Acute Bacterial Meningitis

Meningitis is an infection of the membranes enclosing the brain and spinal cord. Acute bacterial meningitis is the most common type of meningitis, comprising about 80 per cent of cases. In the case of acute meningitis, the onset of symptoms is rapid.

The bacteria causing meningitis are normally abundant in nature, with some residing in parts of the upper respiratory system.

Causes

Infection of the subarachnoid space by normally-benign bacteria usually occurs only when the patient’s immune system has been compromised by another medical condition. Sometimes, however, the area may become infected with no obvious cause.

A number of factors have been identified which increase the risk of developing acute bacterial meningitis, including:

·         Use of drugs to suppress the immune system (immunosuppressants), usually to prevent rejection of transplanted organs;

·         Removal of the spleen (splenectomy);

·         Surgical procedures involving penetration of the skull;

·         Head injuries; and

·         Blood infections.

Pathophysiology

The subarachnoid space is part of the group of tissues surrounding the brain, in which cerebrospinal fluid is located. This substance helps to insulate the brain and spinal cord against shocks.

The presence of bacteria causes the immune system to trigger an inflammatory response.

Intense swelling can cause significantly increased pressure inside the skull, and cause parts of the brain to shift. Pressure on the brain may also lead to the formation of blood clots inside the brain, swelling, and minor bleeding.

Symptoms and diagnosis

For adults and older children, early symptoms of acute bacterial meningitis include:

·         Fever;

·         Headache;

·         A dark red/purple rash;

·         Inability to move head vertically; and

·         Depressed consciousness, leading to coma or death.

In children aged up to two years old, who are at greatest risk of acute bacterial meningitis, other symptoms include:

·         Abnormally high or low body temperature;

·         Irritability;

·         Seizures; and

·         Lethargy.

In diagnosing acute bacterial meningitis, doctors will look for physical signs of the illness, such as an immobile neck or skin rash.

They may analyse a sample of blood to determine the presence of bacteria responsible for infection.

Since acute bacterial meningitis can cause death within hours, however, treatment will often commence before the results of clinical tests are obtained.

Treatment

Treatment for acute bacterial meningitis will often begin before the bacteria causing the infection has been determined.

The patient will be given antibiotics targeting the most likely-responsible bacteria. Once the bacteria have been identified by clinical tests, the patient will be administered antibiotics to specifically target these.

Other drugs are administered over the course of treatment, to reduce inflammation and thus, pressure inside the skull.

Since acute bacterial meningitis affects many bodily systems, specific treatments may be required, depending on individual circumstances.