ISSN: 1391 - 0531
Sunday March 16, 2008
Vol. 42 - No 42

Bugs in the brain

By Dr. Ruvini Abeygunaratne Karunaratne

Our brain and spinal cord, as well as the structures surrounding them, can get infected by a variety of germs (bugs!); these are so small they cannot be seen by the naked eye. The two main types are bacteria and viruses. The germs cause a reaction of the tissues, (an inflammatory response) and this in turn gives rise to the symptoms and signs in the patient.

The exact name of the disease depends on the location in which the inflammation occurs. For example, meningitis is inflammation of the lining and fluid (cerebrospinal fluid) that covers the brain and the spinal cord. The terms encephalitis and myelitis are used to describe the inflammatory processes limited to the brain and spinal cord tissue respectively.

If left untreated these infections can progress leading to an accumulation of infectious material in the brain or spinal cord, which will result in an abscess. Meningitis can be caused by viral or bacterial infections. Viral meningitis is more common and normally presents with milder symptoms compared to bacterial meningitis. Patients may describe headaches, lethargy, neck stiffness and flu type symptoms. Treatment is normally conservative in a similar manner to flu and antibiotics are of limited use.

Bacterial meningitis on the other hand is a serious and life-threatening condition. It may result in long term disabilities such as learning difficulties, hearing impairment, mobility problems, epilepsy, permanent brain damage and even death. About two-thirds of all cases are in children and early diagnosis and treatment is essential to avoid serious consequences.

In children the presentation may be different, depending on their age. In very young children the only features maybe unusual crying, poor feeding, listlessness, vomiting and reduced level of consciousness. Older children may complain of a headache or non specific symptoms such as abdominal pain. In adults, patients normally present with headaches, vomiting, neck stiffness and photophobia (where looking into the light hurts your eyes). Some patients may also appear confused. Signs of meningitis should be recognised as an emergency for the patient must receive urgent medical treatment.

A fever with a blotchy rash over the body which doesn't disappear on compression (commonly called "the glass test") is indicative of meningococcal meningitis. This is caused by specific bacteria and is the deadliest of all types of meningitis, especially if the infection gets into the patient's blood stream (this is known as septicaemia).

Spots or a rash will still be seen when the side of a clear drinking glass is pressed firmly against the skin. Treatment involves urgent admission to hospital where antibiotics will be started immediately. The patient will have sampling of the cerebrospinal fluid carried out, and then according to the isolated germ appropriate antibiotics may further be added or changed. The patient needs to be observed carefully for deterioration and treated appropriately.

Encephalitis by a germ is characterised by clouding of consciousness, odd behaviour and sometimes seizures. An infection causing encephalitis will be associated with a fever, neck stiffness and photophobia. This may progress to meningitis or to the development of a brain abscess. Treatment, as for meningitis is identification of the germ with antibiotics if it is bacterial.

The Glass Test: A fever, together with spots or a rash that do not fade under pressure, is a medical emergency.

A brain or spinal abscess is a very serious condition and may be the result of an infection that has not be treated fully. Even mild infections such as ear infections and gum or tooth infections may progress to an abscess. Patients who are especially prone to abscesses include those who have a weak immune system or are unable to fight infection. Diabetics are also at high risk.

It can be difficult to recognise a patient who has a brain abscess. They may have had a fit, as there is a very high incidence of fits associated with brain abscesses. Also they may complain of significant headaches, neck stiffness and/or photophobia. They may have a deteriorating level of consciousness and be generally very unwell and even have paralysis similar to that seen with a stroke.

With a spinal abscess patients can suffer with severe back pain which may progress to limb weakness. Problems with difficulty in passing urine may also occur. Both conditions are neurosurgical emergencies. The patient is admitted and will have routine blood tests as well as some more specialised tests.

A CT scan is the investigation of choice and normally shows, what is described as a ring enhancing lesion, indicating a brain abscess. The investigation of choice for spinal abscesses is a MRI scan.

When it comes to treating a brain abscess, if the causative bug is known, appropriate antibiotics are started straight away. The patient is then taken for an operation. After a hole is made in the skull bone (called a burr hole or slightly larger hole craniotomy) over the abscess, a needle is introduced and the abscess is aspirated. The aspirated fluid is sent for analysis to identify the germ and then the correct antibiotics are commenced.

Diagram - laminectomy
The Burrhole procedure

Normally such patients need to be on long term antibiotics, through a drip, for at least 4-6 weeks. If it is a very small abscess (<3cm), it may be treated with just antibiotics without the need for an operation but this is only on rare occasions.

They have regular check scans to see whether the infection is settling down. With a spinal abscess the inflammation and the abscess itself can cause pressure effects on the spinal cord, which will, in turn, cause the patient's symptoms and signs. Again if the organism is known, and the patient's only symptom is back pain, then treatment can be limited to antibiotic treatment. If there is weakness of the limbs, which is progressing then an operation is indicated to decompress the area thereby relieving the pressure. This is called a laminectomy, where some bone from the back (called the spinous process and laminar) is removed and the infected material is evacuated. The patient is then again treated with antibiotics.

Infections of the brain and spine are uncommon but serious conditions, which should be promptly diagnosed and treatment without delay to reduce the risk of long-term damage.

(The writer is Specialist Registrar in Neurosurgery, Manchester)

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