Posterior Fossa Abnormalities Seen on Magnetic Resonance Brain Imaging in a Cohort of Newborn Infants

Original ...... Article Posterior Fossa Abnormalities Seen on Magnetic Resonance Brain Imaging in a Cohort of Newborn Infants

Lawrence S. Miall, MBBS, Bsc, MMedSc INTRODUCTION Luc G. Cornette Posterior fossa (PF) and cerebellar abnormalities in infants are Steven F. Tanner difficult to visualize using conventional cranial ultrasound (CUS) Rosemary J. Arthur via the anterior fontanelle because of the presence of the tentorium Malcolm I. Levene and the distance from the ultrasound probe.1 Improved views of the PF can be obtained using the posterolateral fontanelle,2 but magnetic resonance (MR) imaging gives the most detailed diagnostic views of the PF. OBJECTIVE: PF abnormalities are not uncommon. Cerebellar hemorrhage To describe the nature and frequency of posterior fossa (PF) lesions in has been reported in 10 to 25% of low-birth-weight infants at post infants who underwent magnetic resonance (MR) brain imaging in the mortem,3–5 but in only 13 out of 525 infants examined by neonatal period and to correlate with cranial ultrasound (CUS) findings ultrasound in the neonatal period.1 Cerebellar hemorrhage was and clinical outcome. seen on MR in 3% of a cohort of infants <30 weeks gestational 6 STUDY DESIGN: age. Cerebellar infarction and atrophy was recognized in 10 out of A retrospective review of all neonatal MR brain imaging from 1996 to 73 preterm infants examined using MR and the majority of these 7 2001 (n ¼ 558). MR images, CUS and case notes were reviewed in infants infants also had abnormalities elsewhere in the brain. Historically, with PF abnormality. cerebellar hemorrhage was associated with the use of tight-fitting bands used to secure masks during continuous positive airway RESULTS: pressure (CPAP) ventilation.5,8 PF hemorrhage associated with A total of 20 infants had abnormalities in the PF, which represents 4.7% vacuum extraction,9 extra corporeal membrane oxygenation of abnormalities seen on MR. Out of 10, six term infants had PF extra- (ECMO)10 and traumatic delivery11 has been described. axial hemorrhage, three had cerebellar hypoplasia, while one had MR diagnosis of structural abnormalities of the cerebellum cerebellar hemorrhage. In the preterm, 8/10 lesions were unilateral; focal including cerebellar hypoplasia,12 vermian agenesis13 and atrophy cerebellar hemorrhage was seen in 5/10 and extensive hemorrhage with associated with metabolic disorders such as the carbohydrate- secondary atrophy in 3/10. Out of 20, 17 infants also had supratentorial deficient glycoprotein syndrome14 have been well described. lesions. Out of 20, 19 had CUS performed, of which 7/19 showed PF A classification of cerebellar malformations found on MR imaging abnormality. has recently been proposed.15 CONCLUSION: Over 500 newborn infants have undergone MR brain imaging at Intracerebellar hemorrhage was more common in preterm infants than the Leeds General Infirmary over the last 5 years. The aim of this in term infants. These hemorrhages tended to be focal, unilateral and study was to use this cohort of infants to describe the nature and were associated with atrophy. frequency of PF abnormalities seen in preterm and term infants, to Journal of Perinatology (2003) 23, 396–403. doi:10.1038/sj.jp.7210941 describe the outcome of infants with PF abnormalities and to compare the detection rate using conventional CUS and MR imaging.

METHODS Department of Paediatrics and Child Health (L.S.M., L.G.C., M.I.L.), University of Leeds, Leeds, All infants who had undergone MR imaging of the brain as part of UK; Academic Unit of Medical Physics (S.F.T.), University of Leeds, Leeds, UK; and Department of Paediatric Radiology (R.J.A.), The Leeds Teaching Hospitals NHS Trust, Leeds, UK. an ongoing MR research program from January 1996 to February 2001 were included. These infants included all those admitted to Address correspondence and reprint requests to Lawrence S. Miall, MBBS, BSc, MMedSc, Neonatal Intensive Care Unit, Gledhow Wing, St James’s University Hospital, Beckett Street, Leeds LS9 7TF, the neonatal intensive care unit (NICU) with abnormalities on CUS UK. or abnormal neurological examination that required further

