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Neurological Alterations and Management 465

a significant reduction in the number of cases of menin- development of subdural empyema, brain abscess and
97
gococcal disease. Nationally in 2008 only 15 serogroup acute hydrocephalus may require surgical intervention.
C infections were identified and serogroup B accounted Bacterial meningitis with accompanying bacteraemia can
for 88% of all infections. New Zealand has one of the lead to a marked systemic inflammatory response with
highest rates of meningococcal B disease in the developed septic shock, respiratory distress syndrome and dissemi-
world but the incidence has declined. There were 132 nated intravascular coagulation.
cases of meningococcal disease notified in 2009, which
equates to a rate of 3.8 per 100,000 population. The Collaborative care
number of confirmed cases was 117, giving a confirma-
tion rate of 88.6% which is the third-equal-highest con- Neurological derangement often coexists with circulatory
firmation rate since 1991. Five deaths occurred in 2009, insufficiency, impaired respiration, metabolic derange-
giving a case-fatality rate of 3.8%. Since 1991 a total of ment and seizures. Protecting the patient from injury
265 deaths have been recorded, an overall case-fatality secondary to raised ICP and seizure activity is essential.
rate of 4.2%. The policy of giving antibiotics prior to Prevention in relation to complications associated with
hospital admission, implemented in 1995, reduced the immobility, such as decubitus and pneumonia, is
case-fatality rate for those receiving antibiotics. In addi- required. It is important to institute droplet infection
tion this rate has reduced from 470 cases in 2001, prior control precautions in those attending the patient until
to the immunisation for meningococcal B commencing 24 hours after the initiation of antibiotic therapy (oral
98
in 2004. The incidence of meningococcal disease varies and nasal discharge is considered infectious). See Online
seasonally, rising in June and peaking in October each resources for infection control protocols relating specifi-
year. The highest incidence of meningococcal disease was cally to meningitis.
for children aged 4 years and under. A secondary peak in
the incidence of meningococcal disease is seen in adoles- Encephalitis
99
cents and young adults. However, during the H1N1
influenza epidemic there were several cases of H1N1 Encephalitis implies inflammation of the brain substance
influenza-related meningitis. See Table 17.6 for CSF pro- (parenchyma), which may coexist with inflammation
files for acute meningitis and encephalitis and Table 17.7 of the meninges (meningoencephalitis) or spinal cord
for the classification, treatment and clinical presentation (encephalomyelitis). Encephalitis may be mild and self-
of meningitis. limited, or may produce devastating illness.
Complications Aetiology
Complications of meningitis vary according to the Herpes simplex virus (HSV) is the commonest cause
aetiological organism, the duration of symptoms prior of non-seasonal encephalitis in Australia. Without tre-
to initiation of appropriate therapy, and the age and atment, HSV encephalitis is fatal in up to 80% of cases,
100
immune status of the patient. Temporary problems and leaves up to 50% of survivors with long-term
include development of haemodynamic instability sequelae. 101
and disseminated intravascular coagulopathy, particu- ● In the absence of particular risk factors, other
larly in meningococcal infection, SIADH or other common causes are enteroviruses, influenza virus and
dysregulation of the hypothalamic–pituitary axis (e.g. Mycoplasma pneumoniae. However, the likely patho-
diabetes insipidus) and an acute rise in ICP.
gens in encephalitis are dramatically influenced by
Focal neurological signs may develop in the early stages geographic location, history of travel and animal
of meningitis, but are more common later. The exposure, and vaccination.

TABLE 17.6 Typical profiles of cerebrospinal fluid in acute meningitis and encephalitis

Meningitis Encephalitis
Investigation Reference range Bacterial Viral Bacterial/Viral
Opening pressure <30 mmH 2 O Raised Normal Raised
White cells
6
Total count <5 × 10 /L Greatly raised Moderately raised Moderately raised
Differential Lymphocytes (60–70%), Neutrophils predominate Lymphocytes Lymphocytes
monocytes (30–50%), no predominate predominate
neutrophils or red blood cells
Glucose concentration 2.8–4.4 mmol/L Lowered Normal Normal
CSF: serum glucose ratio >60% Lowered Normal Normal
Protein concentration <0.45 g/L Raised Normal or slightly raised Normal or slightly raised