hello this is asap usmle and today we're going to make spinal cord lesions make sense in just a few minutes but first we need to understand the cross-sectional anatomy of the spinal cord assuming you're familiar with the functions of the tracks we will mainly focus on their location anterolaterally here in the front and on the sides we can find the cortical spinal tract which carries upper motor neurons the anterior horn cells carrying lower motor neurons and the spinothalamic tract carrying sensation of pain temperature and crude touch in the posterior side we have mainly the dorsal columns carrying sensation of vibration proprioception and light touch now let's review the symptoms of upper motor neurons and lower motor neurons to keep it simple i like to think of upper motor neuron symptoms as going up and about hyperreflexia the toes going up in positive babinski standing up when you're choking and weight loss from lifting weights just to think of the gym similarly think of lower motor neuron symptoms as passive muscle atrophy because you're not moving and your muscles are wasting and fasciculations which are small and non-purposeful movements once you know the location and function of these trucks you can easily figure out the clinical findings here are some examples anterior cord syndrome as the name suggests only the posterior cord is unaffected meaning the dorsal column everything else is since the injury is bilateral the symptoms will be bilateral as well and they will start at the level of the lesion so you will have the symptoms of the corticospinal anterior horn cells and spinal thalamic tracts moving on to complete transection this one is pretty straightforward your entire spinal cord is affected meaning you will lose everything sensation and motor bilaterally at the level of deletion and below brown support is the most complicated but it's about to make sense we have an injury affecting exactly half of the cord remember that corticospinal tract crosses at the medulla all the way up in the brain stem so the symptoms will be ipsilateral anywhere in the cord at the level of the lesion the dorsal column also crosses at the brainstem so symptoms will again be ipsilateral now spinal thalamic tract is the tricky part as it gives contralateral symptoms starting two levels below the lesion here's why remember that this track crosses in the spinal cord two levels above so let me demonstrate here we have an individual who has an injury on the left side of l1 right side and left side on the individual right side and left side on his spinal cord so let's go ahead and take a lesion on his right side representing l3 i know the dermatome is lower but let's just pretend so we take that lesion is laterally from the right side to the right side at l3 now we're going to go up two levels one two and we're going to attempt to cross we can't there's a lesion therefore l3 will have symptoms but if we go to l2 as it comes it goes one two and then it crosses see how it already bypassed deletion same happens for l1 so the level of the lesion and the level below contralaterally speaking or unaffected whereas l3 and below are affected so in summary at the level of the lesion we will have ipsilateral corticospinal and dorsal column symptoms starting at the lesion down whereas spinothalamic symptoms will be contralateral and starting two levels below the lesion you may be wondering why is it that in anterior cord syndrome the spinal thalamic tract lesions do not start two levels below this is because both of them are affected so it doesn't matter the direction it's coming from it will not be able to bypass the injury so you will have bilateral symptoms starting at the level of the lesion so that is it for classic spinal cord lesions thank you for watching i hope it was helpful good luck studying good luck on your exams and i'll see you on the next one bye