neuroimaging (n ¼ 414) as well as some normal term and data were obtained where possible by contacting the pediatrician preterm infants (n ¼ 144) who were scanned for research looking after the child. purposes. Informed consent was obtained for all MR scans. A retrospective search of a detailed research database was made to identify those infants with abnormalities in the PF on MR imaging. RESULTS The clinical case notes, MR images and CUS findings of these From January 1996 until February 2001, n ¼ 558 newborn infants infants were reviewed in detail. Cranial ultrasound images were were examined with MR imaging. Of these 558 infants, 422 (76%) obtained via the anterior fontanelle by trained ultrasonographers had abnormal MR brain scans. In all, 20 had abnormalities in the using a 7.5 MHz sector transducer (Toshiba) in coronal and PF. The overall frequency of PF lesions on MR was therefore 20/ sagittal planes. At the time of the study, it was not our routine 558 (3.6%). These 20 infants formed the study group whose images practice to obtain images via the posterolateral fontanelle. All MR and case notes were reviewed in detail. images were obtained using a 1.5 T GYROSCAN ACS-NT scanner Of the 20 infants, 10 were born at term (median gestation 40 (Phillips Medical Systems, The Netherlands) with a receive-only weeks, range 47 to 42 weeks) and 10 were preterm (median quadrature head coil. T1-weighted images were acquired in the gestation 28 weeks, range 24 to 36 weeks). Scans were performed at sagittal and axial planes and T2-weighted images in the axial a median postnatal age of 6.5 days in the term group and 65 days plane. A number of infants also had T2-weighted coronal (37.5 weeks corrected gestational age) in the preterm group. The examinations. The acquisition parameters have been described preterm group was scanned later when clinically stable and no 16 previously. Briefly, for T1-weighted spin-echo images the longer receiving intensive care. parameters were repetition time (TR) 800 milliseconds, echo time (TE) 13 milliseconds, field of view (FOV) 180 mm, slice thickness Term Infants 4 mm, with a 0.4 mm gap, acquisition matrix 256 Â 256, scan Clinical details (Table 1). Four infants showed clinical evidence time 3 minutes 52 seconds. For T2-weighted fast spin-echo images; of hypoxic–ischemic encephalopathy (HIE)17 (Subjects 5,7,9,10). TR 6000 milliseconds, TE 200 milliseconds, echo train length of Four (Subjects 1,3,4 and 6) were found to have a congenital or 13, FOV 180 mm, slice thickness 3 mm with a 0.3 mm gap, metabolic disorder (a complex brain malformation in one, l-2- acquisition matrix 256 Â 256, scan time 5 minutes 12 seconds. hydroxy-glutaric-aciduria in one, Joubert’s syndrome in one and Scans were performed after feeding or after chloral hydrate Leigh’s encephalopathy in the other). One term infant had sedation. Infants were monitored with pulse oximetry and an complex congenital heart disease (Subject 2 – hypoplastic left electrocardiogram throughout the examination. Limited follow-up heart and double outlet right ventricle with interrupted aortic arch)

Table 1 Clinical Details and Outcome of Term Subjects

Subject Gestation MR scan at Apgar score Diagnosis and risk factors Outcome (weeks) age (days) (1 minute, 5 minutes)

1 40 6 6,9 Generalized central nervous system malformation, Died aged 4 weeks previous sibling died (sudden infant death syndrome) 2 37 4 8,8 Complex CHD, optic atrophy, absent corpus Died aged 2 months callosum, maternal substance abuse 3 38 10 6,9 l-2-hydroxy-glutaric-aciduria, respiratory arrest, Died aged 8 months hypotension. Previous sibling died age 2 years 4 40 85 8,9 Joubert’s syndrome. Consanguineous parents Severe developmental delay at 4 years, hypotonia, VP shunt 5 42 18 1,4 Asphyxia (HIE 3) due to shoulder dystocia Athetoid cerebral palsy at 16 months 6 40 53 9,10 Leigh’s encephalopathy. Consanguineous parents, Died aged 4 months previous sibling died 7 39 5 4,3 Intracerebral hemorrhage, HIE 3 Slight motor delay at 14 months Microcephaly 8 40 7 8,9 IUGR, significant hypoglycemia No motor deficit but language disorder at 5 years. 9 41 5 2,7 Asphyxia (HIE 2) with umbilical cord tight around Alive. Lost to follow-up neck 10 42 6 0,3 Asphyxia (HIE 2), seizures Dyskinetic cerebral palsy and feeding difficulty aged 3 years

