1 Answer C. The neonatal head ultrasound images demonstrate an echogenic midline mass superior to the third ventricle. There is dilation of the lateral ventricles, colpocephaly, and absence of the corpus callosum. Agenesis of the corpus callosum (ACC) is the most common developmental abnormality, resulting from failure of commissuration and can occur for a number of reasons including genetic, metabolic, or vascular abnormalities, but in most cases, the cause is not found. The term “ACC” implies that the entire structure has failed to form, but in other fetuses, the corpus callosum may fail to form in part leading to the term “hypoplasia of the corpus callosum.” In the context of the detection of antenatal malformations, ACC is much more common than hypoplasia of the corpus callosum.

Imaging findings often include ventriculomegaly, colpocephaly (dilation of the trigones and occipital horns), and absent cavum septum pellucidum. In the sagittal plane, there is a radial, spoke-wheel, or sunray appearance of the gyri from the expected location of the corpus callosum. The echogenic midline mass in this case is consistent with an interhemispheric lipoma. Fifty percent of lipomas are associated with ACC. References: Barkovich AJ, et al. Congenital malformations of the brain and skull. In: Barkovich AJ, Raybaud C (eds). Pediatric neuroimaging, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2012:367-568.

Craven I, Bradburn MJ, Griffiths PD. Antenatal diagnosis of agenesis of the corpus callosum. Clin Radiol 2015;70(3):248-253.

2 Answer D. Brain MRI images demonstrate right open lip schizencephaly with a cleft of CSF extending from the pial margin of the right frontoparietal lobe to the ependymal margin of the right lateral ventricle. This schizencephaly cleft is lined by polymicrogyria. Schizencephaly is a rare cortical malformation that manifests as a gray matter-lined cleft extending from the ependyma to the pia mater. This malformation is thought to be a result of an acquired in utero insult affecting the germinal zone prior to neuronal migration.

There are two types of schizencephaly: type 1 or open lip and type 2 or closed lip. Closed-lip MRI findings include irregular tract of gray matter extending from cortical surface to ventricle. The gray matter lining can appear dysplastic (lumpy/bumpy on margin of cleft or at gray-white interface). Open lip can appear wide and wedge shaped or with nearly parallel walls. The gray matter lining cleft may be harder to discern than in closed lip. The most common signs/symptoms include seizures (more common with unilateral clefts), mild motor deficit (“congenital” hemiparesis), developmental delay, paresis, microcephaly, and spasticity.

Schizencephaly is frequently associated with other cerebral anomalies including:

References: Barkovich AJ, Kjos BO. Schizencephaly: correlation of clinical findings with MR characteristics. Am J Neuroradiol 1992;13(1):85-94.

Nabavizadeh SA, Zarnow D, Bilaniuk LT, Schwartz ES, Zimmerman RA, Vossough A. Correlation of prenatal and postnatal MRI findings in schizencephaly. Am J Neuroradiol 2014;35(7):1418-1424. doi:10.3174/ajnr.A3872.

3 Answer A. Head ultrasound and brain MRI demonstrate a monoventricle, large dorsal cyst, fused thalami, and fused anterior cerebral mantle. Alobar holoprosencephaly is the most severe form of holoprosencephaly and consists of complete lack of separation of the cerebral hemispheres with a large posterior monoventricle. Single midline structures such as the falx, interhemispheric fissure, septum pellucidum, and corpus callosum are absent, whereas paired midline structures are fused, including the thalami and basal ganglia. Affected patients suffer from dysmorphic facies, microcephaly, seizures, and developmental delay.

Diagram of three morphologic types of alobar holoprosencephaly (and semilobar holoprosencephaly) in sagittal view. Pancake type: The flattened residual brain mantle at the base of the brain with a correspondingly large dorsal sac. Cup type: This type has more brain mantle but it does not cover the monoventricle. The dorsal sac communicates widely with the monoventricle. Ball type: Brain mantle completely covers the monoventricle, and a dorsal sac may or may not be present. Th, thalami; V, ventricle. (Modified from McGahn JP, Ellis W, Lindfors KK, et al. Congenital cerebrospinal fluid-containing intracranial abnormalities: sonographic classification. J Clin Ultrasound. 1988;16:531-544.)

Holoprosencephaly is a spectrum of congenital abnormalities characterized by incomplete separation of the cerebral hemispheres. Abnormalities range from incomplete formation of the falx cerebri and interhemispheric fissure to a complete lack of separation of the cerebral hemispheres with a large monoventricle. There are three types which include alobar, semilobar, and lobar (septo-optic dysplasia).

