Meningitis [also known as brain fever] is the inflammation of the membranes that cover the brain and the spinal cord. It is a neurological emergency, as it can become life-threatening if left untreated. It is caused by viral, bacterial or fungal infection. It can also be due the intake of certain drugs and contrast agents used in radiological procedures.
Types and causes
Viral meningitis is the most common of the causes of meningitis, followed by bacterial. Fungal and parasitic meningitis, though uncommon, can occur in individuals with a weak immune system.
Viral meningitis is caused by the herpes simplex virus, varicella zoster virus [known for causing chicken pox and shingles], or even the mumps virus. Causes of bacterial meningitis differ as per age. Some common causes include:
- Skull injury.
- People with a cerebral shunt or related devices are at an increased risk of infection through those devices.
- Head and neck infections.
- Pneumococcal [type of bacteria] meningitis is seen in recipients of cochlear implants for hearing loss.
- Cancer that spreads to the meninges.
- Certain drugs [non-steroidal anti-inflammatory drugs, antibiotics and intravenous immunoglobulin].
- Inflammatory conditions, connective tissue disorders and certain forms of vasculitis [inflammatory conditions of the blood vessel wall].
- Diseases and tumours that erode the skull.
- Cerebrospinal fluid [CSF] leak because of a head injury.
Signs and symptoms
The most common symptoms are severe headache, high fever and inability to flex the head forward due to rigidity of the neck muscles. However, all three features are present in only 44 – 46 per cent of all cases.
A child with meningitis may look unwell, be irritable and restless. Infants up to six months may have a bulging of the fontanelle [the soft spot on top of a baby’s head]. Other signs include leg pain, cold extremities, and abnormal skin colour.
Here is a list of some more signs to look out for:
- Lethargy [decreased consciousness]
- Photophobia [sensitivity to light]
- Phonophobia [intolerance to loud noises]
- Stiff neck
- Skin rashes
- Seizures [fits]
- Altered mental status.
As the pressure inside the skull increases, it may lead to swelling within the brain [oedema]. This could further lead to the obstruction of the flow of CSF in the brain, causing seizures.
Inflammation of the meninges leads to abnormalities of the cranial nerves that cause facial weakness, hearing loss, loss of vision or difficulty in swallowing. Blood clots are formed that result in a deteriorating sensorium [centre for sensation] and focal neurological deficit [nerve function problem].
Severe infection of meningococcal and pneumococcal bacteria may result in haemorrhage of the adrenal glands [leading to Waterhouse-Friderichsen syndrome], which is often lethal.
In patients with symptoms, a complete blood examination should be performed along with markers of inflammation [C-reactive protein]. A blood culture should be done in bacterial meningitis to detect associated organisms and sensitive antibiotics to treat the same.
The most important test in identifying or ruling out meningitis is the analysis of CSF through lumbar puncture. However, lumbar puncture is not suggested if there is a tumour in the brain or the intracranial pressure [ICP] is high, as it may lead to brain herniation. So, getting tests done like neuro imaging with brain CT [computed tomography] scan or MRI [magnetic resonance imaging] scan before the CSF is helpful.
CSF study is helpful to indicate the likely causative organism. In severe forms of meningitis, monitoring of blood electrolytes is suggested.
Treatment with wide-spectrum antibiotics should not be delayed while confirmatory tests are being conducted. Empiric antibiotics must be started even before the results of the lumbar puncture and CSF analysis are known.
Tuberculosis meningitis requires prolonged treatment with anti-tubercular drugs and is typically treated for a year or even longer. Viral meningitis requires supportive therapy, as most viruses responsible for causing meningitis are not amenable to specific treatment. Fungal meningitis is treated with long courses of anti-fungal medicines.
Prevention of meningitis can be short-term [antibiotics] or long-term [vaccines].Immunisation against Haemophilus influenzae type B, which is incorporated in their routine childhood vaccination scheme, has eliminated this pathogen as a cause of meningitis in young children.
Even incidence of mumps meningitis has fallen since immunisation with mumps vaccine. Close contacts like family members and health care professionals may need short-term prophylaxis [prevention], especially in meningococcal meningitis.