[Music] welcome back in this video we'll be going over stroke localization which is the process of figuring out where in the brain a stroke has occurred based purely on the patient's signs and symptoms i don't think i can overstate exactly how much neurologists love stroke localization for once though i can actually kind of see the appeal there's a certain order and logic to the process that's like a medical version of the brain teasers that you might have enjoyed in elementary school as a kid because specific arteries supply specific parts of the brain the signs and symptoms of a stroke are largely dependent upon which areas have been damaged this is the basis of stroke localization you look at what functions have been affected and in what areas and using what we've learned about how these different functions map to different parts of the brain in all the videos in this series so far you can figure out where the stroke has likely occurred in this video we'll first learn how to localize strokes in the cerebral cortex and then discuss strokes in the subcortex in the next video we'll finish off with strokes in the brain stem so first cortical strokes we learned in an earlier video on cerebral blood supply in the circle of willis that there are three pairs of arteries that supply the cerebral cortex the anterior middle and posterior cerebral arteries because the cortex is responsible for higher level functions strokes in these arteries will produce what are known as cortical signs where things like speech awareness and planning are impaired when you see cortical signs such as this you should be thinking of a stroke in the cortex which you can then pair with information about where deficits are occurring in the body to localize the stroke to a specific artery okay let's talk about strokes in specific arteries starting with the anterior cerebral artery in general strokes in the early parts of the anterior cerebral arteries don't cause much damage as there is abundant collateral circulation through the various communicating arteries however occlusions farther down can lead to both paralysis and sensory loss in the contralateral lower limbs as the motor pathways in both sensory pathways all cross over on their way down to the body there can also be dysfunction of lower body organs such as the bladder resulting in urinary incontinence due to damage of the frontal lobe difficulties in executive functioning can occur and in some cases primitive reflexes like the babinski sign which is normally only found in babies can re-emerge overall you can remember the association of the anterior cerebral artery with lower extremities and lower organs by drawing a stick figure where the legs form the letter a for anterior what about a stroke in the middle cerebral artery this is the most common location for a stroke in the cortex as the middle cerebral artery is the continuation of the internal carotid artery so a traveling clot just needs to go straight to block the middle cerebral artery as opposed to veering left or right to enter the anterior or posterior cerebral arteries blockages in the territory of the middle cerebral artery can result in both paralysis and sensory loss in the contralateral upper limbs the language centers also lie in various areas supplied by the middle cerebral artery so lack of oxygen in the dominant hemisphere can lead to various forms of speech deficits depending on what areas have been damaged you can remember the functions of the middle cerebral artery by continuing to add to the stick figure this time using the letter m as their arms as in someone doing the m part of the ymca dance this should help you remember the inclusion of the language centers as well as you can imagine the stick figure yelling out finally a stroke in the territory of the posterior cerebral artery is associated with defects in the visual pathway the most typical pattern scene is contralateral homonymous hemianopsia with macular sparing you can remember the association of the posterior cerebral artery with the visual cortex by drawing two piece like sunglasses on our stick figure okay let's move from strokes in the cortex down to strokes in the subcortex strokes in the subcortex are often called lacunar strokes with lacunar here coming from the latin word for lakes or empty spaces a name that makes more sense when you consider that strokes in the subcortex have a tendency to punch literal holes in brain tissue like cortical strokes lacunar strokes often present with motor deficits and loss of sensation but the intact nature of cortical functions such as speech and awareness helps to place us firmly in the region of the subcortex rather than the cortex there are three main forms of lacunar strokes which we'll go over now as the name implies a pure motor stroke results in hemiparesis of the contralateral face arm and leg without any sensory deficits or associated cortical signs this often results from ischemic damage to the posterior limb of the internal capsule which as you'll recall from a previous video carries the corticospinal and cortical bulbar tracts a pure sensory stroke is also pretty straightforward and features numbness of the contralateral face arm and leg without any motor deficits or associated cortical signs as you might guess a pure sensory stroke often results from ischemic damage to the thalamus since the thalamus processes sensory information finally because the posterior limb of the internal capsule and the thalamus are adjacent to each other occasionally a stroke will produce ischemic damage in both of these regions at once leading to both hemiparesis and numbness of the contralateral face and extremities and that's it those are the three types of lacunar strokes to be aware of if you've been following this video series so far there are no new mnemonics that you'll need here from here we will next turn our attention to brainstem strokes this is going to be the densest part of learning about stroke localization so let's go ahead and take a break once you're feeling refreshed and ready to move on click on to the next video see you soon