Midline facial abnormalities in the setting of alobar holoprosencephaly include:

Facial malformations of any kind should trigger very careful evaluation of brain. “The face predicts the brain.”

References: Barkovich AJ. Congenital malformations of the brain and skull. In: Barkovich AJ (ed). Pediatric neuroimaging, 4th ed. Philadelphia, PA: Lippincott

Williams & Wilkins, 2005:291-439. Winter TC. Diagnostic imaging: obstetrics, 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2011:1-2.

4 Answer D. On CT, there is a mildly hypodense nonenhancing sellar and suprasellar lesion. The sellar component of this mass has associated calcification. MRI demonstrates a T1/T2 hyperintense cystic-appearing sellar and suprasellar mass with peripheral enhancement. There is GRE hypointensity within the sellar component. The lesion causes deformity and displacement upon the optic apparatus. Craniopharyngioma is the most common suprasellar mass in children. Craniopharyngiomas arise from the metaplastic squamous epithelial rests along the hypophysis. They are more common in males. The vast majority arise within the suprasellar cistern; however, they may arise within the sella turcica and occasionally the third ventricle. There is a bimodal age distribution with children between the ages of 5 and 10 exhibiting the adamantinomatous type and second peak in the fifth and sixth decade. Clinical presentation includes visual disturbances related to compression of the optic chiasm, pituitary hypofunction related to compression of the gland or hypothalamus, and/or symptoms of increased intracranial pressure.

Imaging findings typically include a cystic or solid and cyst mass. Approximately 80% to 90% of all craniopharyngiomas have a cystic component. Smaller lesions may be purely solid. The vast majority have calcification and enhance after administration of IV contrast. Rim enhancement may be seen around the cystic portions of these tumors, and the solid portions typically demonstrate more avid, solid enhancement. The cystic component is frequently hyperintense on T2 and may be hypointense, isointense, or hyperintense on T1.

Reference: Sartoretti-Schefer S, et al. MR differentiation of adamantinous and squamous-papillary craniopharyngioma. Am J Neuroradiol 1997;18:77-87.

5 Answer B. There is a nonenhancing mass associated with the tuber cinereum. The pituitary stalk and posterior pituitary bright spot are present. This case illustrates the characteristic appearance of a hamartoma of the tuber cinereum. The mass is isointense to gray matter on T1 imaging and sits just anterior to the mammary bodies at the level of the floor of the third ventricle.

Hamartomas are benign nonneoplastic lesions that are likely congenital in origin. Many are symptomatic, but symptoms may be more common in children and typically include gelastic seizures, “fits of laughter,” and precocious puberty. Knowledge of this lesion and its radiologic and clinical presentations usually allows the diagnosis to be established in most cases. Atypical imaging findings including marked hyperintensity on T2 or lesion larger than 1.5 cm raise the possibility of hypothalamic glioma.

Reference: Boyko OB, et al. Hamartomas of the tuber cinereum: CT, MR and pathologic findings. AJNR Am J Neuroradiol 1991;12:309-314.

6a Answer A.

6b Answer B. MR imaging demonstrates a lobulated mixed cystic and solid enhancing pineal region mass, isointense to gray matter on T2 and T1 images, and containing several small internal foci of GRE hypointensity. There is extension to the left splenium of the corpus callosum and possible involvement of the midbrain. There is associated expansion of the third and lateral ventricles as well as periventricular T2 hyperintensity, consistent with moderate hydrocephalus. There is mild downward displacement of the cerebellar tonsils.

Tumors of pineal cell origin (pineoblastoma and pineocytoma) comprise only 15% of pineal region masses. Unlike germ cell tumors, which show a marked predilection in males, tumors of pineal cell origin occur equally among men and woman. Tumors of pineal origin frequently calcify. Calcification of the pineal gland in a child under 7 years of age should raise suspicion of tumor. After 7 years of age, the pineal gland begins to show calcification, which increases with age. Parinaud syndrome is a cluster of abnormalities of eye movement and pupil dysfunction with paralysis of upward gaze (downward gaze is usually preserved). This syndrome is associated with young patients with brain tumors in the pineal gland or midbrain.

MRI is most useful in characterizing masses in the pineal region. Tumors arising in the parapineal region in a child are usually gliomas arising from the tectal plate, whereas tumor arising in the parapineal region in adults may represent gliomas or meningiomas arising from the tentorium. Tumors of germ cell origin occur in children as do pineoblastomas, whereas pineocytomas are generally seen in adults.

