12.11.13 Neuroradiology review


    • Crescent shape

    • Doesn't cross midline

    • Sub-falcine herniation

      • Innermost part of the frontal lobe is scraped under part of the falx cerebri

      • Can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri

      • May interfere with blood vessels in the frontal lobes that are close to the site of injury

      • Symptoms not well defined

    • Older patients

      • cf Bridging veins

Subarachnoid haemorrhage

    • Check for blood in ventricles

      • Can cause non-communicating hydrocephalus


    • Frontal lobe is everything forward of the central sulcus

      • i.e. Includes the primary motor cortex (pre-central gyrus)

    • Parietal lobe includes the primary somatosensory cortex

    • Omega sign is only present in 80% of people

    • Everything looks a bit out of place on CT because of the tilt

      • Central sulcus is quite far back

      • cf Avoid the eyes


    • Tightly packed stuff => Restricted diffusion

      • Bright on DWI

      • Dark on ADC

Diffusion imaging

    • DWI is bright where there is RESTRICTED DIFFUSION

      • De-phase and then re-phase protons

      • If they've moved, these won't cancel out => Signal loss

    • ADC = Apparent Diffusion Coefficient

      • => Measure of diffusion speed / Freedom

      • So white = Free

    • T2 shine-through

      • Refers to high signal on DWI images that is not due to restricted diffusion, but rather to high T2 signal which 'shines through' to the DWI image

      • T2 shine through occurs because of long T2 decay time in some normal tissue

      • Therefore check the ADC scan, which should be dark if there is genuine DWI signal


    • Sylvian Fissure MCA “Dot” Sign

      • Represents a thromboembolus within a segmental branch of the MCA located within the sylvian fissure (M2 or M3 segment)

    • Striatum

      • Internal capsule runs down the middle

      • Caudate nucleus on the inside

      • Lentiform nucleus (putamen + globus pallidus) on the outside

    • Periventricular or subcortical lesions in MS

    • The posterior end of the corpus callosum is the thickest part, and is termed the splenium

      • Genu is anterior