Cochlear Implantation: Systematic Approach to Preoperative Radiologic Evaluation

Sensorineural hearing loss results from abnormalities that affect the hair cells of the membranous labyrinth, inner ear malformations, and conditions affecting the auditory pathway from the cochlear nerve to the processing centers of the brain. Cochlear implantation is increasingly being performed for hearing rehabilitation owing to expanding indications and a growing number of children and adults with sensorineural hearing loss. An adequate understanding of the temporal bone anatomy and diseases that affect the inner ear is paramount for alerting the operating surgeon about variants and imaging findings that can influence the surgical technique, affect the choice of cochlear implant and electrode type, and help avoid inadvertent complications. In this article, imaging protocols for sensorineural hearing loss and the normal inner ear anatomy are reviewed, with a brief description of cochlear implant devices and surgical techniques. In addition, congenital inner ear malformations and acquired causes of sensorineural hearing loss are discussed, with a focus on imaging findings that may affect surgical planning and outcomes. The anatomic factors and variations that are associated with surgical challenges and may predispose patients to periprocedural complications also are highlighted. ^© RSNA, 2023 Quiz questions for this article are available through the Online Learning Center. Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

Hearing Instability in Children with Congenital Cytomegalovirus: Evidence and Neural Consequences

OBJECTIVE/HYPOTHESIS

Sensorineural hearing loss (SNHL) is a common sequela of congenital cytomegalovirus (cCMV), potentially exacerbating neurocognitive delay. The objectives of this study were to assess: (1) age at which SNHL in children with cCMV; (2) stimulability of the auditory system in children with cCMV following cochlear implantation (CI); and (3) whether features of magnetic resonance imaging (MRI) potentially are predictive of hearing outcomes.

METHODS

In this retrospective study of a prospectively acquired cohort, 123 children with cCMV who were referred for hearing loss at a single tertiary referral hospital over 20 years were compared with an unmatched comparative group of 90 children with GJB2-related deafness. Outcome measures were results of newborn hearing screening (NHS), behavioral audiograms, and, in a subgroup of cochlear implant (CI) users, responses from the auditory nerve and brainstem evoked by CI at initial activation, as well as lesional volume of FLAIR-hyperintense signal alterations on MRI.

RESULTS

All but 3 of 123 children with cCMV had confirmed and persistent SNHL. At birth, 113 children with cCMV underwent NHS, 31 (27%) passed in both ears and 23 (20%) passed in one ear (no NHS data in 10 children). At the first audiologic assessment, 32 of 123 (26%) had normal hearing bilaterally; 35 of 123 (28%) had unilateral SNHL; and 57 of 123 (46%) had bilateral SNHL. More than half (67 of 123, 54%) experienced hearing deterioration in at least one ear. Survival analyses suggested that 60% of children who developed SNHL did so by 2.5 years and 80% by 5 years. In the children who passed NHS in one or both ears, 50% developed hearing loss by 3.5 years in the ear, which passed unilaterally (n = 23 ears), and 50% by 5 years in bilateral passes (n = 62 ears). Hearing loss was significant enough in all but one child with isolated high-frequency loss for rehabilitation to be indicated. Hearing thresholds in individual ears were in the CI range in 83% (102 of 123), although duration of deafness was sufficient to preclude implantation at our center in 13 children with unilateral SNHL. Hearing aids were indicated in 16% (20 of 123). Responses from the auditory nerve and brainstem to initial CI stimulation were similar in children with cCMV-related SNHL compared with GJB2-related SNHL. Characteristic white matter changes on MRI were seen in all children with cCMV-related SNHL (n = 91), but the lesion volume in each cortical hemisphere did not predict degree of SNHL.

CONCLUSIONS

cCMV-related SNHL is often not detected by NHS but occurs with high prevalence in early childhood. Electrophysiological measures suggest equivalent stimulability of the auditory nerve and brainstem with CI in children with cCMV and GJB2-related SNHL. Hyperintense white matter lesions on FLAIR MRI are consistently present in children with cCMV-related SNHL but cannot be used to predict its time course or degree. Combined, the data show early and rapid deterioration of hearing in children with cCMV-related SNHL with potential for good CI outcomes if SNHL is identified and managed without delay. Findings support universal newborn screening for cCMV followed by careful audiological monitoring.

LEVEL OF EVIDENCE

3 Laryngoscope, 2022.

Abusive head trauma: neuroimaging mimics and diagnostic complexities

Traumatic brain injury is responsible for approximately half of all childhood deaths from infancy to puberty, the majority of which are attributable to abusive head trauma (AHT). Due to the broad way patients present and the lack of a clear mechanism of injury in some cases, neuroimaging plays an integral role in the diagnostic pathway of these children. However, this nonspecific nature also presages the existence of numerous conditions that mimic both the clinical and neuroimaging findings seen in AHT. This propensity for misdiagnosis is compounded by the lack of pathognomonic patterns and clear diagnostic criteria. The repercussions of this are severe and have a profound stigmatic effect. The authors present an exhaustive review of the literature complemented by illustrative cases from their institutions with the aim of providing a framework with which to approach the neuroimaging and diagnosis of AHT.

Characteristic Cochlear Hypoplasia in Patients with Walker-Warburg Syndrome: A Radiologic Study of the Inner Ear in α-Dystroglycan-Related Muscular Disorders

BACKGROUND AND PURPOSE

Walker-Warburg syndrome, muscle-eye-brain disease, and Fukuyama congenital muscular dystrophy are α-dystroglycan-related muscular disorders associated with brain malformations and eye abnormalities in which no structural inner ear abnormality has been described radiologically. We collected patients from 6 tertiary pediatric hospitals and reported the radiologic features and frequency of inner ear dysplasias.

MATERIALS AND METHODS

Patients previously diagnosed clinicoradiologically with Walker-Warburg syndrome, muscle-eye-brain disease, or Fukuyama congenital muscular dystrophy were included. We recorded the pathogenic variant, when available. Brain MR imaging and/or CT findings were reviewed in consensus, and inner ear anomalies were classified according to previous description in the literature. We then correlated the clinicoradiologic phenotype with the inner ear phenotype.

