Spinal cord disorders: Pathology review

Definitions & Key takeaways

The spinal cord is a delicate and complex structure that runs from the brain down the center of the back. Some common spinal cord disorders include Spinal cord injury, which occurs when there is damage to the spinal cord from trauma; Spinal cord tumors, which refers to growths that develop within the spinal cord and can cause pressure on the spinal cord; spinal cord infarction, which is the loss of blood flow to the spinal cord, causing damage to the tissue; degenerative spinal disorders, which include conditions such as spinal stenosis, herniated disc, osteoarthritis); and infections and abscesses. Symptoms vary according to etiology but include fever, pain, weakness, loss of sensation, and paralysis.

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Case Study0:00–1:11

At the physician’s office, 55-year-old Mario presents complaining of weakness in his hands and feet. These symptoms have gradually progressed over the past couple of months.
At first, he struggled to manipulate small objects like buttoning his shirt. Now he also often stumbles while walking and recently fell down the stairs.
In addition, his family mentions that his speech has become slightly slurred. He denies any sensory symptoms, memory loss or any bowel or bladder complaints.
Later that day, 43-year-old Donna comes in with difficulty walking. She has fallen several times over the last few weeks.
Her past medical history is significant for HIV infection, which was diagnosed a few years ago. On neurologic examination, her pupils are small and irregularly shaped and do not react to light, but constrict with accommodation.
The sensations of pressure, vibration, fine touch and proprioception are also reduced throughout the lower extremities. She has a wide-based gait and cannot maintain balance with her eyes closed.Based on the initial presentation, both Mario and Donna have some form of spinal cord disorder.

Physiology1:11–5:18

Okay, let’s talk about physiology first real quick. If we zoom in at a cross-section of the spinal cord, we’ll see that it is composed of both grey and white matter.
Grey matter is found within the medial portion of the spinal cord and has two dorsal or posterior horns that contain cell bodies of sensory neurons and two ventral or anterior horns that contain cell bodies of motor neurons.
In the center of the grey matter there’s a small cavity called the central canal which is filled with cerebrospinal fluid that provides nutrients and mechanical support.
Surrounding the grey matter is white matter, which consists of the axons of various neurons and they are organized into tracts that carry information to and from the brain.
For your exams, there are a few main tracts to remember. First, there’s the spinothalamic tract which is an ascending pathway and it’s divided into two parts.
The lateral tract carries sensory information for pain and temperature, while the anterior tract carries information for crude touch, or the sense one has been touched, without being able to localize where they were touched.
For this to happen, a first order neuron, found inside a dorsal root ganglion carries sensory input from the skin to the dorsal horn of the spinal cord, where it synapses with the second order neuron.
And that neuron ascends 1-2 vertebral levels and decussates or crosses to the opposite side of the spinal cord via an area of white matter called the anterior white commissure.
The secondary neuron then ascends up the length of the spinal cord via the spinothalamic tracts, and eventually synapse with a 3rd order neuron located in the ventral posterior nucleus of the thalamus.
This 3rd order neuron then sends its axon up to the sensory cortex of the brain, letting you know that there’s a sensory signal.Next, there are two ascending dorsal column tracts: the fasciculus gracilis which carries sensory information from the lower trunk and legs, and the fasciculus cuneatus which carries sensory information from the upper trunk and arms.
These tracts both carry sensations like pressure, vibration, fine touch, which is where you can localize where you were touched, and proprioception which is an awareness of your body’s position in space.
Once again, for this to occur, a 1st order neuron collects sensory information, but, in this case, ascends up along the same side of the whole length of the spinal cord to reach the lower level of the medulla oblongata where it synapses with the cell body of a 2nd order neuron in the nucleus cuneatus.
The 2nd order neuron then sends off an axon that crosses over to the opposite side of the medulla, and travels up to the ventral posterior nucleus of the thalamus to synapse with a 3rd order neuron.
And then, the 3rd order neuron then sends up an axon that carries the sensory signals to the sensory cortex of the brain.Once your brain receives all that information, it may decide that it wants a muscle to contract.
So, to do that, it sends a signal from an upper motor neuron in the motor cortex through a descending pathway, known as the corticospinal tract, in the midbrain and cross to the opposite side at the medulla before continuing down the spinal cord.
There, it synapses with lower motor neurons in the anterior horn. The lower motor neuron then sends out an axon that synapse with the muscle it innervates.
Similar to that, there’s also the corticobulbar tract. Upper motor neurons from the motor cortex travel through the corticobulbar tract to reach the brainstem and cross over to the opposite side of the pons or medulla, where they synapse directly with the nuclei of lower motor neurons that makes up the cranial nerves.
And these control the muscles of the head and neck. Now, for your exams, it’s important to know that with both an upper and a lower motor neuron lesion, the muscle won’t be able to contract, which will result in muscle weakness, or decrease in muscle power.

