Cranial Ultrasound Findings in Infants with Congenital Cytomegalovirus Infection in a Universal Newborn Screening Study in Minnesota

Abstract

Background:

Congenital cytomegalovirus (cCMV) is the most common infectious cause of neurodevelopmental deficits in US children. To inform patient management, it is important to define whether central nervous system (CNS) manifestations are present at birth. This study characterized neuroimaging findings in infants with cCMV identified by a universal screening study in Minnesota during February 2016 – December 2022.

Methods:

Newborns with cCMV infection (confirmed by urine CMV PCR following a positive screening saliva and/or dried blood spot result) underwent diagnostic evaluation, including cranial ultrasound (cUS), laboratory studies, ophthalmological, and audiological evaluation. Neuroimaging findings and cCMV disease classification were interpreted based on international consensus guidelines.

Results:

Among 87 newborns with confirmed cCMV, 76 underwent cUS. Of these, 53/76 (70%) had normal examinations, while 23/76 (30%) exhibited cUS findings: for 5 infants, these were clearly cCMV disease-defining, while for 18 infants, there were findings of uncertain significance. Magnetic resonance imaging (MRI) results (n=10 infants) aligned with cUS cCMV-disease defining findings in 2 infants, while cCMV-specific abnormalities were noted by MRI in 2 of 6 infants with nondiagnostic/incidental cUS findings. Of 9 infants who had both cUS and MRI examination, the average time interval between studies was 220 days (range, 2 to 1061). Excluding infants with cCMV CNS disease-defining cUS abnormalities, incidental findings were observed more commonly in infants with clinical/laboratory features described in cCMV disease classification guidelines (9/13) than in newborns with completely asymptomatic infections (9/58; p<0.0001).

Conclusions:

Among infants with cCMV identified in a universal screening study, the majority had a normal cUS. CNS disease-defining abnormalities were present in 7%, while 24% had findings of uncertain significance. We propose that many cUS findings are incidental, and not diagnostic of symptomatic cCMV disease instead of infection? . Although insufficient to define symptomatic disease, incidental cUS findings were more common in infants with other manifestations of cCMV.

Main Points/Summary

A cranial ultrasound (cUS) is an appropriate screening study in infants with congenital CMV (cCMV) infection. In addition to widely agreed-upon abnormalities that define central nervous system (CNS) involvement, subtle cUS findings may be noted, which may represent incidental findings of limited diagnostic and prognostic significance.

Introduction

Congenital cytomegalovirus (cCMV) is the most common infectious cause of neurodevelopmental deficits, including sensorineural hearing loss (SNHL). Approximately 1 in 200 infants in the United States (US) are born with cCMV infection [1]. Most infants with cCMV are asymptomatic at birth, and many long-term disabilities associated with this infection are under-diagnosed and under-appreciated [2, 3]. The recent advent of newborn screening programs will enable earlier recognition of cCMV.

Clinical signs of symptomatic cCMV in neonates vary, and include hepatomegaly, splenomegaly, intrauterine growth restriction, hepatitis, and central nervous system (CNS) involvement such as microcephaly, abnormal cerebrospinal fluid indices, and chorioretinitis [2, 4]. Radiographic abnormalities consistent with cCMV CNS disease include intracerebral calcifications, periventricular echogenicity, ventriculomegaly, and cortical or cerebellar malformations [4, 7]. Long-term sequelae include intellectual disabilities, learning delays, cerebral palsy, seizure disorders, and SNHL [5, 6]. The pathogenesis of CNS injury may relate to impaired migration of embryonic/fetal neuronal progenitor cells and/or immune-mediated injury [8, 9].

cUS, computed tomography (CT), and MRI imaging are options used to evaluate infants with cCMV infection [10, 11]. The neuroimaging choice depends on clinical context, resource availability, and provider/parental preference. With the advent of universal newborn screening programs there is a need to clarify the optimal neuroimaging approach for infants with cCMV, particularly for clinically inapparent infections. Here we examined findings and clinical impact of cUS, MRI, and CT scans obtained on infants with confirmed cCMV infection identified by a universal screening study.

