, vomiting, cranial neuropathies, symptoms of elevated intracranial pressure, or focal neurologic deficits (Table 64.1). The most common etiologies of chronic meningitis fall into three broad categories: infectious, autoimmune, and neoplastic. This chapter will focus on the most common infectious etiologies of chronic meningitis. Fungal, bacterial, and parasitic pathogens can invade the central nervous system and present clinically as chronic meningitis. Increasing use of immunosuppressant medications for autoimmune disease and posttransplantation immunosuppression, as well as predisposing conditions, such as impaired cellular and humoral immunity, have led to a larger population at risk for infectious causes of chronic meningitis.

Despite an increasing array of diagnostic assays, there remain a large proportion of patients with chronic meningitis who remain without a definitive pathogen identified. A thorough history and skillful physical examination is the key to guide further diagnostic testing (Table 64.2) and management (Table 64.3). When history, examination, CSF analysis, and imaging fail to yield an etiology, biopsy is required to establish a definitive diagnosis.


FUNGAL MENINGITIS

Fungi exist in two forms, molds and yeasts. Molds are the tubular form, consisting of hyphae that can be branched or contain a single filament. Yeasts are thick-walled, single-celled organisms that live inside cells. Dimorphic yeasts assume tubular forms at lower temperature but become encapsulated at temperatures above 35°C. Either fungal form can infect the nervous system, producing meningitis, vasculitis, abscess, granulomas, or encephalitis.

Fungi are universal saprophytic organisms found as spores in soil, on the skin of mammals and birds, and in bat or bird guano. They commonly enter the body through inhalation; direct invasion through the skin, mucus membranes, or sinuses; or via penetrating wounds. Although invasive fungal disease typically affects immunocompromised individuals, some organisms such as Coccidioides spp. and Cryptococcus spp. can also affect immunocompetent individuals. Fungal infections of the nervous system mainly occur in the presence of immunosuppression as a consequence of AIDS, cancer, hematologic malignancy, hereditary immune defects, organ or stem cell transplantation, or other conditions requiring therapeutic immunosuppression.


CRYPTOCOCCAL MENINGITIS


Epidemiology and Pathobiology

Cryptococcal meningitis is most often caused by the encapsulated yeast Cryptococcus neoformans, but other cryptococcal species, such as Cryptococcus gattii, are emerging as pathogens that affect immunocompetent individuals. With a worldwide distribution, C. neoformans is ubiquitous, found primarily in bird droppings, soil, and citrus peel. C. gattii is more commonly associated with the bark of several tree species. Infection usually occurs through inhalation of the organism, followed by a respiratory infection and dissemination. Cryptococcal meningitis is most common in people with impaired cell-mediated immunity, especially those with HIV infection, hematologic malignancies, solid organ transplant recipients, and patients on chronic corticosteroids or other immunosuppressive therapy. In patients immunocompromised due to HIV infection, cryptococcal meningitis is the most common systemic fungal infection and a frequent etiology of central nervous system (CNS) infection, with a prevalence varying from 10% in the United States to as high as 30% in sub-Saharan Africa.


Clinical Features


CRYPTOCOCCUS GATTII

This is a rare pathogen, with disease confined to tropical and subtropical climates, particularly the highly endemic regions of Australia and Papua New Guinea. In 2004, an outbreak of C. gattii infections was documented in the United States Pacific Northwest states of Oregon and Washington. A large retrospective review of the Pacific Northwest C. gattii infections revealed important clinical differences between C. gattii infections in the United States Pacific Northwest and historically endemic areas. Although C. gattii in historically endemic areas has been reported to infect primarily immunocompetent persons, causing meningoencephalitis, C. gattii infections in Oregon and Washington State occurred frequently in immunocompromised persons and presented most often as respiratory illness. Time from symptom onset to diagnosis of C. gattii infection was significantly longer among patients with pulmonary infections (50 days) than those with either CNS (24 days) or bloodstream infections (27 days). There were no differences in immune status between patients with bloodstream infections and either pulmonary or CNS infections.


CRYPTOCOCCUS NEOFORMANS

The clinical manifestations of C. neoformans infection depends largely on the host immune status. Severity of infection varies from asymptomatic incidental pulmonary nodules to widely disseminated disease. HIV-infected patients with CD4+ counts of less than 50 cells/µL are especially vulnerable to disseminated infection and meningitis. Cryptococcal meningitis typically begins insidiously, with 75% of patients developing headache and fever over a 2- to 4-week period. As the infection evolves, 50% of people develop nausea, vomiting, and altered mental status. Visual symptoms and seizures are also common. Over half of immunocompromised patients develop intracranial hypertension; this is even more common in immunocompetent hosts. As increased intracranial pressure develops, patients become obtunded, and without intervention, herniation will follow.









TABLE 64.1 Neurologic and Systemic Symptoms and Imaging Characteristics of Chronic Infectious Meningitis
















































Condition


Neurologic Presentation


Systemic Symptoms


Neuroimaging


Cryptococcosis


Headache and fever (75%), nausea and vomiting (50%), altered mental status (50%), visual symptoms, seizures


Pulmonary, multiorgan involvement


Hydrocephalus, cerebral edema, leptomeningeal enhancement, and cryptococcomas


Coccidioidomycosis


Headache (75%); nausea and vomiting (40%); altered mental status (39%-73%); focal neurologic deficits, including ataxia, gait disturbance, diplopia, or facial palsies (33%-80%); and nuchal rigidity (20%)


Pulmonary, lymph nodes, skin


Hydrocephalus, meningeal enhancement, nodular enhancement, basilar meningitis, cerebral infarction


Blastomycosis


Focal neurologic deficits, seizures, and altered mental status


Less common: fever, headache, and meningismus


Pulmonary, verrucous or fungating skin lesions, bones, joints, genitourinary system


Single or multiple abscesses, granuloma, meningeal enhancement, epidural extensions, and overlying osteomyelitis


Histoplasmosis


Headache and altered mental status


Acute pulmonary infection with fever, chills, and pulmonary opacities


Multiorgan including bone marrow


Normal, granuloma, meningeal enhancement


Aspergillosis


Solitary mass lesion, cavernous sinus thrombosis, multiple intracranial abscesses, acute or chronic basilar meningitis, vasculitis, or myelitis


Pulmonary, sinusitis, multiorgan involvement


Multiple abscesses, meningeal enhancement, infarction, hemorrhage, sinusitis with extension


Tuberculosis


Headache, vomiting, meningeal signs, focal deficits, vision loss, cranial nerve palsies


Pulmonary, malaise, anorexia, fatigue, weight loss, fever, myalgia


Enhancement of the basilar meninges, thick exudates, obstructive hydrocephalus, miliary pattern, tuberculoma, and periventricular infarcts


Syphilis


Meningitis (headache, photophobia, nausea and vomiting, cranial nerve deficits), general paresis, psychiatric illness, cognitive decline, tabes dorsalis, or vascular disease


Genital ulcers, fever, lymphadenopathy, headache, malaise, myalgia, and a macular or pustular rash of the palms and soles


Multiorgan involvement


Leptomeningeal enhancement, white matter disease in the brain and posterior columns, ischemic stroke


Borreliosis


Early: septic lymphocytic meningitis, cranial neuritis, or painful polyradiculitis


Late: myelitis, encephalitis, and neurobehavioral changes


Rash, fever, diffuse aches and pains, headaches, malaise, fatigue, carditis


White matter edema with enhancement



Jul 27, 2016 | Posted by in NEUROLOGY | Comments Off on Chronic Meningitis
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