Reference: Smirniotopoulos JG, et al. Pineal region masses: differential diagnosis. Radiographics 1992;12:577-596.

7 Answer B. On MRI, there is a large, round right cerebellar mass with T2 hyperintensity, internal mural nodules, and peripheral contrast enhancement. There is mass effect on the fourth ventricle and left midline shift. Astrocytomas are the most common brain tumors of childhood with 60% occurring in the posterior fossa (40% in the cerebellum, 20% in the brain stem). Most of them are juvenile pilocytic astrocytomas (JPA), which are WHO grade 1 benign tumors. Differential diagnosis of cystic cerebellar masses includes hemangioblastomas, which have similar appearance to JPA. These are more common in young adults and children and are usually part of von Hippel-Lindau disease. Medulloblastoma and ependymomas usually have a shorter clinical history. They are typically centered on the fourth ventricle, isodense or hyperdense on nonenhanced CT, and characteristically not cystic. However, purely solid JPAs do occur.

As a rule, JPAs arise from the midline and can extend into the cerebellar hemispheres. Most are large at presentation (>5 cm). The tumor usually consists of a cyst with a solid nodule within the cyst wall. The cyst is most typically adjacent to the tumor (no peripheral enhancement), but in 40%, it may develop within it as a cyst-like necrotic center (peripheral enhancement). The frequency of JPA is equal in boys and girls usually occurring between birth and 9 years of age. The symptoms (headaches, early morning vomiting, ataxia) develop gradually over several months to become persistent and acute.

References: Campbell JW, Pollack IF. Cerebellar astrocytomas in children. J Neurooncol 1996;28:223-231.

Rashidi M, DaSilva VR, Minagar A, Rutka JT. Nonmalignant pediatric brain tumors. Curr Neurol Neurosci Rep 2003;3:200-205.

8a Answer B.

8b Answer A. On CT, there is a heterogeneous soft tissue mass centered at the fourth ventricle with foci of internal calcification. There is lateral and third ventriculomegaly. On MRI, there is an enhancing mass within the posterior fossa in the midline. The mass has restricted diffusion indicating that the mass is densely cellular. There is also GRE susceptibility, which indicates a component of hemorrhage or mineralization. There is extension of the mass out the left foramen of Luschka. There is mass effect on the fourth ventricle causing enlargement of the lateral ventricles. There is also periventricular edema. The major differential diagnostic consideration of a midline posterior fossa mass in children is a fourth ventricular ependymoma. These typically expand rather than compress the fourth ventricle. Less commonly, cerebellar astrocytomas may occur in the midline; however, they are typically hemispheric lesions.

Medulloblastoma comprise up to one-third of all pediatric posterior fossa tumors. They occur more commonly in boys and arise from the medullary velum of the fourth ventricle from primitive neuroectoderm. In children, they are typically midline masses associated with the inferior vermis. Subarachnoid seeding of the leptomeninges is very common at presentation; therefore, screening of the spine is recommended to exclude spread. On unenhanced CT, medulloblastomas are typically hyperdense relative to brain parenchyma because of their dense cellularity. Calcification, cystic change and/or hemorrhage may be present in up to 10% to 20% of lesions. On MRI, most medulloblastomas are mildly hypointense to brain parenchyma on T1 and vary in signal intensity on T2 images. These masses avidly enhance after contrast administration. As CSF seeding is common at presentation, imaging with contrast of the whole neuraxis is recommended to identify drop metastases and leptomeningeal spread. Although rare, extraneural spread is reported. Treatment typically consists of surgical resection, radiation therapy, and chemotherapy, with the prognosis strongly influenced by surgical resection, presence of CSF metastases at the time of diagnosis, and expression of the c-erbB-2 (HER2/neu) oncogene.

Reference: Nueller DP, Moore SA, Sato Y, Yuh WTC. MR spectrum of medulloblastoma. Clin Imaging 1992;16:250-255.

9 Answer C. Fetal MRI demonstrates bilateral ventriculomegaly. The septum pellucidum is absent. There is a small and upward tilted vermis and large posterior fossa CSF intensity space, which is continuous with the fourth ventricle. Postnatal MRI demonstrates marked lateral ventriculomegaly with moderate third ventricular enlargement and a large posterior fossa cyst. There is partial agenesis of the cerebellar vermis with upward tilted vermian remnant. There are bilateral small cerebellar hemispheres.