Methods

Clinical cohort and study design

The study was approved by the Institutional Review Boards at the University of Minnesota (1507M76904), Allina Health, the Minnesota Department of Health, and the Centers for Disease Control and Prevention (CDC).

Screening was conducted at five Minnesota newborn nurseries and three neonatal intensive care units in Minneapolis/St. Paul, and one newborn unit in St. Cloud [12, 13]. Parents provided written informed consent. Screening was by saliva and dried blood spot (DBS), using samples collected between 24 and 48 hours of age. Urine CMV PCR was carried out within 21 days of age for confirmation of positive screens.

For confirmed cases of cCMV, recommended additional follow-up evaluation was based on international consensus guidelines [4], and consisted of a complete blood count, differential leukocyte count, and platelet count; serum alanine transaminase and aspartate aminotransferase; audiological evaluation; ophthalmologic consultation; and cUS. The corresponding author communicated care recommendations, considered clinical care and not research, to the primary care physician, and assisted in interpretation and evaluation of results and, in most cases, evaluated the infant. For well-appearing newborns, some primary care physicians and/or families refused additional studies. cUS was recommended for all confirmed cases. Brain MRI and/or CT were obtained at the primary care physician’s discretion.

cUS findings considered indicative of symptomatic disease with CNS findings included ventriculomegaly, intracerebral calcifications, periventricular echogenicity, and cortical or cerebellar malformations [4]. These infants clearly met the definition of moderately-to-severely symptomatic cCMV disease (diseased involving the CNS) defined by international consensus criteria. For other infants without clear disease-defining CNS abnormalities, the proportions with incidental cUS findings were assessed according to the four clinical disease categorizations of cCMV defined by Rawlinson et al. These infants were categorized as follows: asymptomatic; asymptomatic, but with isolated SNHL; mildly symptomatic; and moderately-to-severely symptomatic [4]. Statistical comparisons were carried out by Chi-square test (Microsoft Excel for Mac, version 16.77.1), with statistical significance ascribed to a p value of <0.05.

Role of the Funding Source

The study funders had no role in the study design, data collection, data interpretation, or writing of this report. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the CDC.

Results

Identification of cCMV and Disease Classification

Clinical evaluations were available for 87 infants with confirmed cCMV infection identified in a newborn screening study in Minnesota of 23,644 newborns between February 2016 – December 2022. The demographics of the study cohort have been reported elsewhere [12, 13]. There were no premature infants in the study cohort. A total of 18/87 infants (21%) were treated with valganciclovir. Of these 87 infants, 68 (78%) infants were categorized as asymptomatic, and 19 (22%) met criteria for the other three disease categories [4]: asymptomatic with isolated SNHL (4), mildly symptomatic (9), or moderately-to-severely symptomatic (6; of these, 2 infants had SNHL at diagnosis, and 2 had delayed-onset SNHL). In total, 10/87 (11.5%) infants have (to date) demonstrated SNHL, either present at birth or of delayed-onset. Specifically, 2 infants in the asymptomatic group had delayed-onset SNHL; 4 infants were classified as asymptomatic with isolated SNHL; and 4 infants in the moderately-to-severely symptomatic group had SNHL.

Neuroimaging Findings: Overall cUS Results

A total of 76 (87%) of these infants had a cUS study. Imaging studies were ordered as standard of care, with the cUS requisition stating that the infant had cCMV infection. No cUS was obtained for 11 infants, based on the primary care provider’s discretion, family refusal, and limitations in obtaining clinical follow-up evaluation.

The median age when cUS was conducted was 23.5 days (interquartile range, 18.25–31.00 days). Among 76 infants, 53 (70%) had a normal examination, and 23 (30%) had findings noted. Five infants had intracranial calcifications on cUS, a cCMV symptomatic disease-defining finding [4]. The incidental findings in the remaining 18 infants included: cystic lesions (subependymal cysts; choroid plexus cysts), mineralizing vasculopathy, LSV, subependymal hemorrhages, and caudothalamic groove heterogeneity (Table 1). Mineralizing vasculopathy and/or LSV was noted in three of 4 infants categorized as asymptomatic, but with isolated SNHL; one of these infants also had bilateral subependymal cysts.

