Risk Factors, Clinical Presentation, and Neuroimaging Findings of Neonatal Perforator Stroke
Background and Purpose—To date, studies on neonatal stroke have mainly focused on cortical stroke. We have focused on perforator strokes, noncortical strokes in the arterial vascular perforator area. We sought to identify risk factors and evaluate clinical presentation and neuroimaging findings for neonatal perforator stroke, which seems to be under-recognized.
Methods—All infants admitted to our tertiary intensive care unit in ≈12 years, whose perforator stroke was diagnosed with postnatal brain imaging, were enrolled in this study. Demographic, perinatal, and postnatal data were evaluated.
Results—Seventy-nine perforator strokes were detected in 55 patients (28 boys), with a median gestational age of 37 1/7 weeks (range 24 1/7 to 42 1/7 weeks, 25 preterm). Perforator stroke was asymptomatic in most patients (58%). Initial diagnosis was predominantly made with cranial ultrasound (80%) in the first week of life (60%). Risk factors for stroke were present in all cases: maternal, fetal, and perinatal. Likely pathogenic mechanisms were prolonged birth asphyxia (16%), hypoxia or hypotension (15%), embolism (15%), infection (15%), acute blood loss (9%), and birth trauma (9%).
Conclusions—Previously described risk factors for developing neonatal main artery stroke are probably also associated with neonatal perforator stroke. Perforator stroke is often asymptomatic, but cranial ultrasound is a reliable diagnostic tool in diagnosing perforator stroke.
Advances in neuroimaging techniques have greatly improved the detection and understanding of neonatal stroke.1 Reported incidence of neonatal stroke in term newborns ranges from 1 in 2300 to 1 in 5900.1–3 Benders et al4 reported an incidence of 7 in 1000 preterm admissions. In most cases of neonatal stroke, the middle cerebral artery (MCA) is involved. For each of the cerebral arteries, main branch (cortical or pial) or perforator branch involvement can be distinguished.5 So far, studies on neonatal stroke have mainly focused on cortical stroke. Perforator stroke is apparently still under-recognized and little is known about risk factors and clinical presentation.
To gain more insight into risk factors, clinical presentation, and neuroimaging findings of neonatal perforator stroke, we report the largest cohort of neonates to date diagnosed with perforator stroke.
Patients and Methods
All infants admitted to our tertiary (neonatal) intensive care unit between August 1999 and April 2011 and in whom perforator stroke was diagnosed by postnatal cranial ultrasound (CUS) or MRI were enrolled. The study was approved by the Medical Ethics Review Committee of the Erasmus Medical Center, Rotterdam, The Netherlands.
Perforator stroke involves the perforators of the anterior choroidal artery, anterior cerebral artery, MCA, posterior cerebral artery, and posterior communicating artery, supplying among others thalamus, striatum, posterior limb of the internal capsule, and centrum semiovale (Table 1).6 The anatomy of basal ganglia perforators is described in detail in previous studies.5,6 Perforator stroke was defined as a well-delineated hyperechoic lesion in thalamus or striatum on CUS (Figure). Isolated lesions in centrum semiovale were not included because these cannot only be caused by focal arterial infarction in a terminal lateral striatal MCA branch. An alternative explanation could be by stroke of a ventriculopetal cortical arterial branch of the MCA with occlusion away from the surface as it courses in white matter. In addition, isolated lesions in the centrum semiovale can be confused with punctuate white matter lesions. On MRI, perforator stroke was defined as a well-lineated lesion, hypointense on T1-weighed imaging, hyperintense in T2-weighed imaging, hypointense on apparent diffusion coefficient maps, and hyperintense on diffusion-weighted imaging.
All preterm infants had been screened by standard local CUS protocol, as a matter of clinical routine. This entailed ≥2 ultrasound studies in the first week of life, followed by weekly ultrasound studies until discharge. Term infants at risk of brain damage were screened with CUS at the discretion of the attending physician. Sonograms were obtained using a Sequoia (Siemens, Mountain View, CA) or an Esaote system (MyLab 70, Genova, Italy). MRI scanning was performed on a 1.5-T GE EchoSpeed scanner (GE Medical Systems, Milwaukee, WI), using an MR-compatible incubator provided with a specialized high-sensitivity neonatal head coil. Perforator strokes, first diagnosed with MRI (Dr Lequin), were reviewed by 2 neonatologists (Dr Dudink and Dr Govaert) who also reviewed all CUS and remaining MRI studies independently and sought consensus for questionable imaging findings.
