IM Board Review #8 - Spinal Cord

We continue our general survey of neurology with an overview of the spinal cord.

Things we cover in this podcast:

• Signs and Symptoms of Myelopathy
• Breakdown of some causes of compressive versus non-compressive myelopathies
  • Infections
  • Neoplasms
  • Transverse Myelitis
  • Metabolic Causes
  • Vascular Myelopathies
  • Genetic Disorders

• Check out our website at www.theneurotransmitters.com to sign up for emails, classes, and quizzes!
• Would you like to be a guest or suggest a topic? Email us at contact@theneurotransmitters.com
• Follow our podcast channel on 𝕏 @neuro_podcast for future news!
• Find me on 𝕏 @DrKentris

The views expressed do not necessarily represent those of any associated organizations. The information in this podcast is for educational and informational purposes only and does not represent specific medical/health advice. Please consult with an appropriate health care professional for any medical/health advice.

Chapters

• 0:00 Spinal Cord Disorders Overview
• 6:27 Diagnostic Considerations in Spinal Disorders

Transcript

Michael Kentris: 0:00

Hello and welcome back to the Neurotransmitters, your source for all things related to clinical neurology. I'm your host, dr Michael Kentris, and today we're going to be talking about spinal cord disorders and it's going to be a relatively short discussion, and that's not because there aren't a lot of things that can go on in the spinal cord, but it is because some of these issues are covered in other recordings and some of these disorders are pretty rare, which means they don't get a lot of screen time in practice questions, nor do they really show up on boards very, very often. So, with all that being said, what are the signs and symptoms that tend to make us think about a myelopathy? So I think we can group these into two main buckets that we're able to observe either by history or on physical exam, and I tend to lump these into motor and non-motor. So if we have some sort of dysfunction in the corticospinal tract, we've got our upper motor neuron signs, which is spasticity, weakness, hyperreflexia and an extensor plantar response or Babinski reflex. Contrast that with our typical lower motor neuron signs, which is more of a flaccid paralysis. Now the tricky thing is that flaccid paralysis can occur in a very early hyperacute situation, say a spinal cord infarct, but over time that should develop into a more hyperreflexic and spastic type picture. But the timing of when you're encountering the patient does matter. Our other typical lower motor neuron signs are things like fasciculations, atrophy, hyporeflexia or decreased reflexes. So you do need to pay attention to what either the vignette is telling you or what your actual physical exam if you're using this in real life is telling you.

Michael Kentris: 1:36

On the non-motor side we've got a few other things as well. One of the big buckets there is sensory testing. So we have proprioception and vibratory sense in the dorsal columns and then we have temperature and pain or pinprick testing in the spinothalamic pathways. And pinprick testing in particular is very helpful if we're concerned about myelopathy, as that can help us find a sensory level which is usually going to be at or a little bit below the level of the lesion. Other symptoms that may come to line, either in the history or physical, are gait issues or difficulties with bowel or bladder control. If you have involvement of the distal spinal cord or the lower roots that is, cauda equina syndrome you may find decreased tone, areflexia and loss of perianal sensation described as well. Etiology-wise we can think in two very broad categories compressive and non-compressive causes of myelopathy, starting with compressive. Very often people will describe pain at the level of compression and in some cases focal percussion may help you figure out which level that is.

Michael Kentris: 2:38

There are several red flag signs that may make you switch over from just back pain into something more suspicious Fevers, focal tenderness. Someone with a recent history of surgery, particularly spinal surgery, or someone with a history of IV drug use. This may make you think about things like an epidural abscess, dysgitis or other types of infection. If someone has a history of cancer, then you start to think about things like bony metastases. If they're on anticoagulation, then you start worrying about things like an epidural hematoma. So the context, as always, does matter.

Michael Kentris: 3:12

Timing also matters. Is this more of a hyperacute, subacute or chronic process? If we have someone who looks myelopathic, chronic spinal stenosis tends to affect the cervical and lumbar spine more than the thoracic spine, but there may be some common symptoms that you can elicit in the history. Some things to ask about progressive leg weakness or trouble walking, which they attribute to stiffness in their legs, but on examination you may find evidence of spasticity. They may also describe some numbness or paresthesias, distally more often in the legs, and they may also describe some bladder control issues, whether this is incontinence or retention. You may also get some symptoms suggestive of claudication, in particular spinal claudication or quote-unquote pseudo-claudication. So they may have some exertional pain around the groin, thighs or buttocks and again there may be some associated weakness and or numbness. Our preferred test is going to be MRI of the spine, aimed at the level that we think is involved. So you do need to base that off of the history and the examination. If someone is hyperreflexic in the legs but not the arms, you're thinking more thoracic spine. If it's the arms and the legs, maybe you're thinking more cervical spine. So you do need to put your exam together with your history so that you know what test is most likely to get you a diagnosis.

