Approach to differentiating lesions (spinal cord): Clinical sciences

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.

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.

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.

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. 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. 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. 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.