Examination of the Cerebellum

00:00 Now we can move on to perform the testing that assesses the functioning of the cerebellum.

00:05 And we're going to first do limb ataxia and then gait ataxia. So, for limb ataxia, we're trying to see if the cerebellum is processing all the inputs from the peripheral nervous system to complete a series of relatively complex tasks of coordination. And the most common ones that we start with are the finger-nose-finger test. "So what I want you to do is just use your index finger, just touch my finger actually. Now you can touch your nose and just keep following my finger in that way with your finger as I move it around in space. Back to your nose. Back to my finger. Back to your nose. Back to my finger." Keep in mind that I'm actually keeping my finger far enough away that he has to fully extend his arm, you don't want to just do it right in front of his face because you're not really getting the full activation of his cerebellum, having to really pinpoint something in 3-dimensional space with using coordination. So that's finger-nose-finger, that's testing cerebellar function particularly of the the upper extremities. "Next up, to check out the lower extremities and their ability to coordinate movements we're going to have you, basically starting with your heel start down right in front of your other foot and go up to your knee and back down again, just like that.

01:16 Great. And then just do it on the other side. Perfect." "You're of course always looking for asymmetry." Patients who have cerebellar function when they do finger-nose-finger, they they have a lot of trouble with grossly trying to figure out where their finger is supposed to be in space. In contrast, a person who just has a tremor will have regular amplitude deviations from the course but they're still at least heading in the right direction even if it's waxing and waning as they get to the target. Next up, we'll do what's called dysdiadochokinesia and it's basically just to assess whether the cerebellum can process rapidly different tests of pronation and supination or flexion and extension in one muscle group. "On the new, you have your hands on your thighs and just quickly turn them over just like that. Great." And patients with either an extrapyramidal problem or cerebellar problem would have problems doing that. Next one is test for rapid alternating movements. "I just want you to do this for me really fast." Typically want to get at least 10 of them in a row, make sure they're big and fast, and that's your best way to assess cerebellar function in that sense." Alright, so now having assessed limb ataxia, we're going to go ahead and assess gait ataxia. "So Sean, if you wouldn't mind just walking towards me. Great, and then turn around and walk back the other way." Now, his gait is perfectly normal. Patients can manifest with a variety of different types of walking depending upon the type of problem or lesion that they have whether it's cerebellar ataxia, sensory ataxia, Parkinson's disease, etc. I will just demonstrate the gait of a Parkinson's patient because it's a common one that's worth looking for. These patients have a so-called shuffling gait kind of walk like these, short steps. They'll have a festinating gait, which is where they lean forward then they have to try and catch up with their feet and also you noticed that when Sean turned he had no problem just quickly turning around whereas patients with Parkinson's when they get to a place where they need to turn they have a lot of trouble making turns in space. They also even can get stuck walking under a door threshold. There are a variety of these kinds of manifestations of Parkinson's that you can detect by simply watching somebody walk for short distance. And the last test that we often use when we're assessing problems with ataxia is called the Romberg test and I want to highlight here that the Romberg test is actually not testing the cerebellum, it's testing the peripheral inputs specifically the spinocerebellar tracts that are going up to the brain and are being processed or interpreted by the cerebellum. Patients who have problems with the spinocerebellar tracts due to whatever problem with potentially a polyneuropathy are not getting input from the muscles and tendons in their limbs telling them about where their joints are in space so when you close your eyes it's really hard to know if you're falling off balance or not. "So, what I'm going to have you do is step forward a few steps or a few inches, and I just want you to close your eyes." A patient who has problems with the spinocerebellar tracts or any kind of peripheral problem with sensory integration is going to start to move around back and forth or having trouble keeping their balance, we typically do this for up to 60 seconds. Patients with a sensory cause of their ataxia are going to start to waddle around after probably 10 seconds or so whereas somebody with a cerebellar problem who doesn't actually have to coordinate any movements in this position should be okay with this. They may have trouble after 30 seconds or so, but they shouldn't have any problems in the same way that a person with a peripheral problem might have. You can accentuate this finding by pushing on the patient, seeing if they're able to maintain their posture. Now we'll move on to the assessment of tremor, which is also a very common complaint amongst patients who present to a doctor's office. Tremors can be broken up into 2 different categories. We have resting tremors and then we have action tremors. And then action tremors have 2 different subtypes. We have postural and intention. So let's first look at a resting tremor. Typically a patient is sitting at rest and you can even distract them by having them maybe tap their foot or do some other sort of activity, but you're watching their hands. A patient with Parkinson's disease or Parkinsonism more generally will start to have a little bit of vibration in their hand, sometimes it's even a little pill rolling type activity where their thumb and their finger are moving together. And as soon as I have them lift up their hands, the tremor completely disappears. So it's exclusively present at rest. In contrast, a person with an action tremor may have issues with posture, maintaining a posture, or during an intention activity. "So what I would like you to do now is just put your hands out straight in front of you. This is a test for postural tremor. It's extremely common to have a postural tremor so-called benign essential tremor and as people get older it tends to come out a bit more. If you drink a lot of caffeine, it's going to come out a bit more and in contrast you can treat it with taking a beta-blocker that sort of thing to cool down that increased sympathetic tone that's causing it. If you're trying to accentuate a postural tremor, you could put a piece of paper on a person's hand because it will kind of quiver if somebody has a significant tremor. You're looking for asymmetry that can be helpful as well in the diagnosis. And then lastly, "you can put your hands down now," we're going to see if the patient has an intention tremor. We've already kind of assessed that when we were doing the finger-nose-finger test. Patients with purely an essential tremor, like again a benign essential tremor, will vacillate and oscillate as they head towards the target, but they will eventually get there and they'll be heading in the right direction. Whereas with the cerebellar problem, which is what you're really picking up with an intention tremor, is widely wrong inaccurate excursions as they're moving their hand around trying to get to the target. So that would be characteristic of an intention tremor oftentimes related to a cerebellar problem.

07:23 With that, I want to do 2 last tests of motor function before we move on to the rest of the neurologic exam. When we did the neuromuscular exam in a different lecture, we covered the nerve roots and sensory inputs, etc., these are 2 tests that are also looking for muscular problems weakness but that can be a bit more subtle and would not be detected when you're just doing routine strength testing. And they are the pronator drift, which we'll start with first. So, a patient who has a subtle or small hemispheric stroke, you may not detect any strength or weakness problems, but they may have a positive pronator drift. "So what I'm going to have you do is put your hands out straight in front of you like you're carrying a big pizza with your thumbs out as much as you can. And now I want you to close your eyes.

08:15 A patient with a pronator drift will start to have this arm will fall and pronate exactly like you see him doing there. It may take 30 seconds, it may take a minute, "you can relax now," but that finding of a pronator drift is highly specific for a hemispheric stroke. And again, it's subtle enough that you wouldn't pick it up by just doing strength testing. And the second one, which is even better in terms of predicting a hemispheric stroke or any kind of hemispheric lesion honestly, even a tumor would do this, is called the forearm rolling test.

08:46 "And I want you to basically roll your forearms like you're a boxer. Exactly." And he's perfectly symmetric in terms of one arm and the other arm are moving evenly. In contrast, if a person has a left hemispheric stroke, you may find that he starts to preferentially have one turn but not the other. And that's something which, since there are so many muscle groups involved in regulating this activity, that lost of any part of the motor strip could manifest with that subtle distinction, and that is a very useful sign with a high likelihood ratio for hemispheric stroke.