**8. Diagnosis**

Many experts accept 20–30/μL as the cutoff value for pleocytosis. Decreased CSF glucose, increased CSF protein, and pleocytosis may indicate either bacterial or viral (especially HSV) meningitis. If only one of these parameters is in the normal range, this cannot be accepted as an evidence against the presence of meningitis. If all three parameters are normal, then it can be presumed that meningitis is not present; nevertheless, keeping in mind that completely normal CSF findings may be observed during the very early course of neonatal meningitis, the most prudent approach would be to repeat LP after 24–72 h in such borderline cases. If the infant had meningitis, pleocytosis and other abnormalities consistent with meningitis would be detected in CSF obtained in this second LP [3]. Ample number of erythrocytes in CSF may be interpreted as a clue to HSV meningitis if the physician is sure that the LP was not traumatic. Pleocytosis is more marked in bacterial and Gram-negative meningitides than in viral

CSF protein concentrations higher than 100 mg/dL in term infants and 150 mg/dL in preterm neonates are consistent with bacterial meningitis. CSF protein may also be found to be high in parameningeal infections like brain abscess, congenital infections, and intracranial hemor-

The glucose concentration is said to be consistent with bacterial meningitis if it is below 30 mg/dL in term newborns and 20 mg/dL in preterm infants. CSF glucose to serum glucose ratio is not a reliable indicator of meningitis in the first 28 days of life, because newborns often receive intravenous glucose infusions and serum glucose concentrations can rise abruptly with stress [3]. In case of a bloody tap, assessing the CSF leucocyte count by correcting it with respect to that of the peripheral blood is not recommended in that it decreases the sensitivity and provides only a slight increase in specificity. When LP is traumatic, the wisest thing to do is to assume the patient as if she/he had meningitis and start empirical therapy [17]. Since sitting position with the legs flexed provides the widest interspinous spaces and it is sufficiently safe, it should be favored for sick neonates when-

Although, as noted above, signs of sepsis and meningitis intertwine in the newborn period, some neonatologists consider that it is unnecessary to perform LP on neonates evaluated for sepsis, especially those with early neonatal sepsis [19, 20]. Blood cultures are negative in onethird of neonates with meningitis who are very low birth weight and born over 34 weeks of gestation [1]. Thus, in case LP is not performed, a significant portion of neonates with meningitis would not get a correct diagnosis and would not be observed for the likely complications of meningitis; for that reason, the author is in favor of the opinion that LP should always be performed as soon as the infant becomes clinically stable and can tolerate the procedure if it has not been possible to be performed at the first suspicion of meningitis. It should be kept in mind that findings of CSF inflammation last for a considerably long duration (days, sometimes weeks), which allows the clinician diagnose or exclude the diagnosis of meningitis.

Ultrasonography is valuable in the follow-up, especially for the cases, in which hydrocephalus has developed as a complication of meningitis. If the disadvantage of radiation exposure is left aside, computed tomography can accelerate the decision making of ventriculostomy in cases of hydrocephalus and surgical drainage in patients with cranial abscesses. Magnetic resonance (MR) is the imaging modality of choice in conditions, such as focal neurologic

and Gram-positive meningitides [1].

90 Selected Topics in Neonatal Care

ever the infant's condition permits a spinal tap [18].

rhage [3].

History of premature or prolonged labor, intrauterine scalp monitorization, traumatic birth, and maternal peripartum infection should be noted.

Physical signs may be subtle in neonatal meningitis, in which either fever or hypothermia may be the only clue to diagnosis. Pleocytosis under direct microscopy or the presence of bacteria in Gram smear suggests meningitis. Definitive diagnosis is made with the isolation of causative organism in CSF.

The differential diagnosis includes other causes of neonatal seizures, partially treated meningitis, intracranial abscess, intracranial hemorrhage, intracranial aneurysm, cerebral vein thrombosis, head trauma, and congenital metabolic diseases.
