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Introduction

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Bacterial meningitis is a medical emergency especially meningococcus meningitis which can cause rapid deterioration of the patient. Consider it if a sudden onset of the classical triad is accompanied by high fever and the signs of a very sick child. Meningococcal meningitis may be accompanied by a petechial rash and septic shock (Waterhouse–Friderichsen syndrome).

Anisha Bahra & Katia Cikurel, Neurology, 19991

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Infections of the central nervous system will cover general conditions such as meningitis and encephalitis and specific organisms such as syphilis and polio. This section is highlighted because the conditions that are difficult to diagnose can have morbid outcomes, especially if the conditions are misdiagnosed. They are representative of classic ‘not-to-be-missed’ conditions.

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Key symptoms suggestive of cerebral infection are headache, seizures and altered conscious level.

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Meningitis
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Meningitis is inflammation of the meninges (pia and arachnoid) and the cerebrospinal fluid (CSF).

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The classic triad is:

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  • headache

  • photophobia

  • neck stiffness

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Other symptoms include malaise, vomiting, fever and drowsiness.

++ Causes (organisms)1,2
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Bacteria
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  • Streptococcus pneumoniae, Haemophilus influenzae (especially children), Neisseria meningitides (the big three)

  • Listeria monocytogenes, Mycobacterium tuberculosis, Group B Streptococcus, Strep. agalactiae (common in newborn), Staphylococcus spp., Gram –ve bacilli, such as Escherichia coli, Borrelia burgdorferi, Treponema pallidum

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Viruses
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  • Enteroviruses (Coxsackie, echovirus, poliovirus) mumps, herpes simplex HSV type 1, 2 or 6, varicella zoster virus, EBV, HIV (primary infection)

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Fungi
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  • Cryptococcus neoformans or C. gattii

  • Histoplasma capsulatum

++ Investigations
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  • Lumbar puncture (see Table 30.1)

  • CT scan

  • Blood culture and CSF microculture/PCR

    (PCR useful even if antibiotics given)

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Table Graphic Jump Location
Table 30.1

CSF findings in meningitis

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Bacterial meningitis2
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Bacterial meningitis is basically a childhood infection. Neonates and children aged 6–12 months are at greatest risk. Meningococcal disease can take the form of either meningitis or septicaemia (meningococcaemia) or both. Most cases begin as septicaemia, usually via the nasopharynx. The onset is usually sudden (see CHAPTER 96).

++ Clinical features (typical)
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Infancy
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  • Fever, pallor, vomiting ± altered conscious state

  • Lethargy

  • Increasing irritability with drowsiness

  • Refusal to feed, indifference to mother

  • Neck stiffness (not always present)

  • Cold extremities (a reliable sign)

  • May be bulging fontanelle

  • Kernig sign (see FIG. 30.1): unreliable

  • Opisthotonos ...

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