Thangamadhan Bosemani

Congenital Abnormalities of the Posterior Fossa

The frequency and importance of the evaluation of the posterior fossa have increased significantly over the past 20 years owing to advances in neuroimaging. Nowadays, conventional and advanced neuroimaging techniques allow detailed evaluation of the complex anatomic structures within the posterior fossa. A wide spectrum of congenital abnormalities has been demonstrated, including malformations (anomalies due to an alteration of the primary developmental program caused by a genetic defect) and disruptions (anomalies due to the breakdown of a structure that had a normal developmental potential). Familiarity with the spectrum of congenital posterior fossa anomalies and their well-defined diagnostic criteria is crucial for optimal therapy, an accurate prognosis, and correct genetic counseling. The authors discuss the spectrum of posterior fossa malformations and disruptions, with emphasis on neuroimaging findings (including diagnostic criteria), neurologic presentation, systemic involvement, prognosis, and risk of recurrence.

Susceptibility-Weighted Imaging in Pediatric Neuroimaging

Susceptibility‐weighted imaging (SWI) has become a key MR sequence in pediatric neuroimaging. The usage of SWI has significantly expanded recently. The strength of SWI lies not just in its ability to identify hemorrhage, calcium or nonheme iron by virtue of its susceptibility artifact, but also more importantly, the blood oxygen level dependent venography principle whereby several diseases can be diagnosed earlier. We are continuing to harness the power of SWI in the field of pediatric neuroimaging. In this paper, we will make a comprehensive review and discuss the utility of SWI in pediatric neuroimaging in establishing the diagnosis, differential diagnosis, and also understanding the pathomechanism of various pediatric brain pathologies. J. Magn. Reson. Imaging 2014;40:530–544.

Pediatric hemiplegic migraine: Role of multiple MRI techniques in evaluation of reversible hypoperfusion

Background Hemiplegic migraine (HM) is a rare type of migraine with aura that involves motor weakness. Data on conventional and advanced neuroimaging findings during prolonged attacks of HM are limited, particularly in children. Case A 13-year-old-female with a history of migraine had a typical attack of HM characterized by right-sided hemiplegia, deterioration of vigilance and paraphasia. MRI performed 3 hours after hemiplegia onset revealed normal diffusion tensor imaging (DTI) sequences, but perfusion weighted imaging (PWI) showed a large area of hypoperfusion within the left cerebral hemisphere and susceptibility weighted imaging (SWI) demonstrated a matching area with prominent, hypointense draining sulcal veins. Magnetic resonance angiography (MRA) revealed subtle narrowing of the left middle cerebral artery. The neuroimaging abnormalities completely resolved 24 hours after the attack onset. Conclusion Multiple conventional and advanced MRI techniques including SWI play a key role in an HM attack to (1) exclude acute arterial ischemic stroke and (2) further understand the pathophysiology of HM.

Pediatric skull fracture diagnosis: should 3D CT reconstructions be added as routine imaging?

OBJECT The authors compared the efficacy of combining 2D+3D CT reconstructions with standard 2D CT images in the diagnosis of linear skull fractures in children with head trauma. METHODS This was a retrospective evaluation of consecutive head CT studies of children presenting with head trauma. Two experienced pediatric neuroradiologists in consensus created the standard of reference. Three readers independently evaluated the 2D CT images alone and then in combination with the 3D reconstructions for the diagnosis of linear skull fractures. Sensitivity and specificity in the diagnosis of linear skull fractures utilizing 2D and 2D+3D CT in combination were measured for children less than 2 years of age and for all children for analysis by the 3 readers. RESULTS Included in the study were 250 consecutive CT studies of 250 patients (167 boys and 83 girls). The mean age of the children was 7.82 years (range 4 days to 17.4 years). 2D+3D CT combined had a higher sensitivity and specificity (83.9% and 97.1%, respectively) compared with 2D alone (78.2% and 92.8%, respectively) with statistical significance for specificity (p < 0.05) in children less than 2 years of age. 2D+3D CT combined had a higher sensitivity and specificity (81.3% and 90.5%, respectively) compared with 2D alone (74.5% and 89.1%, respectively) with statistical significance for sensitivity (p < 0.05) in all children. CONCLUSIONS In this study, 2D+3D CT in combination showed increased sensitivity in the diagnosis of linear skull fractures in all children and increased specificity in children less than 2 years of age. In children less than 2 years of age, added confidence in the interpretation of fractures by distinguishing them from sutures may have a significant implication in the setting of nonaccidental trauma. Furthermore, 3D CT is available at no added cost, scan time, or radiation exposure, providing trainees and clinicians with limited experience an additional valuable tool for routine imaging of pediatric head trauma.

