25 Common Congenital Malformations of the Brain on

Computed Tomography and Magnetic Resonance Imaging

CLINICAL IMAGAGINGAN ATLAS OF DIFFERENTIAL DAIGNOSIS

EISENBERG

DR. Muhammad Bin Zulfiqar PGR-FCPS III SIMS/SHL

• Fig SK 25-1 Occipital encephalocele. Parasagittal MR image shows brain parenchyma that has herniated through a posterior calvarial defect. Although the protrusion contains a large vessel, represented by a linear signal void, it is difficult to identify possible ventricular structures because of distortion.39

• Fig SK 25-2 Agyria.40

• Fig SK 25-3 Pachygyria. Coronal MR scan shows broad gyri, an abnormally thick cortex, and poor arborization of white matter.40

• Fig SK 25-4 Heterotopia. (A) Coronal scan shows hemiatrophy and a gray matter mass bridging from ventricular to cortical surfaces (arrowheads). The intensity of the abnormal bridge of tissue was the same as that of gray matter on all pulse sequences.39 (B) Gray matter collections lining the subependymal regions of both lateral ventricles.41

• Fig SK 25-5 Schizencephaly. (A) Proton-density and (B) T2-weighted MR scans show bilateral full-thickness clefts (more marked on the right) that are lined by gray matter. Note the absence of the septum pellucidum.40

• Fig SK 25-6 Holoprosencephaly. Nonsequential transverse CT scans show a monoventricle with anteriorly fused thalami (arrow). There is absence of the interhemispheric fissure, third ventricle, and corpus callosum. A crescent-shaped anterior cerebral mantle represents the undivided prosencephalon, the posterior margin of which cannot be identified on the CT scan. The monoventricle is distorted by a large compression dorsal cyst, the anterior border of which is approximated by the hippocampal fornix (arrowheads).39

• Fig SK 25-8 Agenesis of the corpus callosum. (A) Associated findings include a posterior interhemispheric cyst and a Dandy-Walker cyst of the posterior fossa. (B) In this patient, there is a lipoma involving the anterior aspect of the interhemispheric region.41

• Fig SK 25-9 Dandy-Walker malformation. (A) Sagittal and (B) axial40 MR scans in two different patients show large posterior fossa cystic masses associated with agenesis of the vermis and separation of the cerebellar hemispheres.

• Fig SK 25-10 Cerebellar hypoplasia. Sagittal MR scan shows almost total absence of the cerebellum except for a small portion of the superior vermis.41

• Fig SK 25-11 Chiari I malformation. Caudal displacement of the cerebellar tonsils 15 mm below the foramen magnum. Note the associated hydromyelia.

Fig SK 25-12 Chiari II malformation. Markedly elongated and inferiorly displaced fourth ventricle (arrow).41

• Fig SK 25-12 Chiari II malformation. Markedly elongated and inferiorly displaced fourth ventricle (arrow).41

• Fig SK 25-13 Chiari III malformation with cervico-occipital encephalocele. Sagittal MR scan shows the bony defect involving the inferior occiput, foramen magnum, and posterior elements of C1 and C2 with herniation of the cerebellum (black arrow), dilated posterior aspect of the fourth ventricle (white arrow), brainstem, upper cervical cord (black arrowheads), and meninges (white arrowhead) into the posterior sac.41

• Fig SK 25-14 Neurofibromatosis with hamartoma (arrows).

• Fig SK 25-15 Tuberous sclerosis. (A) Axial T2-weighted MR image shows multiple subcortical and periventricular bright hamartomas. (B) Noncontrast axial T1-weighted MR image of a different patient shows slightly bright periventricular hamartomas (arrows). (C) CT scan of a different patient shows multiple calcified periventricular hamartomas.6

• Fig SK 25-16 Sturge-Weber syndrome. (A) Postcontrast T1-weighted MR image shows extensive enhancement of the leptomeningeal angioma in the right occipital lobe and a prominent glomus of the right choroids plexus, which served for collateral venous drainage. (B) Axial CT scan in a different patient shows the classic parenchymal calcification in the right parietal lobe.6

• Fig SK 25-17 von Hippel-Lindau disease. Axial postcontrast T1-weighted MR image shows a left-sided cystic hemangioblastoma with an enhancing nodule and multiple small enhancing solid lesions in the right cerebellar hemisphere.6

• Fig SK 25-18 Congenital aqueductal stenosis. (A) Midsagittal T1-weighted MR image shows marked dilatation of the lateral and third ventricles with a normal-sized fourth ventricle. (B) Midsagittal T1-weighted image in another patients shows absence of the lumen in the aqueduct (arrow). The tectum is deformed but was of normal signal intensity on a T2-weighted scan (not shown). The lateral and third ventricles are large, for the fourth ventricle is normal in size.6

• Fig SK 25-19 Arachnoid cyst. Axial T2-weighted MR image demonstrates a collection of cerebrospinal fluid anterior to the cerebellum in the cerebellopontine angle region. Note the small cerebellum (C) on the left. (B) Left parasagittal T1-weighted MR image shows the lowsignal-intensity fluid lesion.42

• Fig SK 25-20 Vein of Galen malformation. (A) Sagittal T1-weighted MR image shows an apparent cystic mass in a supracerebellar location. The dilated vein of Galen communicates with a persistent falcine sinus (arrow). Note the extensive phase artifact due to the malformation. (B) Lateral MR venogram shows numerous dilated arteries and drainage of the large vein of Galen malformation (arrowheads) into a prominent torcular through a persistent falcine sinus (arrows).42