Michael Kentris: 4:30

For most causes of compressive myelopathy, surgical decompression is often going to be required, but it does depend on the underlying cause. Now in most of these acute onset emergent treatment is going to be more important, as significant symptoms, that is to say significant neurologic decline at the time of surgery, can be associated with worse post-op outcomes. So mostly what we're doing with this surgery is we're preventing further neurologic deterioration. So if a neurologic deficit is considered-unquote, completed surgery may be deferred as these can be quite high risk and if there is low potential for benefit, the risk may not be worth the potential benefit. Other adjunctive treatments to consider. If it is a bleeding diathesis and they have an epidural hematoma, you're obviously going to want to reverse that anticoagulation If they have had spinal cord trauma or an abscess, steroids are considered controversial and are not routinely recommended. However, they could be considered on a case-by-case basis if the process is thought to be more neoplastic.

Michael Kentris: 5:34

Moving on to the non-compressive myelopathy camp and this is where a lot of the quote weird stuff might hang out let's start off with transverse myelitis, and we're talking specifically about quote idiopathic end quote transverse myelitis. Now I am throwing a lot of quotes in here because transverse myelitis is more of a syndrome and less of a diagnosis. There are a lot of things that you have to investigate before settling on idiopathic transverse myelitis as a diagnosis. So historically this is considered a monophasic inflammatory demyelinating disorder. It can occur both parainfectious and post-infectious and the most common symptoms typically include subacute weakness, sensory changes and bowel or bladder dysfunction. People may also describe a thoracic banding sensation and on examination they will often have a sensory level on examination.

Michael Kentris: 6:27

Now I want to take a moment and this may be more detail than what people need for their IM boards, but I think it's an important point. So, on MRI of the spine it's an important point. So, on MRI of the spine, typical MS lesions are usually one to two vertebral segments long and there is an entity, what we call longitudinally extensive transverse myelitis, which is usually three or more levels long and that has a different differential diagnosis and we'll talk about that in a minute. But those imaging characteristics should raise some red flags that we're not dealing with. Maybe just plain Jane MS or an idiopathic transverse myelitis, and we definitely need to go looking for secondary causes. So, as we had discussed in previous recordings about MS, specifically, if the MRI of the brain doesn't show any lesions, if on the spinal fluid testing there is no evidence of oligoclonal bands, ms is less likely and perhaps this will be a monophasic event, as is historically recorded. However, if we have lesions on the brain, if we have O-bands, then we might be leaning more away from just an idiopathic transverse myelitis towards an actual diagnosis of multiple sclerosis. Similarly, if we have longitudinally extensive transverse myelitis, then we need to go looking for other entities such as neuromyelitis optica or NMO with aquaporin-4 antibodies. You may also go look for other causes depending on the CSF profile.

Michael Kentris: 7:55

If it looks infectious, there are a number of entities that we have to keep in mind. Fortunately, there are different panels and PCR panels that can check for a lot of infectious etiologies relatively quickly these days. So some viruses to keep in mind herpes simplex virus, varicella, zoster virus, west Nile virus, which can look very similar to polio, human T lymphotropic virus or tropical spastic paraparesis, lyme disease, neurosyphilis, hiv. And HIV is a little unique. It can happen at the time of seroconversion or, in the more long term you can get a vacuolar myelopathy in people who have chronic low CD4 counts. Tuberculosis could also potentially present with similar symptoms of myelopathy. So you've ruled out infection. It looks inflammatory, maybe demyelinating.

Michael Kentris: 8:44

You're going to start some treatment. What are you going to start? Well, like with so many things in neurology, we're going to fall back on steroids. Our first line is usually IV methylprednisolone, one gram per day for about five days. If you can't use steroids for some reason or they're not working, you might consider plasma exchange for those refractory cases.

Michael Kentris: 9:03

Moving on to subacute combined degeneration, this one's a little bit unique. Often due to B12 deficiency, it typically presents with sensory disturbances, often loss of proprioception, vibratory sense, paresthesias, weakness, ataxia, difficulty walking. Obviously, one of our first steps in suspected cases of subacute combined degeneration is to check a vitamin B12 level. You'll also be checking for methylmalonic acid and homocysteine levels. So in the typical subacute combined degeneration picture, b12 is low, methylmalonic acid and homocysteine are high. In people with low normal B12, you may also get some mild cases of subagute combined degeneration. So it is very common for people to use B12 as a screening test and to only check the methylmalonic acid and homocysteine if there is a high clinical suspicion. So if you have that low normal B12, but your clinical suspicion is high, do check those confirmatory labs. You may have a macrocytic anemia, you may not, so that is not necessarily going to point you away from it if your clinical suspicion is high.

