Video: White matter

Ever feel like you have no control over your life? Like someone is pulling your strings for you. Feel like you’re someone’s puppet? Well, you are! Okay, I’m just joking, but your body does work in a similar way to a marionette. Let me paint you a picture. Your brain is the puppeteer. It comes up with every decision about how each tiny part of your body will work. While the brain is infinitely complex and interesting, it’s not our main topic today. What we want to know is how it controls the body.

Similar to a marionette, the body is actually controlled by a bunch of string-like structures. However, in contrast to a puppet, these strings are enclosed in the spinal cord, specifically in the white matter and are called white matter tracts.

Let’s go back for a moment to the spinal cord and puppeteer string analogy. If a crazy-theater hater attacked a puppet with a pair of scissors and cut off one of the strings, the puppeteer could no longer move the arm the rope was attached to. Well, the spinal cord works under a very similar principle, but the control is much more fine-tuned, so even a tiny nick on the spinal cord could leave half of your body limp and senseless. Just like the brain, it is complex and beautiful, and the best way to learn about it is to study it in cross-section.

Well, I hope you’re in the mood to learn because we’re about to find out all about the intricacies of the spinal cord cross-section and especially the white matter tracts.

You may be thinking the spinal cord sounds like a super complicated structure, but worry not. Throughout this tutorial, we’ll break it down for you in a logical, easy-to-understand way. We’ll start with a quick recap of the gross anatomy of the spinal cord. We’ll then take a look at a basic view of the spinal cord in cross-section before we move on to the white matter, its anatomical subdivisions, and the bundles of axons called tracts. Throughout this tutorial, we’ll address the different functions that all these structures have and the variation of the spinal cord at different spinal levels. We’ll finish up with some clinical notes to give you an appreciation of why the function of the white matter tracts is so important.

Right, let’s get straight into it.

In order to better visualize the elements of the white matter and their extent in the body, we’ll have a really brief recap of the gross anatomy of the spinal cord. The spinal cord is a tubular structure occupying the vertebral canal between the foramen magnum and around L1 to L2 vertebrae. It begins as an elongation of the medulla oblongata of the brain and terminates as a conus medullaris with loose spinal nerves below it forming the cauda equina. There are two enlargements along the length of the spinal cord – one in the cervical and one in the lumbosacral region. At each vertebral level, a bilateral pair of nerve roots leaves the spinal cord via rootlets to form the spinal nerves.

We’ll now take a closer look at the cross-section of the spinal cord because it is full of landmarks and areas important for a good understanding of the white matter of the spinal cord. Let’s start with orienting ourselves.

Anatomists like to complicate things, so while anterior and posterior are fine terms to use in most cases, when talking about the spinal cord, we’ll also often encounter the term ventral in place of anterior and the term dorsal for posterior. To keep things simple, we’ll stick to the terms anterior and posterior in this tutorial.

The first thing you’ll notice in any image of a cross-sectional area of the spinal cord are the distinct gray and white matter areas. The gray matter is in the center and the white matter surrounds it. The gray matter has a distinct shape that you’ll recognize anywhere because it looks like a little butterfly. It’s easy to remember what comprises the spinal cord because it’s just an extension of the brain, so naturally it’s made up of neurons, which are simply nerve cells.

The gray matter is mostly made up of cell bodies, but some myelinated and unmyelinated axons are present, too. The white matter mostly consists of myelinated axons which gives the white matter its light appearance because of the lipids in myelin. The gray and white matter, of course, contain a small proportion of other elements such as support cells known as glial cells. We’ll be focusing on white matter in this tutorial, but we have a separate video in gray matter which you can find on Kenhub.

So, the thing about white matter is that it’s divided into different regions, but these regions have no clear boundaries. Instead, they’re defined by the anatomical landmarks we find in a cross-section of the spinal cord. So, I want to talk about it in a bit more detail.

The spinal cord is very clearly divided into right and left halves – anteriorly by the anterior median fissure and posteriorly by the posterior median septum. The small indent we’d see on the posterior aspect of the spinal cord is called the posterior median sulcus. A similar, but smaller indentation is found bilaterally at the site where the posterior roots attach to the spinal cord. It’s called the posterolateral sulcus.