RESULTS

Thirteen patients fulfilled the criteria for the Walker-Warburg syndrome phenotype, 8 for muscle-eye-brain disease, and 3 for Fukuyama congenital muscular dystrophy. A dysplastic cochlea was demonstrated in 17/24. The most frequent finding was a pronounced cochlear hypoplasia type 4 with a very small anteriorly offset turn beyond the normal-appearing basal turn (12/13 patients with Walker-Warburg syndrome and 1/11 with muscle-eye-brain disease or Fukuyama congenital muscular dystophy). Two of 8 patients with muscle-eye-brain disease, 1/3 with Fukuyama congenital muscular dystrophy, and 1/13 with Walker-Warburg syndrome showed a less severe cochlear hypoplasia type 4. The remaining patients without Walker-Warburg syndrome were healthy. The vestibule and lateral semicircular canals of all patients were normal. Cranial nerve VIII was present in all patients with diagnostic MR imaging.

CONCLUSIONS

Most patients with the severe α-dystroglycanopathy Walker-Warburg syndrome phenotype have a highly characteristic cochlear hypoplasia type 4. Patients with the milder variants, muscle-eye-brain disease and Fukuyama congenital muscular dystrophy, more frequently have a normal cochlea or milder forms of hypoplasia.

Ectopic cervical thymus in children: Clinical and radiographic features

OBJECTIVES

Ectopic thymus is rare and can be a diagnostic challenge. This study evaluated the management of children radiographically diagnosed with ectopic cervical thymus.

METHODS

A retrospective review of 100 patients was performed. Data related to clinical presentation, radiological imaging, pathology, and management were collected. Changes in lesion volume were tracked over time. Clinical characteristics were compared based on lesion location in the neck using analysis of variance modelling.

RESULTS

There were 115 lesions with radiographic features of ectopic cervical thymus (15 children had bilateral lesions). Diagnosis was based on ultrasound in 98% of patients, magnetic resonance imaging in 18%, and computed tomography in 11%. Mean (SD) follow-up duration was 2 (2.2) years. Forty-four percent (51/115) of lesions involved the thyroid gland, 29% (33/115) were in the central neck but separate from the thyroid, 18% (21/115) had mediastinal extension, and 8% (9/115) involved the submandibular region. Location was unclear for two patients. Submandibular lesions were on average 12.4 cm³ larger (95% CI, 8.2, 16.6) than mediastinal lesions at diagnosis, P ≤ .001. Volume of thymic tissue decreased over time, from a mean (standard deviation [SD]) volume of 4.3 cm³ (9.2) at initial ultrasound to 2.7 cm³ (6.1) at final ultrasound (paired t-test, P = .008). Only two patients required surgery: one for compressive symptoms, and the other to rule out malignancy.

CONCLUSION

Ninety-eight percent of children with ectopic cervical thymus were managed conservatively without issues. We propose a classification system based on location to ease communication among clinicians and to help follow these lesions over time.

LEVEL OF EVIDENCE

4, case series Laryngoscope, 130:1577-1582, 2020.

Efficacy of a selective imaging paradigm prior to pediatric cochlear implantation

OBJECTIVES/HYPOTHESIS

There is no consensus on the necessary preoperative imaging in children being evaluated for cochlear implantation (CI). Dual-imaging protocols that implement both magnetic resonance imaging (MRI) and high resolution computed tomography (HRCT) create diagnostic redundancy in the face of potentially unnecessary radiation and anaesthetic exposure. The objectives of the current study were to examine the efficacy of an MRI-predominant with selective HRCT imaging protocol.

STUDY DESIGN

Retrospective review.

METHODS

The protocol was implemented over a 4-year period, during which HRCT was obtained in addition to MRI only if specific risk factors on clinical assessment were identified or if imaging findings in need of further evaluation were detected on initial MRI evaluation. Retrospective review of operative reports and prospective review of imaging were performed; anesthetic exposure and costing information were also obtained.

RESULTS

Of the 240 patients who underwent assessment, seven (2.9%) had combined HRCT and MRI performed concurrently based on initial clinical assessment, 15 (6.3%) underwent HRCT based on imaging anomalies found on MRI, and MRI alone was ordered for the remaining 218 (90.1%). All patients were implanted without complication. Overall, radiation exposure, general anesthesia (GA), and healthcare costs were reduced.

CONCLUSIONS

MRI alone can be used in the vast majority of cases for preoperative evaluation of pediatric CI candidates resulting in a significant reduction in healthcare costs, radiation, and GA exposure in children. The additional need for HRCT occurs in a small proportion and can be predicted up front on clinical assessment or on initial MRI.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:2627-2633, 2019.

Transmastoid access in branchio-oto-renal syndrome: A reappraisal of computed tomography imaging

OBJECTIVE

To evaluate for temporal bone abnormalities that might affect transmastoid surgery such as cochlear implantation in cases of branchio-oto-renal syndrome (BOR).

STUDY DESIGN

Retrospective review.

METHODS

Qualitative assessment of temporal bone computed tomography imaging was performed by a neuroradiologist for 30 individuals with BOR (60 ears) and 20 controls with normal hearing (20 ears). Transmastoid access was assessed categorically across 4 features: tip development, cortex pneumatization, tegmen height, and facial recess pneumatization. The appearance of 4 standard landmarks (Koerner's septum, antrum, prominence of the horizontal semicircular canal, incudal short process) was also dichotomized as normal or abnormal. Data were compared using Fisher's exact testing.

RESULTS

Mastoid height differed between the groups with tip underdevelopment noted in 72% of BOR ears vs. 40% of controls (p = 0.02), and a low tegmen was seen in 68% of BOR ears and 25% of controls (p < 0.01). Significant differences in pneumatization were also found for the mastoid cortex (28% non-pneumatized in BOR vs. 5% in controls; p = 0.03) and the facial recess (27% non-pneumatized in BOR vs. 0% in controls; p = 0.01). Standard landmarks were easily identified in all of the control mastoids. In the BOR group, Koerner's septum was abnormally located or absent in 45%, and the antrum was severely hypoplastic or absent in 50%. Similarly, the prominence of the horizontal semicircular canal and the short process of the incus were dysplastic in 73% (44/60) and 62% (37/60), respectively.

