SDH- 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
Subarachnoid haemorrhage- Check for blood in ventricles
- Can cause non-communicating hydrocephalus
Lobes
- 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
Abscess
- Tightly packed stuff => Restricted diffusion
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
Notes- 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
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