MM 331-337; 586-588, ID 1132-1140
CHRONIC MENINGITIS
NAMES OF DISEASE:
Tubercular meningitis
Cryptococcosis
Fungal meningitis
Torulosis
Syphilitic meningitis
Amoebic meningitis
OVERVIEW:
This is a fungal disease which begins with a lung infection due to inhalation of the organism. This organism is commonly present in avian feces, especially pigeon feces. Almost every person in this country has been exposed to the organism yet there are only 200-300 cases per year of fungal meningitis. It is thought that the host must be compromised in some respect in order to develop fungal meningitis, although the fungal pneumonia is fairly common. Predisposing factors include:
1. AIDS
2. Genetic impairment of host defense mechanisms - T-cell diseases (Di George Syndrome, Nezelof's syndrome)
3. Diabetes mellitus
4. Glucosteroid therapy
5. Malignancy (particularly of the lymphoreticular system)
6. Alcoholism
7. Collagen - vascular disease
(particularly disseminated lupus erythematosus - an acute or subacute,
remitting febrile
disease
principally of young women, with widespread collagen damage in many organs
and systems)
8. Sarcoidosis - a disorder involving many organs where there is formation of epithelioid cell tubercles.
9. Pregnancy
When aerosols containing C. neoformans are inhaled, the cells are engulfed by pulmonary alveolar macrophages. In people with a normal immune system, the fungus either fails to survive intracellularly or is quickly contained so that either no disease, or mild, subclinical illness occurs. If the infecting dose is so large that normal cellular defenses are overwhelmed or if the host is compromised, a chronic pneumonia ensues. The growing cryptococci do not elaborate toxins or engender hypersensitivity. They cause disease by compression of surrounding structures as an infected focus enlarges. Because the lungs are readily compressible, there is little or no clinical manifestation of the lung infection. However, the lesions are evident on chest x-rays. If C. neoformans cells are not successfully restrained in the pulmonary parenchyma they will pass to the hilar lymph nodes. Again there is little or no clinical response. From here they may become blood borne and lodge in any organ or tissue where they may give rise to lesions. However, they show a predilection for the CNS.
ETIOLOGICAL AGENTS:
Mycobacterium tuberculosis
Cryptococcus neoformans (Serotypes A,B,C,D)
Human immunodeficiency virus
Coccidioides immitis
Treponema pallidum
Naegleria fowleri
PATHOLOGY:
In the CNS, deep space-occupying lesions are most likely to occur in the grey matter around the ventricles and aqueduct, in the basal ganglia, cerebral white matter and cerebellar dentate nucleus. Infection of the meninges leads to seeding of the CSF and spread throughout the subarachnoid space. A grayish, mucinous exudate accumulates at the base of the brain and over the cerebellum; leptomeningitis is most pronounced in the same areas. In most patients there are lesions in the brain and the meninges-a meningoencephalitis. Each lesion will be the site of granuloma and abscess formation.
If the cells lodge in the skin or mucous membranes they grow and form nodules which may ulcerate.
If the fungi grow in bone, there is destruction of the bone.
CLINICAL SYMPTOMS:
The course of cryptococcoses is typically indolent and protracted with symptoms waxing and waning for weeks or months before the diagnosis is made. The patient may feel unwell, lose some weight and have no other symptoms. There may be no fever or low fever (102°F, 39°C). In the normal host the symptoms are mild. In the compromised host, the course may be acute or chronic. In almost all patients there is a mingling of the manifestations of encephalitis and meningitis. Patients present with:
1. Headache - frontal, temporal or retro-orbital. Most common feature and it becomes progressively more frequent and severe.
2. Mental aberrations (from simple irritability to psychosis)
3. Motor abnormalities (altered reflexes to paralyses)
4. Cranial nerve dysfunctions (aphasia, visual disturbances, hearing loss)
5. Cerebellar signs (dyssynergia, dysmetria, dysrhythmia, intentional tremor, slurring of speech)
6. Evidence of increased intracranial pressure
7. Fever in about 1/3 of
patients
DIAGNOSIS:
In a differential diagnosis consider:
Cryptococcal
meningitis
Tubercular
meningitis
HIV meningitis
Coccidioides
meningitis
Syphilitic
meningitis
Amoebic
meningitis
As the manifestations of cryptococcoses are nonspecific, the diagnosis is often arrived at by eliminating neoplastic disease, TB and other fungal diseases. Exposure to pigeon or other avian feces is a good clue. All blood and urine analyses are normal. REMEMBER: you cannot test for antibodies to C. neoformans because (1) the immune system is generally defective and (2) fungi do not elicit a strong antibody response in normal people. Best evidence is from CSF.
1. Increased CSF pressure
2. Protein is elevated
3. Glucose is decreased (45% of blood glucose)
4. Leukocytosis (40-400/mm3 - mostly mononuclear cells)
5. C. neoformans present in India ink preparations
6. Serological tests for
cryptococcal antigen
PROGNOSIS:
Almost always fatal if it
goes untreated (90% of patients die within one year).
TREATMENT:
1. Amphotericin B injected
I.V. and into the subarachnoid space. NOTE: This is poorly
absorbed into CSF. Treat for 6 weeks.
Toxic.
Amphotericin B is also available in a liposomal preparation that has enhanced
penetration.
2. Fluconazole
3. Ketoconazole
4. Itraconazole
5. Flucytosine (5-fluorocytosine)-penetrates into all body fluids, including CSF. Less toxic but higher doses required.
Whatever regimen of antifungal
drug therapy is used, surveillance is an essential part of treatment. Examine
CSF weekly for all parameters.