Ventricular System

Hydrocephalus

  • Multiple types

  • If you see transependymal resorption —> likely acute or progressive hydrocephalus —> warrants surgical evaluation

Obstructive Hydrocephalus

  • Intraventricular

  • Obstruction is located proximal to the 4th ventricle

  • Extraventricular

  • Obstruction is located distal to the 4th ventricle

Interpreting CSF flow study

  • Major uses

    • Chiari malformation

    • Arachnoid cyst

    • Aqueductal stenosis

    • NPH

    • Shunt tube evaluation

  • You are basically looking for lack of the bright white lines in the CSF spaces that represents flow

  • Phase contrast is type of MRI

    • The lines that look like the csf is moving (bright and dark lines) is actually aliasing artifact

    • Note that when doing the study the velocity parameter (some shit that you pick i guess idk) should be set to the higher end of what you expect it to be otherwise it will throw the scale off and then the aliasing artifact wont be seen well <— thats the stupid people version

  • Will see pulsating light and dark areas in the distribution of CSF flow

    • This is because CSF pulsation is related to cardiac activity with systole and diastole

    • Bright signal —> systole —> CSF moving caudal to cranially (forward)

    • Dark signal —> diastole —> CSF moves cranial to caudal (backwards)

    • So can detection motion, and direction of CSF flow. Velocity can therefore be measured

    • CSF velocities

      • Normal —> 5-8 cm/s

      • Arachnoid cyst —> 2-4 cm/s

      • NPH —> 20-25 cm/s

  • Normal pressure hydrocephalus

    • Dilatation of ventricles out of proportion to extra-axial spaces (sulci)

    • Prominent flow void within aqueduct on sagittal images

    • On the CSF flow study you are looking for

      • Hyperdynamic flow at the aqueduct with velocity > 42 ml/s

    • On chart add all the negative numbers and divide by how many numbers you added to get mean, then divide by the duration (get from graph as how long it was negative or below the line because this is systole)

  • Chiari 1 malformation

    • Qualitative evaluation (no numbers, just looking for lack of flow)

    • Look for lack of the bright white lines representing CSF flow typically in the posterior fossa

  • Aqueductal stenosis

    • Qualitative evaluation (no numbers, just looking for lack of flow)

    • Look for lack of the bright white lines representing CSF flow typically in cerebral aqueduct (will proximal dilatation of ventricles obviously)

    • May see a small web like structure in the aqueduct which may be responsible for this

  • Arachnoid cyst

    • Qualitative evaluation (no numbers, just looking for lack of flow)

    • Want to see if the cysts are communicating with the extra-axial spaces or not

      • Basically just look to see if you get the bright white and dark pulsing shit in the area that the cyst is located, if so state it is communicating, if not, say it is not communicating

  • Shunt patency

    • Subtle - look for pulsing the white signal in the shunt lumen, should not really see the dark signal because it is unidirectional flow because of a valve in the tube

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