Approach to differentiating lesions (spinal cord): Clinical sciences

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Introduction0:00–0:51

Spinal cord lesions occur as a result of damage or injury to the spinal cord, which can eventually lead to various clinical manifestations below the lesion, including loss of function and sensation.
The anterior spinal cord, which contains the corticospinal and spinothalamic tracts, is supplied by a singular anterior spinal artery; while the posterior spinal cord, which contains dorsal columns, is supplied by a pair of posterior spinal arteries.
Now, there are several different spinal cord syndromes, including conus medullaris and cauda equina syndromes, as well as central cord-, anterior cord-, posterior cord-, hemicord-, and complete cord syndrome.

Unstable Patient0:51–1:53

Now, if your patient presents with chief concerns suggestive of a spinal cord lesion, first, perform an ABCDE assessment to determine if they are unstable or stable.
If unstable, stabilize the airway, breathing, and circulation. At this point, you might even have to intubate the patient and start mechanical ventilation.
Next, obtain IV access, consider starting IV fluids, and place your patient on continuous vital signs monitoring, including heart rate, blood pressure, and pulse oximetry, as well as cardiac telemetry.
Now, here’s a clinical pearl to keep in mind! Acute spinal cord injury above the T6 level can disrupt sympathetic innervation to the heart and peripheral vasculature and cause unopposed parasympathetic activity through the vagus nerve.
Eventually, this can result in hypotension, bradycardia, and subsequent neurogenic shock. In addition, high cervical lesions can cause respiratory failure because C3 to C5 nerve roots innervate the diaphragm.

Stable Patient1:53–3:13

Now, let’s go back to the ABCDE assessment and take a look at stable individuals. In this case, you should obtain a focused history and physical exam.
The patient will describe numbness with or without weakness of the limbs and trunk, depending on lesion type and affected spinal tracts.
Also, the patient might report bowel or bladder dysfunction, due to autonomic and somatic pathway dysfunction. On examination, you will notice normal cranial nerve function and speech.
There is sensory loss with or without motor weakness in the limbs and trunk. Additionally, you might identify a sensory level in the trunk, meaning a level below which there is sensory loss.
Remember that the chest is at the level of the T4 sensory dermatome, and the umbilicus is at T10. Next, there will be abnormal tone or reflexes; There will be a positive Romberg test if the dorsal columns are affected, this indicates impaired proprioception.
Finally, they may have an abnormal gait due to motor or sensory loss. These findings are highly suggestive of a spinal cord lesion.
Once you’ve determined this, your next step is to assess for weakness or sensory loss in the cervical or thoracic regions.

Conus medullaris syndrome3:13–3:57

If these deficits are absent, you should consider conus medullaris- or cauda equina syndrome. First, let’s focus on conus medullaris syndrome, which is associated with symmetric weakness in the lower extremities and loss of sensation in the peri-anal region, buttocks, and inner thighs.
This specific loss of sensation is also known as saddle anesthesia. Also, you will notice decreased or absent ankle reflexes and positive Babinski reflexes.
These findings are highly suggestive of conus medullaris syndrome. Conus medullaris refers to the most distal part of the spinal cord.
Now let’s go back to our assessment and look at cauda equina syndrome. This condition is associated with asymmetric weakness in the lower extremities, saddle anesthesia, and decreased or absent knee and ankle reflexes.

Cauda equina syndrome3:57–4:43

Also, keep in mind that these individuals will typically present with absent Babinski reflexes and back pain. At this point, you should think of cauda equina syndrome.
The cauda equina is a bundle of nerve roots at the end of the spinal cord and consists of the lumbar, sacral, and coccygeal nerves.
Now, here’s a clinical pearl to keep in mind! In both conus medullaris and cauda equina syndrome, bowel and bladder dysfunction are often present.
Both syndromes should be evaluated emergently, as surgical intervention might be needed to prevent permanent neurologic deficits.
Now, let’s go back and take a look at individuals with deficits in the cervical or thoracic region. In this case, your first step is to assess the pattern of sensory loss.

Syringomyelia4:43–5:52

If there is a bilateral loss of pain and temperature sensation, indicating injury of the spinothalamic tracts, assess the distribution of weakness.
If the weakness affects the upper extremities only, diagnose cervical central cord syndrome. Here’s a high-yield fact!
These patients will present with a cape-like distribution of sensory loss over the shoulders, chest, and arms. Unless the lesion is large, there is usually no leg weakness because the leg fibers run in the lateral aspect of the lateral corticospinal tracts.
Next, obtain a spine MRI.If you identify a fluid-filled cavity in the central cervical spine cord, diagnose syringomyelia, which is often associated with a Chiari type I malformation, neck trauma or hyperextension, and cervical spine tumor.