Demographic, perinatal, postnatal, and short-term follow-up data were retrieved from the medical records. Perinatal data included delivery, gestational age, sex, birth weight, Apgar score, and umbilical cord pH. Postnatal data included respiratory support, Clinical Risk Index for Babies score,7 the presence of central venous catheters, necrotizing enterocolitis, hypoglycemia, sepsis, and congenital heart disease. Clinical symptoms and neuroimaging findings preceding the radiological diagnosis of perforator stroke were reviewed.
Clinical phenotypes for perinatal stroke were classified by etiologic mechanisms of neonatal stroke: infection, birth trauma, embolism, arteriopathy, blood loss, extracorporeal membrane oxygenation, asphyxia, prothrombotic condition, or unclassifiable.8
Patient Characteristics and Risk Factors
Fifty-five patients were included in this study, 0.7% of all 7713 patients admitted to our neonatal intensive care unit (NICU) during the study period, 0.5% admitted were preterm infants, and 0.6% admitted were very-low-birth-weight infants (birth weight <1500 g). Patient characteristics are shown in Table 2. Twenty-five patients were born preterm (<37 weeks postmenstrual age), 17 of whom were born before 32 weeks’ postmenstrual age. Eight mothers had received antenatal betamethasone. Vacuum extractor was used in 5 cases and was unsuccessful in 1, in which emergency cesarean delivery was then needed. Sixteen other patients were delivered by emergency cesarean section because of suspected fetal distress. Birth asphyxia was diagnosed in 18 patients according to Levene’s criteria.9
Risk factors for developing stroke are summarized in Table 3. Data on placental histology were recorded in only 15 cases. These data could not be retrieved for the 39 outborn children. In 8 of 15 cases, the placenta was classified as abnormal (Table 3). There were no cases reported on perinatal stroke in a sibling. In 2 cases, family history was positive for stroke. In both, multiple family members had a stroke before the age of 50 years.
Thirteen children had culture-proven sepsis and 5 had culture-proven meningitis (1 Listeria monocytogenes, 1 Escherichia coli, and 3 Group B Streptococcus). Forty-five children had ≥1 central venous catheters before the diagnosis of perforator stroke. Diagnosis of perforator stroke was followed by ultrasound evaluation of the catheter and major veins or heart in 24 cases. This revealed thrombosis in 5 (n=2 thrombosis around the tip of the catheter and n=3 venous thrombosis) and multiple air configurations in the liver in 1 patient (with an umbilical vein catheter). Prothrombotic screening was performed in 27 patients, revealing heterozygosity for factor V Leiden in 2 cases. Etiologic mechanisms leading to the perforator stroke are summarized in Table 4.
Neuroimaging revealed 79 perforator strokes in 55 patients (Table 5): right-sided in 21, left-sided in 20, and bilateral in 14. These 14 patients had 2 to 4 perforator strokes each. Of these 14, none had symmetrical deep gray matter injury and birth asphyxia was diagnosed in only 1 according to Levene’s criteria.10
In 44 patients (80%), the stroke was first identified with CUS. In 27 of them, additional MRI was obtained, confirming the diagnosis of perforator stroke. In 10 patients (18%), the stroke was first detected by MRI. In 1 patient, the stroke was first diagnosed on a computed tomographic scan made elsewhere because of convulsions and later confirmed with MRI in our hospital.
In 33 patients (60%), the perforator stroke was diagnosed in the first week of life. Perforator stroke was diagnosed with routine CUS in 3 patients with prior normal CUS findings after the age of 28 days. They were born preterm (between 28 and 31 weeks gestational age) and were diagnosed at term equivalent age.
Thirteen patients had concomitant cortical stroke. In none of these patients, perforator stroke could be explained solely by the concomitant cortical stroke. Table VI in the online-only Data Supplement gives an overview of all associated intracerebral lesions in this cohort.
Presenting Symptoms and Clinical Course
Perforator stroke was asymptomatic in 32 patients (58%), who were diagnosed with routine neuroimaging. Twenty other patients (36%) had clinical seizures before the diagnosis of perforator stroke. Conditions that are known to cause seizures, such as cortical stroke, birth asphyxia, and meningitis, were diagnosed in 18 of these 20 patients. Eight patients presented with apnea, which was probably related to prematurity, not to perforator stroke. One patient with meningitis presented with hypertonia. One patient presented with unexplained diminished arousal response, and multiple perforator strokes (right MCA lateral striate stroke, left circle of Willis, and left posterior cerebral artery thalamic stroke) were later diagnosed in that patient.