Susceptibility-Weighted Imaging in Pediatric Arterial Ischemic Stroke: A Valuable Alternative for the Noninvasive Evaluation of Altered Cerebral Hemodynamics

Based on imaging findings in 24 pediatric patients,the authors conclude that SWI-DTI mismatch predicts progression in pediatric arterial ischemic stroke. SWI-hyperintense signal is not useful for predicting the development of malignant edemabut SWI should be routinely added to the neuroimaging diagnostic protocol of pediatric arterial ischemic stroke. BACKGROUND AND PURPOSE: SWI provides information about blood oxygenation levels in intracranial vessels. Prior reports have shown that SWI focusing on venous drainage can provide noninvasive information about the degree of brain perfusion in pediatric arterial ischemic stroke. We aimed to evaluate the influence of the SWI venous signal pattern in predicting stroke evolution and the development of malignant edema in a large cohort of children with arterial ischemic stroke. MATERIALS AND METHODS: A semiquantitative analysis of venous signal intensity on SWI and diffusion characteristics on DTI was performed in 16 vascular territories. The mismatch between areas with SWI-hypointense venous signal and restricted diffusion was correlated with stroke progression on follow-up. SWI-hyperintense signal was correlated with the development of malignant edema. RESULTS: We included 24 children with a confirmed diagnosis of pediatric arterial ischemic stroke. Follow-up images were available for 14/24 children. MCA stroke progression on follow-up was observed in 5/6 children, with 2/8 children without mismatch between areas of initial SWI hypointense venous signal and areas of restricted diffusion on DTI. This mismatch showed a statistically significant association (P = .03) for infarct progression. Postischemic malignant edema developed in 2/10 children with and 0/14 children without SWI-hyperintense venous signal on initial SWI (P = .07). CONCLUSIONS: SWI-DTI mismatch predicts stroke progression in pediatric arterial ischemic stroke. SWI-hyperintense signal is not useful for predicting the development of malignant edema. SWI should be routinely added to the neuroimaging diagnostic protocol of pediatric arterial ischemic stroke.

Genotype–Phenotype Correlation of Congenital Anomalies in Multiple Congenital Anomalies Hypotonia Seizures Syndrome (MCAHS1)/ PIGN-Related Epilepsy

Mutations in PIGN, resulting in multiple congenital anomalies‐hypotonia‐seizures syndrome, a glycosylphosphatidylinositol anchor deficiency, have been published in four families to date. We report four patients from three unrelated families with epilepsy and hypotonia in whom whole exome sequencing yielded compound heterozygous variants in PIGN. As with previous reports Patients 1 and 2 (full siblings) have severe global developmental delay, gastroesophageal reflux disease, and minor dysmorphic features, including high palate, bitemporal narrowing, depressed nasal bridge, and micrognathia; Patient 3 had early global developmental delay with later progressive spastic quadriparesis, intellectual disability, and intractable generalized epilepsy; Patient 4 had bilateral narrowing as well but differed by the presence of hypertelorism, markedly narrow palpebral fissures, and long philtrum, had small distal phalanges of fingers 2, 3, and 4, absent distal phalanx of finger 5 and similar toe anomalies, underdeveloped nails, unusual brain anomalies, and a more severe early clinical course. These patients expand the known clinical spectrum of the disease. The severity of the presentations in conjunction with the patients’ mutations suggest a genotype–phenotype correlation in which congenital anomalies are only seen in patients with biallelic loss‐of‐function. In addition, PIGN mutations appear to be panethnic and may be an underappreciated cause of epilepsy.

Pitfalls in Susceptibility‐Weighted Imaging of the Pediatric Brain

Susceptibility‐weighted imaging (SWI) is a recently developed high resolution 3‐dimensional gradient‐echo pulse sequence that accentuates the magnetic susceptibility of blood, calcium, and nonheme iron. The clinical applications of SWI in pediatric neuroimaging have significantly expanded recently. Potential pitfalls related to blood oxygenation, blood flow, magnetic field strength, and misinterpretation of localization as well as possible mimickers may be misleading and affect the correct interpretation of SWI images. Familiarity with these potential diagnostic pitfalls is important to prevent misdiagnosis and will further enhance the ability of SWI in becoming a robust and reliable technique.

Christianson syndrome: spectrum of neuroimaging findings.

