A FEBRILE, DROWSY CHILD
History
Alison is a 9-year-old girl who is referred to the A&E department by her GP. She was seen in surgery a few days ago with a temperature and a widespread non-specific rash, and a diagnosis of a probable viral infection was made. Her temperature has persisted although the rash is fading. Today she has been complaining of worsening headache, dislike of light and pain in her neck, back and legs. Her mother has found it difficult to wake her and she has been a bit confused. She has vomited twice and, most unusually, wet the bed. She has no significant past medical history and is taking no regular medication. She is fully immunized. Her mother has recurrent cold sores, the last about 2 weeks ago. Nobody in the family is unwell or taking medications. Her school progress is good.
Examination
Alison is lying in bed in a darkened room with her eyes closed. She is reluctant to be examined and wants to go back to sleep. Her temperature is 39.7C. She has a fading macular rash over her trunk, back, arms and legs. Her pulse is 130 beats/min. Her BP is 85/60 mmHg and the capillary refill time 2 s. There are no murmurs. She has moderate neck stiffness. She is difficult to wake but when she does she recognizes her parents but appears disorientated, thinking that she is at home. There are no focal neurological signs. Examination of the respiratory, abdominal and ENT systems is normal.
INVESTIGATIONS
Haemoglobin 12.6 g/dL 11.5–15.5 g/dL
White cell count 11.2 109/L 4.5 – 13.5 109/L
Neutrophils 5.6 109/L 3.0–5.8 109/L
Lymphocytes 5.0 109/L 1.5–3.0 109/L
Platelets 365 109 /L 150–400 109/L
Sodium 138 mmol/L 138–146 mmol/L
Potassium 4.5 mmol/L 3.5–5.0 mmol/L
Urea 4.2 mmol/L 1.8–6.4 mmol/L
Creatinine 46 µmol/L 27–62 µmol/L
C-reactive protein 23 mg/L 6 mg/L
Questions • What is the most likely diagnosis? • What would be your immediate management of this patient? • What further investigations would you request and when?
Medicine
The most likely diagnosis is a viral meningoencephalitis. Typically there is a prodrome of a non-specific febrile illness, possibly accompanied by a rash, followed by the onset of a progressive headache and photophobia. Any virus can be responsible, but at least 80 per cent of cases are caused by enteroviruses. Of the other infectious agents mimicking viral meningoencephalitis, by far the most important are bacteria, because they require prompt treatment with antibiotics. The other major differential is a brain abscess. Remember the maxim ‘treat the treatable’. Pending culture results, the assumption has to be that a bacterial cause is possible even when, as in this case, the blood tests are not supportive. A broad-spectrum antibiotic such as cefotaxime should be started immediately following blood cultures. Most causes of viral meningoencephalitis have no specific treatment and the management is supportive. However, herpes simplex virus type 1 (HSV-1) is an important cause (note her mother’s cold sores) and without treatment 70 per cent progress to coma and death. Brain involvement is focal and patients frequently present with focal seizures. All patients with meningoencephalitis should therefore be started on aciclovir. Mycoplasma pneumoniae can also cause meningoencephalitis and Alison should also be treated with a macrolide antibiotic such as clarithromycin. An EEG is valuable in supporting the diagnosis. Typically it shows slow-wave activity without focal features, except in HSV-1 infection where there may be evidence of temporal lobe involvement. A magnetic resonance imaging (MRI) or computed tomography (CT) scan may show brain swelling and is mandatory if there are focal signs. It will also exclude a brain abscess. At some stage a lumbar puncture (LP) will be necessary but it is currently contraindicated because this girl is drowsy and disorientated, is likely to have raised intracranial pressure and could cone if an LP is performed. There is no urgency because she is already receiving the appropriate treatment. Cerebrospinal fluid (CSF) analysis should help differentiate between the various potential diagnoses (see Table 62.1).
Table 62.1 Cerebrospinal fluid findings in the commonest central nervous system infections
Condition Pressure White cells Protein Glucose Comments (mmH2O) (mm3 ) (g/L) (mmol/L)
Normal 50–80 5 0.2–0.4 70 per cent Clear and blood glucose colourless Viral Normal or Rarely 1000. 0.5–2.0 Normal Clear.
Viral slightly ↑ Neutrophils early Grossly culture and but thereafter mostly ↑ in HSV PCR lymphocytes
Bacterial Usually ↑ 100–10 000 1.0–5.0 ↓ 50 per cent Turbid. Mostly neutrophils blood glucose Organisms seen on Gram stain. Culture and PCR
Most patients with viral meningoencephalitis make a complete recovery, except for HSV1 where sequelae, sometimes severe
KEY POINTS
• Patients with clinical features of meningoencephalitis should be assumed to have a bacterial cause and started immediately on appropriate antibiotics as well as aciclovir.
• An LP should not be performed on a child in a coma or with raised intracranial pressure because of the risk of coning.
• Unlike most viral causes, herpes simplex type 1 meningoencephalitis is associated with significant morbidity and mortality
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