Anterior spinal cord infarction5:52–7:00

On the other hand, if weakness affects both upper and lower extremities, diagnose anterior cord syndrome and obtain a spine MRI.
If the MRI shows restricted diffusion in the anterior cord, then you can diagnose an anterior spinal cord infarction. Another common cause of anterior cord syndrome is cervical disc herniation which is associated with spinal cord compression.
Remember that there is only one anterior spinal artery, which provides vascular supply to the anterior two-thirds of the spinal cord.
In contrast, there are two posterior spinal arteries, one on the left and one on the right, that supply the posterior third of the spinal cord.
Here's another clinical pearl! A spinal cord infarction most often occurs in the thoracolumbar spine from occlusion of the artery of Adamkiewicz, an artery that comes off the aorta and supplies the lower two-thirds of the spinal cord.
Because of this anatomy, the arms are usually spared. Alright, shifting gears and moving on to patients with unilateral or bilateral loss of vibration and proprioception.These findings suggest injury to the posterior columns, so diagnose posterior cord syndrome.

Subacute combined degeneration7:00–8:21

Posterior cord syndrome is associated with a stomping gait, characterized by forceful steps, allowing the patient to know when their foot lands.
The gait is also wide-based and unsteady, and balance will be worse if patients’ eyes are closed and when you take away visual cues.
Once you identify posterior cord syndrome, your next step is to assess for muscle weakness. If present, the likely diagnosis is subacute combined degeneration from B12 deficiency.
This condition affects posterior columns and lateral corticospinal tracts. Remember that in early or mild B12 deficiency, the vitamin level might be normal, so send for methylmalonic acid and homocysteine levels, both of which will be elevated!
Common causes of B12 deficiency include strict vegan diets and malabsorption, which can be seen in conditions like inflammatory bowel disease and gastric bypass.
Additionally, B12 deficiency can occur due to B12 inactivation, such as with recreational inhalant use of nitrous oxide, also known as “whippets”.
Now, let’s discuss patients with isolated dorsal column dysfunction with absent motor weakness. In these individuals, the first step is to assess the underlying cause with additional history and physical exam findings to determine whether the cause is Tabes dorsalis or posterior spinal cord infarction.

Tabes dorsalis8:21–9:19

In Tabes dorsalis, history will reveal shooting pain in the legs and remote untreated syphilis. On examination, you will identify Argyll Robertson pupils, meaning that the pupils constrict with accommodation, but not with light.
The reflexes will be decreased or absent, particularly in the legs, the Romberg test will be positive, and you will notice a stomping ataxic gait.
With these findings, the likely diagnosis is Tabes dorsalis, but to confirm the diagnosis, be sure to obtain additional tests to identify syphilis infection.
On the flip side, in posterior spinal cord infarction, history will reveal a sudden onset of sensory loss and back pain.

Posterior spinal cord infarction9:19–9:58

Additionally, the patient might have a medical history of significant aortic disease or surgery. In addition to vibratory and proprioceptive sensory loss, you will also identify decreased or absent reflexes in the same distribution as the sensory loss.
Next, if the symptoms are bilateral, there might be a positive Romberg test or stomping, ataxic gait. These findings are suggestive of posterior spinal cord infarction, but you should confirm the diagnosis by obtaining a spine MRI.
Okay, now let’s move on to hemicord syndrome. These patients present with unilateral loss of vibration and proprioception and contralateral loss of pain and temperature sensation.

Hemicord syndrome9:58–11:06

Of note, there will also be weakness on the same side of the spinal cord injury. With these findings, you should think of hemicord syndrome, which is also known as Brown-Séquard syndrome.
This phenomenon occurs because the spinothalamic tract fibers cross soon after entering the spinal cord, while the dorsal column fibers ascend ipsilaterally in the spinal cord and decussate in the medulla.
Next assess the underlying cause by obtaining further history. If the patient reports trauma, such as a stab wound or gunshot to the back, the likely cause is penetrating trauma.
On the other hand, if the patient reports progressive worsening of weakness and sensory loss, neck or back pain, and possibly a known history of degenerative disc disease or malignancy, think of spinal cord compression.

Complete cord transection11:06–12:05

Finally, let’s discuss patients presenting with bilateral loss of all sensory modalities. In this case, the dorsal columns and spinothalamic tracts are affected, meaning the anterior and posterior parts of the spinal cord are injured, so you can also expect bilateral weakness below the level of injury.
In these individuals, diagnose complete cord syndrome. Next, assess the underlying cause.
If the patient reports a sudden onset of symptoms and has just suffered severe trauma, like a high-impact car crash, assault, or a high-level fall, the likely cause is cord transection.
On the flip side, if the patient reports progressive symptoms, typically over a few hours to days, which could be associated with recent fever and infectious symptoms, or autoimmune conditions like multiple sclerosis or systemic lupus erythematosus, the diagnosis is probably transverse myelitis.

Review12:05–12:54

Alright, as a quick recap... Spinal cord lesions can cause motor, sensory, and autonomic dysfunction, depending on which part of the spinal cord is affected.
If your patient presents with chief concern suggestive of a spinal cord lesion, your first step is to assess for deficits in the cervical and thoracic regions.
If absent, you should think of lesions related to the distal part of the spinal cord. This includes conus medullaris syndrome and cauda equina syndrome.
On the flip side, if you identify deficits in the cervical or thoracic regions, your next step is to assess the pattern of sensory loss.
This will help you determine the specific spinal cord syndrome, including central-, anterior-, posterior-, hemi-, or complete cord syndromes.