Table 1:

Cranial Ultrasound Results from a CMV Universal Screening Study

Cranial Ultrasound Result	Number of Infants
Normal	53
Cystic lesions (subependymal cysts; choroid plexus cysts)	10f
Mineralizing vasculopathy, lenticulostriate vasculopathy, leukostriate vasculopathy	6
Intracranial calcifications	5*†
Subependymal hemorrhages	1
Caudothalamic groove heterogeneity	1
TOTAL	76

^fThree infants in this group also had mineralizing vasculopathy.

^*cCMV-defining abnormality for assignment to “CMV disease” category.

^†One infant in this group also had mineralizing vasculopathy, one other infant in this group also had cystic lesions.

Correlation of cUS with MRI and CT Results

MRI examinations and, in some infants, cranial CT scans were obtained during the course of the child’s care. These studies were generally not performed contemporaneously with the cUS in the newborn period, and were often done for other indications (i.e., evaluation for cochlear implantation surgery).

Ten infants underwent MRI studies, at median age of 202 days (range 2 to 2399 days). These encompassed 2 cases with cCMV-disease defining cUS abnormalities, 6 with incidental cUS findings, 1 with a normal cUS, and 1 child who had not had cUS performed. The infant who had a normal cUS result at birth had a brain MRI later in childhood (because of delayed-onset CMV retinitis) which demonstrated multiple foci of abnormal subcortical white matter T2 signal, a result that, in retrospect, was compatible with moderately-to-severely symptomatic cCMV disease at birth (Figure 1, Panels A and B). MRIs were not conducted for the other 52 infants with normal cUS examinations. Among the five infants who had disease-defining intracranial calcifications on cUS, two had an abnormal brain MRI later in childhood; in both cases, finding aligned with the neonatal cUS exam.

Figure 1:

cUS and MRI comparisons. Top row. This patient had a clinical inapparent cCMV infection identified by universal screening, and was initially classified as asymptomatic. The patient had a normal cUS during the initial diagnostic evaluation (panel A) but was found to have multiple foci of abnormal subcortical white matter T2 signal (panel B; arrows) on a later MRI study that was obtained for late-onset CMV retinitis. Bottom row: This patient had the incidental finding of linear branching echogenicities in the thalami consistent (panel C) with mineralizing vasculopathy (arrowheads) on cUS and was found to have multiple abnormal subcortical foci of increased T2 signal intensity on a subsequent MRI (panel D).

There were 18 infants with what we interpreted as non-cCMV disease-defining cUS findings. Of these, 6 infants had a brain MRI; 4 of this group had normal findings. Of the two infants with abnormal MRI findings, one had mineralizing vasculopathy on cUS. This infant had prominence of the ventricles and extra-axial spaces, and fluid signal in the mastoid air cells, on a subsequent brain MRI. This infant also displayed normal brain and left-sided mastoid air cell opacification by brain/temporal bone CT study (both sets of studies were obtained later in childhood because of the presence of SNHL, in order to assess for possible cochlear implantation surgery). The second infant had a non-specific finding of diffuse linear echogenicities in the thalmi bilaterally by cUS. A subsequent MRI (obtained because of SNHL) indicated diffuse multiple abnormal subcortical foci of increased T2 signal intensity (Figure 1, Panels C and D). Brain and temporal bone CT were normal. Overall, 9 infants who had both a cUS and an MRI examination, with an average time interval of 220 days (range, 2 to 1061 days) between the studies. Only 2 infants had an MRI within 30 days from the cUS examination.