In the cervical region between the posterior median sulcus and the posterolateral sulcus, you’ll also find a longitudinal furrow called the intermediate posterior sulcus. It separates the gracile fasciculus from the cuneate fasciculus, but we’ll learn more about these white matter structures later on in the tutorial.

The anterolateral sulcus is found at the site of anterior roots joining the spinal cord. The two sides of the white matter meet in the midline via the anterior white commissure. Immediately posterior to it, you’ll find the gray commissure connecting the two halves of grey matter. And bang in the middle of it is the central canal – a thin tube filled with cerebrospinal fluid, which runs the entire length of the spinal cord. It is the continuation of the fourth ventricle of the brain, and therefore, communicates with the intracranial ventricular systems and cisterns. Some myelinated fibers run across the gray commissure just posterior to the central canal and form the posterior white commissure.

So, we’ve just covered the basics, which means that we can finally move on to our main topic of this tutorial – the white matter.

So, we’ve learned the anatomical landmarks of the cross-section, which means that we can now look at the anatomical divisions of the white matter. There are three areas identified in each of the two halves, meaning each part comes in a bilateral pair. Between the anteromedian fissure and the anterior horn of gray matter or anterolateral sulcus, we find the anterior funiculus. The area between the anterolateral and posterolateral sulci is defined as the lateral funiculus. And, finally, the area between the posterolateral sulcus or the posterior gray horn and the posteromedial septum is referred to as the posterior funiculus. Pretty straightforward so far, right?

Now, we’ve already discussed that the white matter mostly consists of myelinated axons. We’ll also briefly mention the structures that they formed called white matter tracts. In this image that now appears on the right side of your screen, it shows the pathway of a corticospinal tract. Don’t worry about the specifics of it just now, but let’s look at the image and figure out what a tract is and what it does. We can see that it connects the two points. Something else you’ll see if you look closely is that it’s drawn on several lines, rather than just one, to illustrate that it is a collection of axons rather than just one lonely axon trying to find his place in the world. These axons are united by their common origin, common course, and common termination.

Based on their functionality, the white matter tracts are divided into ascending and descending tracts. If you think about it, any information that goes into the brain is just feedback from different parts of the body such as pain, temperature, proprioception, or sensation of joint position, etc., so naturally, the ascending tracts going up to the brain will be carrying sensory information.

Descending tracts do the opposite job. They carry information away from the brain down towards the body with a stopover in the gray matter of the spinal cord. So, it’s no surprise that descending tracts carry motor information, the orders for what the body should do – remember the marionette puppet analogy from earlier on? All that is very much how descending tracts operate.

The naming of these tracts is also pretty straightforward. Let’s take, for example, the anterior corticospinal tract, which is the tract you can see on your screen. The first part of the name refers to the funiculus it’s found in, the next part shows its origin, and finally, we have its destination. The names of the white matter tracts are often like double cheat sheets hiding in plain sight.

Alright, so I think we got all the basics down. Let’s move on to the descending tracts of the spinal cord. It might seem that there’s a lot to know, but I’ll break it down into manageable little trunks for you. Let’s get started.

An important concept that we need to understand before we move any further is upper and lower motor neurons. Upper neurons will be those whose cell bodies reside in the brain while their axon stretch to deliver information to the spinal cord. Lower neurons are those with their cell bodies in the gray matter of the spinal cord, which extends their axons to deliver motor information to skeletal muscles.

Time to move on to some specific tracts. The good news is that we’ll start with the tracts that we’ve already met, so let’s cue the corticospinal tract.

As this is a descending tract, we already know it will carry motor innervation. In this case, it’s voluntary movement specifically. Now, let’s look at its pathway. The upper neurons in this tract originate in the motor centers of the cerebral cortex and descends through the midbrain, pons, and medulla oblongata of the brainstem. This part of the pathway is also sometimes referred to as the corticobulbar tract. This is where things get interesting.

In the lower portion of the medulla, around eighty percent of the fibers cross over to the other side. That’s right. Our bodies are very strange in that the left hemisphere actually mostly controls the right side of the body and vice versa. This crossover is called the great pyramidal decussation and you can see that really well in the enlarged section of the image. We say that fibers which cross over to the other side decussate.

The fibers will then travel downwards in the lateral funiculus of the white matter of the spinal cord forming the lateral corticospinal tract. You can see the location of the tract in relation to other tracts in this image of the transverse section of the spinal cord seen here.