HIE=hypoxic–ischemic encephalopathy, IUGR=intrauterine growth retardation, CHD=congenital heart disease, VP=ventriculoperitoneal.

Journal of Perinatology 2003; 23:396–403 397 Miall et al. Posterior Fossa Abnormalities

Table 2 MR Findings in Term Infants

Subject Supratentorial abnormalities Posterior fossa extra-axial spaces Cerebellar hemispheres

1 Agenesis of corpus callosum Increased, hypoplastic brainstem Hypoplastic cerebellum 2 Agenesis of corpus callosum Bilateral Increased with subarachnoid blood Slight hypoplasia of cerebellum punctate PVWM lesions 3 White matter atrophy, delayed myelination Increased, enlarged fourth ventricle Bilateral cerebellar atrophy 4 Thinning of corpus callosum, massive Massively increased. Splayed cerebellar hemispheres ventriculomegaly Agenesis of vermis 5 Ischemic changes in basal ganglia R sided subarachnoid blood Rim of hemorrhage around R hemisphere 6 Abnormal white matter signal in parieto-occipital Increased Abnormal white matter signal in vermis areas 7 Intraventricular hemorrhage with dilatation, Massive hemorrhage in posterior fossa R hemisphere indented by extra-axial blood abnormal signal in subcortical areas 8 R germinal layer hemorrhage with mild Normal Crescentic rim of hemorrhage around R hemisphere ventriculomegaly. Punctate lesions in PVWM on R 9 Normal Subdural hemorrhage R hemisphere compressed 10 Cortical highlighting in Sylvian ﬁssure bilaterally. Extensive posterior fossa hemorrhage Normal Supratentorial bleeding

CSF=cerebrospinal ﬂuid, PVWM=periventricular white matter, L=Left, R=Right.

Figure 1. T2-weighted axial (left) and T1-weighted axial (right) MR images of a term infant with severe hopoxic–ischemic encephalopathy and a coagulopathy (Subject 7). The arrow marks the extensive posterior fossa hemorrhage disrupting the right cerebellar hemisphere. Hemorrhage is shown as low signal intensity on the T2 image. and the other intrauterine growth retardation with hypoglycemia severe hypoglycemia (blood sugar 0.4 mmol/l)) had evidence of (Subject 8). subarachnoid bleeding around the cerebellar hemispheres with additional punctate hemorrhages18 in the periventricular cerebral MR findings (Table 2). Six infants had MR evidence of extensive white matter. PF hemorrhage. In five subjects, the hemorrhage was The other four term infants all showed MR evidence of predominantly subarachnoid, while in one it was subdural. Four of structural CNS abnormality. Subject 1 demonstrated gross these infants showed a clinical pattern suggestive of HIE ( Subjects hypoplasia of the cerebellar hemispheres and vermis, absent corpus 5,7,9,10) and in Subject 7 there was an associated coagulopathy callosum and brain-stem hypoplasia. There was also evidence of (see Figure 1). Subject 2 showed absence of the corpus callosum, delayed myelination. Subject 3 had cerebellar atrophy and delayed optic nerve atrophy and cerebellar hypoplasia in addition to an myelination (see Figure 2). A diagnosis of l-2-hydroxy-glutaric- extensive subarachnoid hemorrhage. Subject 8 (who had suffered aciduria was confirmed by urine analysis. Subject 4 showed