CONCLUSIONS

Mastoid abnormalities are common in BOR syndrome. Restricted transmastoid access and abnormal or absent mastoid landmarks should be anticipated in those patients with BOR who become cochlear implant candidates.

LEVEL OF EVIDENCE

4.

Children with unilateral cochlear nerve canal stenosis have bilateral cochleovestibular anomalies

OBJECTIVES/HYPOTHESIS

To investigate the cochleovestibular apparatus bilaterally in children with isolated unilateral bony cochlear nerve canal (bCNC) stenosis.

STUDY DESIGN

Retrospective review.

METHODS

Imaging studies of children with unilateral bCNC stenosis (<1.0 mm) on computed tomography imaging (N = 36) were compared with controls imaged due to trauma without temporal bone injury (N = 32). Twenty-six measurements were obtained in each ear, assessing the bony internal auditory canal (IAC), cochlea, and vestibular end-organs, and were analyzed using one-way analysis of variance for intersubject comparisons and paired t tests for intrasubject comparisons with a Bonferroni adjustment for multiple comparisons (P = .0006).

RESULTS

Patients with bCNC stenosis had a smaller IAC (P < .000) and cochlea (P < .000) on the stenotic side as compared with controls. Although the vestibular end-organ was also smaller in bCNC ears, this difference was not significant. The contralateral ear also had a smaller bCNC (P < .000) and cochlea (P < .000) as compared with controls, although to a lesser degree than the stenotic side.

CONCLUSIONS

Children with unilateral bCNC stenosis have abnormal biometry of both the cochlea and the vestibular end-organ in the affected and the normal contralateral ear as compared with controls.

LEVEL OF EVIDENCE

3b Laryngoscope, 129:2403-2408, 2019.

Warsaw breakage syndrome: Further clinical and genetic delineation

Warsaw breakage syndrome (WBS) is a recently recognized DDX11-related rare cohesinopathy, characterized by severe prenatal and postnatal growth restriction, microcephaly, developmental delay, cochlear anomalies, and sensorineural hearing loss. Only seven cases have been reported in the English literature, and thus the information on the phenotype and genotype of this interesting condition is limited. We provide clinical and molecular information on five additional unrelated patients carrying novel bi-allelic variants in the DDX11 gene, identified via whole exome sequencing. One of the variants was found to be a novel Saudi founder variant. All identified variants were classified as pathogenic or likely pathogenic except for one that was initially classified as a variant of unknown significance (VOUS) (p.Arg378Pro). Functional characterization of this VOUS using heterologous expression of wild type and mutant DDX11 revealed a marked effect on protein stability, thus confirming pathogenicity of this variant. The phenotypic data of the seven WBS reported patients were compared to our patients for further phenotypic delineation. Although all the reported patients had cochlear hypoplasia, one patient also had posterior labyrinthine anomaly. We conclude that while the cardinal clinical features in WBS (microcephaly, growth retardation, and cochlear anomalies) are almost universally present, the breakage phenotype is highly variable and can be absent in some cases. This report further expands the knowledge of the phenotypic and molecular features of WBS.

Assessment of Mastoid Function with Magnetic Resonance Imaging after Canal Wall Up Cholesteatoma Surgery

OBJECTIVE

To use magnetic resonance imaging (MRI) to assess the extent of mastoid opacification after canal wall up (CWU) cholesteatoma surgery.

MATERIALS AND METHODS

Thirty-five children in whom post-operative MRI had been obtained after CWU surgery. Cholesteatoma confined to the meso- and/or epi-tympanum was removed using a transcanal approach (n=18). More extensive disease required a combined approach tympanomastoidectomy (CAT, n=17). Mastoid opacification was assessed in both ears by a neuroradiologist blind to surgical details using an ordinal scale from 0 (no opacification) to 6 (completely opacified). The primary outcome measure was presence of normal mastoid ventilation, defined by evaluation of non-operative ears as a score ≤2. The presence of normal ventilation, as well as the raw opacification scores, were compared according to type of cholesteatoma surgery: 1) transcanal, with no mastoidectomy and 2) CAT.

RESULTS

Mastoid ventilation was normal in 18 post-operative ears (51%). There was no significant difference in the proportion of normally ventilated mastoids in the CAT (n=17) and transcanal (n=18) groups (p=0.318; Fisher's exact). However, mastoid opacification scores were significantly higher in the CAT group than in the transcanal group (p=0.036; Mann-Whitney U).

CONCLUSION

The mastoid frequently fails to become normally ventilated after cholesteatoma surgery. Subgroup analysis suggests cortical mastoidectomy does not increase the likelihood of normal mastoid ventilation after CWU cholesteatoma surgery. MRI provides a non-invasive tool to assess mastoid function, which contributes to the current debate on optimum surgical strategies for management of the mastoid in cholesteatoma surgery. Further research will determine whether this measure of mastoid health correlates with risk of recurrent cholesteatoma.

Validation of the finding of hypertrophy of the clava in infantile neuroaxonal dystrophy/PLA2G6 by biometric analysis

INTRODUCTION

Infantile neuroaxonal dystrophy (INAD), an autosomal recessive neurodegenerative disorder due to PLA2G6 mutation, is classified both as a PLA2G6-associated neurodegeneration (PLAN) disorder and as one of the neurodegeneration with brain iron accumulation (NBIA) disorders. Age of onset and clinical presentation in INAD is variable. Typically described imaging features of cerebellar atrophy, cerebellar cortex bright FLAIR signal, and globus pallidus iron deposition are variable or late findings. We characterize clinical and neuroimaging phenotypes in nine children with confirmed PLA2G6 mutations and show a useful imaging feature, clava hypertrophy, which may aid in earlier identification of patients. Measurements of the clava confirm actual enlargement, rather than apparent enlargement due to volume loss of the other brain stem structures.

METHODS

A retrospective clinical and MRI review was performed. Brain stem measurements were performed and compared with age-matched controls.

