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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 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 is inflammation of the meninges (pia and arachnoid) and the cerebrospinal fluid (CSF).
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headache
photophobia
neck stiffness
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Other symptoms include malaise, vomiting, fever and drowsiness.
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Causes (organisms)1,2
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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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Enteroviruses (Coxsackie, echovirus, poliovirus) mumps, herpes simplex HSV type 1, 2 or 6, varicella zoster virus, EBV, HIV (primary infection)
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Lumbar puncture (see TABLE 30.1)
CT scan
Blood culture—all patients with suspected meningitis
CSF microculture/PCR (PCR useful even if antibiotics given)
Specific serology, e.g. HIV, EBV
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Note: If significant delay with these, do not withhold treatment.
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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).
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Clinical features (typical)
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Fever, pallor, vomiting ± altered conscious and mental 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
Brudzinski sign (see FIG. 30.2): more reliable sign of meningeal irritation
Opisthotonos (see FIG. 30.3): rare
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Children over 3 years, adolescents, adults
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Meningeal irritation more obvious (e.g. headache, fever, vomiting, neck stiffness)
Later: delirium, altered conscious state
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Note: Antibiotics may mask symptoms. Suspect meningitis if fever >3 days in reasonably well child on antibiotics.3
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Dramatic sudden-onset shock, purpura (does not blanch on pressure) ± coma
Usually due to meningococcal septicaemia, also H. influenzae type B, Streptococcus pneumoniae, Listeria monocytogenes
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Note: septic shock may ensue without signs of meningitis.
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Treatment (suspected meningitis)4
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First: oxygen + IV access and consult
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Take blood for culture (within 30 minutes of assessment)—ideally prior to hospitalisation
For child give bolus of 10–20 mL/kg of N saline with added bolus up to total 60 ml/kg if signs of hypoperfusion
Admit to hospital for lumbar puncture (preliminary CT scan to assess safety of LP in adults)
Dexamethasone 0.15 mg/kg up to 10 mg IV (start at same time as antibiotics—shown to improve outcome)5
Ceftriaxone 2 g (child >1 month: 50 mg/kg up to 2 g) IV statim then 12 hourly for 4 days
or
Ceftriaxone 2 g (child <1 month: 50 mg/kg up to 2 g) IV statim then 12 hourly for 4 days
or
cefotaxime 2 g (child: 50 mg/kg up to 2 g) IV 6 hourly for 3–5 days (note that IM injection is painful)
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Note: IV preferable but IM or interosseous better than nothing.
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Antibiotics of proven effectiveness are cefotaxime, ceftriaxone, meropenem and penicillin.
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Treatment (meningococcaemia—all ages)
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Treatment is extremely urgent once suspected (e.g. petechial or purpuric rash on trunk and limbs) (see FIG. 30.4). It should be given before reaching hospital. Empirical treatment is:
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benzylpenicillin 2.4 g (child: 60 mg/kg IV up to 2.4g) statim (continue for 5 days)
if IV access not possible give IM
or
ceftriaxone 2 g (child >1 month 50 mg/kg up to 2 g) IV or IM 12 hourly for 5 days
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Note: Penicillin dose guide for suspected meningitis in child: <1 year 300 mg, 1–9 years 600 mg, 10+ years 1.2 g.
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Specific organisms—streptococcus pneumoniae: benzyl penicillin or cephalosporin; Group B streptococcus: benzyl penicillin; H influenza: cephalosporin.
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This is basically a childhood infection. The most common causes are human herpes virus 6 (the cause of roseola infantum) and enteroviruses (Coxsackie and echovirus).
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Most cases are benign and self-limiting, but the clinical presentation can mimic bacterial meningitis although there are fewer obvious signs of meningeal irritation. Lumbar puncture is important for diagnosis and also PCR for enterovirus. If positive it can allow early cessation of antibiotics if commenced empirically.2 Treatment which is symptomatic includes rehydration and analgesics. Acyclovir is given for herpes meningitis. The immunocompromised require special management.
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Practice tip
Very cold hands? Think meningitis.