398 Journal of Perinatology 2003; 23:396–403 Posterior Fossa Abnormalities Miall et al.

Figure 2. T1 sagittal (left) and T2 coronal MR images (right) from a term infant (Subject 3) who collapsed at 12 hours of age with l-2-hydroxy- glutaric-aciduria. Note the cerebellar atrophy, with a large extra-axial space around the cerebellum in the posterior fossa. Cerebrospinal fluid is shown as low signal intensity on T1 imaging and high intensity on T2 imaging. absence of the cerebellar vermis with splaying of the cerebellar requiring inotropic support (five infants), confirmed sepsis (four hemispheres, consistent with Joubert’s syndrome. The parents were infants), NEC (two infants), seizures (two infants), patent ductus consanguineous and there was a family history of Joubert’s arteriosus requiring indomethacin (one infant) and cardiac arrest syndrome. Subject 6 demonstrated extensive abnormal signal in (one infant). the cerebellar vermis and occipitoparietal area of the cerebral white matter. The parents were consanguineous and Leigh’s MR findings (Table 4). Five infants showed evidence of focal encephalopathy was diagnosed in this infant. intraparenchymal cerebellar hemorrhage (Subjects 13,16,17,19,20) (see Figures 3 and 4). Three infants had much more extensive Outcome (Table 1). The outcome among the term group was cerebellar hemorrhage with destruction or secondary atrophy of poor. Four infants died within the first year of life (Subjects 1, 2, 3 most of one cerebellar hemisphere (Subjects 11,12,14) (see and 6). Of those who survived, two have cerebral palsy (subjects 5 Figure 5). The remaining two infants were those with the and 10) and Subject 4 has severe developmental delay, hypotonia associated cardiac abnormalities. Subject 15 showed evidence of and a shunt for hydrocephalus. The remaining three infants aqueduct stenosis with massive dilatation of the lateral and third (Subjects 7,8,9) have only mild deficits or were lost to follow-up ventricles, and Subject 18 showed generalized cerebellar atrophy (Subject 7 has microcephaly and a left-sided squint, Subject 8 has with reduced white matter throughout the cerebral hemispheres. no motor deficit but a higher-order language disorder). None of the preterm group showed evidence of extra-axial hemorrhage. Preterm Infants Clinical details (Table 3). The gestational age of these infants ranged from 24 to 36 weeks (median 28 weeks). Eight of the Outcome (Table 3). The outcome data for the preterm group are infants were being treated for complications of prematurity. Three not yet complete as many were scanned recently. All 10 infants of these had intestinal perforation, one spontaneously (Subject 13) survived. Subject 11 has a flaccid paralysis of both legs but normal and two in association with necrcotizing enterocolitis (NEC) cognitive function. Subject 12 is blind following retinal (Subjects 12 and 17). Two of the more mature babies were being detachment. Subject 14 has mild motor delay with some hypotonia. treated for congenital heart disease. Subject 18 had DiGeorge’s Subject 15 has a shunt for hydrocephalus. Subject 17 has syndrome with an interrupted aortic arch and a ventricular septal microcephaly but no focal motor deficit at 20 months. Subject 19 defect, while the other (Subject 15) had Goldenhar’s syndrome has no motor deficit but has speech and language delay secondary with transposition of the great arteries and aqueduct stenosis to deafness. (detected antenatally by the presence of severe hydrocephalus). Antenatal risk factors in addition to prematurity, included maternal Cranial ultrasound. In our cohort, CUS had been performed in sepsis, antepartum hemorrhage and maternal lupus requiring 19 of the 20 infants. Although CUS did detect abnormalities in the plasmaphoresis. Postnatal risk factors included hypotension brain in 15/19, only seven of these were within the PF. In the

Journal of Perinatology 2003; 23:396–403 399 Miall et al. Posterior Fossa Abnormalities

Table 3 Clinical Details and Outcome of Preterm Infants

Subject Gestation MR scan at Apgar score Diagnosis and Risk Factors Outcome (weeks) age (days) (1 minute, 5 minutes)

