GS Stroke: fMRI, PET, CT scans Flashcards
- List the impacts of acute stroke on individuals and the NHS
Greatest disability impact than any other chronic disease
NHS cost of £2.8 billion. 20% of acute hospital beds, 25% of long term beds
- Describe the pathophysiology of haemorrhagic and ischaemic strokes
Stroke injury starts the ischaemic cascade.
The loss of glucose and oxygen delivery to neurons. Cessation of normal electrophysiological function of the cells, producing oedema. Results in further damage to surrounding tissues
- List the signs of acute stoke on non-enhanced CT
The main CT finding is an abnormal cortical-subcortical area within a vascular territory – be warned this may be very subtle! This area is typically darker (termed HYPOattenuation) than normal brain due to oedema.
Sulci are also effaced (gone) due to swelling
4 Explain why MRI is more sensitive to stroke detection, with reference to techniques such as diffusion weighted imaging techniques
Conventional MR imaging is more sensitive and more specific than CT for the detection of acute cerebral ischemia within the first few hours after the onset of a stroke. It has the additional benefit of depicting the pathologic entity (stroke and its mimics) in multiple planes. Typical MR imaging findings in patients with hyperacute cerebral ischemia include hyperintense (whiter than normal) signal in white matter on T2-weighted images and fluid-attenuated inversion recovery images, with a resultant loss of gray matter.
DWI used in hyperacute strokes. Area of stroke appear bright on the scan due to the restricted mobility of the water molecules. Resulted from decreased rate of extracellular diffusion, hence excess intracellular water accumulation.
- Describe the significance of ischaemic penumbra with reference to potentially salvageable brain with early revascularisation
In an acute stroke the ischaemia is often incomplete i.e. the injury brain tissue receives a collateral blood supply
acute cerebral ischemia may result in a central irreversibly infarcted tissue core surrounded by a peripheral region of stunned cells with a reduced blood supply called the penumbra. Evoked potentials in the peripheral region are abnormal, and the cells have ceased to function, but this region is potentially salvageable with early revascularization
- Describe techniques which can identify penumbra in the hyperacute state.
Perfusion CT: in prenumbra the blood flow/ diffusion will be less than normal brain but MORE that the infracted core. This is potentially salvageable brian.
ACA stroke clinical presentation?
Anterior cerebral artery occlusions primarily affect frontal lobe function and can result in disinhibition and speech perseveration, producing primitive reflexes (eg, grasping, sucking reflexes), altered mental status, impaired judgment, contralateral weakness (greater in legs than arms), contralateral cortical sensory deficits gait apraxia, and urinary incontinence. This is the rarest type of stroke
MCA stroke clinical presentation
Middle cerebral artery occlusions commonly produce contralateral hemiparesis, contralateral hyperaesthesia, ipsilateral hemianopia (blindness in one half of the visual field), and gaze preference toward the side of the lesion. Agnosia is common, and receptive or expressive aphasia may result if the lesion occurs in the dominant hemisphere. Neglect, and inattention may occur in nondominant hemisphere lesions. Since the MCA supplies the upper extremity motor strip, weakness of the arm and face is usually worse than that of the lower limb. This is the most common type of stroke
PCA stroke clinical presentation?
Posterior cerebral artery occlusions affect vision and thought, producing contralateral homonymous hemianopia, cortical blindness, visual agnosia, altered mental status, and impaired memory.
apraxia
unable to perform purposeful actions
Agnosia
unable to interpret sensation s
aphasia
unable to understand and produce speech