The tract has a somatotropic arrangement, meaning that in the spinal cord, its fibers are arranged in an organized fashion. The fibers from upper parts of the body are more medial and the fibers from lower parts of the body are more lateral.

Let’s now go back to the lower medulla where we said goodbye to the fibers forming the lateral corticospinal tract and see what happens to the small amount of fibers which do not decussate. You can see in the image that they travel caudally in the anterior funiculus to form the anterior corticospinal tract. Here, you can see it in relation to the other tracts. It’s a little bit different from its lateral brother in its function as it only synapses with the gray matter in the cervical and superior thoracic regions to only supply those regions. It joins the gray matter of the opposite side by crossing over through the anterior white commissure. It controls axial and girdle muscles of the opposite side.

Okay, so let’s meet this little guy – the rubrospinal tract. It has a much simpler pathway compared to the corticospinal tract we just looked at. It arises in the red nucleus on the upper portion of the midbrain. The term rubro- is derived from its Latin name nucleus ruber, which as you may have rightly already guessed, means red nucleus. It then crosses over at the level of the red nucleus at the ventral tegmental decussation through the pons and the medulla oblongata and descends caudally in the lateral fasciculus of the white matter of the spinal cord.

Some of the fibers become intermingled with the fibers of the corticospinal tract and you can see it highlighted in green in the image lying immediately anterior to the lateral corticospinal tract. The axons making up the tract terminate as they synapse with the neurons in the anterior horn of gray matter. It is said to facilitate the activity of flexors and inhibit the activity of extensor muscles, but in humans, it is underdeveloped.

Another cute little pathway is the tectospinal tract. It gets its name because it originates from the superior colliculus, which is in the tectum of the midbrain. It decussates at the upper part of the tegmentum of the brain and makes its way down through the pons and the medulla to end up at the anterior fasciculus close to the anterior median fissure. Most fibers terminate in the upper cervical region of the spinal cord and are believed to play a role in reflex postural movements in response to visual stimuli.

Okay, so these guys again are a little different to the tracts we’ve encountered. They don’t strictly share their origin or any portion of the pathway, but ultimately have the same function. The tracts start in different locations of the reticular formation, which is a collection of groups of nerve cells and fibers scattered in the midbrain, pons, and medulla oblongata.

The medial reticulospinal tract arises in the medial part of the reticular formation, mainly in the pons and descends in the anterior funiculus, close to the anterior median fissure. It is often referred to as the pontine reticulospinal tract. Its main function is to adjust the posture by facilitating extensor muscles of the trunk and inhibiting some neck muscles.

The lateral reticulospinal tract starts in the lateral section of the reticular formation of the medulla oblongata and is sometimes called the medullary reticulospinal tract. It travels in the lateral funiculus to synapse with the anterior horn of the gray matter. It facilitates the action of flexor muscles in the limbs and the trunk. It may also carry some ascending fibers related to pain transmission.

And now for a bit of a disclaimer. Unfortunately, for the time being, there isn’t a universal agreement about whether some of the fibers of this pathway are crossed or if they’re all uncrossed.

This next tractor system – the vestibulospinal tract – is actually split into two – the medial and lateral vestibulospinal tracts. They arise from the medial and lateral vestibular nuclei respectively in the medulla oblongata at the floor of the fourth ventricle. These nuclei receive information from the inner ear via the vestibular nerve and some innervation from the cerebellum.

The inner ear sends information on the position of the body so it makes sense that the tract related to it would send motor information to the muscles that are responsible for balance. Imagine if there was a problem with the inner ear. It would be misfiring signals about the position of the body and their related muscles would be doing pretty strange things. The feeling of dizziness that often comes with people swaying, leaning, and sometimes falling over is called vertigo.

The medial vestibulospinal tract naturally arises from the medial nucleus and travels down in the anterior funiculus. Interestingly, some of its fibers are crossed and some are uncrossed. Ultimately, this tract inhibits the action of the neck and the upper back muscles related to maintaining balance. The lateral vestibulospinal tract descends from the lateral vestibular nucleus ipsilaterally. What does that mean? Well, that just means it travels on the same side and doesn’t cross over to the other side of the body. It acts to stimulate the extensors and inhibit the flexor muscles in the neck, the back, and the limbs that are related to balance.

There are a few tracts that allow communication between the brain and the autonomic nervous system and we’ll try to whizz through them right now.