The Dandy-Walker complex (which includes Dandy-Walker malformation [DWM] and its variants) is a congenital anomaly believed to be related to an in utero insult to the fourth ventricle leading to complete or partial outflow obstruction of CSF. As a result, there is cyst-like dilation of the fourth ventricle, which protrudes up between the cerebellar hemispheres to prevent their fusion, and there is incomplete formation of all or part of the inferior vermis. DWMs are associated with hydrocephalus in 75% of cases. In addition, a significant number of patients are associated with supratentorial anomalies including dysgenesis of the corpus callosum, migrational anomalies, and encephaloceles. The radiologic hallmark of DWM is communication of a retrocerebellar cyst with the fourth ventricle.

Reference: Barkovich AJ, Kjos BO, Norman D, Edwards MS. Revised classification of posterior fossa cysts and cyst-like malformations based on the results of multiplanar MR imaging. AJR Am J Roentgenol 1989;153:1289-1300.

10 Answer D. MRI demonstrates a hypoplastic superior cerebellar vermis and dysplastic inferior cerebellar vermis. There is a dysmorphic fourth ventricle, which has “batwing” appearance. There is a hypoplastic cerebellar vermis with hypoplasia of the superior cerebellar peduncle resembling the “molar tooth sign” in the midbrain. There is an elongated and thinned superior cerebellar peduncle and interpeduncular fossa. The size of the brainstem is smaller than the normal appearance. There is a retrocerebellar mega cisterna magna with supracerebellar extension. There is partial agenesis of the septum pellucidum.

Joubert syndrome (JS) is a very rare, autosomal recessive condition. It is characterized by agenesis of cerebellar vermis, abnormal eye movements with nystagmus, episodes of hyperpnea and apnea, delayed generalized motor development, retinal coloboma and dystrophy, and, sometimes, multicystic kidney disease. A spectrum of cerebellar developmental anomalies are categorized into compete or incomplete cerebellar agenesis, medial aplasia/hypoplasia, and lateral aplasia/hypoplasia. These anomalies in cerebellar development may result in prominent CSF spaces or CSF collections/cystic dilation of the fourth ventricle (giant cisterna magna, Dandy-Walker malformations) in the posterior fossa. The predominant abnormality in Joubert syndrome is aplasia or hypoplasia of the vermis, particularly the superior portion. These patients have dysplastic cerebellar tissue including heterotopic and dysplastic cerebellar nuclei; abnormal development of the inferior olivary nuclei; and incomplete formation of the pyramidal decussation. It is an autosomal recessive disorder.

The characteristic appearance of Joubert syndrome includes:

Reference: Friede RL, Boltshauser E. Uncommon syndromes of cerebellar vermis aplasia. I: Joubert Syndrome. Dev Med Child Neurol 1978;20:758-763.

11 Answer D. There is an absent septum pellucidum and dysmorphic appearance of the lateral ventricles. The corpus callosum is present but is dysmorphic. Right cerebral gray matter-lined cleft extending to the right lateral ventricle, compatible with closed-lip schizencephaly. There is extensive polymicrogyria in the left parietal occipital lobe and right occipital, parietal, and temporal lobes. The cerebellar vermis appears small and dysplastic. The optic nerves and chiasm appear small.

Septo-optic dysplasia (SOD), also known as de Morsier syndrome, is a condition characterized by optic nerve hypoplasia and absence of septum pellucidum and, in two-thirds of patients, hypothalamic-pituitary dysfunction. It is best thought of as being part of the holoprosencephaly spectrum. Clinical presentation of septo-optic dysplasia is varied and mostly dependent of whether or not it is associated with schizencephaly (˜50% of cases). This association is used to define two forms of the condition:

MRI is the modality of choice for assessing septo-optic dysplasia. Imaging may demonstrate a “point down” appearance of the lateral ventricular frontal horns on coronal images, absent septum pellucidum, hypoplastic pituitary stalk, hypoplastic optic chiasm/optic nerves, and globes.

References: Barkovich AJ, Fram EK, Norman D. Septo-optic dysplasia: MR imaging. Radiology 1989;171(1):189-192.

Sener RN. Septo-optic dysplasia associated with cerebral cortical dysplasia (cortico-septo-optic dysplasia). J Neuroradiol 1996;23(4):245-247.

12a Answer B.

