The role of lumbar puncture in children with suspected central nervous system infection
© Kneen et al; licensee BioMed Central Ltd. 2002
Received: 20 May 2002
Accepted: 2 September 2002
Published: 2 September 2002
The use of the lumbar puncture in the diagnosis of central nervous system infection in acutely ill children is controversial. Recommendations have been published but it is unclear whether they are being followed.
The medical case notes of 415 acute medical admissions in a children's hospital were examined to identify children with suspected central nervous system infection and suspected meningococcal septicaemia. We determined whether lumbar punctures were indicated or contraindicated, whether they had been performed, and whether the results contributed to the patients' management.
Fifty-two children with suspected central nervous system infections, and 43 with suspected meningococcal septicaemia were identified. No lumbar punctures were performed in patients with contraindications, but only 25 (53%) of 47 children with suspected central nervous system infection and no contraindications received a lumbar puncture. Lumbar puncture findings contributed to the management in 18 (72%) of these patients, by identifying a causative organism or excluding bacterial meningitis.
The recommendations for undertaking lumbar punctures in children with suspected central nervous system infection are not being followed because many children that should receive lumbar punctures are not getting them. When they are performed, lumbar puncture findings make a useful contribution to the patients' management.
The use of the lumbar puncture (LP) in the diagnosis of central nervous system (CNS) infection in children is controversial [1–3]. In the UK, the use of the LP in CNS infections has declined dramatically since the 1960's, when it was considered an essential investigation for such patients . LP use began to decline after concerns were expressed that they may be precipitating brainstem herniation and death in some patients [5–7]. Although the causal association between LP and cerebral herniation remains unproven, recommendations were published as to which patients should and should not receive a LP [1, 2, 8]. However, the role of the LP has been questioned again recently because of the suggestion that, since the arrival of newer diagnostic techniques – especially the polymerase chain reaction (PCR), the LP now contributes little to patient management . The purpose of this study was to determine whether the recommendations for LP are being followed, and whether the CSF findings obtained contributed to patients' management. We show that only 53% of patients that should have received an LP had one, yet in nearly three quarters of these patients it helped in the management.
Case notes of children admitted to this paediatric secondary and tertiary referral hospital from January 1st to April 30th 2000 were reviewed to see if a CNS infection or meningococcal septicamia were included in their differential diagnosis at admission. To identify such patients the notes of all patients with the following discharge diagnoses were looked at: acute respiratory, urinary, viral and meningococcal infection; febrile convulsions, tonsillitis, otitis media, meningitis or encephalitis, septicaemia and rash. Then it was determined whether there was clinical evidence to suspect CNS infection or meningococcal septicaemia. CNS infections were suspected in children with a febrile illness, and at least one of the following : neck stiffness, bulging fontanelle, photophobia, severe headache (severe enough to require assessment in hospital), irritability, reduced level of consciousness, focal neurological signs or convulsions (excluding simple febrile convulsions) . This included all sick infants less than six months of age who had no obvious focus for infection. Case notes of children with long-term medical problems were excluded.
