Meningitis Children

1.

You suspect meningitis in a 2 year old girl with fever, vomiting, irritability and a stiff neck. You perform a lumbar puncture. (Only one is correct)

A.

An absence of bacteria on gram film excludes bacterial meningitis
B.

A normal white cell count and a normal glucose exclude meningitis
C.

A predominance of neutrophils indicates bacterial infection
D.

Febrile children without meningitis can have up to 48% neutrophils and a low glucose in their CSF
E.

You should correct the white cell count according to how many red cells you see, otherwise a blood stained tap will have an artificially high count

Correct Answer
D. Febrile children without meningitis can have up to 48% neutrophils and a low glucose in their CSF

Explanation
No bacteria on gram film are seen in up to 40% of bacterial meningitis even without prior antibiotics. Normal white cell counts and glucose in meningitis have been described but only where LP has been done within 12 hours of onset of symptoms. 57% of aseptic meningitis cases in 1 study had a neutrophil predominance. Acutely unwell children without meningitis can have white cell counts up to 16, with neutrophils up to 48%, and low glucose (seen in 25%) even without CNS infection. Correcting for blood staining does not improve diagnostic accuracy.

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2.

Contraindications to lumbar puncture include: (tick all that apply)

A.

Erratic breathing pattern
B.

Petechial rash (but with normal platelets and coagulation)
C.

Hypertension
D.

Double vision
E.

Impaired conscious level

Correct Answer(s)
A. Erratic breathing pattern
B. Petechial rash (but with normal platelets and coagulation)

Explanation
Fear is of raised intracranial pressure, leading to coning. Abnormal respiratory pattern eg Cheynes Stokes is one sign, focal neurological signs esp pupil abnormalities and decerebrate/decorticate posturing are other indicators. Double vision would only be a contraindication if there was impairment of eye movements suggesting a cranial nerve palsy, or fixed deviation. In meningococcal septicaemia (suggested by a petechial rash), the yield from cultures is higher for blood/skin scraping culture and PCR, and lumbar puncture does not add much (but if meningitis is the predominant clinical symptom, then LP would be indicated). Cardiovascular instability eg hypotension demands resuscitation and stabilization prior to LP, as the procedure itself may increased oxygen demand. Impaired conscious level is not an absolute contraindication, but if there is progressive deterioration in coma score then raised intracranial pressure should be suspected and LP deferred. If comatose (ie GCS less than 8), then clinical assessment is of limited value and CT should be done first.

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3.

Regarding investigations in meningitis: (Tick the one correct answer):

A.

CT scanning is a good way of excluding raised intracranial pressure
B.

Antibiotics prior to LP make it difficult to diagnose bacterial meningitis
C.

Blood cultures are not very useful in meningitis
D.

Latex antigen tests are helpful when culture/microscopy are negative
E.

Coning can happen in meningitis without lumbar puncture

Correct Answer
E. Coning can happen in meningitis without lumbar puncture

Explanation
CT scan does not estimate intracranial pressure, and coning has been reported after normal CT. On the other hand, if it shows an intracranial lesion eg tumour, haemorrhage then you will be more suspicious of raised pressure. Antibiotics do reduce the yield of positive cultures but will not correct all CSF abnormalities and PCR may still be positive so urgent treatment is preferred.
Latex antigen tests have suboptimal sensitivity and specificity and in 1 study had only 7% sensitivity for culture negative clinically suspected meningitis.

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4.

A young child presents with a first seizure. He has no past medical history of note. In the morning he was a bit lethargic but otherwise had no specific symptoms. On arrival he is febrile (39degC) and post-ictal. (tick all that are true)

A.

He should have an LP to exclude meningitis
B.

Seizures can cause CSF abnormalities even if there is no CNS infection
C.

Partial, multiple or prolonged (over 30 mins) seizures make the diagnosis of febrile convulsion less likely
D.

Classic meningism may not be detected in infants with meningitis

Correct Answer(s)
C. Partial, multiple or prolonged (over 30 mins) seizures make the diagnosis of febrile convulsion less likely
D. Classic meningism may not be detected in infants with meningitis

Explanation
Bacterial meningitis can present with fever and seizures, but the prevalence of meningitis is falling with the introduction of Hib, MenC and Pneumococcal vaccines. In the typical patient with febrile convulsion, you would have to do over 200 LPs to detect one case of meningitis. Seizures have been reported to increase protein counts (up to 0.5) and neutrophil %(up to 55%), but not total white cell count so probably not clinically significant.

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5.

In a child with meningitis, the following are reliable indicators of a bacterial rather than a viral cause: (tick all that apply)

A.

CSF Protein = 1
B.

CSF Glucose = 2.5
C.

Blood WBC = 25
D.

CRP = 50

Correct Answer(s)
C. Blood WBC = 25
D. CRP = 50

Explanation
Big overlap in CSF values for viral and bacterial meningitis. CSF protein over 1.5 or glucose under 2 are predictive of bacterial cause. CSF white cell count not very reliable until you get up to values of 10 000+! Blood is also useful (and presence of bacteria, obviously).

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6.

A child presents with fever, progressive deterioration in conscious level, and partial seizures. Regarding investigations for encephalitis, the following are true:

A.

EEG is abnormal in more than 80%
B.

EEG abnormalities are seen particularly in the temporal lobes
C.

MRI is the best imaging technique
D.

Normal CSF and negative PCR excludes HSV encephalitis

Correct Answer(s)
A. EEG is abnormal in more than 80%
B. EEG abnormalities are seen particularly in the temporal lobes
C. MRI is the best imaging technique

Explanation
Various EEG abnormalities are described - often just non-specific. MRI is better than CT and usually shows temporal or frontal lesions, but can be normal early on. Normal CSF and negative PCR are well described in first few days of illness esp where symptoms mild and child is under 1yr.

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7.

In HSV encephalitis the following are true:

A.

A history of previous cold sores makes HSV unlikely
B.

With aciclovir, mortality is less than 10%
C.

Aphasia and focal neurological signs are common
D.

Long term complications are common in survivors

Correct Answer(s)
C. Aphasia and focal neurological signs are common
D. Long term complications are common in survivors

Explanation
HSV encephalitis can occur in primary infection, as reactivation or as re-infection. Aciclovir reduces mortality from 70% to 30%.

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8.

Apart from HSV, other causes of encephalitis include:

A.

Varicella zoster virus; encephalitis can occur without chickenpox rash
B.

Enterovirus; cause winter epidemics
C.

Mumps and measles; if unimmunized
D.

West Nile Virus is an important cause of encephalitis in Florida
E.

Acute disseminated encephalomyelitis (ADEM) is distinguised by spinal cord signs and multiple focal white matter abnormalities

Correct Answer(s)
A. Varicella zoster virus; encephalitis can occur without chickenpox rash
C. Mumps and measles; if unimmunized
D. West Nile Virus is an important cause of encephalitis in Florida
E. Acute disseminated encephalomyelitis (ADEM) is distinguised by spinal cord signs and multiple focal white matter abnormalities

Explanation
Enterovirus epidemics occur in summer/autumn. Wide regional variations world wide in predominant causes. Arboviruses are important globally - esp tick borne encephalitis (common in forests of mainland Europe), West Nile Fever (now endemic in US), Japanese encephalitis (seen across Asia).
ADEM is post infectious (or post vaccination), does not usually manifest as a febrile illness, and spinal cord signs if present will be a big clue. The MRI changes are focal rather than diffuse, tend to be multiple (whereas in viral encephalitis there may only be 1 or 2), and often affect brainstem and cerebellum (less common in viral encephalitis)

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