12b Answer A. There are multiple calcified subependymal nodules and cortical thickening in all lobes of the brain. There are enhancing tubers in the left frontal lobe. There are enhancing subependymal nodules at the right foramen of Monro. Tuberous sclerosis was classically described as presenting in childhood with a triad (Vogt triad) of:

Tuberous sclerosis has a significant number of manifestations, involving many organ systems. The most common manifestations are:

After the neurological manifestations of TS, renal manifestations are the second most common clinical feature; four types of lesions can occur: autosomal dominant polycystic kidney disease lesions, isolated renal cyst(s), angiomyolipomas (AMLs), and renal cell carcinomas.

Cortical/subcortical tubers are commonly located in the frontal lobe and demonstrate high T2 and low T1 with only 10% of tubers showing enhancement. The tubers frequently calcify after 2 years of age. The subependymal hamartomas are often associated with calcification. Lesion enhancement is variable and is not a useful feature in distinguishing them from subependymal giant cell astrocytomas (SEGA). Subependymal giant cell astrocytomas’ peak occurrence is 8 to 18 years of age and tends to be large and demonstrates growth. These lesions tend to have intense enhancement. The white matter abnormalities demonstrate variable appearance, with nodular, ill-defined, cystic and band-like lesions seen. One way to differentiate tuberous sclerosis from multiple sclerosis is that radial bands are thought to be relatively specific for tuberous sclerosis.

References: Goh S, Butler W, Thiele EA. Subependymal giant cell tumors in tuberous sclerosis complex. Neurology 2004;63(8):1457-1461.

Takanashi J, Sugita K, Fujii K, et al. MR evaluation of tuberous sclerosis: increased sensitivity with fluid-attenuated inversion recovery and relation to severity of seizures and mental retardation. AJNR Am J Neuroradiol 1995;16(9):1923-1928.

13 Answer C. Aqueductal stenosis. Head ultrasound demonstrates that the lateral ventricles are moderately enlarged and very little extra-axial fluid is seen. The fourth ventricle is decompressed. Brain MRI demonstrates moderate to marked ventriculomegaly with enlargement of the lateral and third ventricles. The fourth ventricle is normal in size. The cerebral aqueduct is incompletely visualized and appears narrow. Aqueductal stenosis (AS) is the most common cause of congenital obstructive hydrocephalus but can also be seen in adults as an acquired abnormality. Antenatal ultrasound can show features of fetal hydrocephalus with a near-normal posterior fossa. There can be secondary thinning of the cortical mantle as well as secondary macrocephaly. MRI demonstrates enlargement of the lateral and third ventricles. The aqueduct may show narrowing and funnelling superiorly. The fourth ventricle is classically not dilated. One must exclude causes of secondary obstruction such as aqueductal or tectal plate tumor. An MRI CSF flow study is helpful, and the absence of a flow void signal intensity on sagittal T2 images at the aqueductal level has been suggested as a sign of aqueductal stenosis.

References: Mcmillan JJ, Williams B. Aqueduct stenosis. Case review and discussion. J Neurol Neurosurg Psychiatr 1977;40(6):521-532. doi:10.1136/jnnp.40.6.521.

Stoquart-El Sankari S, Lehmann P, Gondry-Jouet C, et al. Phase-contrast MR imaging support for the diagnosis of aqueductal stenosis. AJNR Am J Neuroradiol 2009;30(1):209-214.

14 Answer A. MRI images demonstrate a mass in the caudal aspect of the fourth ventricle. This rounded mass has high T1 signal, isointense T2 signal, areas of low signal on GRE, and homogeneous enhancement. Differential consideration for a mass centered in the fourth ventricle include:

There are three types of choroid plexus tumor (CPT):

Classic imaging appearance of CPP is a child with enhancing lobulated (cauliflower-like) mass in atrium of lateral ventricle. CPPs occur in proportion to amount of choroid plexus. CPP is typically located in the following locations:

References: Jaiswal AK, Jaiswal S, Sahu RN, et al. Choroid plexus papilloma in children: diagnostic and surgical considerations. J Pediatr Neurosci 2009;4(1): 10-16.

Smith A, Smirniotopoulos J, Horkanyne-Szakaly I. From the radiologic pathology archives: intraventricular neoplasms: radiologic-pathologic correlation. Radiographics 2013;33(1):21-43.