11 27 65 5, 7 Premature, asphyxia, hypotension. Age 30 months. Flaccid paralysis of legs Spinal cord injury 12 25 183 ?, ? Prematurity, PDA, NEC with perforation, Blind, moderate developmental delay. No focal ROP motor deﬁcit at 30 months 13 24 82 2, 3 Prematurity, breech delivery, sepsis and Normal at 16 months hypotension, isolated bowel perforation, seizures 14 29 79 6, 8 Prematurity, maternal SLE, Hypotonia. Slight motor delay at 19 months hypotension, sepsis, pulmonary hemorrhage, episode of cardiac arrest. 15 34 8 8, 9 Goldenhar syndrome, TGA, VP shunt. Hypotonia at 20 months hydrocephalus, GBS sepsis with hypotension 16 24 94 4, 10 Prematurity, APH, chronic lung disease, Normal at 15 months ROP 17 35 28 9, 10 Prematurity, abnormal antenatal Microcephaly at 20 months, development normal Doppler studies, NEC with perforation 18 36 44 9, 9 DiGeorge syndrome, interrupted aortic Deaf arch, seizures 19 30 9 5, 8 Prematurity, maternal GBS Speech delay caused by deafness 20 26 65 6, 9 Prematurity, sepsis, chronic lung disease Normal at 11 months

NEC=necrotizing enterocolitis, SLE=systemic lupus erythematosis, VP=ventriculoperitoneal, GBS=group B streptococcus, APH=antepartum hemorrhage, ROP=retinopathy of prematurity, PDA=patent ductus arteriosus, TGA=transposition of the great arteries.

Table 4 MR Findings in Preterm Infants

Subject Supratentorial abnormalities Posterior fossa extra-axial spaces Cerebellar lesion

11 L germinal matrix hemorrhage. Punctate Increased Extensive hemorrhage (mT2, mT1) with lesions bilaterally in PVWM destruction and atrophy of L hemisphere 12 Moderate bilateral ventriculomegaly Increased Extensive hemorrhage (mixed signal, mT2, kT1), within L hemisphere with destruction of hemisphere 13 Normal Normal Focal old hemorrhage (kT2) lateral to vermis on R with mild atrophy of R hemisphere 14 Moderate ventriculomegaly on L Normal Extensive old hemorrhage (?) with destruction of L hemisphere 15 Massive bilateral ventriculomegaly Aqueduct stenosis Hypoplastic cerebellum 16 Bilateral germinal matrix hemorrhage. Linear Normal Several focal petechial hemorrhage in R punctate lesions in PVWM bilaterally. hemisphere (kT2) 17 Bilateral germinal matrix hemorrhage. Normal Focal hemorrhage in R hemisphere, within Punctate lesions in PVWM in R parieto- area of possible infarction (mT2, kT1) occipital area. 18 Ventriculomegaly with extensive white matter Increased. Enlarged fourth ventricle Generalized bilateral atrophy of cerebellar atrophy hemispheres 19 Bilateral mild ventriculomegaly. Punctate Normal Small focal hemorrhage at periphery of L lesions in PVWM bilaterally, especially on R. hemisphere (kT2, mT1) 20 Normal Normal Small focal old hemorrhage at inferior aspect of L hemisphere (kT2)

CSF=cerebrospinal ﬂuid, PVWM=periventricular white matter, L=Left, R=Right.