None of the patients in this cohort received thrombolytic therapy. Six patients died before the age of 1 month. None of these deaths was related to perforator stroke, but they were rather related to cardiopulmonary insufficiency because of other neonatal complications.
To our knowledge, this is the largest cohort of newborns with perforator stroke studied. Both preterm and term infants were included. We found that perforator stroke was asymptomatic in most patients (58%). Most strokes were first diagnosed using CUS (80%), predominantly in the first week of life (60%). Still, 40% were diagnosed after the first week of life and 5% were diagnosed with routine CUS after the age of 28 days. These numbers illustrate the importance of routine serial CUS screening in infants admitted to a NICU. Right-sided lesions occurred as frequently as left-sided lesions. Various likely pathogenic mechanisms for the development of perforator stroke could be distinguished, most often birth asphyxia, prolonged hypoxia or hypotension, embolism, and infection. It seems likely that previously described risk factors for developing neonatal main artery stroke can also be applied to neonatal perforator stroke. Maternal, fetal, or perinatal risk factors were present in all cases.
Pregnancy is considered to be a natural prothrombotic state. Thrombosis on the fetal side of the placenta can potentially lead to embolism in the fetal brain as a result of right-to-left direction of blood flow in the fetal ductus arteriosus and patency of the foramen ovale. Placental disorders may be under-recognized in neonatal stroke because placentas are often not adequately examined or have been discarded before stroke becomes apparent.11 We had data on placental abnormalities for only 15 mothers. More than half of them had placental abnormalities that could be regarded as a risk factor for developing stroke, specifically placental infarction, chorioamnionitis, and placental abruption.12–14
In 5 patients, birth trauma was considered responsible for the occurrence of perforator stroke. Breech or forceps delivery can lead to indirect arterial injury by traction–elongation–torsion. Subdural bleeding after a complicated delivery can lead to compression and spasm of the MCA or its branches, thus leading to stroke. In 1 case, birth trauma led to tentorium tear and uncal herniation, presumably leading to compression of the posterior cerebral artery and thus to posterior cerebral artery stroke.15
Perinatal arterial ischemic stroke has been reported to coincide with hypoxic-ischemic encephalopathy; hypoxic-ischemic encephalopathy has been suggested to be a risk factor for perinatal stroke.16 Birth asphyxia can lead to congestion, endothelial injury, and intravascular coagulation, thus leading to stroke.17 Hypoxic-ischemic encephalopathy is more often present in full-term infants than in preterm infants with stroke.18 This was also the case in this study.
In this cohort, 5 perforator strokes were most likely related to meningitis. The perforator arteries course through the infected meninges to reach the brain parenchyma, and subarachnoid inflammation may encompass the major vessels of the circle of Willis. It has been suggested that local vasculopathy induced by infection and inflammation leads to thrombosis, resulting in occlusion of the arteries.19
Embolism was the most likely mechanism of stroke in 15% of patients in this cohort. In 2 cases, embolism was suspected, but not proven by ultrasound imaging: in one case from a femoral vein catheter used for exchange transfusion for jaundice and in another case from a suspected thrombus in a patient with an indwelling femoral vein catheter and abnormal anatomy of the inferior vena cava. In 5 cases, proven thrombosis of a venous catheter or proven venous thrombosis most likely led to perforator stroke. In 1 patient, abdominal ultrasound imaging revealed multiple air configurations in the liver, which probably led to air embolism, causing stroke. These events could have been prevented by avoiding the use of central venous catheters. However, this is not always feasible, especially in an NICU setting. We recommend to evaluate critically the necessity of maintaining a central venous catheter.