The hypothalamospinal tracts arise in the paraventricular nucleus of the hypothalamus and stretch down to the parasympathetic and sympathetic preganglionic cells in the posterior gray horn. They are affected by hormones oxytocin, vasopressin, and dopamine. Catecholaminergic tracts start at the locus coeruleus and the medulla oblongata and terminate in presynaptic ganglia in the posterior and lateral horns. They’re controlled by epinephrine, norepinephrine, and dopamine. Finally, the raphespinal tracts connect the raphe nuclei to the spinal cord, and they are influenced by serotonin and play a part in nociception and movement.

Alright, so we’ve covered the descending tracts. Let’s now jump into the wide world of ascending tracts of white matter of the spinal cord.

Okay, so before we jump into the individual tracts, I just want to quickly run you through the tracts that you would find in the sensory pathway.

So, normally, they are separated into first, second, and third order neurons. The cell bodies of the first order neurons huddle together in the dorsal nerve root ganglia. In these pseudounipolar neurons, the peripheral process stretches to receptors to collect sensory information and form peripheral nerves. Through the dorsal nerve roots, their central processes enter the gray matter and synapse with cell bodies residing in the nuclei in the posterior horn. These cells in the gray matter are the second order neurons in the ascending fiber pathway. When the cerebral cortex is involved in the pathway, the fibers first reach the thalamus, and this is where the third order neurons reside. They then convey the information to the appropriate area of the cerebral cortex.

Okay, so now that we understand the usual order of the sensory pathway, let’s start by having a look at the exception to the rule.

Fasciculus gracilis and fasciculus cuneatus are two rebel tracts occupying the posterior funiculus of the white matter. You can see the labeled tracts on the image. What’s so special about them, I hear you ask. Well, instead of synapsing with the second order neurons in the gray matter, the first order neurons extend their central processes from the dorsal root ganglia cranially and so the tracts are formed by first order rather than second order fibers. There’s quite a logical arrangement to fibers in these tracts. The most medial fibers arise from the lowest ganglia, while the most lateral fibers arise from the highest ganglia.

Fasciculus gracilis lies medially and contains fibers from the coccygeal, sacral, and lower thoracic regions, which means that it stretches the length of the spinal cord while fasciculus cuneatus lies laterally and consist of fibers from upper thoracic and cervical spinal ganglia, which means it would only be visible in a cross-section through these regions. These tracts extend cranially to the lower part of the medulla. The fasciculus gracilis then terminates in the nucleus gracilis, while the fasciculus cuneatus terminates in the nucleus cuneatus.

The first order neurons never crossed the midline, so they are considered to be ipsilateral. From here, second order neurons cross over in the medulla and travel to the posterior thalamus. Third order neurons finally deliver the information to the somatosensory cortex. They carry information on proprioception, fine touch, vibration, and two-point discrimination.

Alright, guys, now let’s get back to the tracts that actually obey the rules. Well, mostly.

The anterior and lateral spinothalamic tract cell bodies of first order neurons are situated in the spinal ganglia and extend their central processes to synapse with neurons in the gray matter. The only out-of-ordinary thing is that they can travel for a short distance in the dorsolateral tract near the tip of the posterior horn before they enter the gray matter. They then make connections with neurons in laminas I through V, mostly in the substantia gelatinosa of Rolando and the nucleus proprius. These fibers then cross to the opposite side through the white commissure to form anterior and lateral spinothalamic tracts. The main difference here is that the fibers making up the lateral spinothalamic tract will cross on the same level, while the anterior tract may ascend a vertebral level or a few before they cross over. A small amount of the fibers remains uncrossed.

While the tracts are considered separate and even travel in different funiculi, they actually form one continuous band. The fibers of the anterior tract carry information on crude touch and pressure while the lateral tract is concerned with sensations of pain and temperature.

Despite different fibers having different functions, they make up one functional unit, and as the name suggests, the second order fibers of the tract travel up to the thalamus where they synapse with third order neurons which carry the information to the cortex.

The spinocerebellar tracts are another little duo. They carry proprioceptive impulses from muscle spindles, Golgi tendon organs, and other receptors to the cerebellum, which helps the brain to coordinate muscle movement. These tracts can be subdivided into anterior and posterior spinocerebellar tracts.