RESULTS

We identified nine patients, all with novel PLA2G6 gene mutations. MRI, available in eight, showed clava hypertrophy, regardless of age or the absence of other more typically described neuroimaging findings. Brain autopsy in our cohort confirmed prominent spheroid bodies in the clava nuclei.

CONCLUSION

Clava hypertrophy is an important early imaging feature which may aid in indentification of children who would benefit from specific testing for PLA2G6 mutations.

Neurometabolic diseases of childhood

Metabolic diseases affecting the pediatric brain are complex conditions, the underlying mechanisms leading to structural damage are diverse and the diagnostic imaging manifestations are often non-specific; hence early, sensitive and specific diagnosis can be challenging for the radiologist. However, misdiagnosis or a delayed diagnosis can result in a devastating, irreversible injury to the developing brain. Based upon the inborn error, neurometabolic diseases can be subdivided in various groups depending on the predominantly involved tissue (e.g., white matter in leukodystrophies or leukoencephalopathies), the involved metabolic processes (e.g., organic acidurias and aminoacidopathies) and primary age of the child at presentation (e.g., neurometabolic disorders of the newborn). This manuscript summarizes these topics.

Subcutaneous fat pads on body MRI--an early sign of congenital disorder of glycosylation PMM2-CDG (CDG1a)

Infants with phosphomannomutase 2 - congenital disorder of glycosylation (PMM2-CDG), formerly known as CDG1a, present with failure to thrive, visceral dysfunction, thromboembolic events and developmental delays noted before 6 months of age. Diagnosis is often delayed due to the considerable variability in phenotype. Characteristic, but not universal, features include inverted nipples and abnormal subcutaneous fat pads. Neuroimaging performed in the first 4 months of life may be normal, although cerebellar and brainstem atrophy is usual after 3 months of age. Cerebellar and brainstem atrophy have been noted as early as 11 days of life. We present an infant whose typical subcutaneous and retroperitoneal fat deposits were clinically occult, but identified on body MRI.

Diffusion-weighted imaging of the cerebellum in the fetus with Chiari II malformation

BACKGROUND AND PURPOSE

Diffusion-weighted imaging can be used to characterize brain maturation. MR imaging of the fetus is used in cases of suspected Chiari II malformation when further evaluation of the posterior fossa is required. We sought to investigate whether there were any quantitative ADC abnormalities of the cerebellum in fetuses with this malformation.

MATERIALS AND METHODS

Measurements from ROIs acquired in each cerebellar hemisphere and the pons were obtained from calculated ADC maps performed on our Avanto 1.5T imaging system. Values in groups of patients with Chiari II malformations were compared with those from fetuses with structurally normal brains, allowing for the dependent variable of GA by using linear regression analysis.

RESULTS

There were 8 fetuses with Chiari II malformations and 23 healthy fetuses, ranging from 20 to 31 GW. There was a significant linear decline in the cerebellar ADC values with advancing gestation in our healthy fetus group, as expected. The ADC values of the cerebellum of fetuses with Chiari II malformation were higher [1820 (±100) × 10⁻⁶ mm²/s] than ADC values in the healthy fetuses (1370 ± 70) × 10⁻⁶ mm²/s. This was statistically significant, even when allowing for the dependent variable of GA (P = .0126). There was no significant difference between the pons ADC values in these groups (P = .645).

CONCLUSIONS

While abnormal white matter organization or early cerebellar degeneration could potentially contribute to our findings, the most plausible explanation pertains to abnormalities of CSF drainage in the posterior fossa, with increased extracellular water possibly accounting for this phenomenon.

Neonatal neuroimaging findings in inborn errors of metabolism

Individually, metabolic disorders are rare, but overall they account for a significant number of neonatal disorders affecting the central nervous system. The neonatal clinical manifestations of inborn errors of metabolism (IEMs) are characterized by nonspecific systemic symptoms that may mimic more common acute neonatal disorders like sepsis, severe heart insufficiency, or neonatal hypoxic-ischemic encephalopathy. Certain IEMs presenting in the neonatal period may also be complicated by sepsis and cardiomyopathy. Early diagnosis is mandatory to prevent death and permanent long-term neurological impairments. Although neuroimaging findings are rarely specific, they play a key role in suggesting the correct diagnosis, limiting the differential diagnosis, and may consequently allow early initiation of targeted metabolic and genetic laboratory investigations and treatment. Neuroimaging may be especially helpful to distinguish metabolic disorders from other more common causes of neonatal encephalopathy, as a newborn may present with an IEM prior to the availability of the newborn screening results. It is therefore important that neonatologists, pediatric neurologists, and pediatric neuroradiologists are familiar with the neuroimaging findings of metabolic disorders presenting in the neonatal time period.

Abnormal corpus callosum in neonates after hypoxic-ischemic injury

BACKGROUND

Literature regarding callosal injury after hypoxic-ischemic injury (HII) is scant.

OBJECTIVE

To present the MRI and US findings of callosal injury after HII.

MATERIALS AND METHODS

MRI and US studies of 76 neonates were evaluated for HII and 53 were considered positive.

RESULTS

Of the 53 neonates with HII, 40 demonstrated restricted diffusion on DWI; of these, 30 revealed callosal involvement. Nine of the 13 neonates with normal DWI, whose routine MRI images were compatible with HII, were imaged after 1 week of age. Five out of ten neonates imaged during the 1st week of life who did not show callosal restriction on DWI had predominantly basal ganglia injury. Callosal US images were regarded as abnormal in 16 out of the 53 neonates with HII, 15 of which revealed concomitant restricted diffusion on DWI.

CONCLUSION

Callosal injuries are common after HII. DWI is effective in confirming these injuries and easily demonstrates injury if performed prior to 1 week of age. The restricted diffusion demonstrated after this time could be attributed to continued injury. US is not a sensitive modality for callosal injury detection; however, abnormally increased callosal echogenicity might be a specific marker of injury in this setting.