Christianson syndrome (CS) is caused by mutations in SLC9A6 and is characterized by severe intellectual disability, absent speech, microcephaly, ataxia, seizures, and behavioral abnormalities. The clinical phenotypes of CS and Angelman syndrome (AS) are similar. Differentiation between CS and AS is important in terms of genetic counseling. We report on two children with CS and confirmed mutations in SLC9A6 focusing on neuroimaging findings and review the available literature. Cerebellar atrophy (CA) occurs in approximately 60% of the patients with CS and develops after the age of 12 months. Hyperintense signal of the cerebellar cortex (CbC) is less common, and may be diffuse, patchy, or involve only the inferior part of the cerebellum and is best seen on coronal fluid attenuation inversion recovery images. CA and CbC-hyperintensity are not neuroimaging features of AS. In a child with the phenotype of AS, CA and/or CbC-hyperintensity are rather specific for CS and should prioritize sequencing of SLC9A6.

Diffusion Tensor Imaging Detects Occult Cerebellar Injury in Severe Neonatal Hypoxic-Ischemic Encephalopathy

Background: Despite the benefits of whole-body hypothermia therapy, many infants with hypoxic-ischemic encephalopathy (HIE) die or have significant long-term neurodevelopmental impairment. Prospectively identifying neonates at risk of poor outcome is essential but not straightforward. The cerebellum is not classically considered to be a brain region vulnerable to hypoxic-ischemic insults; recent literature suggests, however, that the cerebellum may be involved in neonatal HIE. In this study, we aimed to assess the microstructural integrity of cerebellar and linked supratentorial structures in neonates with HIE compared to neurologically healthy neonatal controls. Methods: In this prospective cohort study, we performed a quantitative diffusion tensor imaging (DTI) analysis of the structural pathways of connectivity, which may be affected in neonatal cerebellar injury by measuring fractional anisotropy (FA) and mean diffusivity (MD) within the superior, middle, and inferior cerebellar peduncles, dentate nuclei, and thalami. All magnetic resonance imaging (MRI) studies were grouped into 4 categories of severity based on a qualitative evaluation of conventional and advanced MRI sequences. Multivariable linear regression analysis of cerebellar scalars of patients and controls was performed, controlling for gestational age, age at the time of MRI, and HIE severity. Spearman rank correlation was performed to correlate DTI scalars of the cerebellum and thalami. Results: Fifty-seven (23 females, 40%) neonates with HIE and 12 (6 females, 50%) neonatal controls were included. There were 8 patients (14%) in HIE severity groups 3 and 4 (injury of the basal ganglia/thalamus and/or cortex). Based on a qualitative analysis of conventional and DTI images, no patients had evidence of cerebellar injury. No significant differences between patients and controls were found in the FA and MD scalars. However, FA values of the middle cerebellar peduncles (0.294 vs. 0.380, p < 0.001) and MD values of the superior cerebellar peduncles (0.920 vs. 1.007 × 10-3 mm/s2, p = 0.001) were significantly lower in patients with evidence of moderate or severe injury on MRI (categories 3 and 4) than in controls. In patients, cerebellar DTI scalars correlated positively with DTI scalars within the thalami. Conclusion: Our results suggest that infants with moderate-to-severe HIE may have occult injury of cerebellar white-matter tracts, which is not detectable by the qualitative analysis of neuroimaging data alone. Cerebellar DTI scalars correlate with thalamic measures, highlighting that cerebellar injury is unlikely to occur in isolation and may reflect the severity of HIE. The impact of concomitant cerebellar injury in HIE on long-term neurodevelopmental outcome warrants further study.

Pediatric spinal trauma.

Pediatric spinal trauma is unique. The developing pediatric spinal column and spinal cord deal with direct impact and indirect acceleration/deceleration or shear forces very different compared to adult patients. In addition children are exposed to different kind of traumas. Moreover, each age group has its unique patterns of injury. Familiarity with the normal developing spinal anatomy and kind of traumas is essential to correctly diagnose injury. Various imaging modalities can be used. Ultrasound is limited to the neonatal time period; plain radiography and computer tomography are typically used in the acute work‐up and give highly detailed information about the osseous lesions. Magnetic resonance imaging is more sensitive for disco‐ligamentous and spinal cord injuries. Depending on the clinical presentation and timing of trauma the various imaging modalities will be employed. In the current review article, a summary of the epidemiology and distribution of posttraumatic lesions is discussed in the context of the normal anatomical variations due to progressing development of the child.