Pathology5:18–6:37

But there are a few key facts that will help you differentiate between the two. So with an upper motor neuron lesion, muscle tone or resistance to passive stretch will be increased, also known as spastic paralysis, muscle bulk will be normal, and deep tendon reflexes will be hyperactive.
And there’s also a unique feature, known as the Babinski reflex. So, normally when stroking the lateral aspect of the sole of the foot, there’s plantar or downward flexion of all toes.
When there’s dorsiflexion of the big toe and fanning of the other toes, that’s called Babinski reflex. In contrast, in a lower motor neuron lesion, muscle tone will be decreased, which is known as flaccid paralysis, there’ll be muscle atrophy and deep tendon reflexes will be hypoactive or absent.
And the unique feature will be fasciculations, which are small muscle twitches under the skin.Okay, so let’s take a closer look at the different types of spinal cord disorders, starting with the ones affecting motor neurons of the two anterior horns.

Spinal muscular atrophy6:37–8:36

The first is spinal muscular atrophy, or SMA. This is actually a group of hereditary disorders that cause degeneration of lower motor neurons.
For your test, remember that they are all a result of a deletion of the “survival motor neuron” gene or SMN1 gene found on chromosome 5, and are inherited in an autosomal recessive pattern.
SMA type 1, also called Werdnig-Hoffmann disease, is the most common subtype, where babies often appear normal at birth and then in the first few weeks of life develop hypotonia or low muscle tone and symmetric flaccid paralysis, which is worse proximally than distally, and is initially more obvious in the legs, making it hard for them to do things like sit up.
This is why they are sometimes described as “floppy babies”. They can also have weakness in the muscles involved in sucking, chewing, and swallowing.
Another characteristic finding is tongue fasciculations. Over time, the diaphragm might be affected leading to breathing difficulties and eventually respiratory failure.
For these reasons, remember that most of these babies survive less than a couple of years. For SMA types II, III, and IV, the only thing you need to know is that they are each successively milder and have a later age of onset.
Diagnosis is done with genetic testing for the SMN1 mutation. And, though no cure is available at this time, there are some new FDA approved treatment options, including nusinersen, onasemnogene abeparvovec and risdiplam.Next up is amyotrophic lateral sclerosis, or ALS.

ALS8:36–10:54

This is a degenerative disorder, which in many cases, is caused by a mutation in superoxide dismutase 1, which is an enzyme important for removing free oxygen radicals from neurons.
So, without superoxide dismutase 1, we’re gonna have increased free radical injury, which will lead to neuron death. Now, this primarily affects the anterior horn neurons, leading to lower motor neuron signs, like symmetric flaccid paralysis with muscle atrophy, hypoactive deep tendon reflexes, and fasciculations.
Now, the unique thing about the ALS is that it also affects the cortical motor neurons of the corticospinal and corticobulbar pathways, causing upper motor neuron problems like spastic paralysis with hyperactive deep tendon reflexes, and a Babinski sign.
So if a test question combines signs of a lower and upper motor neuron lesion, the answer is probably ALS. Now, depending on which tract it happens to affect first, it may start with an inability to manipulate small items, or frequent falls.
When the corticobulbar tracts of the cranial nerves are affected, we can have head and neck weakness, dysarthria, and dysphagia, or difficulty swallowing.
And since the nuclei of these nerves are not affected, this is referred to as “pseudobulbar palsy”. Eventually, the disease might progress to involve the breathing muscles and can lead to respiratory failure and death.
Now, another extremely high- yield fact is that ALS is a purely motor disorder, so keep in mind that through all this, there are no sensory or cognitive symptoms.
Also, bowel and bladder function are spared. Diagnosis is mainly clinical and a new, but commonly tested treatment option is riluzole.
This is a medication that’s a sodium channel blocker, but it’s unclear how it helps with ALS.Moving on to occlusion of the anterior spinal artery, this can cause a spinal cord infarction, and can be iatrogenic, such as during surgery for aortic aneurysm repair.