Indications for LP in children with suspected CNS infections*
All children with suspected CNS infections#, except those with the following contraindications:-
Shock present (tachycardia and poor peripheral perfusion and/or hypotension)
Reduced level of consciousness (Glasgow Coma Score <13)
Focal neurological signs present:
Unequal, dilated or poorly responsive pupils
Decerebrate or decorticate posturing
Absent doll's eye movements
Hypertension and relative bradycardia
Within 30 minutes of a short convulsive seizure
Following a prolonged convulsive seizure (lasting >30 minutes) or tonic seizure
Local superficial infection
Clinical and microbiological details of 52 children with suspected CNS infection and 43 with meningococccal septicaemia
Initial Clinical Impression
LP Not performed
No. of patients
CSF findings and microbiology results
No. of patients
Suspected meningoencephalitis, no rash
Pleocytosis, N. meningitidis in CSF *
N. meningitidis in BC & PCR 
Pleocytosis, N. meningitidis in BC 
N. meningitidis by PCR 
Pleocytosis, E. coli in CSF 
Pleocytosis, cultures negative 
Suspected meningitis with meningococcal rash
Pleocytosis, cultures negative 
N. meningitidis in BC (6, including 4 PCR +)
N. meningitidis by PCR 
H. Influenzae in endotracheal aspirate 
Septic screen in infants <6 months old
E. coli in BC 
Meningococcal septicaemia (LP Contraindicated)
N. meningitidis in BC (7, including 5 PCR +)
N. meningitidis by PCR 
N. meningitidis by antigen test only 
CSF analysis was abnormal in seven of the 25 patients (28%). CSF bacterial culture was positive in three of these patients, all with negative blood cultures (table 2). N. meningitidis was cultured from the blood of one of the seven patients, and three had aseptic meningitis. Sterile CSF cultures at 48 hours enabled 15 patients to have antibiotics discontinued, one of whom also had acyclovir discontinued. Thus 15 (60%) of 25 patients that received a LP had antibiotics stopped early, compared with three of 22 patients that should have received and LP but did not do so (P < 0.001). Of the 43 children with suspected meningococcal septicaemia, 20 (46%) had microbiological evidence of N. meningitidis infection either from blood cultures or PCR on a blood sample.
This retrospective case note review has suggested that the recommendations for undertaking LP in cases of suspected childhood CNS infection are not being followed. Although no LPs were performed in patients who should not have had them, only 53% of those patients who should have received an LP actually got one. Furthermore, in only eight of the 25 patients (32%) who had an LP was the CSF examined fully, including a CSF/plasma glucose ratio. Although the reasons for this are unclear, it may be the well-publicised guidelines relating to emergency management of meningococcal septicaemia [3, 9] have become more widely and inappropriately applied to any patient with suspected CNS infection, whether or not there is an accompanying rash . In addition, because children with suspected CNS infection are usually treated with antibiotics and/or antiviral drugs pending CSF culture results, some physicians may believe that CSF findings do not contribute to patient management. However, in our study, LP findings identified the causative organism in three of the four patients with proven bacterial meningitis and excluded bacterial meningitis in a further 15 patients, allowing antibiotics to be discontinued and an earlier discharge from hospital. Therefore CSF analysis gave additional clinically useful information in 18 (72%) of the 25 patients in whom it was performed. The role of CSF analysis in patients with meningism and a suspected meningococcal rash remains controversial [3, 9]. In our study seven such patients did not have an LP, and blood cultures or PCR was positive in five. Whether the remaining two children genuinely had meningococcal meningitis is not known, but a LP would clearly have confirmed or refuted the diagnosis. The advantages of obtaining a microbiological diagnosis extend beyond individual patient management. Knowing the organism allows appropriate prophylaxis to be recommended for close contacts, and it allows the PHLS to determine whether a series of meningitis cases really is an outbreak due to a single organism, or a cluster of unrelated cases.
The reduction in the number of LPs being performed by junior doctors may have wide-reaching consequences. What was once considered to be a routine and relatively safe investigation now appears to be relatively rare in our setting. This is in contrast to other parts of the world, particularly the tropics, where LP is still considered an essential investigation [15, 16]. Whereas 10 years ago most doctors in the UK learnt to do LPs as medical students or house officers, this does not appear to be the case now . The recent trend towards ward-based and shift work, where-by juniors often do not follow up patients they admit, has meant they are less likely to see the benefits of investigating patients fully.
Our study has shown that the recommendations for undertaking LPs in children with suspected CNS infection are not being followed, because many children that should receive LPs are not getting them. There are clear individual patient-management, public health and health economic implications if the findings of this study are mirrored in other paediatric units.
We thank our clinical colleagues for supporting this work and Pat McCarrick for help with chart retrieval.
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