Occipital lobe injury and cortical visual outcomes after neonatal hypoglycemia

OBJECTIVES

Hypoglycemia is a significant problem in neonates, and a pattern of parietooccipital diffusion restriction on MRI scans has been reported. The purpose of this study was to determine whether hypoglycemic injury, as indicated by diffusion restriction in the occipital lobes, correlated with visual evoked potentials and long-term cortical visual dysfunction.

METHODS

A cohort of 45 neonates from 2000-2005 with diffusion-weighted MRI studies after hypoglycemia was studied retrospectively. Perinatal history and follow-up data were analyzed, and results were correlated with diffusion-weighted imaging findings.The presence of occipital diffusion restriction was assessed qualitatively, and the mean apparent diffusion coefficients of mesial occipital lobes were calculated.

RESULTS

Among 25 patients who underwent diffusion-weighted imaging within 6 days after the onset of hypoglycemia, restricted diffusion in the occipital lobes was found in 8 (50%) of 16 term infants but not in preterm infants. For the remaining 20 patients, who had diffusion-weighted imaging performed >6 days after the initial onset of hypoglycemia, occipital diffusion restriction was not seen, even if hypoglycemia was ongoing. Restricted diffusion was associated with abnormal visual evoked potentials detected within 1 week after birth. Cortical visual deficits were seen in a significant proportion of patients with recurrent hypoglycemia and were correlated significantly with low mesial occipital apparent diffusion coefficient values.

CONCLUSIONS

Diffusion-weighted imaging studies performed within 6 days after initial hypoglycemia were sensitive in term but not preterm neonates. Diffusion restriction, with low apparent diffusion coefficient values, in the mesial occipital poles may indicate the prognosis for visual outcomes in acute settings after neonatal hypoglycemia.

Neurologic abnormalities in patients with adenosine deaminase deficiency

Defects in adenosine deaminase enzyme cause severe immunodeficiency. Without enzyme replacement or allogeneic bone marrow transplantation, patients often suffer fatal infection in infancy. Adenosine deaminase is expressed ubiquitously; deficiency may affect various organs, including the brain. Neurologic abnormalities occur in some adenosine deaminase-deficient patients, mostly in association with infection or after bone marrow transplantation. Three cases with significant neurologic abnormalities, including hypotonia, head lag, nystagmus, difficulty in focusing gaze, seizure disorder, and moderate-severe developmental delay but with no evidence of infection or transplant-related medication toxicity are presented. Computed tomographic scans and cranial MRI revealed volume loss and abnormalities of basal ganglia and thalamus, which may reflect accelerated nerve cell death or altered stimulation of adenosine receptors. Detailed neurologic and neuroimaging evaluation should be performed for all patients with adenosine deaminase deficiency upon diagnosis, to identify potentially significant brain lesions.

Imaging the complications of bone marrow transplantation in children

Bone marrow transplantation is frequently performed to restore hematologic and immunologic competence after chemotherapy and radiation therapy for a range of childhood malignancies, as well as to treat various congenital conditions in which hematologic and immunologic functions are depressed or absent. Potentially devastating complications may occur during the pre-engraftment period after bone marrow transplantation, when marrow aplasia may supervene for several weeks until engraftment occurs, as well as during the post-engraftment period (the 3 months after engraftment) and in subsequent months and years. Complications of bone marrow transplantation may be classified either according to the time interval between transplantation and the occurrence of the complication or according to the organ system affected. The range of complications that may affect the central nervous system and the rest of the body may be detected with ultrasonography, computed tomography, and magnetic resonance imaging. Neurologic, paranasal sinus, pulmonary, and abdominopelvic complications all may be seen after bone marrow transplantation. Graft-versus-host disease and lymphoproliferative disorders also may occur. The increasing use of bone marrow transplantation mandates that the radiologist be familiar with the full range of potential complications and their imaging appearances.

Neuroradiologic characteristics of astroblastoma

INTRODUCTION

Astroblastoma is a rare glial tumor of uncertain origin. Only a few scattered case reports and one small case series have described the radiologic appearance of this uncommon tumor. Many features previously identified are similar to those of other primary malignant brain tumors. We report the largest imaging series to date and further delineate the CT and MRI features of astroblastoma. We identify those features that may be useful in distinguishing astroblastoma from other neoplasms.

METHODS

The radiologic images, pathology reports, and clinical information of 12 patients with pathology-confirmed astroblastoma were retrospectively reviewed. CT and MRI findings including location, morphology, signal intensity, and presence and patterns of enhancement were tabulated.

RESULTS

Patients ranged in age from 0 (newborn) to 50 years with a mean of 20 years at the time of initial diagnosis. A striking female preponderance (11:1) was found. All tumors were supratentorial. There were multiple intratumoral cysts in 7 (58%) of the 12 patients. Nine (75%) showed strong rim enhancement and 3 (25%) showed no rim enhancement.

CONCLUSION

The imaging features of astroblastoma are identified in 12 previously unreported cases. Distinguishing features that can be used to narrow the differential diagnosis with more common primary brain neoplasms reflect a combination of age, anatomic location, and specific imaging findings such as demarcation, heterogeneous tumor enhancement, rim enhancement, and a multicystic "bubbly" appearance. Intraventricular location, intratumoral hemorrhage with a fluid-fluid level, and dural "tails" are less common but important additions to the imaging spectrum.

Differential Diagnosis of Intracranial Cystic Lesions at Head US: Correlation with CT and MR Imaging

The differential diagnosis of intracranial cystic lesions at head ultrasonography (US) includes a broad spectrum of conditions: (a) normal variants, (b) developmental cystic lesions, (c) cysts due to perinatal injury, (d) vascular cystlike structures, (e) hemorrhagic cysts, and (f) infectious cysts. These lesions vary in prevalence from common (cavum of the septum pellucidum, subependymal cyst, choroid plexus cyst) to rare (vein of Galen malformation). US can provide important information about the anatomic location, size, and shape of the lesions as well as their mass effect on adjacent structures. Differential diagnosis may be difficult because there is substantial overlap of US features between many of these conditions. However, if careful attention is paid to the location and characteristics of the cyst, a more specific diagnosis may be suggested. Understanding the spectrum of appearances of the various intracranial cystic lesions at head US improves the diagnostic yield, enables one to understand their pathogenesis, and facilitates patient care.