Ant. Spinal A. Occlusion10:54–13:06

It may also occur as a complication of trauma, aortic dissection, thrombosis, embolism, vasculitis, and severe hypotension.
For your exams, it’s important to remember that the area most susceptible to ischemia is below the level of T8. So, normally, above the level of T8, the anterior spinal artery arises from branches of the vertebral arteries, while below the level of T8, it’s only supplied by the artery of Adamkiewicz, which is a branch of the aorta.
And this artery is particularly vulnerable during aneurysm repair, so if it’s traumatized, it can lead to anterior spinal artery occlusion.
Now, in this case, the anterior two-thirds of the spinal cord will be more affected since these are the areas supplied by the anterior spinal artery.
As a result, at the level of lesion, the lower motor neurons of the anterior horns will be damaged, causing lower motor neuron signs bilaterally, like flaccid paralysis and hypoactive deep tendon reflexes.
Meanwhile, below the level of lesion, the lower motor neurons on both sides are no longer receiving signals from the corticospinal tract, so over time, there’ll be signs of an upper motor neuron lesion, like bilateral spastic paralysis, hyperactive deep tendon reflexes and a Babinski reflex.
In addition to that, spinothalamic tracts on both sides will be affected, so, below the level of the lesions, individuals also have bilateral loss of pain and temperature.
Bear in mind though that this does not affect the dorsal columns, so pressure, vibration, fine touch, and proprioception will be spared.
Diagnosis is confirmed with spinal MRI, and there is usually no effective treatment.Okay, now next, there’s poliomyelitis or polio for short.

Poliomyelitis13:06–16:43

This is a viral infection caused by the poliovirus. For your test, remember that poliovirus is an RNA virus spread by fecal-oral transmission, meaning through contaminated food and water.
It can also get transmitted via respiratory droplets when an infected person sneezes or coughs. Once the virus enters the body, it gets into mucosal cells of the small intestine and oropharynx and makes its way to nearby lymph nodes and eventually into the bloodstream.
What you should absolutely remember is that in most cases, poliovirus stays there, so most individuals have no symptoms, except for maybe, unspecific signs of infections, like fever, headache, nausea and vomiting.
But about 1% of the time, it will get into the interstitial muscle tissues and make its way to the neuromuscular junction where it will go on to invade the motor neuron.
Once there, it will travel retrograde, meaning backwards, up through the axon to the anterior horn of the spinal cord. As infected lower motor neurons die, they will have flaccid paralysis and muscle atrophy as well as hypoactive or absent reflexes and fasciculations.
Now, the important thing to highlight here is that the paralysis is asymmetric, which helps us differentiate polio from SMA and ALS, where paralysis is symmetric.
On rare occasions, poliovirus can attack the brain stem and damage the motor nerves involved in speaking and swallowing.
This part of the brain stem also sends motor nerves to the diaphragm and so if they get damaged, it can cause difficulty breathing.
Another thing to know is that some people develop weakness decades after the initial infection, which is called post-polio syndrome.
This is because when polio damages some motor neurons, other nearby healthy motor neurons form collateral branches to innervate the muscles that have lost their innervation.
Now, over time, the natural process of aging causes motor neurons to die off. So when a motor neuron dies from the aging process, the muscles innervated by its collateral branches will also be affected.
Diagnosis of polio is based on the recovery of poliovirus from a stool sample or a throat swab. A lumbar puncture can be also done, where cerebrospinal fluid might have an increased number of white blood cells or poliovirus RNA.
There’s no treatment for polio, but fortunately, it’s possible to prevent infection with vaccination, an extremely high-yield topic for your exams!
There’s inactivated poliovirus vaccine, or IPV for short, also known as Salk vaccine which is made from dead or inactive viruses that’s injected into the muscle.
There’s oral poliovirus vaccine, or OPV for short, also known as Sabin vaccine, which is a weakened strain of the live virus, also called a live attenuated vaccine.
However, very rarely, poliomyelitis can develop after administration of the oral live-attenuated polio vaccine. And this is called vaccine-associated paralytic poliomyelitis.
Now, another viral infection that can affect the lower motor neurons is West Nile fever. For your test, the only thing you need to remember is that it is transmitted through mosquitoes.

