Tuberculous (TB) meningitis is correctly characterized as a meningoencephalitis, as it affects not only meninges but also brain parenchyma and vasculature. The primary pathologic event is formation of thick TB exudate within subarachnoid space, most prominently at the base of the brain.70 Accompanying this exudate is inflammation affecting adjacent blood vessels. Ischemic cerebral infarction, resulting from vascular occlusion, is a common sequela most often found in the distribution of the middle cerebral artery (reflecting presence of TB exudate within sylvian fissure) and striate arteries as they penetrate the base of the brain.70 Another characteristic feature of TB meningitis is hydrocephalus secondary to CSF dynamic disturbance.
TB meningitis is divided into three clinical stages:
|I (early)||Nonspecific (e.g., generalized malaise)|
Moderate focal neurologic deficits
(e.g., cranial nerve palsies)
|III (advanced)||Seizures |
Severe neurologic deficits (e.g., paresis)
Stupor or coma
Seizures are a presenting complaint in 10–20% of children, and more than 50% can develop seizures during their initial hospitalization.71 Seizures are generally more frequent in younger children.70 For adults, seizures are the initial presenting manifestation in 10–15% of cases.70
Diagnosis of CNS tuberculosis begins with the usual investigations required for diagnosing TB:
The usefulness of the tuberculin test in diagnosing acute TB is controversial, and its use in diagnosing TB meningitis is of similarly questionable value. Up to 60% of patients with TB meningitis do not react to PPD testing.72,73
Characteristic lumbar puncture results include:
No radiologic changes are pathognomonic, but some are sufficiently characteristic to raise clinical suspicion:
Principles guiding treatment of TB meningitis are similar to those for other forms of TB, with the added requirement that antimycobacterial agents must penetrate the blood-brain barrier. Therapeutic options depend upon the probability of drug resistance:70
Low probability of drug resistance:
High probability of drug resistance:
The use of steroids in TB meningitis is controversial. Amelioration of symptoms (including seizure control, spinal block prophylaxis, and reported mortality reduction in children) is the prime benefit, but this must be balanced against the risks of systemic steroid complication, steroid withdrawal, and reports of worsening of long-term neurologic outcome. Most authorities now advocate steroid use in TB meningitis only in the context of extreme neurologic compromise, elevated intracranial pressure, impending herniation, or impending spinal block.
Reviewed and revised March 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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