A summary chart of cUS findings and any subsequent MRI and/or CT examination is shown in Figure 2. The five infants evaluated by CT all had temporal bone CT examinations, and some had concomitant CT evaluation of the brain, at a median age of 959 days (range 198 to 2399 days). Four of these infants had SNHL. Two had normal CT findings and three had abnormal findings in the mastoid/temporal region. One had partial opacification of the left mastoid air cells; as noted above, this infant had mineralizing vasculopathy on cUS and an abnormal MRI that did not support a classification of symptomatic cCMV disease [4]. The second infant had bilateral cochlear malformation and mild vestibular dilation; this infant had calcifications on initial cUS but did not have an MRI. The third infant had bilateral otomastoiditis; this infant had calcifications on cUS, and an abnormal MRI that confirmed this as a symptomatic cCMV disease case. One child with normal CT findings, evaluated due to delayed-onset SNHL at 5 years 7 months of age, did not have a cUS, but had an abnormal MRI. There were 4 infants who had both a cUS and a CT scan. On average, for these infants a CT scan was obtained 596 days (range, 218 to 1069 days) after the cUS examination. CT was not typically performed to clarify incidental findings on cUS exam, but rather because clinical management concerns (such as progressive SNHL) warranted the study.

Figure 2.

cUS, MRI and CT of infants identified with cCMV infection in a universal newborn screening study in Minnesota. 53 infants had a normal cUS, 23 had an abnormal cUS, for 11 cUS was not performed. 10 had MRI (1 had normal cUS, 2 had intracranial calcifications on cUS, 3 had mineralizing vasculopathy on cUS, 3 had other incidental findings, and for 1, cUS was not done). 5 had CT (2 had intracranial calcifications on cUS [1 abnormal MRI, 1 no MRI], 2 mineralizing vasculopathy on cUS and abnormal MRI, 1 without cUS and abnormal MRI).

* Child was asymptomatic with delayed-onset SNHL.

** One infant had patchy white matter T2 hyperintensity and periventricular calcifications, bilateral middle ear and mastoid fluid, and a small arachnoid cyst in the left aspect of the posterior cranial fossa; this infant’s head CT had limited results due to motion, but showed right otomastoiditis and left mastoiditis. The other infant had microcalcifications and microhemorrhages, delayed cortical folding and focal pachygyria in the temporal lobes anteriorly and in the occipital regions.

• § Infant had a normal newborn screening cUS and was considered asymptomatic at birth, but developed late-onset retinitis prompting MRI scan.

Incidental Cranial Ultrasound Findings and Symptomatic cCMV

Excluding infants with cCMV infection with moderately-to-severely symptomatic disease-defining cUS abnormalities, we observed that incidental findings were more common among infants with cCMV-related manifestations [4], including asymptomatic infection with isolated SNHL, mild cCMV disease, or moderately-to-severely symptomatic cCMV disease (9/13 [69%], as defined in Table 2). For infants that were categorized as asymptomatic cCMV infection, only 9/58 (16%) had an incidental cUS finding (p < 0.0001, Chi-square test).

Table 2:

Comparison of Ultrasound Results and Symptom Classification. Table demonstrates comparison between “incidental cUS findings” or “normal cUS findings” with respect to being categorized in the “asymptomatic” cCMV classification or any of the cCMV disease-defining categories as designated by Rawlinson et al. criteria [4[ including: 1) asymptomatic with SNHL; 2) mildly symptomatic; or (3) moderately-to-severely symptomatic. Chi-square analysis demonstrated that incidental cUS findings were more common among infants with various clinical and/or laboratory manifestations observed in other cCMV disease categories (9/13) than in infants with completely asymptomatic infections (9/58; p<0.0001). This table excludes babies who had cCMV disease involving the CNS as identified by cUS (ventriculomegaly, periventricular calcifications, etc).

	Moderately-to-Severely Symptomatic, Mildly Symptomatic, or Asymptomatic with SNHL*	Asymptomatic
Incidental Ultrasound Results	9	9
Normal Ultrasound Results	4	49

^*Excluding infants with symptomatic cCMV disease with CNS involvement defined by intracranial calcifications (n=5; Table 1).

Discussion

In this study of neuroimaging findings among infants with cCMV identified in a universal screening study in Minnesota, incidental cUS findings were common among infants with mildly-to-moderately symptomatic cCMV disease, as well as infants with asymptomatic cCMV, with or without isolated SNHL. Using international consensus criteria, five of 76 infants (7%) had a symptomatic cCMV-defining abnormality [4] on cUS, consisting of periventricular and intraparenchymal calcifications.