West Nile fever16:43–17:05

And, presents with fever, rash, myalgias, and meningitis or encephalitis, along with an acute asymmetric flaccid paralysis.Next, there are central cord lesions near the central canal of the spinal cord.

Syringomyelia17:05–21:00

The most important one is syringomyelia. This occurs when the central canal of the spinal cord that houses the cerebrospinal fluid gradually expands.
For your exams, the high-yield fact is that the main cause of syringomyelia is a congenital condition called Chiari malformation type I.
In this condition the cerebellar tonsils slip down into the foramen magnum, which is the opening at the base of the skull.
Now, the hallmark of this malformation is hydrocephalus, which is an abnormal accumulation of cerebrospinal fluid in the brain.
Normally cerebrospinal fluid would flow through the four ventricles of the brain, and after the 4th ventricle, the fluid would either exit through two openings into the subarachnoid space where it’s reabsorbed or, alternatively, move down into the spinal canal.
In Chiari malformations, however, the displacement of the cerebellum ends up blocking these openings. As a result, the fluid backs up within the spinal canal, eventually causing the spinal canal to widen, and this leads to syringomyelia.
It’s important to know that it’s typically asymptomatic in childhood but adults may have headaches and symptoms from pressure on the cerebellum, like problems with coordination and balance.
Aside from Chiari malformations, syringomyelia can also be caused by any acquired condition that blocks the flow of cerebrospinal fluid, like a spinal cord trauma, spinal tumors, and spinal cord abscess.Regardless of the cause, the most important concept to keep in mind is that the expansion of the central canal in syringomyelia interferes with the fibers within the anterior white commissure of the spinothalamic tract.
And this primarily occurs at the level of the cervical spine, usually C4-C6, leading to the bilateral loss of the sensation of pain, pressure, temperature, and crude touch in the upper extremities and back.
A common term to describe the location of these defects is "cape-like" distribution. However, syringomyelia could also lead to dysesthetic pain, which is typically described as an abnormal, burning pain in the shoulder and neck regions.
As the central canal cavity expands it can also knock out the lower motor neurons connected to the corticospinal tract which leads to muscle atrophy, muscle weakness, and paralysis.
For your test, remember that syringomyelia classically spares the dorsal column, so sensations of pressure, vibrations, fine touch, and proprioception typically remain intact.Now, syringomyelia can also lead to several high-yield complications.
One of these is neuropathic arthropathy or Charcot joints, which is when there’s repeated trauma to the joints in the affected region since there’s no pain response.
In syringomyelia, this is most commonly seen in the shoulders. Also, the widening spinal canal can also lead to changes in the spine like scoliosis, which is a sideways curvature of the spine.
And these might be the only clues in a test question! Diagnosis is done with a brain and spine MRI and for treatment, a posterior fossa decompression surgery is sometimes required.
This is a type of craniotomy where a portion of the back of the skull is removed in order to widen the foramen magnum which helps release the buildup of pressure.
If hydrocephalus is present, a shunt can be placed to drain the excess fluid within the brain. Now, let’s move on to disorders that primarily affect the dorsal column.

