Diseases of the central nervous system. Meningitis and encephalitis.

Common forms of bacterial meningitis Acute bacterial meningitis results from invasion and subsequent inflammation of the meninges by bacteria. Early diagnosis, followed by appropriate antibacterial treatment, should result in cure-while late or inappropriate treatment ends in death or disablement. In spite of the ready availability of effective anti-bacterial agents the mortality and morbidity from this potentially curable condition remain unacceptably high, especially in neonatal meningitis and pneumococcal meningitis in people over 50. In Britain most cases of bacterial meningitis are caused by the Meningococcus, Pneumococcus, and Haemophilus influenzae, other forms being relatively uncommon. MENINGOCOCCAL MENINGITIS Meningococcal meningitis is the commonest form of acute bacterial meningitis in Britain and affects all age groups, with a particularly high mortality at the extremes of life. The onset of the disease may be remarkably sudden and the patient may die of the sequelae of meningococcaemic consumption coagulopathy before the full-blown meningitic picture arises. More usually the picture is one of acute meningeal irritation in a child or a young adult with fever, variable clouding of consciousness, and an associated petechial or purpuric rash, which is often sparse. Infants may present with grand mal seizures and fever without localising signs. The clinical diagnosis should be confirmed by examination of the cerebrospinal fluid (CSF) and blood culture. Because of an increasing worldwide incidence of sulphonamide-resistant meningococci, treatment with benzylpenicillin should always be started except in the patient allergic to penicillin, when cephaloridine should be used 1 g six-hourly intravenously in the adult, perhaps with 50 mg intrathecally daily for 3 days. Four-hourly bolus intravenous pulse injections of 2-4 MU in the adult, for five days, should be followed by a further five days of phenoxy-methyl penicillin 2 g daily with probenecid. The pulse injections of potassium penicillin should be slow lest ventricular tachyarrhythmias are induced, while fluid retention may result with the sodium salt. Total daily doses greater than 25 MU of benzylpenicillin should be avoided because of the possibility of inducing encephalopathy. A definitive bacterial diagnosis is unlikely in patients who have received antibacterial treatment before admission. Most of the young patients will have meningococcal and many of the older pneumococcal meningitis, so that, if the clinical picture fits, benzylpencillin in full dosage should be given, except in children , when ampicillin should be used. For the patient in agony with headache, diamorphine or pethidine should be given as necessary. Those patients who have fulminant …