The most common incidental findings on cUS in our study were cystic lesions (10 infants), including subependymal cysts and choroid plexus cysts. These types of cysts are relatively common, usually having a favorable prognosis, and, we believe, may be an isolated incidental finding in asymptomatic infants with cCMV, just as they are in CMV-uninfected normal newborns [14]. The relationship of such cysts to cCMV requires further clarification. Similarly, mineralizing vasculopathy (also known as LSV) – a finding of uncertain significance in cCMV – was observed in five infants. Giannattasio et al. observed that LSV was a common cUS finding among both symptomatic and asymptomatic infants with cCMV [15], but as an isolated finding it was not associated with adverse outcomes, nor was it considered as an indication for antiviral therapy. Other studies, however, have suggested that LSV may be associated with cCMV CNS involvement and SNHL [16, 17], and further study is warranted to clarify this uncertainty.

With the expansion of cCMV screening, there has been considerable discussion about CNS neuroimaging screening strategies. In a survey of North American pediatric infectious diseases practitioners [18], 95% stated they would obtain neuroimaging in infants with cCMV: 34.4% (n = 11/32) would order cUS for all cases, whereas 21.9% (n = 7/32) would order brain MRI for all cases. The preferred approach in the setting of universal cCMV screening, where most infections are clinically inapparent, is unclear. A majority of survey respondents would pursue a staged approach, with a brain MRI obtained only if an abnormality was noted on cUS. Although recommended at one time [19], the proportion of infants with cCMV disease who undergo CT imaging has declined significantly in recent years [20].

The results of our study suggest that cUS is a reasonable screening tool for asymptomatic infants with cCMV infection. Only one infant in our series initially defined as a case of asymptomatic cCMV (with a normal cUS) ended up demonstrating brain MRI abnormalities. We do not recommend cranial CT for evaluation for CNS findings in the majority of infants with cCMV. Notably, there are no formal guidelines from the American Academy of Pediatrics (AAP) regarding which neuroimaging modality is preferred in the initial evaluation of cCMV infection. An international consensus expert panel has recommended the use of cUS as a screening modality [4]. The Canadian Pediatric Society (CPS) suggests that cUS be performed as an initial study, “unless there are neurological concerns”, in which case MRI is recommended [21]. MRI is also recommended by the CPS in the setting of cUS abnormalities.

Expert groups do not agree on the specific neuroimaging findings that definitively indicate whether a cCMV infection is considered ‘symptomatic.’ This lack of consensus complicates diagnosis and management. Rawlinson et al. defined findings indicative of moderately-to-severely symptomatic as in other places? cCMV disease, based on CNS involvement, as ventriculomegaly, intracerebral calcifications, periventricular echogenicity, and cortical or cerebellar malformations [4]. A consensus panel convened by the European Society of Paediatric Infectious Diseases published guidelines in 2017 [22] that included other, additional findings as indicative of symptomatic cCMV involving the CNS. These included the neuroimaging findings of calcifications, periventricular cysts, ventricular dilatation, subependymal pseudocysts, germinolytic cysts, white matter abnormalities, cortical atrophy, migration disorders, cerebellar hypoplasia, and LSV. Similar recommendations were offered in a publication by the European Congenital CMV Initiative (ECCI) in 2024 [23]. The 2027 Red Book [24], does not specify Revise since the new Red Book describes as indicative of moderately-to-severely symptomatic disease central nervous system involvement: microcephaly, radiographic abnormalities (ventriculomegaly, intracerebral calcifications, white matter changes, periventricular echogenicity, cortical or cerebellar malformations, migration abnormalities)? the neuroimaging criteria that constitute cCMV with CNS involvement, simply noting that the presence of microcephaly and intracerebral (typically periventricular) calcifications indicate symptomatic CMV disease. The CPS notes that ventricular/periventricular calcifications, ventriculomegaly ± atrophy, cerebellar/ependymal/parenchymal cysts, polymicrogyria, lissencephaly, porencephaly, schizencephaly, and extensive encephalopathy are findings indicative of CNS involvement, but also notes that LSV is of “questionable clinical significance”. Achieving an international consensus of what kinds of imaging findings indicate bona fide CNS involvement as well as how these findings are to be incorporated into definitions of symptomatic disease, is a high priority for future study. The various expert interpretations of these issues are summarized in Table S1.