In a study on risk factors for perinatal arterial stroke in preterm infants, hypoglycemia was the only independent risk factor identified in the neonatal period.18 In this study, hypoglycemia was present in 8 patients, 7 of whom were preterm. In the subgroup of preterm infants, 7 of 25 (28%) had hypoglycemia preceding the diagnosis of perforator stroke, compared with 1 of 33 term infants. It is not certain whether hypoglycemia did indeed precede perforator stroke, in view of the delay in detecting ultrasound abnormalities in infants with stroke.18
Prothrombotic screening at our institution has evolved over the years. Currently, it entails antithrombin, protein S and protein C levels, factor V Leiden mutation, and factor II G20210A mutation. In some cases, screening is broadened to include lupus anticoagulans, methylenetetrahydrofolate C677T mutation, and homocysteine levels. Twenty-eight patients (51%) in our study were not adequately screened for prothrombotic factors. Furthermore, protein S, protein C, and antithrombin levels were often not repeated after the neonatal period, and therefore, congenital deficiencies could not be ruled out. Isolated perforator stroke was diagnosed in 2 patients with factor V Leiden heterozygosity. It is unlikely that only the presence of factor V Leiden led to isolated perforator stroke.20 These patients had multiple other risk factors, particularly acute blood loss. Earlier studies have found that prothrombotic coagulation factors are present in more than half of neonatal main artery strokes, but it has been suggested that they likely play only a minor role in the pathogenesis of stroke.11,20
In 2 patients, stroke was most likely related to arteriopathy. One of these patients had Miller–Dieker lissencephaly and the other idiopathic infantile arterial calcification. Infantile arterial calcification has been related to cerebral infarction.21
Perinatal stroke is probably under-recognized because symptoms are subtle or absent and neonates may not undergo appropriate neuroimaging to identify stroke. It may be diagnosed serendipitously, as in the case of a term infant who was a control subject in a study of perinatal stroke and in whom stroke was diagnosed with MRI.22 In this study, perforator stroke was usually first identified with CUS, probably because CUS is the first choice imaging modality at our NICU. There is no evidence that CUS is superior to MRI in detecting a stroke. In 27 of 44 patients, in which perforator stroke was first identified with CUS, subsequent MRI was obtained. MRI confirmed the diagnosis of perforator stroke in all these 27 cases, illustrating that CUS is reliable in diagnosing perforator stroke. CUS is an essential part of the routine care in high-risk infants admitted to our NICU. Its major advantages are its safety, relatively low cost, and it can be performed at bedside and can be repeated as often as necessary, making it the most suitable tool for serial imaging of the neonatal brain.23 The value of CUS in detecting neonatal stroke has been described previously.5,24
In preterm neonates, sequential routine neuroimaging led to the diagnosis of perforator stroke. In term infants, indications for neuroimaging such as birth asphyxia and convulsions ultimately led to the diagnosis. Cortical stroke in full-term infants most often presents with seizures, apnea, and nonfocal neurological signs.1,25 Preterm infants are often free of symptoms, and cortical stroke is often diagnosed using routine cranial imaging. In the present study, perforator stroke was indeed asymptomatic in more than half of the patients. Convulsions were a possible presenting symptom in one third of patients, mostly term neonates. In all but 2 patients, these could be related to a more likely cause, such as concurrent cortical stroke, birth asphyxia, and meningitis. The remaining 2 patients had multiple perforator strokes, possibly explaining the clinical presentation of seizures.
In term infants with perinatal stroke, the left MCA is preferentially affected.4 In our cohort, however, there was no side preference. We have no obvious explanation for this. It is not explained by preferential direction of emboli; there was also no left-sided preference in the subgroup of patients in whom embolism was the most likely pathogenic mechanism.
According to the definition provided by the Workshop on Ischemic Perinatal Stroke, neonatal ischemic stroke is diagnosed after birth and on or before the 28th postnatal day.26 We chose to also include 3 neonates diagnosed after 28 days of life. They had normal CUS results before the detection of perforator stroke. They were born preterm and diagnosed at term-corrected age with routine CUS while still admitted. Two of them had proven thrombosis of a central venous catheter; 1 was diagnosed after developing necrotizing enterocolitis. This illustrates that perforator strokes in preterm infants can be diagnosed after the 28th day of life, especially when multiple risk factors are present.
Our report has limitations inherent to its retrospective design. As risk factors were studied retrospectively, risk analysis was incomplete and possibly biased. In relating the cases of perforator stroke to a clinical phenotype, ascertainment bias is inevitable.
In this cohort of neonatal perforator stroke, various likely pathogenic mechanisms could be distinguished, notably prolonged hypoxia or hypotension, birth asphyxia, embolism, infection, acute blood loss, and birth trauma. Previously described risk factors for developing neonatal main artery stroke can probably also be applied to neonatal perforator stroke. In experienced hands, CUS is reliable in diagnosing perforator stroke. Isolated perforator strokes are most likely under-recognized, as clinical symptoms are almost always lacking. Routine serial CUS is therefore recommended, especially in preterm neonates. In combination with cortical stroke, hypoxic-ischemic encephalopathy, or meningitis, convulsions can be a presenting symptom, especially in term neonates. Insight gained from the ongoing follow-up of this neonatal perforator stroke cohort will help more accurately predict neurodevelopmental outcome.
The online-only Data Supplement is available with this article at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.113.001064/-/DC1.
- Received February 7, 2013.
- Accepted April 23, 2013.
- © 2013 American Heart Association, Inc.
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