May Also Follow Other Types of Meningitis in Children.
Prolonged unexplained fever, confusion despite adequate antimicrobial therapy, and convulsions after the apparent subsidence of infection are classic manifestations of accumulating subdural fluid that is usually sterile. Aspiration of this fluid, which may need to be repeated, results in relief of symptoms. Residual damage to the nervous system occurs in. 10 to 20 percent of patients, and is more common following pneumococcal meningitis than infection with LT influenza and meningococci. Deafness remains the most common sequel of pyogenic meningitis; hemiparesis, convulsive disorders, and dementia are seen occasionally.
General Considerations. 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 pres-ent besides 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, delirium 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 ulceration 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 fluid 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 cerebrospinal 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 immuno-fluorescent 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. The number of cells in the cerebrospinal fluid is always elevated and varies between 100 and 100,000 per cubic millimeter. Initially, polymorphonuclear leukocytes predominate; these are replaced by lymphocytes as the inflammatory process progresses. Early in the infection, one may find a plethora of bacteria with only a few cells. This is particularly true in pneumococcal and staphylococcal infections. A low cerebrospinal fluid sugar is the hallmark of bacterial meningitis and distinguishes it from the viral meningitides. Usually, the value is below 40 mg.
Per 100 ml. and maybe close to 0. Patients who have diabetes mellitus or who are receiving intravenous infusions of glucose may have falsely high glucose values. However, the ratio of blood to cerebrospinal fluid sugar in these patients is always higher than the normal value of 1.5 to 1. For example, a cerebrospinal fluid sugar of 150 mg. per 100 ml. in the presence of blood sugar of 500 mg. per 100 ml. is highly significant. The information obtained from blood sugar, which should be obtained routinely at the time of initial lumbar puncture, is frequently critical.
The protein content of the cerebrospinal fluid is generally elevated and may be as high as 800 mg. per 100 ml. Higher values are usually obtained in pneumococcal meningitis than in infections with other pathogens. The development of subarachnoid block is usually heralded by very high CSF protein values (800 to 1500 mg. per 100 ml.). Other Cultures. Blood cultures should be obtained routinely in patients suspected of having meningitis; they are positive in approximately 50 percent of cases. Occasionally, when the cerebrospinal fluid .cultures are negative, the blood cultures may provide the only clue to the etiologic agent.
Nose, throat, and ear cultures may not reflect the meningeal pathogen and are misleading too often to be of more than the ancillary value in diagnosis. Roentgenographic Studies. All patients with meningitis should have roentgenograms of the chest, skull, mastoid, and paranasal sinuses as soon as their condition permits. Frequently these provide the clue to the portal of entry of the pathogen. Eradication of these foci with antimicrobial therapy or surgical drainage may be essential for control of the meningeal infection.