Michael Kentris: 10:10

Also. Another reason this may happen is recreational nitrous oxide use. This can happen if you're breathing the nitrous oxide out of a whipped cream can or people who are buying what are called whippets from gas stations or other kind of unreputable places, and this can in turn lead to a B12 deficiency. You can also see similar symptoms from a copper deficiency. So this can be from malabsorption, nutritional deficiencies or excessive zinc use. So sometimes you'll see this in people who are taking a lot of supplements or take a lot of zinc when they're not feeling well and if their copper status is a little borderline, this may push them over into developing some neurologic symptoms. Both B12 and copper deficiencies can be more common in people who have had bariatric surgery. So definitely things to keep in mind in terms of prior surgical history.

Michael Kentris: 10:58

Let's move on to a couple of vascular causes. So a spinal cord infarct. Most often this is going to be in the anterior spinal artery distribution, and this is because there is one anterior spinal artery as opposed to the two posterior spinal arteries. So there's more redundancy in the posterior spinal artery territory than there is anteriorly. Typically we're going to see someone presenting with acute onset of flaccid paralysis. Very often there will be some pain associated with this as well, and over time they may develop the typical spasticity. But in the hyperacute phases you may not see that on exam. In fact you probably won't. They will typically also have preserved vibratory and proprioceptive sense right those dorsal columns, because it is the anterior spinal artery territory that is infarcted. Unfortunately, that means that's our motor pathways are getting knocked out there pretty hard.

Michael Kentris: 11:49

Some causes that may make you consider this more in your differential diagnosis. If someone just recently woke up from anesthesia after a complicated cardiovascular or aortic surgery and they had a lot of hypertension during the procedure, that may raise a red flag. An area that's at particular risk is the artery of Adamkiewicz, which is a large radicular artery, often in the lower thoracic around TA to T12 territory, although there is some variability, and so that is very susceptible to hypotension, in particular in older adults who may have some superimposed stenosis or atherosclerosis of that vessel, and then you throw that hypotension on top of it during a prolonged surgery that may lead to a spinal cord infarct. Another potential cause of vascular myelopathy are dural arteriovenous fistulas, or dural AVFs. Now these are a little bit more subacute to chronic in their onset and it's thought that they're mostly causing these symptoms due to venous congestion, although they may present as an infarct as well. On imaging, typically MRI, we're going to be looking for vascular flow voids, particularly on T2 sequences. So if you see these little dark spots in the bright CSF, that should raise your suspicion for a possible dural AVF. However, it is a very challenging diagnosis to make and if the clinical suspicion is high. Even with normal MRI, you may need to ask your neurointerventionalist for a spinal angiogram. So definitely a very challenging diagnosis in these patients. Who is it going to happen to? It's a little more common in men over the age of 50 and those with a history of prior spinal surgery.

Michael Kentris: 13:30

Last category I wanted to touch on during this recording genetic disorders. Most of these are fairly rare and in these cases family history is going to be of the utmost importance. Starting with that is hereditary spastic paraplegia. So again, family history very important, and the severity and progression of these symptoms can vary significantly from person to person. Lastly, I'll mention adrenomyeloneuropathy, which can sometimes be seen in female carriers of X-linked adrenoleukodystrophy. So they'll have a lot of the same symptoms that we mentioned before in terms of spasticity, bowel bladder issues, difficulty walking, etc. But there will oftentimes be something in the story to suggest adrenal insufficiency. So in these patients we may also be sending out very long-chain fatty acid profiles or genetic testing, depending on the presentation. That is all I have for you today If you made it this far.

Michael Kentris: 14:23

Thank you so much and if you enjoyed this podcast, please leave us a five-star review on Apple Spotify, wherever you get your podcasts. If you found the information today helpful, please share it with your friends, subscribe for future episodes, and you can find me on X, formerly known as Twitter, at DrKentris D-R-K-E-N-T-R-I-S. And you can find the official show at Neuro underscore podcast N-T-R-I-S. And you can find the official show at neuro underscore podcast. You can also find more of our resources on the website online at theneurotransmitterscom. Thank you again for listening and we'll see you next time.