400 Journal of Perinatology 2003; 23:396–403 Posterior Fossa Abnormalities Miall et al.

Figure 3. T2-weighted axial MR image from a 35-week infant Figure 4. T2-weighted axial MR image from a 24-week gestation (Subject 17). Arrow indicates the focal hemorrhagic lesion in the right infant performed at 12 weeks of age (Subject 16). Note the multiple cerebellar hemisphere. punctate hemorrhagic lesions in the right cerebellar hemisphere (arrows). remaining 12 infants, the lesions seen on MR had not been detected on a contemporaneous CUS. to estimate an overall incidence in the preterm and term population. In our study, the infants were highly selected in that Associated pathology. MR imaging demonstrated additional they were being treated in a regional NICU that receives tertiary pathology above the tentorium (i.e. outside the PF) in 17/20 cases. referrals, and many of the infants had abnormal CUS imaging or This included dilatation of the lateral ventricles in 9/20 (four term, clinical evidence of an intracranial abnormality (e.g. seizures or five preterm) and intraventricular hemorrhage (IVH) in 6/20 (two abnormal neurological signs). The fact that the incidence of PF term, four preterm). In one preterm infant, there was evidence of abnormalities is low (3.6%) despite this selection bias towards IVH on early CUS that had resolved by the time of the MR scan. sicker infants is reassuring. Cerebral white matter abnormality was seen on MR in 10/20, the The preterm infants were scanned at a postmenstrual age of majority of lesions being punctate lesions in the periventricular 37.5 weeks and it is possible that in this group minor degrees of PF white matter (high T1, low T2).18 Subject 14 had ischemic change hemorrhage may have resolved spontaneously, but it is most in the basal ganglia (high T1, low T2) and Subject 20 showed unlikely that larger or more significant lesions would not have still cortical ‘highlighting’ (high T2). Two infants (Subjects 17 and 20) been evident. The optimal time to scan infants using MR is had extensive extra-axial bleeding above the tentorium as well as contentious. Most would recommend an early scan 10 to 14 days in the PF. after the insult has occurred. However, these lesions are often clinically silent and practical considerations of scanning sick, often ventilated infants mean that in some imaging may have to be DISCUSSION delayed. Late scanning at 36 weeks or later may be better at Frequency of Cerebellar and Other PF Abnormalities predicting subsequent neurodevelopment.19 The overall frequency of PF lesions seen on MR was lower than the incidence reported in other studies using MR1 and post-mortem CUS versus MR for Imaging the PF examination3–5 but comparable to the findings of Merrill et al.,1 The fact that routine CUS detected the PF abnormality in only 7/19 who found PF lesions in 13/525 neonates using ultrasound via the cases confirms the view that many PF lesions may be missed by posterolateral fontanelle. All these studies show some selection bias, conventional CUS via the anterior fontanelle.1 There is evidence since the study populations were sick preterm infants receiving that a posterolateral fontanelle approach improves the sensitivity of intensive care, often in tertiary referral units. It is therefore difficult ultrasound at detecting PF lesions.1,2 This approach was not

Journal of Perinatology 2003; 23:396–403 401 Miall et al. Posterior Fossa Abnormalities

Figure 5. T2-weighted coronal and axial MR images from a 29-week gestation infant (Subject 14). Arrows indicate the extensive destruction of the left cerebellar hemisphere. routinely used for CUS during the study period at our institution. hemorrhages have been described in six very-low-birth-weight Comparative studies of MR and post-mortem histological findings (VLBW) infants, and were not associated with instrumental or show that even high-resolution MR may not detect some cerebellar traumatic delivery.1 None of our infants had mask CPAP requiring injury.20 Amongst our cohort of 20 infants, seven had congenital an occipital band, which has been reported to cause intra- abnormalities, metabolic or neurodevelopmental disorders cerebellar hemorrhage.5 These peripheral cerebellar hemisphere associated with brain malformations. The high frequency of these hemorrhages may represent germinal matrix bleeding within the associated abnormalities is not unexpected since cerebellar lesions subpial external granule cell layer, which is particularly prominent are often associated with more widespread CNS malformation from 24 to 30 weeks gestation.1 Three preterm infants showed syndromes and metabolic disorders.15,21 In this group of infants, extensive destruction of one or both cerebellar hemispheres with MR is invaluable at accurately demonstrating neuroanatomical secondary atrophy. These changes probably represent extensive old abnormalities, including characteristic cerebellar appearances hemorrhage, although infarctions of cerebellar tissue in preterm associated with several metabolic disorders14,21 and neuronal infants in the distribution of the posterior cerebellar arteries have migration disorders. been reported.7 Cerebellar infarction seen on MRI has been associated with later cerebral palsy and visual problems in a cohort PF Lesions in Term Infants of extremely low-birth-weight infants.22 The exact etiology of these In the term group, all the acquired PF lesions (n ¼ 6) were extra- hemorrhagic cerebellar infarctions remains unclear.7,22 axial hemorrhages and 4/6 of these infants showed evidence of Cerebellar hemorrhages destroying part or all of a cerebellar HIE. In one subject, the extra-axial hemorrhage was associated hemisphere were reported in 14% of infants less than 32 weeks at with other CNS abnormalities and congenital heart disease. The post mortem.4 A post-mortem study described two distinct patterns other term infants had PF abnormalities associated with their of cerebellar hemorrhage: (1) massive hemorrhage that destroyed underlying metabolic or neurodevelopmental disorders. Only one more than one-third of the cerebellum and was usually associated infant had intracerebellar hemorrhage with a rim of blood at the with intraventricular hemorrhage and (2) small multiple periphery of each hemisphere. The poor outcome among the term microscopic and macroscopic punctate cerebellar hemorrhages, infants reflects the frequency of serious congenital abnormality and which were present in up to 21% of neonatal specimens at post the high incidence of asphyxia. mortem.3 Such multiple punctate hemorrhages were seen in at least one of our cases (Subject 16). Similar punctate lesions have PF Lesions in Preterm Infants been described in the periventricular white matter and do not seem In the preterm group, the majority of the PF abnormalities were to be associated with significant adverse outcome, if found in acquired and were intracerebellar hemorrhages. In the majority, isolation.18 These punctate lesions that give a low signal on T2- these hemorrhages were focal and unilateral, often towards the weighted images probably represent small areas of hemorrhage or periphery (dorsal area) of the cerebellar hemisphere. Similar hemorrhagic infarction. The outcome of infants with punctate

