Indications Trauma: fractures,hemorrhage Stroke: Initial evaluation Hydrocephalus Mass effect/ midline shift Detect calcification Advantages Detect calcification Quick, readily available Better at evaluating the bony structures especially for fractures Disadvantages Radiation Not as good as MRI at evaluating the soft tissue structures CT Indications Tumors Stroke Epilepsy Demyelination Infection Cranial Nerve palsy Chronic headache Dementia Advantages Exquisite soft tissue contrast between normal tissue and pathologic tissue. Customize imaging technique to answer specific questions. No ionising radiation. Ability to do functional MRI Disadvantage Higher cost, limited access Difficult for unstable pts Claustrophobia Not as great for bony detail MRI
Corpus callosum Mamillary body Pituitary gland Pons Fourth ventricle Medulla Thalamus Fornix Superior sagittal sinus Cerebellum
Always remember to say left or right! 4. Caudate nucleus 5. Internal capsule 6. Putamen 7. Thalamus 8. Fornix
Circle of Willis Internal carotid artery Vertebral artery Common carotid artery Subclavian artery Brachiocephalic trunk Basilar artery What level does the common carotid artery bifurcate? C4
Anterior cerebral artery Internal carotid artery Middle cerebral artery Posterior communicating artery Posterior cerebral artery Watershed infarct: Area supplied by Anterior cerebral and Middle cerebral artery (man in a barrel) OR Area supplied by the Middle cerebral artery and the Posterior cerebral artery. Watershed infarct: Area supplied by Anterior cerebral and Middle cerebral artery (man in a barrel) OR Area supplied by the Middle cerebral artery and the Posterior cerebral artery.
Intracranial bleeds: Intra axial – Intraparenchymal, Intraventricular. Extra axial – Extradural (Epidural), Subdural, subarachnoid.
Intraparenchymal haemorrhage In this case the bleed has spread into the lateral ventricles. Usually in a hypertensive patient. The basal ganglia is particularly susceptible to hypertensive bleeds. Risk factors?
Intraventricular haemorrhage: Third ventricle Which ventricle is the bleeding occurring in? More common in premature babies but can also be due to trauma. Common presentation?
Extradural haemorrhage: Between the dura mater and the skull. Lentiform (lens shape) Shape? Injury followed by a lucid interval before sudden onset of symptoms Trauma (coup) History? Middle meningeal artery rupture Most common cause?
Subdural heamorrhage: Between the dura mater and the arachnoid mater Crescent shaped Shape on a CT? The elderly and alcoholics – Cerebral atrophy Babies – Shaken baby syndrome Who’s most at risk? Slower onset of symptoms than for an extradural haematoma. Trauma – Especially involving shearing forces (Contrecoup) History? Tearing of the bridging veins Most commonly?
Sub-arachnoid heamorrhage: Sometimes a CT is delayed while other causes eg. Meningitis are ruled out. What would you see on the CT? Thunderclap headache Trauma but sometimes spontaneously (aneurism) History? Between the arachnoid and pia mater. Bleed that follows the contour of the brain
Herniations Midline shift Sub falcine herniation
Cushing’s triad Raised ICP causes compression of the cerebral arterioles, leading to ischaemia. Sympathetic nervous system response causes vascular constriction and so a raised BP (in an effort to restore blood supply to the brain). This is then detected by baroreceptors which causes a decrease in heart rate medicated by the vagus nerve. The pressure on the brainstem leads to irregular breathing. Irregular breathing Low heart rate Raised Blood pressure Nervous system response to raised ICP. Indication of imminent brain herniation.