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Response to Letter by Temesvári
genesis of perinatal stroke.10,11 Based on the design of our
study, we could not identify new risk factors of PS but only
describe the frequency of previously known risk factors in our
study population. An important limitation of our study, rising
from its largely retrospective nature, is that some of the most
frequently suggested risk factors of PS like thrombophilias
and cardiac disorders3,4 were not studied in all infants. In our
study group, 17/38 infants were studied in detail for cardiac
disorders and a complex screening for prothrombotic disorders was performed in 27/38, in many cases months to years
after the acute event. Anticardiolipin antibodies, identified as
the most common coagulation abnormality in the subgroup of
the Canadian childhood stroke study may be transient.10,11
Thrombophilia screening in our study group did not include
lipoprotein measurement, the most significantly acute ischemic stroke associated prothrombotic abnormality according to
the case-control study by the German childhood stroke study.12
Thus, as has been pointed out in the discussion, we cannot claim
to have identified the final prevalence of these possible risk
factors in our study group.
In conclusion, we believe that air embolism as the causative
mechanism of perinatal stroke may be considered in single cases
but cannot be a predominant cause of perinatal stroke in term and
near-term infants.
Response:
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We thank Professor Temesvári for his comments regarding
our recent article about the epidemiology of perinatal stroke
(PS) in Estonia.1 The hypothesis of pneumothorax with
subsequent air-embolism as a possible cause of neonatal
ischemic stroke is interesting and has been demonstrated in
piglet experimental model by professor Temesvári and his
group.2 However, epidemiological studies of PS risk factors in
term and near-term infants have not identified this association.3,4 Though intrapartum complications including the need
for resuscitation and positive pressure ventilation are more
common in infants with perinatal stroke,3 case-control studies
have failed to identify these variables as independent riskfactors for PS suggesting a different cause-result relationship.5 A recent case-control study on risk factors of PS in
preterm infants failed to show any difference in the use of
positive pressure ventilation between cases and controls.6
Actually, the time course of the events is likely to be vice
versa: in infants with PS central nervous system injury often
precedes respiratory problems, as was also documented in 3 of
the 5 infants requiring positive pressure ventilation in our
study population—1 was intubated at birth because of asphyxia and the other 2 because of seizure syndrome, reflecting
already present brain injury at the age of 6 and 26 hours,
respectively. Only 2 of the 5 patients needing respiratory
support were ventilated for concomitant lung disease—meconium aspiration syndrome. All infants had at least 1 thoracic
x-ray taken during the acute period with none having pneumothorax or any other air leak syndrome diagnosed.
Clinical cases of air embolism with or without ischemic
stroke have been described in association with pulmonary air
leak syndromes, most often pulmonary interstitial emphysema
associated with positive pressure ventilation in preterm infants.7–9 Air leak syndromes are increasingly rare since the era
of surfactant therapy and patient-synchronized ventilation. In
contrast to the 30% to 50% suggested by Professor Temesvári
in the Neonatal Intensive Care Unit of Tartu University
Hospital, the incidence of air leak syndromes in ventilated
neonates has varied between 5.7% to 7.5% over the last 8
years, with 80% occurring in preterm neonates. Other situations associated with documented air embolism in neonates
include instrumental interventions like central venous catheters, ECMO and heart surgery with cardiopulmonary bypass.
However, these presently identifiable risk factors for air
embolism are rare in term or near-term neonates experiencing
PS. We would consider air embolism rather a possibility,
which cannot be ruled out in single cases, than a frequent
cause of PS.
We quite agree that the proportion of infants with identifiable risk factors for perinatal stroke in our study is low
although there are other series where no obvious precipitating
cause has been identified in as many as 25% to 47% of cases
owing probably to the still existing obscurities in the patho-
Disclosures
None.
Tuuli Metsvaht, MD
Department of Pediatric Intensive Care
Anesthesiology and Intensive Care Clinic of Tartu University
Hospital
Tartu, Estonia
Rael Laugesaar, MD
Children’s Clinic of Tartu University
Tartu, Estonia
Anneli Kolk, PhD
Tiina Talvik, PhD
Unit of Neurology
Children’s Clinic of Tartu University Hospital
Tartu, Estonia
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© 2008 American Heart Association, Inc.
Stroke is available at http://stroke.ahajournals.org
DOI: 10.1161/STROKEAHA.107.510404
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Letters to the Editor
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