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Encephalitis is inflammation of the brain parenchyma. It is mainly caused by viruses although other organisms including some bacteria, Mycoplasma, Rickettsia and Histoplasma can cause encephalitis. Suspect it when a viral prodrome is followed by irrational behaviour, altered conscious state and possibly cranial nerve lesions.
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Practice tip
Consider the possibility of (non-infective) autoimmune encephalitis.
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These can vary from mild to severe.
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Constitutional: fever (not inevitable), malaise, myalgia
Meningeal features: headache, photophobia, neck stiffness
Cerebral dysfunction: altered consciousness—confusion, drowsiness, personality changes, irrational behaviour, seizures, coma
Focal neurological deficit
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Causes (viral organisms)
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Herpes simplex type 1 or 2, enteroviruses, mumps, CMV, EBV, HIV, measles, influenza, arboviruses, for example, Japanese B, West Nile, Murray Valley encephalitis, Ross River
Consider cerebral malaria in the differential diagnosis
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There are three forms of mediated viral encephalitis: direct, delayed (latent) and immune mediated (postinfectious encephalomyelitis).
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A protozoal infection seen in immunocompromised patients, especially HIV. Refer for specialist advice.
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Lumbar puncture: CSF (usually aseptic meningitis)
CSF PCR for viral studies, esp. HSV, toxoplasma
CT scan—often shows cerebral oedema
Gadolinium enhanced MRI
EEG—characteristic waves
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Organise hospitalisation where treatment will be supportive. Suspected herpes simplex encephalitis should be treated with IV aciclovir immediately.
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Note: Meningoencephalitis is meningitis plus some parenchymal involvement of brain substance.
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Autoimmune encephalitis
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This is a recently identified group of neuropsychiatric disorders seen typically in young people.7 There is a prodrome of fever and headache followed by days or weeks of psychiatric behavioural problems with bizarre symptoms and movements. It may be related to a paraneoplastic manifestation, e.g. ovarian cancer. Diagnosis is confirmed by blood and CSF antibody testing (anti-NMDA receptor). Specialist referral for diagnosis and specific immunotherapy is appropriate.
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Brain abscess and subdural empyema4,8
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A brain (cerebral) abscess is a focal area of infection in the cerebrum or cerebellum. It presents as a spaceoccupying intracerebral lesion. Suspect in any patient with a raised intracranial pressure. The infection can reach the brain by local spread or via the bloodstream, for example, endocarditis or bronchiectasis. There may be no clue to a focus of infection elsewhere but it can follow ear, sinus, dental, periodontal or other infection and also a skull fracture. The organisms are polymicrobial, especially microaerophilic cocci and anaerobic bacteria in the non-immunosuppressed. In the immunosuppressed, Toxoplasma, Nocardia sp. and fungi.
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Raised intracranial pressure
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Headache
Nausea and vomiting
Altered conscious state
Papilloedema
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Focal neurological signs such as hemiplegia, dysphasia, ataxia
Seizures (30%)
Fever (may be absent)
Signs of sepsis elsewhere, e.g. teeth, endocarditis
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MRI (if available) or CT scan
FBE, ESR/CRP, blood culture
Note: lumbar puncture is contraindicated.
Consider endocarditis
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Management is urgent neurosurgical referral. Aspiration or biopsy is essential to guide antimicrobial treatment which may (empirically) include metronidazole IV and a cephalosporin, e.g. ceftriaxone IV. Nocardiosis is treated with other antibiotics.
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Spinal subdural or epidural abscess9
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These uncommon focal infections can be extremely difficult to diagnose so an index of suspicion is required to consider such an abscess. The usual organism is Staphylococcus aureus.
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Back pain (increasing) ± radiculopathy
Percussion tenderness over spine
Evolving neurological deficit, e.g. gradual leg weakness and sensory loss ± fever (may be absent)
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Associated infection: furuncle, decubitus ulcer, adjacent osteomyelitis, discitis, other
Back trauma with haematoma
Post-subdural or epidural anaesthetic block
One-third is spontaneous
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Urgent neurosurgical referral. Empirical therapy while awaiting culture results may include di/flucloxacillin IV, + gentamicin IV or vancomycin IV.