MRI criteria for multiple sclerosis: Evaluation in a pediatric cohort

This study assessed the validity of established MRI criteria for multiple sclerosis (MS) in a cohort of 20 children with clinically definite MS. The authors found that many pediatric MS patients did not meet the MRI criteria established for adult-onset MS, particularly the McDonald MRI criteria for dissemination in space. The authors thus suggest that MRI criteria for adult MS be applied cautiously to pediatric MS patients.

Neurocognitive outcome after acute disseminated encephalomyelitis

Cognitive dysfunction has been demonstrated in multiple sclerosis but has not been extensively studied after acute disseminated encephalomyelitis (ADEM). Because ADEM often presents with widespread demyelination, which may not completely resolve, these patients may be at risk for persistent cognitive dysfunction. The study objective was to explore the profile and severity of neurocognitive sequelae in pediatric ADEM. Children aged 6-15 years diagnosed with ADEM were invited to participate in a structured neurologic assessment, neuropsychological evaluation, and a follow-up magnetic resonance imaging. Nine of 15 children diagnosed with ADEM met the age criteria and six participated in the study. The mean age at presentation was 7.7 years; the mean duration of follow-up was 3.5 years. As a group, these children with prior ADEM performed within the average range on cognitive testing. However, a variety of mild cognitive deficits were demonstrated in each of the children, even in those whose magnetic resonance imaging studies had completely normalized. Four children demonstrated a cognitive profile of relatively poorer visuospatial/visuomotor function. The cognitive deficits observed in these children are similar but less severe than those previously reported in adults and children with multiple sclerosis, which may reflect the monophasic nature of ADEM, compared with the chronic, recurrent demyelination characteristic of multiple sclerosis.

Ocular findings in lissencephaly

PURPOSE

To report our retrospective study of 20 cases with lissencephaly and describe ocular and visual abnormalities associated with this disorder.

METHODS

Patients with lissencephaly were identified and classified into classic (type I) or cobblestone (type 2) lissencephaly on the basis of a review of clinical records and neuroimaging studies. Only patients examined by an ophthalmologist were included in the study.

RESULTS

Only 1 patient had a normal ocular examination. Ocular abnormalities included optic nerve hypoplasia and atrophy, retinal dysplasia, retinal nonattachment, macular hypoplasia, anterior segment malformation, and strabismus.

CONCLUSIONS

Ocular abnormalities in classic (type 1) lissencephaly are less severe. Central, steady, and maintained fixation may be present despite the presence of optic nerve hypoplasia, optic atrophy, macular hypoplasia, strabismus, or refractive errors. Retinal and anterior segment abnormalities were observed only in cobblestone (type 2) lissencephaly. These patients often have severe visual impairment because of retinal or cortical disease.

Disorders of cortical formation: radiologic-pathologic correlation

The advent of newer imaging techniques, such as high-resolution MR imaging and surface reconstructions of three-dimensional data sets, has led to a greater in vivo understanding of cortical malformations of the brain. Disorders of cortical formation are illustrated with routine imaging, surface reconstruction, and pathogenic specimens.

Pediatric tumefactive demyelination: case series and review of the literature

Tumefactive demyelinating lesions may be misdiagnosed as brain neoplasms or abscesses. In this paper, we present four cases of pediatric tumefactive demyelination. Twelve cases of pediatric tumefactive demyelination previously reported in the English literature are also summarized. We describe the neuroimaging characteristics and clinical presentation of tumefactive demyelination and how these features may be used in differentiating demyelination from other mass lesions.

Cyclosporine A neurotoxicity in a patient with idiopathic renal magnesium wasting

We report a female child who had idiopathic renal magnesium wasting secondary to suspected Gitleman syndrome and cyclosporine A neurotoxicity after a heart transplant. The child had acute, progressive encephalopathy, intractable seizures, quadriparesis, and extensive, bilateral cortical involvement on neuroimaging. Two days after discontinuation of the cyclosporine, the child's condition improved dramatically, including an improved level of consciousness, and she became seizure free. By 6 weeks, she was fully ambulatory. Follow-up magnetic resonance imaging and electroencephalograms demonstrated significant improvement. This patient had drug-induced neurotoxicity, exacerbated by hypomagnesemia. Cyclosporine should be used cautiously in transplant patients with Gitelman syndrome or other acquired magnesium homeostasis disorders because of the possible increased risk of neurotoxicity. This report is the first case of a patient with both cyclosporine neurotoxicity and magnesium-wasting nephropathy.

Disorders of cortical formation: radiologic-pathologic correlation

The advent of newer imaging techniques, such as high resolution MR imaging and surface reconstructions of 3-dimensional data sets, has led to a greater in-vivo understanding of cortical malformations of the brain. The disorders of cortical formation are illustrated with routine imaging, surface reconstruction, and pathologic specimens.

Schimke immunoosseous dysplasia complicated by moyamoya phenomenon

Schimke immunoosseous dysplasia (SID) is an autosomal recessive spondyloepiphyseal dysplasia that was first described by Schimke et al. [1971: Lancet 2:1088-1089]. It is associated with premature arteriosclerosis and cerebral ischemia; however, the cerebral vascular abnormalities causing ischemia have not been described [Spranger et al., 1991: J Pediatr 119:64-72; Ehrich et al., 1995: Clin Nephrol 43:89-95]. Based on magnetic resonance angiography (MRA) and magnetic resonance venography (MRV), we now report on 2 girls with SID who have cerebral ischemia associated with moyamoya phenomenon. In addition, one patient also has an absent or occluded left transverse sinus and diffuse aortic narrowing. This is the first characterization of the cerebral vascular abnormality found in SID and raises the possibility that cerebral moyamoya may represent another major manifestation of the underlying genetic defect in SID.

