186 CHRONIC MENINGITIS
Harrison’s Manual of Medicine
Chronic inflammation of the meninges (pia, arachnoid, and dura) can produce profound neurologic disability and may be fatal if not successfully treated. The causes are varied. Five categories of disease account for most cases of chronic meningitis: (1) meningeal infections, (2) malignancy, (3) noninfectious inflammatory disorders, (4) chemical meningitis, and (5) parameningeal infections. Neurologic manifestations consist of persistent headache with or without stiff neck and hydrocephalus, cranial neuropathies, radiculopathies, and cognitive or personality changes (Table 186-1). On occasion the diagnosis is made when a neuroimaging study shows contrast enhancement of the meninges. Once chronic meningitis is confirmed by CSF examination, effort is focused on identifying the cause (Table 186-2 and Table 186-3) by (1) further analysis of the CSF, (2) diagnosis of an underlying systemic infection or noninfectious inflammatory condition, or (3) pathologic examination of meningeal biopsy specimens.
Table 186-1 Symptoms and Signs of Chronic Meningitis
Table 186-2 Infectious Causes of Chronic Meningitis
Table 186-3 Noninfectious Causes of Chronic Meningitis
Approach to the Patient
Proper analysis of the CSF is essential; if the possibility of raised intracranial pressure (ICP) exists, a brain imaging study should be performed before LP. In pts with communicating hydrocephalus caused by impaired resorption of CSF, LP is safe and may lead to temporary improvement. However, if ICP is elevated because of a mass lesion, brain swelling, or a block in ventricular CSF outflow (obstructive hydrocephalus), then LP carries the potential risk of brain herniation. Obstructive hydrocephalus usually requires direct ventricular drainage of CSF.
Contrast-enhanced MRI or CT studies of the brain and spinal cord can identify meningeal enhancement, parameningeal infections (including brain abscess), encasement of the spinal cord (malignancy or inflammation and infection), or nodular deposits on the meninges or nerve roots (malignancy or sarcoidosis). Imaging studies are also useful to localize areas of meningeal disease prior to meningeal biopsy. Cerebral angiography may identify arteritis.
A meningeal biopsy should be considered in pts who are disabled, who need chronic ventricular decompression, or whose illness is progressing rapidly. The diagnostic yield of meningeal biopsy can be increased by targeting regions that enhance with contrast on MRI or CT. In a series from the Mayo Clinic, biopsy of an enhancing region was diagnostic in 80% of cases; biopsy of nonenhancing regions was diagnostic in only 9%; sarcoid (31%) and metastatic adenocarcinoma (25%) were the most common conditions identified.
In approximately one-third of cases, the diagnosis is not known despite careful evaluation. A number of the organisms that cause chronic meningitis may take weeks to be identified by cultures. It is prudent to wait until cultures are finalized if symptoms are mild and not progressive. In many cases progressive neurologic deterioration occurs, and rapid treatment is required. In general, empirical therapy in the U.S. consists of antimycobacterial agents, amphotericin for fungal infection, or glucocorticoids for noninfectious inflammatory causes. It is important to direct empirical therapy of lymphocytic meningitis at tuberculosis, particularly if the condition is associated with hypoglycorrhachia and sixth and other cranial nerve palsies, since untreated disease is fatal in 4–8 weeks. Carcinomatous or lymphomatous meningitis may be difficult to diagnose initially, but the diagnosis becomes evident with time. Important causes of chronic meningitis in AIDS include infection with Toxoplasma, Cryptococcus, Nocardia, Candida, or other fungi; syphilis; and lymphoma.
For a more detailed discussion, see Koroshetz WJ and Swartz MN: Chronic and Recurrent Meningitis, Chap. 374, p. 2481, in HPIM-15.