Neurosyphilis21:00–25:26

Here we have neurosyphilis, which is a manifestation of tertiary syphilis. Syphilis is a sexually transmitted disease caused by the spirochete Treponema pallidum.
The first stage of the disease is localised primary syphilis, and this produces hard chancres. The second is disseminated secondary syphilis, which produces widespread maculopapular rash, and the third is systemic tertiary syphilis, which develops 15-20 years after the initial infection.
This stage affects various organs, and when it damages the brain and spinal cord, it’s called neurosyphilis. Neurosyphilis is rare, and the population at risk include males who have sex with males and individuals with HIV.
In fact, for your exam, remember that HIV infection may accelerate the rate of progression from primary syphilis to neurosyphilis.
Now, what happens in neurosyphilis is that the spirochetes invade the dorsal columns of the spinal cord, resulting in a loss of the sensations of pressure, vibrations, fine touch, and proprioception.
This is also known as “tabes dorsalis”. For your test, you need to know that without the sensations of vibration and proprioception, the individual will often stumble in the dark and have difficulty in coordination while walking, also known as sensory ataxia.
These individuals have a wide-based gait, meaning that their feet are wide apart, and they take small, slow steps. Another telltale sign is a positive Romberg sign which means that they’re unable to maintain balance with their eyes closed.
Remember that the vestibular organs in the ears, the eyes, and the nerves that sense proprioception all take part in maintaining balance.
You need at least two of these systems working to maintain balance. So when people with neurosyphilis close their eyes, only the vestibular system is working, so they can’t maintain balance.
Now, it’s also common for spirochetes to invade dorsal nerve roots that carry sensory information to the spinal cord. Irritation of these sensory roots typically manifests as sharp, shooting pains as well as hypoactive or absent deep tendon reflexes.
This is because for a deep tendon reflex to occur, the signal that the muscle has been stretched has to be transmitted via the dorsal nerve roots to the spinal cord to excite the lower motor neurons and cause muscle contraction.
The dorsal nerve roots that carry sensory signals from the bladder to the spinal cord can be also affected. This means that as the bladder fills to capacity and stretches, that sensory information is not received.
The bladder starts to overflow, and his results in a high yield condition known as neurogenic urinary incontinence. If spirochetes go even further and invade the brain, then that can cause slurred speech and altered behavior, or memory loss.
What’s extremely high yield for your exams is that they can also affect the eye, causing the characteristic Argyll Robertson pupil.
This means the pupils lose their light reflex, but it still have their accommodation reflex, which means the pupils do not constrict when exposed to light but they do when focusing on a close by object.
Now, bear in mind that examiners may also try to clue you towards neurosyphilis with other manifestations of tertiary syphilis.
The most characteristic ones are ascending aortic aneurysms with aortic valve insufficiency and gummas. These are painless, indurated, granulomatous lesions that most commonly appear on the skin, but can also involve the subcutaneous tissue, bones and other organs.
Okay now, if neurosyphilis is suspected, a venereal disease research laboratory, or VDRL test, as well as a rapid plasma reagin, or RPR test can be obtained from the CSF.
The main treatment is penicillin.Similarly, the dorsal columns can be affected by vitamin B12 or cobalamin deficiency. Specifically, B12 deficiency can result in neurological dysfunction, called subacute combined degeneration or SCD.