An observation in the current study that allowed us to put incidental cUS findings into context was the finding of other clinical or laboratory signs suggestive of cCMV disease (Table 2). Excluding those infants with clear-cut CNS disease-defining cUS abnormalities, 69% of infants classified in moderately-to-severely symptomatic, mildly symptomatic, or asymptomatic with associated SNHL categories had incidental cUS findings. Thus, if incidental cUS findings are noted in infants with audiological abnormalities, or other clinical and/or laboratory findings suggestive of cCMV disease, then MRI may be a consideration. MRI for asymptomatic infants with negative diagnostic evaluations is not usually warranted, even in the face of incidental cUS findings.

The “added value” of MRI in the evaluation of cCMV has been evaluated by other groups. Smiljkovic et al. found that most infants’ cUS and MRI results demonstrated concordance [25], and that obtaining MRI in infants with abnormal cUS but who were asymptomatic did not change treatment decisions for the majority of these patients. On the other hand, Capretti et al. noted that MRI did in fact elucidate important additional findings that were not seen on cUS [26]. In a study of 639 children with cCMV, Keymeulen et al. found that cUS and MRI complemented each other, in that some cCMV-defining results were found on one modality or the other, and some results were found on both cUS and MRI [27]. At present, it is unknown if such incidental findings have any implications for long-term outcomes (such as hearing loss) if they are independent of symptomatic disease, although a recent paper suggests that the prognosis in the setting of incidental findings such as subependymal cysts is generally quite favorable [28].

Our study had several potential limitations. Although the majority of the infants with cCMV did have cUS conducted, 11 infants (13%) did not, due to primary care provider preference or parental refusal. The evaluation of infants identified with cCMV through universal screening is challenging for families [29]. There may be potential negative consequences of universal screening, such as discovering incidental changes of unclear clinical significance that result in unwarranted and costly evaluations. We did not obtain MRI as a component of routine clinical care for the majority of infants, even if findings were observed by cUS. Indeed, in our analysis we noted there were only 9 infants who had both a cUS and an MRI examination, with an average time interval of 220 days (range, 2 to 1061 days) between the studies. Only two infants had a brain MRI within 30 days of their screening cUS. We recommend obtaining a screening cUS in infants with no clinical manifestations of cCMV disease at birth who are identified by universal screening. MRI may be warranted, however, in those infants with other signs/symptoms of disease, and/or those infants with abnormal laboratory markers at birth, irrespective of the presence or absence of incidental cUS abnormalities.

These questions are likely to be amplified as more and more US states and Canadian provinces engage in universal cCMV screening. Indeed, the American Academy of Otolaryngology and Head and Neck Surgeons recently endorsed universal cCMV screening [30] and these questions will take on more clinical urgency as screening becomes more commonplace. It will be of interest to continue to analyze the role of neuroimaging in cCMV cases identified by universal screening in Minnesota, and other states, particularly in otherwise well-appearing infants.

Conclusions

In this universal screening study for cCMV, most infants had normal cUS results. Of those with cUS findings, most were not clearly causally related to cCMV infection. Expert groups lack consensus on which cUS observations define whether an infant has cCMV disease (Table S1). In our study, little clinically relevant information was added by performance of MRI scans for infants with incidental cUS findings. However, if other signs/symptoms of disease or abnormal laboratory markers are noted, then MRI may have added value.

Abbreviations

AAP

American Academy of Pediatrics

cCMV

Congenital CMV infection

CPS

Canadian Pediatric Society

SNHL

Sensorineural hearing loss

cUS

Cranial ultrasound

CNS

Central nervous system

CT

Computed tomography scan

LSV

Lenticulostriate (leukostriate) vasculopathy

Data Availability.

The data that support the findings of this study will be available from the corresponding author upon reasonable request.