MRI findings in macrocephaly-cutis marmorata telangiectatica congenita

We describe a child with macrocephaly-cutis marmorata telangiectatica congenita (M-CMTC), cherry red macules, megalencephaly with hemifacial and segmental overgrowth, macrosomia, and cutis marmorata telangiectasia congenita of the trunk, and visceral and subcutaneous cavernous hemangiomas. The megalencephaly is accompanied by MRI findings of CNS dysgenesis with protrusion of the cerebellar tonsils through the foramen magnum (Chiari I), lumbar syrinx, and hydrops of the optic nerves. The report of this additional patient further confirms the newly described macrocephaly-cutis marmorata telangiectatica congenita as a distinct clinical phenotype.

Central nervous system malformations in ethylmalonic encephalopathy

Central nervous system malformations have been reported in a number of inherited enzyme defects. Ethylmalonic encephalopathy, an organic aciduria of unknown pathogenesis, has not been reported previously in association with brain or spinal cord malformations. We report on 2 sibs with confirmed ethylmalonic encephalopathy and malformations of the central nervous system; one with tethered cord, the other with cerebellar tonsillar ectopia (Chiari I malformation).

Recurrent seizures in metachromatic leukodystrophy

The unusual presentation of juvenile onset metachromatic leukodystrophy (MLD) and frequent complex partial seizures in a patient led us to perform a retrospective study of 18 patients with MLD to identify the prevalence and type of recurrent seizures during the first 2 years of the disease. Five of 17 patients (29%) had developed recurrent seizures within 12 months of the onset of symptoms, and one patient was lost to follow-up. By 24 months after onset of symptoms, 5 patients were lost to follow-up, and 6 of the remaining 13 patients (46%) had developed recurrent seizures. In all, 7 patients, 4 with late infantile-onset and 3 with juvenile-onset disease, developed recurrent seizures. Four patients, including 3 with juvenile-onset disease had complex partial seizures. We conclude that recurrent seizures are common in MLD and may occur at any stage of the disease, particularly in patients with juvenile onset. Generalized seizures are more frequent in patients with late infantile-onset, whereas partial seizures are more common in those with juvenile-onset disease.

Immunoablation does not delay the neurologic progression of X-linked adrenoleukodystrophy

We report the results of a near total myeloablation in preparation for bone marrow transplantation in a boy with minimal symptoms of X-linked adrenoleukodystrophy. Severe cerebral X-linked adrenoleukodystrophy developed in the patient after failure of bone marrow transplantation. This experience suggests that immunotherapy alone is not responsible for the improvement observed in some patients with X-ALD after BMT.

Long-term survival of an infant with 'anaplastic' astrocytoma

Anaplastic astrocytomas are intermediate in differentiation between astrocytoma and glioblastoma multiforme. Survival with anaplastic astrocytoma is favorably affected by extensive anaplasia, maximal resection and presentation in early life. We report a 2-month-old infant who had a tumor of astrocytic lineage with anaplastic features of necrosis, nuclear atypia and mitotic activity. Following subtotal resection the child is alive but has a radiologically visible tumor.

Spinal subdural enhancement after suboccipital craniectomy

PURPOSE

To characterize transient intraspinal subdural enhancement (potentially mimicking the subarachnoid spread of tumor) seen on MR images in some children after suboccipital craniectomy for posterior fossa tumor resection.

METHODS

Radiologic and medical records of 10 consecutive children who had MR imaging for spinal staging after resection of posterior fossa tumor during a 9-month period were reviewed retrospectively. In addition, one case with similar findings of intraspinal enhancement on spinal staging MR images obtained at another institution was included in the review.

RESULTS

Intraspinal enhancement thought to be subdural was seen in four of 10 patients undergoing spinal staging MR imaging 6 to 12 days after surgery. In these four patients, MR studies 50 to 18 days later, without intervening treatment, showed resolution of the abnormal enhancement. A fifth patient (from another institution) with similar intraspinal enhancement underwent CT myelography 4 days later, which showed no subarachnoid lesions. No metastases have developed in any of these five patients during the 2.5- to 3.5-year follow-up period. conclusions: From analysis of the MR appearance and on the basis of prior myelographic experience, we suggest an extraarachnoid, probably subdural, location of this enhancement. Awareness of this phenomenon will reduce the rate of false-positive diagnoses of metastatic disease. Preoperative spinal staging should be considered for patients undergoing suboccipital craniectomy.

Neuroradiology of pediatric posterior fossa medulloblastoma

Medulloblastoma of the cerebellum is a common intracranial neoplasm in children and presents many faces in medical imaging. Characteristic or classic features, such as increased attenuation on unenhanced CT, midline location and well defined margins, are commonly present in childhood cases of posterior foassa medulloblastoma, although atypical imaging features are being noted more frequently with the increased dependence on MR as the diagnostic modality of choice. Carefully performed CT and MR both initially provide suitable geography and characteristics, but MR is superior in the detection of pre- or post-operative neoplastic spread elsewhere in the subarachnoid space. Accurate establishment of disease extent is essential in planning both surgical resection and adjuvant therapy.

Evolution of the neuroimaging changes in fucosidosis type II

We report on clinical and neuroradiological findings in two patients with fucosidosis type II; a 7-year-old Jordanian boy and a 3 1/2-year-old Anglo-Canadian girl. This rare, autosomal recessive disorder is caused by deficiency of lysosomal alpha-fucosidase and is manifested clinically by progressive mental and motor deterioration, coarse facies, growth retardation, recurrent infections, dysostosis multiplex, angiokeratoma corporis diffusum, visceromegaly and seizures. Cranial CT and magnetic resonance imaging showed density and signal abnormalities in the thalamus, globus pallidus and internal capsules bilaterally, as well as progressive CT density alterations in supratentorial white matter including the internal medullary laminae of the thalami and the internal capsules.