15 Answer D. There is mid to posterior sagittal synostosis as well as synostosis of the right lambdoid suture resulting in some scaphocephaly and asymmetric posterior brachycephaly. There is also likely synostosis of the transverse occipital suture/synchondrosis between the occipital portion of the basiocciput and the squamosal occipital bone. Craniostenosis or craniosynostosis refers to premature closure of one or more of the cranial sutures. Isolated premature closure of the sagittal suture is most common. Unilateral or bilateral premature closure of the coronal suture is the next most common followed by premature of the metopic suture. Depending on which suture prematurely fuses, there are characteristic deformities of the skull and orbits. For example, premature closure of the sagittal suture results in limited transverse growth of the skull, namely, dolichocephaly or scaphocephaly, which is an increased anterior-posterior dimension. Plagiocephaly refers to premature closure of a single coronal or lambdoid suture. In the majority of cases, plagiocephaly is seen with closure of a single coronal suture, resulting in elevation of the lesser wing of the sphenoid bone leading to the “harlequin” appearance of the orbit.

Craniosynostosis is usually an isolated abnormality although it can be associated with a variety of syndromes. Such conditions include Apert syndrome, hypophosphatasia, Crouzon disease (craniofacial dysostosis), and Treacher Collins syndrome (mandibulofacial dysostosis).

Reference: Mafee MF, Valvassori GE. Radiology of the craniofacial anomalies. Otolaryngol Clin North Am 1981;14:939-988.

16 Answer B. There is a mass within and expanding the left midanterior nasal cavity. The mass is noted to extend superiorly to the level of the cribriform plate. This mass is hypointense on T1 and hyperintense on T2. There is no internal enhancement within the mass. Nasal encephaloceles are in most cases a form of neural tube defect particularly common in Southeast Asia. They are herniation of cranial content through a bony defect in the anterior skull base into the nasal area. Nasal encephaloceles usually present at birth with symptoms of obstruction or other complications. It presents as an external swelling on the nose. The swelling is usually soft, with normal overlying skin, and increases in size on coughing/straining. Symptomatic patients usually present with obstruction or rhinorrhea. Nasal encephaloceles are typically identified in association with a discernible cranial bone defect. Best imaging practices include multiplanar MRI to delineate soft tissues and intracranial relationships and bone CT to define osseous anatomy (except nasofrontal region in infants).

Reference: Tirumandas M, et al. Nasal encephaloceles: a review of etiology, pathophysiology, clinical presentations, diagnosis, treatment, and complications. Childs Nerv Syst 2013;29(5):739-744.

17 Answer B. There is an 11-mm-wide crescent-shaped hyperdense extra-axial hematoma overlying the left posterior convexity parietal region. Extradural hematoma (EDH), also known as an epidural hematoma, is a collection of blood that forms between the inner surface of the skull and outer layer of the dura, which is called the periosteal layer. They are commonly associated with a history of trauma and associated skull fracture. The source of bleeding is usually a torn meningeal artery (most commonly, the middle meningeal artery). EDHs are typically biconvex in shape and can cause a mass effect with herniation. They are usually limited by cranial sutures, but not by venous sinuses. Both CT and MRI are suitable to evaluate EDHs. When the blood clot is evacuated promptly (or treated conservatively when small), the prognosis of EDHs is generally good.

Reference: Irie F, Le Brocque R, Kenardy J, et al. Epidemiology of traumatic epidural hematoma in young age. J Trauma 2011;71(4):847-853.

18a Answer D.

18b Answer A. US demonstrates an anechoic, vascular structure at the level of the tentorium with mild mass effect on the right lateral ventricle. MRI and MRA demonstrate prominent galenic/transfalcine perimesencephalic vein with associated hypogenesis of the corpus callosum posteriorly. Vein of Galen aneurysmal malformations (VGAM), probably better termed as median prosencephalic arteriovenous fistula, are uncommon intracranial anomalies that tend to present dramatically during early childhood with features of a left-to-right shunt and high-output cardiac failure. These malformations account for <1% to 2% of all intracranial vascular malformations but are the cause of 30% of cerebral vascular malformations presenting in the pediatric age group. It is also the most common antenatally diagnosed intracranial vascular malformation. There may be an increased male predilection.

Angiography remains the gold standard in full characterization of the lesion. It enables to individually catheterize feeding vessels. Venous drainage is via the median prosencephalic vein (MPV), the straight sinus (if present) and then out via the transverse/sigmoid sinuses. By definition, there should be no drainage to other components of the deep venous system. Prior to endovascular intervention, prognosis was dismal, with 100% mortality without treatment and 90% mortality following surgical attempts. Ideally, embolization is deferred until 6 months of age for choroidal VGM and later for mural types, to allow the cavernous sinus to mature. If cardiac failure is refractory to medical management, embolization may be performed sooner. Both venous and arterial embolization is possible, depending on the number of feeders, and controversy persists in regard to the optimum approach.