Vitamin B12 deficiency25:26–28:23

The reason why this happen is that vitamin B12 is an important cofactor that aids the conversion of methylmalonyl CoA to succinyl CoA.
So, with B12 deficiency, there’s too much methylmalonic acid in the body, which builds up in the neurons, specifically, in their myelin sheath, causing it to degenerate.
What you should definitely remember is that the main https://www.merriam-webster.com/dictionary/thrombocytopeniasites of involvement are the spinocerebellar tract, resulting in ataxia and recurrent falls, the corticospinal tracts causing spastic paralysis, increased deep tendon reflexes and a Babinski reflex and the dorsal columns, causing decreased vibratory and position sense.
A good way to remember that is by thinking of SCD as spinocerebellar, corticospinal and dorsal columns. It can also affect the cerebrum, causing dementia or psychiatric symptoms.
These are actually early signs of B12 deficiency. In some cases, peripheral nerves carrying sensory input can also degenerate, resulting in numbness or paresthesia.
Now, for your exams, it’s important to remember that vitamin B12 is used to synthesize DNA precursors, which is essential for cell division.
When B12 levels are low or absent, cell division is impaired, so rapidly dividing cells, like those in the bone marrow, are the most affected.
This includes precursors for platelets, and both red and white blood cells, leading to thrombocytopenia, anemia, and possibly to leukopenia.
When all three blood cell lines are affected, it’s called pancytopenia. As a response to anemia, the bone marrow compensates by releasing abnormally developed red blood cell precursors, called megaloblasts, into the blood, and the final result is megaloblastic anemia.
Another high-yield cause of pancytopenia with megaloblastic anemia is folate deficiency. Now, it’s important to differentiate between these two, since folate deficiency doesn’t cause SCD.
In fact, if you just give folate, it will mask vitamin B12 deficiency by correcting the megaloblastic anemia without correcting the neurological damage that also occurs.
Another way to differentiate between these two is serum levels of methylmalonic acid, which will only be elevated in vitamin B12 deficiency.
Treatment is with B12 supplements. Finally, there are two unique spinal cord disorders, the first of which Friedreich ataxia.

Friedreich ataxia28:23–30:51

This is an autosomal recessive disorder caused by a mutation in the frataxin gene on chromosome 9. This occurs when there’s an abnormal repetition of the trinucleotide guanine, adenine, and adenine or GAA sequence.
Frataxin is essential for mitochondrial iron regulation, so without frataxin, iron builds up inside the cell and reacts with oxygen to create free oxygen radicals, which may lead to cell death.
In the nervous system, neuronal death classically affects neurons of the spinocerebellar tract, which transmits sensations about the position of your body parts like your stance, and how flexed your knees, elbows, and wrists joints are.
And that leads to progressive problems with coordination and balance, known as ataxia. These problems usually begin in childhood, and affected individuals often fall or stagger when they walk.
If the corticospinal tracts are affected, we’ll also have upper motor neuron signs like spastic paralysis. Likewise, dorsal column damage will lead to loss of the sensations of pressure, vibrations, fine touch, and proprioception while loss of neurons in the dorsal root ganglia will lead to hypoactive or absent deep tendon reflexes.
Now, the unique thing is that Friedreich ataxia also affects the heart, causing hypertrophic cardiomyopathy, which, in fact, is the most common cause of death in these individuals.
And at the same time, in the pancreas, insulin production is impaired as beta cells are affected, leading to diabetes mellitus.
For your exams, it’s also important to know that skeletal deformities are also common, including kyphoscoliosis and foot deformities, like pes cavus, which is high arch of the foot that does not flatten with weight bearing.
So, ataxia plus hypertrophic cardiomyopathy, diabetes mellitus, and skeletal deformities points to Friedreich ataxia! Diagnosis can be done with genetic testing to look for uninterrupted GAA repeat.
Currently there are no treatments available.The second one is Brown-Séquard syndrome, where there’s a complete hemisection of the spinal cord.