Neurologic manifestations of pediatric systemic lupus erythematosus

Central nervous system involvement is a common but rarely reviewed feature of pediatric systemic lupus erythematosus (SLE). We retrospectively reviewed the charts of 91 patients with pediatric SLE and using a standardized data abstraction form documented 40 patients with central nervous system (CNS-SLE) involvement. The mean age of onset of SLE was 13.3 years. In 19 patients the CNS manifestation was a presenting symptom, in 12 patients CNS involvement was present within the first year of diagnosis, and in 9 patients it took up to 7 years for CNS disease to become evident. Nineteen children (48%) manifested neuropsychiatric SLE, which included depression, concentration or memory problems, and frank psychosis. Seizures were present in 8 patients (20%), 6 had cerebral ischemic events (15%), 1 had chorea (3%), 2 had papilledema (5%), and 2 patients had a peripheral neuropathy (5%). Nine patients (22%) had severe headache consistent with lupus headache. Seven children had more than one CNS manifestation. In the investigation of CNS-SLE, computed tomography and/or magnetic resonance imaging scans were helpful in patients with focal ischemic lesions and venous sinus thrombosis. Electroencephalography was abnormal only in 33% of patients with seizure disorders and rarely helpful in patients with diffuse neuropsychiatric symptoms. Single-photon emission computed tomography scans were abnormal in most patients with neuropsychiatric SLE, especially in those with frank psychosis. The lupus anticoagulant was present in the patient with chorea and was frequently present in patients with cerebral vascular events. Long-term outcome was good: only 1 child died of cerebral hemorrhagic infarction and 3 others had significant persistent CNS deficits. The majority of patients (90%) had excellent recovery from CNS-SLE.

Eye problems in children with multiple sclerosis

In a retrospective review, the eye symptoms of 17 children (mean age: 13 1/2 years) who had definite multiple sclerosis (Poser's criteria) and 15 who had probable multiple sclerosis over the last 18 years were evaluated. Follow-up varied from 3 weeks to 6 years. Of 94% of children (16 of 17) with ophthalmologic symptoms, 47% (8 of 17) presented with an initial disturbance of vision. Twelve children had optic neuritis, 1 progressive uveitis, and 4 brainstem symptoms (i.e., VIth nerve palsy, 1 1/2 syndrome, internuclear ophthalmoplegia). Four children had cerebellar signs (nystagmus, saccadic pursuit). In 4 children, clinical localization was less specific. Recovery was generally good in most of the children; cerebellar problems were most persistent. Multimodal potentials were more helpful for investigation of optic neuritis and cerebellar lesions than for brainstem lesions. In the cohort of probable multiple sclerosis of 15 children, 11 had eye symptoms (5 with neuromyelitis optica, 4 optic neuritis, 1 internuclear ophthalmoplegia, and 1 cerebellar symptoms). Ophthalmologic symptoms are slightly more frequent in children with multiple sclerosis than in adults and should be specifically investigated to establish the diagnosis.

Neuroradiology of lysosomal disorders

The role of neuroimaging in the lysosomal disorders has previously been limited to the initial evaluation and diagnosis of these disease processes and to the detection of treatable disease-related complications, such as hydrocephalus. Localization of changes to the gray or the white matter was useful in guiding the metabolic evaluation when clinical findings were indeterminate or unclear. Imaging features such as dilated VR spaces in MPS storage disease or focal calcifications in Krabbe's disease were occasionally pathognomonic for or highly suggestive of a specific disorder. Now that treatment options, including enzyme replacement therapy and bone marrow transplantation, are available for some of the neurometabolic disorders, staging before the initiation of therapy and evaluation throughout therapy are additional important roles. Even in those disease processes that are currently untreatable, imaging is useful in defining the radiographic appearance of the natural course of a given disorder, to aid in staging and treatment evaluation of future patients with that same disorder when treatment becomes available.

Radiology of the developing central nervous system

Functional and anatomical imaging of the developing central nervous system continue to engender considerable interest. Structural anomalies have been further defined and catalogued, aiding in the diagnosis and genetic counseling of children with developmental delay. Anomalous development of the brain has recently been linked to certain neuropsychiatric disorders. The natural course of many of the metabolic brain disorders has now been chronicled with imaging studies, rendering standards on which to evaluate efficacy of treatment.

Aggressive surgical management of craniopharyngiomas in children

The cases of 50 patients with craniopharyngioma operated on at The Hospital for Sick Children in Toronto between January, 1975, and December, 1989, are reviewed. All patients were under 18 years of age (mean 9.39 years). Headaches, endocrine deficiencies, and visual deficits were the most common symptoms on admission. Forty-five patients underwent what was considered by the surgeon to be total excision of their tumor, and five had subtotal excision. Tumors recurred in 17 patients (mean time of recurrence 32.6 months after surgery). One patient died in the postoperative period and three have been lost to follow-up study. Of the remaining 46 patients, 28 are leading a normal or nearly normal life, although all are receiving endocrine replacement and some have required help to overcome mild deficits in memory or visual acuity. Twelve patients are able to function reasonably well and attend school despite being hampered by intellectual or visual deficits or problems with weight control; four have a significant handicap, and two have died.

Arteriopathy and coarctation of the abdominal aorta in children with mucopolysaccharidosis: imaging findings

Eight children with mucopolysaccharidosis I (MPS I), representing 33% of all children with MPS I seen at our institution during an 18-year period, developed hypertension. Five of these hypertensive children also exhibited symptoms of aortic coarctation. The radiographic evaluation of four of these children with MPS I (three with Hurler syndrome, MPS I H, and one with Scheie disease, MPS I S) and arteriopathy affecting the thoracic aorta, abdominal aorta, and visceral and renal arteries is presented. Hypertension developed in all four children before they were 4 years old; three had differences between upper- and lower-extremity blood pressures. Irregular narrowing of the abdominal aorta with either multiple minor asymmetric wall lesions (n = 2) or abrupt concentric narrowing (n = 2) was present in all children as shown by aortography (n = 3), sonography (n = 3), MR imaging (n = 2), and/or autopsy (n = 1). A variety of other vessels also were involved, including the ascending aorta (n = 1) and vertebral (n = 1), axillary (n = 1), intercostal (n = 2), lumbar (n = 2), mesenteric (n = 3), renal (n = 2), and iliac arteries (n = 3). Autopsy in one child demonstrated thickened heart valves, narrowing of the coronary arteries, and irregularity of the aorta due to deposition of mucopolysaccharide material within the intima. Our series demonstrates various facets of the arteriopathy of MPS I as shown by sonography, MR imaging, and angiography.