References: Bhattacharya JJ, Thammaroj J. Vein of galen malformations. J Neurol Neurosurg Psychiatr 2003;74(Suppl 1):i42-i44.

Nicholson AA, Hourihan MD, Hayward C. Arteriovenous malformations involving the vein of Galen. Arch Dis Child 1989;64(12):1653-1655.

19 Answer A. US demonstrates bilateral ventriculomegaly, bilateral periventricular hyperechogenicity with shadowing consistent with calcification, and bilateral complex but predominantly cystic changes in both germinal matrices consistent with subacute hemorrhage. The lenticulostriate arteries are hyperechogenic consistent with vasculopathy. MRI demonstrates moderate dysmorphic ventriculomegaly, periventricular calcifications, and subependymal cysts, including prominent bilateral subependymal cysts near the foramen of Monro. Abnormal gyration pattern with bilateral polymicrogyria as well as frontal predominant undersulcation.

Congenital cytomegalovirus infection results from intrauterine fetal infection by cytomegalovirus (CMV). CMV is the most common cause of intrauterine infection and most common cause of congenital infective and brain damage. Antibodies to CMV are seen in 30% to 60% of pregnant women, but only 2.5% have a primary infection during pregnancy, and this can result in fetal infection in approximately 30% of cases. The vast majority (90%) of infected babies are asymptomatic at birth, but some may go on to develop symptoms after 6 to 9 months.

US imaging findings include fetal intracranial calcification: mainly periventricular calcification (hyperechogenic foci), considered one of the most common features; fetal hydrocephalus; heterogeneous appearing brain parenchyma; microcephaly; and intraventricular adhesions.

MR brain imaging findings include:

References: Ceola AF, Angtuaco TL. US case of the day. Congenital cytomegalovirus infection. Radiographics 1999;19(5):1385-1387.

Malinger G, Lev D, Zahalka N, et al. Fetal cytomegalovirus infection of the brain: the spectrum of sonographic findings. AJNR Am J Neuroradiol 2003;24(1):28-32.

20 Answer A. Chest radiography demonstrates bilateral healing rib fractures. Noncontrast head CT demonstrated intermediate density extra-axial (subdural) fluid at the frontal convexities and hyperdense extra-axial (subdural) hemorrhage along the posterior interhemispheric fissure and at the apex. The presence of skull fractures and/or intracranial hemorrhage particularly in infants in the absence of known trauma to explain such injuries should raise the suspicion of child abuse. Head injury is the leading cause of morbidity and mortality in these abused children. Brain injury may be the result of direct trauma, aggressive shaking, or strangulation/suffocation. There is little or no evidence of external trauma.

The most common type of intracranial hemorrhage in the setting of child abuse is subdural hematoma although subarachnoid, epidural, intraventricular, and cortical hemorrhages are also manifestations of NAT. Bilateral retinal hemorrhages are highly suggestive of child abuse. Complex skull fractures and cerebral infarction are also diagnostic harbingers of child abuse.

Reference: Sato Y, Yuh WTC, Smith WL. Head injury in child abuse: evaluation with MR imaging. Radiology 1989;173:653-657.

21 Answer B. Images demonstrate two lytic lesions in the left parietal region and one at the apical parietal region. The skeleton is the most commonly involved organ system in Langerhans cell histiocytosis (LCH) and is by far the most common location for single-lesion LCH, often referred to as eosinophilic granuloma (EG). Patients may have one or, less commonly, many lesions. The most common locations are the skull and long bones:

Skull radiographic imaging findings include:

Prognosis is excellent when disease is confined to the skeleton, especially if it is a solitary lesion, with the majority of such lesions spontaneously resolving by fibrosis within 1 to 2 years.

Reference: David R, Oria RA, Kumar R, et al. Radiologic features of eosinophilic granuloma of bone. AJR Am J Roentgenol 1989;153(5):1021-1026.

22 Answer C. MRI demonstrates multifocal areas of FLAIR hyperintensity throughout the cerebral white matter, as well as left optic nerve thickening, extraocular muscle thickening, and nerve sheath enhancement. Acute disseminated encephalomyelitis is an immune-mediated demyelinating disease related to an antecedent viral infection or vaccination. The cause is believed to be an allergic or autoimmune (cell-mediated) response against the myelin basic protean because of cross-reaction with viral proteins. ADEM has most commonly been associated with measles; however, it has also been associated with chickenpox, rubella, mumps, and other viral agents.