402 Journal of Perinatology 2003; 23:396–403 Posterior Fossa Abnormalities Miall et al.

hemorrhages isolated to the cerebellum has not been systematically 2. Luna JA, Goldstein RB. Sonographic visualization of neonatal posterior studied.19 Peripheral cerebellar hemorrhages appear to be clinically fossa abnormalities through the posterolateral fontanelle. AJR 2000; silent, often found on routine imaging.1 Interestingly, six of the 10 174:561–7. preterm infants that we studied had significant hypotension 3. Martin R, Roessmann U, Fanaroff A. Massive intracerebellar hemorrhage in requiring inotropic support. Other studies have described a very low-birth-weight infants. J Pediatr 1976;89:290–3. high proportion of preterm infants with cerebellar hemorrhage 4. Grunnet ML, Shields WD. Cerebellar hemorrhage in the premature infant. J Pediatr 1976;88:605–8. needing cardiac massage or resuscitation with epinephrine.1 It 5. Pape KE, Armstrong DL, Fitzhardinge PM. Central nervous system pathology seems likely that major cardiovascular instability in the perinatal associated with mask ventilation in the very low birthweight infant: a new period represent a risk factor for cerebellar hemorrhage. etiology for intracerebellar hemorrhages. Pediatrics 1976;58:473–83. Limited follow-up in previous studies suggest that these lesions 6. Rutherford MA. Haemorrhagic lesions of the newborn brain. In: Rutherford MA have a good outcome with normal motor development at 13 to 37 (ed). MRI of the Neonatal Brain. London: W.B. Saunders; 2001. p. 171–200. months but with some cognitive delay.1 It is increasingly 7. Mercuri E, He J, Curati WL, Dubowitz LM, Cowan FM, Bydder GM. recognized, however, that the cerebellum has important functions Cerebellar infarction and atrophy in infants and children with a history of other than the control of voluntary movement. There is increasing premature birth. Pediatr Radiol 1997;27:139–43. clinical and experimental evidence that the cerebellum is involved 8. Tuck S, Ment LR. A follow-up study of very low-birthweight infants receiving in cognitive functions and other nonmotor behaviors.23 In our ventilatory support by face mask. Dev Med Child Neurol 1980;22:633–41. study, the follow-up data are insufficient to draw any firm 9. Huang LT, Lui CC. Tentorial hemorrhage associated with vacuum conclusions, although in general the outcome in the preterm extraction in a newborn. Pediatr Radiol. 1995;25( Suppl 1 ):S230. 10. Bulas DI, Taylor GA, Fitz CR, Revenis ME, Glass P, Ingram JD. Posterior group was better than in the term group. fossa intracranial hemorrhage in infants treated with extracorporeal membrane oxygenation: sonographic findings AJR AM J Roenterol CONCLUSION 1991;156(3):571–5. 11. Serfontein GL, Rom S, Stein S. Posterior fossa subdural hemorrhage in the Cerebellar and other PF lesions may have important newborn. Pediatrics 1980;65:40–3. neurodevelopmental sequelae. Lesions in the PF are well visualized 12. deSouza N, Chaudhuri R, Bingham J, Cox T. MRI in cerebellar hypoplasia. using MR imaging. We would recommend that MR imaging be Neuroradiology 1994;36:148–51. considered in the investigation of any infant thought to have a 13. Adamsbaum C, Moreau V, Bulteau