The diagnosis of bacterial meningitis is not difficult, providing that a high index of suspicion is maintained. Meningeal infection should be considered in every patient with a history of upper respiratory illness interrupted by vomiting, headache, lethargy, confusion, or stiff neck. When first seen, some of these patients present only with low-grade fever, mild headache, or occasional emesis. Nevertheless, the possibility of meningeal infection must be carefully considered. In patients with pneumonia, it is particularly dangerous to ascribe confusion to age or “toxemic” depression. Meningitis may be present in addition to pulmonary infection, and the dosage of an antimicrobial drug used to treat pneumonia is often inadequate to control meningeal infection. The susceptibility of alcoholics to meningitis cannot be emphasized too strongly. Fever and confusion in these patients should -not be attributed to alcoholic intoxication, Delerium Tremens, or hepatic encephalopathy unless the cerebrospinal fluid has been examined.
Two unusual types of recurrent meningitis may mimic bacterial infection, at least initially. Mollaret’s meningitis consists of recurrent febrile attacks, malaise, headache, and meningeal signs accompanied by a marked polymorphonuclear inflammatory reaction in the CSF. Attacks last two to three days and subside spontaneously. Behcet’s syndrome is characterized by recurrent oral and genital ulcerations’ and relapsing ocular lesions along with meningitis. Other neurologic abnormalities may include cranial nerve palsies, seizures, hemiparesis, extrapyramidal signs, and chronic brain syndromes.
Cerebrospinal Fluid. The cerebrospinal fluid should be examined in any patient with evidence of meningeal irritation. In patients with papilledema or other evidence of elevated cerebrospinal f l uid pressure, lumbar puncture should be performed with care, employing a small gauge needle. Papilledema does not constitute a contraindication to lumbar puncture in patients in whom the diagnosis of meningitis is suspected. The Cerebro-spinal fluid pressure is usually elevated, and the gross appearance of the fluid may vary from slight turbidity to gross pus.
The fluid should be centrifuged immediately, and the sediment stained by Gram’s method and cultured on blood and chocolate agar under increased CO, tension and anaerobically in thioglycollate. Some common pitfalls encountered in Gram staining include washing the organisms off the slide, decolorizing gram-positive bacteria, and interpreting particles of the stain as bacteria. Nevertheless, carefully performed Gram stains are accurate in 90 percent of cases in which organisms are seen. Pneumococci are more easily identified than meningococci. Although immune-fluorescence techniques have been used to expedite the diagnosis in a variety of bacterial meningitis, they appear to be no more accurate than a well-performed Gram stain.