Both clinically and on MRI, ADEM may appear identical to the initial presentation of multiple sclerosis. Patients may present with symptoms and focal neurologic deficits typically within 2 to 3 weeks following a viral illness. In addition to focal neurologic deficits, unlike multiple sclerosis, ADEM is not infrequently associated with seizures. ADEM more common involved white matter especially in the subcortical region; however, gray matter may also be involved. MRI typically demonstrates multiple hyperintense foci on T2. These lesions may or may not enhance. ADEM is a monophasic process; therefore, no new lesions should develop after 6 months following initial presentation. The diagnosis of ADEM can usually be made by clinical history and CSF analysis.

Reference: Mader I, Stock KW, Ettlin T, Probst A. Acute disseminated encephalomyelitis: MR and CT features. AJNR Am J Neuroradiol 1996;17:104-109.

23 Answer C. There is a well-circumscribed and heterogeneously enhancing extradural mass extending dorsally from the posterior sphenoid body and clivus. The mass is T2 bright and has some internal areas of mixed signal and areas of mineralization. Chordomas arise in locations where notochordal remnants are found. They occur most commonly at the sacrum although not infrequently found at the clivus or upper cervical spine. They are considered benign neoplasms; however, they grow quite invasively especially at the skull base where they can invade the neural foramen and cavernous sinus or extend into the middle cranial fossa.

On CT, a calcified matrix may be present and regions of bony erosion or destruction are best visualized. On MRI, the signal characteristics of chordoma are variable. These tumors are typically hypointense on T1 and hyperintense on T2. Most chordomas enhance. The differential considerations include chondrosarcoma, metastatic disease, multiple myeloma, and lymphoma.

Reference: Myers SP, Hirsch WJ Jr, Curtin HD, Barnes I, Skhear LN, Sen C. Chordomas of the skull base: MR features. AJNR Am J Neuroradiol 1992;13:1627-1636.

24a Answer B. CT is excellent at evaluating the neck soft tissues in an emergency setting when there is potential narrowing of the patient’s airway. CT imaging of the neck should be performed with intravenous contrast to differentiate fluid masses (abscess) from phlegmonous thickening (retropharyngeal cellulitis). It is important to note that CT imaging can lead to false-positive and false-negative results with respect to detecting pus. Therefore, surgical exploration may need to be carried out on the basis of clinical presentation.

24b Answer B. Neck radiograph demonstrates abnormal thickening of the prevertebral soft tissues. CT demonstrates a low-density collection with incomplete peripheral enhancement in the left parapharyngeal space consistent with a retropharyngeal abscess. Retropharyngeal abscesses are most frequently encountered in children, with 75% of cases occurring before the age of 5 years and often in the first year of life. This is likely due to the combination of prominent retropharyngeal nodal tissue and frequency of middle ear and nasopharyngeal infections. There may be a slight male predilection. Presentation is variable. In some instances, children present with nonspecific symptoms including generalized irritability, fever, and decreased appetite.

Radiographs demonstrate soft tissue swelling posterior to the pharynx, with a widening of the prevertebral soft tissues. This appearance cannot be distinguished from a prevertebral abscess, and careful evaluation of the vertebral bodies and disc spaces is important. CT is excellent at evaluating the neck, and timeliness is essential given potential narrowing of the airway. CT imaging should be obtained with IV contrast to allow differentiation of fluid collections from phlegmonous thickening (retropharyngeal cellulitis). It is important to note however that CT has a insignificant rate of both false-positive (10%) and false-negative (13%) rates with respect to detecting pus, and as such, surgical exploration may need to be carried out on the basis of clinical presentation. Treatment is similar in principle to that of other infected collections usually requiring both surgical drainage (usually performed via a transoral route) and intravenous antibiotics. In some instances, antibiotics alone may suffice, when collections are small.

With a prompt diagnosis, appropriate antibiotics and drainage when necessary, almost all patients recover uneventfully. Serious complications in developed nations with prompt access to imaging and antibiotic are uncommon; however, complacency needs to be avoided as retropharyngeal can lead to potentially lifethreatening complications.

References: Coulthard M, Isaacs D. Retropharyngeal abscess. Arch Dis Child 1991;66(10):1227-1230.

Craig FW, Schunk JE. Retropharyngeal abscess in children: clinical presentation, utility of imaging, and current management. Pediatrics 2003;111(6 Pt 1):1394-1398.