CNS infections

Question 1

what is meningitis

Answer 1

grey matter becomes inflamed

blood vessels entering the brain become damaged

Question 2

causes of meningitis

Answer 2

Viral
Many different types including mumps, echovirus, etc. Usually relatively benign with good recovery.

Bacterial
Classic tria of Neisseria meningitidis (meningococcus). Haemophilus influenza and Streptoccocus pneumonia. Mycobacter tuberculum is also important.

In children with impaired immunity, e.g. neonates, a very wide range of gram positive and gram negative organisms are possible causes. Typically agents picked up during birth such as E.coli and group B streptococcus are important.

Parasitic and fungal infections are rare causes in the UK.

Meningococcal infection is particularly important in young children. It is also much more common in developing countries. It naturally occurs in epidemics during most winters. It usually colonises the nasopharynx (up to 10% of children during epidemics) but only rarely invades the body to cause disease. Precipitating factors include other infections and smoking. If confined to the blood stream, the infection is called septicaemia (characterised by severe illness and a non blanching rash) which has a high mortality rate. However, meningitis if treated usually has a good outcome.

H influenza is now much less common following the success of immunisation campaigns. Both it and pneumococcus cause a more severe meningitis with a higher risk of long term effects even after treatment.

Question 3

treatment of meningitis

Answer 3

Clinical Features
As with all infection, the child will be ill and have a fever. Because the brain is infected other features include a reduced level of consciousness or coma, seizures, headache and vomiting. Irritation of the meninges cause neck stiffness and neck traction. Photophobia is also common. However, in children with lower levels of immunity, such as neonates, many of these features will be absent.

Treatment
Antibiotics (high penetrance to CNS)
General nursing care
Treatment of complication, e.g. seizures
?steroids – probably not now that H influenza is less common
Contact tracing (secondary prevention)

Outcome
Before antibiotic treatment was available, mortality was greater than 85% and most survivors had severe after effects. With early treatment over 80% of children with meningococcal meningitis have a good outcome.

Bad outcomes include death, blindness or reduced visual acuity, deafness, learning difficulties, physical handicap, epilepsy and hydrocephalus. A combination of these can occur.

Prevention
Immunisation if possible
Public Health measures
Secondary prevention

Question 4

encephalitis is

Answer 4

inflammation of the entire brain

Question 5

causes of encephalitis

Answer 5

Viral causes predominately; the others are rare. World-wide cerebral malaria is one of the most important infections affecting the CNS but this is by an indirect mechanism as it impairs blood supply to the brain.

Important viral causes include herpes simplex, Herpes Zoster (chicken pox) Rubella (measles) and increasingly HIV. Acute and chronic forms can occur. The outcome depends on the organism concerned. Before effective treatment herpes simplex caused devastating encephalitis with a high death rate and serious after effects in survivors. Chicken pox rarely causes severe infection mainly affecting the cerebellum and causing ataxia for some weeks, except in the new born where it too can cause a devastating infection.

Question 6

features of encephalitis

Answer 6

Clinical Features
Unwell; febrile
Reduced level of consciousness/coma
Seizures
Focal features, e.g. hemiparesis, dysphasia

Treatment
Specific anti-viral agent if available, e.g. Acyclovir
General nursing care (probably ITU)
Treatment of complications, e.g. seizures

Outcome
Death, visual impairment, hearing impairment, learning difficulties, physical handicap, seizures.

Prevention
Immunisation. However, immunisation with live virus itself carries a small risk of encephalitis.

Question 7

chronic viral encephalitis

Answer 7

Chronic Viral Encephalitis
Classic form of SSPE. Rubella can also cause a chronic form. More recently HIV can too.

Prion Diseases
Creutzfeldt-Jakob Disease can rarely affect children.

Congenital Infections
This term describes infections of the growing foetus before birth. Typical organisms include rubella, CMV, herpes viruses; syphilis; toxoplasma. As the brain is affected during development, effects are widespread. In severe cases, severe intellectual difficulties, physical handicap (cerebral palsy), deafness and hydrocephalus are typical outcomes. Retinitis is also common.

Question 8

clinical features of encephalitis

Answer 8

Clinical Features
At the time of infection the mother may have little or not symptoms and signs. At the time of birth the baby will be found to have microcephaly and if looked for retinopathy. Other features will not become apparent until the child is older. In some cases, particularly with rubella, a child may initially be normal but may then develop later deafness and/or dementia due to persisting chronic infection.

Treatment
None

Prevention
Immunisation and public health measures

Other Infections
More rarely abscesses can also develop in the central nervous system or adjacent to it.
Some infections, both viral and bacterial, can cause demyelination in the brain and/or spinal cord.

Direct viral infections in the spinal cord also occur. The classic is poliomyelitis.