We will start with the posterior spinocerebellar tract, also known as the dorsal spinocerebellar tract. This tract carries unconscious proprioceptive information from the lower limb and the lower part of the trunk. The peripheral processes of the first order neurons carry information from these areas to the cell bodies located in the spinal ganglia at spinal levels below C8. Their central processes extend into the gray matter. Here they synapse with the cell bodies of second order neurons in the posterior thoracic nucleus, which is also commonly known as the nucleus dorsalis or Clarke’s nucleus.

The posterior thoracic nucleus only extends between spinal level C8 and L3, so central processes of first order neurons below the level of L3 hitch a ride in the gracile funiculus to reach L3 where they can synapse with the second order neurons in the posterior thoracic nucleus.

The axons of the second order neurons ascend in the posterior spinocerebellar tract located in the lateral funiculus on the same side of the body to the level of the medulla. Here the fibers enter the paravermal region of the cerebellum via the inferior cerebellar peduncle.

Moving on to the anterior spinocerebellar tract, which is also known as the ventral spinocerebellar tract. As its name suggests, it is located anterior to the posterior spinocerebellar tract and carries unconscious proprioceptive fibers from the lower limb to the cerebellum.

First order neuron cell bodies are located in the spinal ganglia at lumbosacral levels L2 to S5 with their central processes synapsing with second order neurons in the zone between the anterior and posterior horns of gray matter or laminae V, VI, and VII. The second order neurons also communicate with descending motor fibers destined for the lower limb. Most of their axons cross over and ascend in the anterior spinocerebellar tract proper, which is located in the lateral funiculus of the spinal cord. At a supraspinal level, it passes through the medulla, pons, and midbrain. Here the fibers enter the cerebellum via the superior cerebellar peduncle.

As if this pathway wasn’t strange enough, the second order neurons then cross back to the side they originated from. So, the information from one side of the body is received by the ipsilateral part of the cerebellum. This is known as a double decussation of fibers.

Both the posterior and anterior spinocerebellar tracts we just discussed have a counterpart, which carries information from the upper part of the trunk and the upper limb. The cuneocerebellar tract is the equivalent of the posterior spinocerebellar tract. Its first order neurons originate in the upper limb and torso and into the spinal cord in the spinal region C1 to C8. While their cell bodies are still found in the spinal ganglia, the central processes of these first order neurons do not synapse in the gray matter of the spinal cord. Instead, they ascend in the cuneate fasciculus on the same side of the body and synapse with second order neurons located in the accessory cuneate nucleus. From here, the axons of the second order neurons enter the cerebellum via the inferior cerebellar peduncle.

Of course, we also have the equivalent of the anterior spinocerebellar tract, and it’s the rostral spinocerebellar tract. Its first order neurons originate from level C8 and above and synapse with second order neurons in the intermediate zone of gray matter. The axons of these neurons ascend ipsilaterally to enter the cerebellum via both superior and inferior cerebellar peduncles.

Right, guys, don’t give up on me now, we only have a couple of simple ascending tracts to get through.

So first up is the spinoreticular tract. It’s a collection of fibers mainly arising in lamina VII, and with some fibers from lamina V and VIII. Part of the fibers cross over and part stay on the same side. They then ascend in the anterolateral portion of the spinal cord intermingling with spinothalamic tracts. They finish in the reticular formation of the medulla and pons, and it’s hypothesized that these fibers carry pain.

This little baby tract, the spino-olivary tract, consists of crossed fibers which arise in the spinal cord, travels in the lateral funiculus of the spinal cord, and terminates in the inferior olivary nucleus.

Okay, guys, so we’re done with all the difficult stuff, so if you’d made it this far, well done! Now, we know what’s in the white matter of the spinal cord, let’s see how that changes the appearance of white matter along the length of the spinal cord.

If you look at the image, you’ll notice white matter gets progressively bigger as it travels more cranially. And if you think about it, more and more fibers get added to the ascending tracts as we move up, and in the cervical region, you would have the fibers carrying information for a pretty much the whole body. Similarly, the descending pathways have the most fibers higher up on the spinal cord because moving caudally, the fibers split off to supply structures at different vertebral levels.

Before we wrap up for the day, I want to take a quick look at what happens when things go wrong with the white matter tracts.

So, there are a multitude of injuries, lesions, and conditions that affect the white matter tracts and we’d be here all day if I try to talk about them all. So, let’s instead take the upper motor neuron lesions of the corticospinal tracts as an example – specifically, how would you test for this type of damage.

