Inflammation affecting the membranes of the BRAIN or SPINAL CORD, or usually both. Meningitis may be caused by BACTERIA, viruses (see VIRUS), fungi, malignant cells or blood (after SUBARACHNOID HAEMORRHAGE). The term is, however, usually restricted to inflammation due to a bacterium or virus. Viral meningitis is normally a mild infection of a few days’ duration needing no treatment except pain relief. It does, however, occasionally cause ENCEPHALITIS, a potentially dangerous illness and it can lead to deafness (particularly mumps). A variety of viruses can cause meningitis, including: ENTEROVIRUSES; those causing MUMPS, INFLUENZA, HERPES SIMPLEX; and HIV.
Bacterial meningitis is life-threatening especially if it is co-existent with SEPSIS: in the United Kingdom, 1–5 per cent of children who contract the disease may die. Most cases of acute bacterial meningitis in the UK are caused by two bacteria: Neisseria meningitidis (meningococcus), and Streptococcus pneumoniae (pneumococcus); other bacteria include Haemophilus influenzae (a common cause until virtually wiped out by immunisation) and Mycobacterium tuberculosis (see TUBERCULOSIS). Of the bacterial infections, meningococcal group B is the type that causes a large number of cases in the UK, while group A is less common. Pneumococcal disease is now largely under control because of herd immunity as a result of immunisation.
Bacterial meningitis may occur by spread from nearby infected foci such as the nasopharynx, middle ear, mastoid and sinuses (see EAR, DISEASES OF). Direct infection may be the result of penetrating injuries of the skull from accidents or gunshot wounds. Meningitis may also be a complication of neurosurgery despite careful aseptic precautions. Immuno-compromised patients – those with AIDS or on CYTOTOXIC drugs – are vulnerable to infections.
Spread to contacts may occur in schools and similar communities. Many people harbour the meningococcus without developing meningitis.
are urgent and, if bacterial meningitis is suspected, antibiotic treatment should be started even before laboratory confirmation of the infection. Analysis of the CEREBROSPINAL FLUID (CSF) by means of a LUMBAR PUNCTURE is an essential step in diagnosis, except in patients who have signs of raised intracranial pressure, for whom the test would be dangerous. The CSF is clear or turbid in viral meningitis; turbid or viscous in tuberculous infection; and turbulent or purulent when meningococci or staphylococci are the infective agents. Cell counts and biochemical make-up of the CSF are other diagnostic pointers.
General practitioners are encouraged to give a dose of intramuscular penicillin before sending the child to hospital, where treatment is usually with a cephalosporin, such as ceftazidime or ceftriaxone and attention to co-existing SEPSIS, likely to require full intensive care with aggressive intravenous fluid replacement and, control of electrolyte balance, blood clotting and blood pressure. If bacterial meningitis causes CONVULSIONS, these are controlled with ANTICONVULSANTS. Local infections such as SINUSITIS or middle-ear infection require treatment, and appropriate surgery for skull fractures or meningeal tears is carried out when necessary. Treatment of close contacts such as family, school friends, medical and nursing staff is recommended if the patient has H. influenzae or N. meningitidis: RIFAMPICIN provides effective prophylaxis. Vaccines for meningococcal meningitis may be given to family members in small epidemics and to any contacts who are especially at risk such as infants, the elderly and immuno-compromised individuals.
The outlook for a patient with bacterial meningitis depends upon age – the young and old are vulnerable; speed of onset – sudden onset worsens the prognosis; and how quickly treatment is started – hence the urgency of diagnosis and admission to hospital. Some children who suffer meningitis in their first year of life sustain serious brain damage; most recover completely but some may have subtle signs of learning problems only apparent in later years.
Bacterial meningitis has been largely controlled by IMMUNISATION. In 2013/4 there were 724 reported cases of invasive meningococcal disease in England, a reduction of 75% since 1999/2000. The fall with meningococcus C was by about 96%, to just 30 cases, reflecting the introduction of vaccine. Occasional outbreaks of other types occur, for example of Meningococcal W in a party of pilgrims returning from the Hajj. With the introduction of immunisation against Meningococcus B of all infants from June 2015, the incidence is likely to fall even further.
Symptoms include malaise accompanied by fever, severe headache, PHOTOPHOBIA, vomiting, irritability, rigors, drowsiness and neurological disturbances. Neck stiffness and a positive KERNIG'S SIGN appearing within a few hours of infection are key diagnostic signs. Meningococcal and pneumococcal meningitis may co-exist with SEPSIS, a much more serious condition in terms of death rate or organ damage, and one which constitutes a grave emergency demanding rapid treatment.