Intracranial Cysts: Lateral



Intracranial Cysts: Lateral


Anne Kennedy, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Choroid Plexus Cyst


  • Arachnoid Cyst


Less Common



  • Schizencephaly


  • Arteriovenous Fistula


Rare but Important



  • Porencephaly


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Assessment of fluid-filled intracranial structure


  • Could it be a prominent normal structure such as lateral ventricle?



    • Mild ventriculomegaly



      • Choroid displaced from medial wall


      • Atria of lateral ventricle measures 10-12 mm


      • Look for signs of trisomy 21


      • Look for additional brain abnormalities


    • Colpocephaly: Tear drop shape to dilated occipital horns seen in agenesis of corpus callosum



      • Ventricles parallel


      • Absent cavum septi pellucidi


      • Loss of normal branch pattern of anterior cerebral artery


      • Stenogyria


  • Once abnormal lateral ventricle excluded, determine location



    • Is it in the choroid plexus?


    • Is it in the brain substance (i.e., intra-axial)?


    • Is it outside the brain substance (i.e., extra-axial)?


  • Is it replacing normal brain tissue?



    • Porencephaly


    • Schizencephaly


  • Is it a space-occupying lesion displacing brain tissue?



    • Arachnoid cyst


    • Arteriovenous fistula


  • Is it vascular?


  • Could it be a thrombosed vascular structure?



    • Hypoechoic structure with increased through transmission


    • Often contains faint low level echoes


    • Usually tubular or round


Helpful Clues for Common Diagnoses



  • Choroid Plexus Cyst



    • Cyst > 2 mm with defined wall, within choroid plexus


    • Variable size


    • Variable number


    • May be unilateral or bilateral


    • May be single or multiple


    • Look for associated signs of trisomy 18



      • Abnormal posturing


      • Facial cleft


      • Congenital heart disease


      • Neural tube defects


      • Omphalocele


  • Arachnoid Cyst



    • Extra-axial cyst displaces brain parenchyma


    • Unilocular


    • Avascular


    • Most common over convexities



      • 1/3 fetal cases are in posterior fossa


    • May enlarge and cause hydrocephalus due to mass effect at foramen of Monro or aqueduct of Sylvius


Helpful Clues for Less Common Diagnoses



  • Schizencephaly



    • Wedge-shaped defect in brain parenchyma


    • Extends from lateral ventricle to inner table of skull


    • Edges of cleft are lined by gray matter


    • Unilateral or bilateral


    • Open lip or closed lip



      • Open lip: Wedge-shaped defect, edges separated by cerebrospinal fluid-filled cleft


      • Closed lip: Edges of defect are in contact; unlikely to be detected on prenatal ultrasound


    • Size varies from small to “giant”


    • Consider MR to look for associated heterotopia, polymicrogyria, pachygyria, septo-optic dysplasia


  • Arteriovenous Fistula



    • Hypoechoic structure on grayscale images



      • Blood flow on Doppler evaluation when patent


      • Thrombosed AVF is tubular/round structure with low level internal echoes but no flow on Doppler evaluation



    • MR will show blood product signal even when flow is absent


    • May be intra-axial, but dural (i.e., extra-axial) more common in fetus


    • May be associated with high output cardiac failure


    • May be associated with polyhydramnios


    • Look for associated intraventricular or parenchymal hemorrhage


    • Look for associated ischemic damage secondary to vascular “steal”



      • Cortical thinning, ventriculomegaly, microcephaly


      • MR more sensitive than ultrasound for detection of encephalomalacia


Helpful Clues for Rare Diagnoses



  • Porencephaly



    • Porencephalic cyst replaces damaged brain



      • Intracerebral cavitation due to injury


      • Usually connected with lateral ventricle


    • Look for associated intracranial hemorrhage


    • Destructive process may present with mild ventriculomegaly and progress to encephalomalacia/porencephaly over time


Other Essential Information

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Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Intracranial Cysts: Lateral

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