Page 308 - Medicine and Surgery

P1: FAW
BLUK007-07 BLUK007-Kendall May 25, 2005 18:18 Char Count= 0

304 Chapter 7: Nervous system

sensitivity, as a single sample is only positive in less than Table 7.6 Differential diagnosis of aseptic meningitis
50%.
Examples
CTandMRIimagingmaydemonstratehydrocephalus
Bacterial Partially treated bacterial meningitis
and basilar meningeal enhancement – both together are
Parameningeal bacterial infection
strongly suggestive of TB, MRI may demonstrate a focal e.g. subdural abscess, sinusitis
vasculitis. Mycobacterium tuberculosis
Polymerase chain reaction (PCR) testing is useful but Leptospirosis
not reliable, with only 60% positive in proven cases. Lyme disease (Borrelia burgdorferi)
Syphilis
In addition, suspected cases should be screened with
Viral Echovirus
achest X-ray, sputum culture and in confirmed cases an Enteroviruses
HIV test should be performed. HIV
HSV
Mumps
Management Polio
A minimum of 12 months therapy with rifampicin and Fungal/Parasitic Particularly in immunocompromised
isoniazid supplemented by pyrazinamide and a fourth patients –
drug for at least the first 2 months is recommended. Cryptococcus, Candida, Aspergillus
Toxoplasmosis, Amoeba
The fourth drug may be ethambutol or streptomycin
Malignancy Lymphoma
but these only penetrate the CNS adequately in the Leukaemia
earlystages,whilstthemeningesareinflamed.Treatment Metastatic carcinoma and
should be initiated on clinical suspicion, before confir- adenocarcinomas
mation, as deterioration can occur within days, and even Auto-immune/ Systemic lupus erythematosus
Inflammatory Behcˆet’s disease
when treated mortality is as high as 15–40%.
Sarcoid
Corticosteroids have been shown to reduce vascular
Drugs Particularly nonsteroidal
complications, and improve survival and neurological anti-inflammatory drugs
function. High dose prednisolone is used in cases with
rapid progression, cerebral oedema, hydrocephalus or
basilar enhancement on CT, with high levels of CSF pro-
the patient does not improve. Further investigations may
tein (>0.5 g/L) and in cases where there is a clinical de-
include:
terioration with the onset of therapy, due to the increase
CT/MRI scanning of the brain and sinuses.
in inflammatory response which may occur.
Repeated lumbar punctures, including further fluid
for cytology, specific CSF antibody. titres, e.g. for
Other causes of meningitis mumps, and PCR for, e.g. TB, HSV, enterovirus.
CSF staining for acid-fast bacilli, fungi.

Definition TB cultures, viral cultures and fungal cultures (al-
In some cases of clinical meningitis, initial investigations though these take days to weeks).
may demonstrate meningeal inflammation but routine Serum serology (acute and convalescent samples).
blood and CSF cultures are negative. HIV testing.
If it is not clear whether the process is bacterial or vi-
Aetiology ral, antibiotics may be given empirically whilst awaiting
The differential diagnosis for these cases of ‘aseptic further investigation.
meningitis’ is wide (see Table 7.6).

Acute viral encephalitis
Investigations/management
In many cases of aseptic meningitis, the diagnosis is of Definition
aself-limiting, benign viral meningitis. However, it is Inflammation of the brain parenchyma caused by
important to consider these other causes, particularly if viruses.