So, there are three reflex-related indicators suggesting damage to the corticospinal tracts of the neurons. First is the Babinski sign. So, in a healthy individual when the lateral edge of the sole of the foot is stroked, the toes all exhibit plantarflexion. If damage is present, the big toe becomes dorsally flexed or points up and the upper toes abduct or fan out, if that’s a little easier to imagine. So, you could also test the superficial abdominal reflex. That is, the abdominal muscles should contract in a normal individual when the abdomen is scratched, but the reflex is absent with corticospinal tract damage.

The next test is quite a fun one. Unfortunately, it only applies to roughly fifty percent of the population. It’s the cremasteric reflex. When the upper medial thigh is stroked, the testicle on the same side contracts. The reflex is absent with corticospinal damage.

Okay, so that’s us finished. Let’s recap everything that we learned today.

We learned that each half of the spinal cord has an anterior funiculus, a lateral funiculus, and a posterior funiculus. We then moved on to bundles of myelinated axons found in the white matter that are called tracts. We found out that tracts are simply structures connecting two points in gray matter, one being in the spinal cord and one in the brain. The tract starting in the brain and carrying motor information to the spinal cord are called descending tracts, while the fibers carrying sensory information from the spinal cord to the brain are referred to as ascending tracts.

We first learned about the general organization of the descending tracts with upper motor neurons residing in the brain and lower motor neurons residing in the spinal cord. And then we moved on to learn about specific tracts. We started with the corticospinal tract whose fibers originate in the cerebral cortex. We saw the lateral corticospinal tract which is the major supplier of information for voluntary movement. We also looked at fibers which do not cross over, descend in the anterior funiculus, and form the anterior corticospinal tract. They then supply motor information to axial and girdle muscles.

We also learned about the rubrospinal tract originating in the red nucleus crossing over at the same level to descend in the lateral fasciculus and synapse with the anterior horn of the gray matter. Next, we looked at the tectospinal tract – a collection of fibers originating in the superior colliculus decussating in the upper part of the tegmentum and descending in the anterior fasciculus.

We also learned about the reticulospinal tracts which originate in different locations of the reticular formation in the midbrain, pons, and medulla. We looked at two tracts – the medial reticulospinal tract which plays a role in posture adjustment and the lateral reticulospinal tract which plays a part in flexor muscle action in the limbs and trunk.

Next, we looked at vestibulospinal tracts. We looked at two tracts which both arise from the vestibular nuclei and communicate with the inner ear via the vestibular nerve. We looked at the medial vestibulospinal tract which arises in the medial vestibular nucleus and the lateral vestibulospinal tract which originates in the lateral vestibular nucleus.

After the descending tracts, we moved on to the ascending tracts with a super quick look at neurons that form ascending tracts. The first order neuron cell bodies reside in the dorsal root ganglia, the second order in the gray matter of the spinal cord, and the third in the thalamus. We first looked at the posterior funiculus of the spinal cord which was occupied by the fasciculus gracilis and the fasciculus cuneatus. We saw that they carry information on proprioception, fine touch, vibration, and two-point discrimination from different vertebral levels to the somatosensory cortex. Their little special feature was that the tracts were actually formed by first order rather than second order neurons which form most of the upper tracts.

We then looked at the spinothalamic tracts – the anterior spinothalamic tract which travels in the anterior funiculus and carry sensations of crude touch and pressure and the lateral tract which travels in the lateral funiculus and carry sensations of pain and temperature.

Remember we also looked at the anterior spinocerebellar tract and the posterior spinocerebellar tracts. We saw that the anterior part arises in laminae V to VII and decussates while the posterior part starts at Clarke’s nucleus and travels ipsilaterally. Although they take a different path, they eventually both arrive at the vermis and paravermal region and are responsible for carrying proprioceptive impulses from various receptors.

One of the last ascending tracts we looked at was the spinoreticular tract arising mainly in lamina VII and making its way to the reticular formation partly intermingling with the spinothalamic tracts. The spino-olivary tract connects the spinal cord to the accessory olivary nuclei and with the last tracts that we looked at.

Finally, in our clinical note section, we looked at a few tests which can be used to test for corticospinal tract damage.

So that’s it for our tutorial. Thanks for watching and see you next time!