C, Burstyn J, Lair MF, Kalifa G. Vermian complex brain malformation, metabolic disorder or in whom there agenesis without posterior fossa cyst. Pediatr Radiol 1994;24:543–6. is antenatal suspicion of PF abnormality. While CUS is still the 14. Antoun H, Villeneuve N, Gelot A, Panisset S, Adamsbaum C. Cerebellar most convenient imaging modality in the sick preterm infant atrophy: an important feature of carbohydrate deficient glycoprotein receiving intensive care, MR imaging of the PF should be syndrome type 1. Pediatr Radiol 1999;29:194–8. 15. Patel S, Barkovich AJ. Analysis and classification of cerebellar malforma- considered in any preterm infant found to have parenchymal tions. Am J Neuroradiol 2002;23:1074–87. lesions elsewhere in the brain and in any infant who has major 16. Childs AM, Ramenghi LA, Evans DJ, et al. MR features of developing episodes of cardiovascular instability. Infants found to have periventricular white matter in preterm infants: evidence of glial cell cerebellar hemorrhage or infarction will require careful migration. Am J Neuroradiol 1998;19:971–6. neurological follow-up. 17. Sarnat HB, Sarnat MS. Neonatal encephalopathy following fetal distress. A In our cohort, there was a higher incidence of intracerebellar clinical and electroencephalographic study. Arch Neurol 1976;33:696–705. hemorrhage in preterm infants compared with term infants. These 18. Cornette LG, Tanner SF, Ramenghi LA, et al. Magnetic resonance imaging intracerebellar hemorrhages tended to be focal, unilateral and were of the infant brain: anatomical characteristics and clinical significance of often unsuspected clinically. Further long-term follow-up studies punctate lesions. Arch Dis Child Fetal Neonatal Ed 2002;86:F171–7. are required to determine the neurodevelopmental significance of 19. Roelants-van Rijn AM, Groenendaal F, Beek FJ, Eken P, van Haastert IC, de these focal cerebellar lesions in preterm infants. Vries LS. Parenchymal brain injury in the preterm infant: comparison of cranial ultrasound, MRI and neurodevelopmental outcome. Neuropediatrics 2001;32(2):80–9. Acknowledgements 20. Felderhoff-Mueser U, Rutherford MA, Squier WV, et al. Relationship between We are indebted to all the staff of the neonatal unit and the MR department for MR imaging and histopathologic findings of the brain in extremely sick their assistance. We are also grateful to all the pediatricians who provided us with preterm infants. Am J Neuroradiol 1999;20:1349–57. follow-up data. We particularly thank the parents of the babies for allowing their 21. Steinlin M, Blaser S, Boltshauser E. Cerebellar involvement in metabolic infants to be scanned. disorders: a pattern-recognition approach. Neuroradiology 1998;40:347–54. 22. Johnsen SD, Tarby TJ, Lewis KS, Bird R, Prenger E. Cerebellar infarction: an unrecognized complication of very low birthweight. J Child Neurol References 2002;17:320–4. 1. Merrill JD, Piecuch RE, Fell SC, Barkovich AJ, Goldstein RB. A new pattern 23. Boltshauser E. Cerebellar imaging F an important signpost in paediatric of cerebellar hemorrhages in preterm infants. Pediatrics 1998;102:E62. neurology. Childs Nerv Syst 2001;17:211–6.

Journal of Perinatology 2003; 23:396–403 403