Brown-Séquard syndrome30:51–33:57

The most common cause is a penetrating trauma like a gunshot injury or stab wound in the back, but a large spinal cord tumor can lead to this syndrome.
The high yield concept is the presentation of symptoms and on which side they manifest. So, let’s say there’s a complete right hemisection of the spinal cord.
This means all the principal neural tracts in the right side of spinal cord are now damaged. Damage to the right sided corticospinal tract means that, below the level of lesion, the lower motor neurons, like those going to the right leg, are no longer receiving signals from the upper motor neuron, so there’ll be signs of an upper motor neuron lesion, like ipsilateral spastic paralysis, hyperactive deep tendon reflexes and a Babinski reflex.
Meanwhile, at the level of lesion, the lower motor neuron of the right anterior horn will also be damaged, causing right-sided flaccid paralysis and hypoactive deep tendon reflexes.
Similarly, there’s damage to the dorsal column on the right side, which will lead to loss of fine touch, pressure, vibration, and proprioception in the right side of the body at the level of the injury and below it.
Now the spinothalamic tract is a bit different because it crosses over to the opposite side of the spinal cord 1 or 2 spinal segments above where the 1st order neurons enter.
So, damage to the right spinothalamic tracts will cause loss of pain, temperature and crude touch sensation from the opposite or left side beginning one or two segments below the lesion.
But, at the level of the lesion, the spinothalamic tract of the right side will be damaged too. This will lead to complete loss of all cutaneous sensation at the level of lesion on the right.
Besides those three tracts, very rarely, a hemisection of the spinal cord above the T1 spinal level can also damage the sympathetic chain that runs alongside the spinal cord and supplies the facial region.
This leads to Horner’s syndrome on the same side of the face as the lesion which include symptoms of miosis or constricted pupil, ptosis or droopy eyelid, and anhidrosis or failure to sweat.
So, for your test, remember that ipsilateral to the lesion, there’s spastic paralysis and loss of pressure, vibrations, fine touch, and proprioception below the level of the lesion, flaccid paralysis at the level of the lesion, and maybe Horner sign.
And contralaterally, there’s loss of pain and temperature sensation one or two levels below lesion. Diagnosis can be confirmed with MRI.All right, as a quick recap, the first group of spinal cord disorders causes anterior horn lesions and includes spinal muscular atrophy which is an autosomal recessive group of hereditary disorders, with type 1 or Werdnig-Hoffmann disease being the most common and manifesting as a “floppy baby”, and amyotrophic lateral sclerosis, which combines upper and lower motor neuron lesion signs, with no sensory, cognitive, bowel or bladder symptoms.

Review33:57–36:43

There are also infections which include poliomyelitis, caused by the poliovirus and rarely West Nile fever, which is transmitted by mosquitoes.
Both infections cause asymmetric paralysis. The second group includes central spinal cord lesions and here we have syringomyelia.
This occurs when the central canal of the spinal cord gradually expands, most commonly due to a Chiari malformation. The key symptom is loss of pain, pressure, temperature, and crude touch in a cape like distribution, as well as Charcot joints and scoliosis.
Third, there are disorders affecting the dorsal column. These include neurosyphilis, which is a manifestation of tertiary syphilis and usually affects the dorsal spinal columns, causing loss of pressure, vibrations, fine touch, and proprioception, ataxia, wide-based gait and positive Romberg sign.
A key sign is Argyll Robertson pupil. Next we have vitamin B12 deficiency.
Which can cause subacute combined degeneration. This presents as impaired sensation of pressure, vibrations, fine touch, and proprioception, spastic paralysis, numbness or paresthesias.
Remember to look for macrocytic anemia in these individuals. Finally, other spinal cord disorders include Friedreich ataxia, which is an autosomal recessive disorder due to trinucleotide repeat.
It presents with ataxia, spastic paralysis, loss of pressure, vibrations, fine touch, and proprioception and deep tendon reflexes, as well as hypertrophic cardiomyopathy, diabetes mellitus and skeletal deformities.
Lastly, there’s Brown Séquard syndrome, which is when there’s a hemisection of the spinal cord, resulting in paralysis and loss of pressure, vibrations, fine touch, and proprioception on the same side as the lesion, and loss of pain and temperature sensation on the opposite side of the lesion.

Summary36:43–37:58

Okay, back to our cases. Mario presented with progressive muscle weakness, which started with an inability to manipulate small items, and progressed into frequent falls and difficulty with speech.
In the absence of any sensory, cognitive, bowel or bladder symptoms, we know that only motor neurons are affected. On neurological exam, we had upper motor neuron signs like increased muscle tone, and deep tendon reflex, and fasciculation which is associated with lower motor neuron lesions.
So this should make you suspect amyotrophic lateral sclerosis. On the other hand, Donna came in with ataxia, a wide-based gait and positive Romberg sign, as well as loss of pressure, vibrations, fine touch, and proprioception.
These sensory defects suggest a problem with the dorsal column. Now, a key sign on physical exam was the Argyll Robertson pupil, which are all characteristic for neurosyphilis.
The fact that she is HIV-positive was another clue since it’s a major risk factor. Neurosyphilis was confirmed with a lumbar puncture which was positive for VDRL.