There are four important clinical patterns to recognize that signify localization to particular parts of the spinal cord, each with a particular differential diagnosis (Fig. 5-4A and Table 1-1).
Schematic of spinal cord lesions. A: Brown-Séquard (hemicord) syndrome. B: Anterior cord syndrome. C: Central cord syndrome. D: Subacute combined degeneration. Reproduced with permission from Aminoff M, Greenberg D, Simon R: Clinical Neurology, 9th ed. New York: McGraw-Hill Education; 2015.”
TABLE 5–1Spinal Cord Syndromes. ||Download (.pdf) TABLE 5–1 Spinal Cord Syndromes.
| ||Brown-Séquard Syndrome ||Anterior Cord Syndrome ||Central Cord Syndrome ||Subacute Combined Degeneration |
|Ipsilateral ||Contralateral |
|Motor ||Affected ||Spared ||Affected bilaterally ||Spared bilaterally (until very advanced) ||Affected bilaterally |
|Vibration/proprioception ||Affected ||Spared ||Spared bilaterally ||Spared bilaterally ||Affected bilaterally |
|Pain/temperature ||Spared ||Affected ||Affected bilaterally ||Affected bilaterally (in hands/upper extremities first) ||Spared bilaterally |
Brown-Séquard (Hemicord) Syndrome
Hemicord syndrome affects all pathways on one side of the spinal cord (Fig. 5–4A). The corticospinal tracts cross in the medulla, which is just above their entry into the cervical spinal cord. Therefore, motor deficits caused by a unilateral spinal cord lesion will cause ipsilateral weakness below the level of the lesion. The dorsal column pathways remain ipsilateral until they cross in the medulla, so unilateral spinal cord lesions will cause ipsilateral deficits of proprioception and vibration sensation below the level of the lesion. Since the anterolateral (spinothalamic) tracts cross as they enter the spinal cord, lesions of one side of the spinal cord will affect already-crossed spinothalamic fibers, causing contralateral deficits in pain and temperature sensation below the level of the lesion (a small region of ipsilateral pain and temperature sensation loss may also be seen at the levels over which the pathway is crossing).
In summary, a lesion affecting one lateral half of the spinal cord will cause:
Ipsilateral weakness below the level of the lesion
Ipsilateral loss of vibration sense and proprioception below the level of the lesion
Contralateral loss of pain and temperature sensation below the level of the lesion
For example, in a lower thoracic Brown-Séquard syndrome affecting the right hemicord, there will be right-sided (ipsilateral) weakness and vibration sense/proprioception loss with spared pain/temperature sensation, and the opposite pattern on the left (contralateral) side: preserved strength and vibration sense/proprioception but impaired pain/temperature sensation.
Hemicord syndrome is most commonly caused by penetrating trauma (e.g., stab or gunshot wound), but can also be caused by a neoplasm compressing the cord from one side (e.g., meningioma) or a unilateral demyelinating lesion (e.g., transverse myelitis).
Anterior cord syndrome involves nearly the entire cross sectional area of the spinal cord with the exception of the dorsal columns (Fig. 5–4B). Therefore, motor function and pain and temperature sensation are impaired below the level of the lesion but proprioception and vibration are spared. Both upper and lower motor neuron signs may be seen: upper motor neuron signs due to interruption of the descending corticospinal tracts and lower motor neuron signs due to involvement of the gray matter at the affected level(s) of the spinal cord. Anterior cord syndrome occurs most commonly due to infarction in the territory of the anterior spinal artery of the spinal cord, which is most often caused by abdominal aortic aneurysm (AAA), AAA rupture, or in the setting of surgery for AAA repair. The reasons why the anterior spinal cord is more vulnerable to ischemia than the posterior cord are discussed in Chapter 19 (see “Ischemic stroke of the Spinal Cord”).
Central cord syndrome occurs most commonly due to syrinx, a dilatation of the central canal of the spinal cord (Fig. 5-4C). When the central canal enlarges in a syrinx, this usually occurs in the cervical spinal cord. The closest structure to the central canal is the anterior commissure where the anterolateral tracts cross. Since the upper extremity spinothalamic fibers enter and cross in the cervical spinal cord, these are affected first. This leads to bilateral loss of pain and temperature sensation in the upper extremities, which can cause a “cape-like” distribution of sensory deficits. As a syrinx continues to expand, spinothalamic (and, in some cases, corticospinal) tracts may be compressed from medially to laterally. Since upper extremity fibers are medial in both pathways, these are affected first leading to involvement of the upper extremities before affecting the lower extremities if the syrinx progresses.
Syrinx can occur in the setting of a Chiari malformation (see “Chiari Malformation” in Ch. 26), or any lesion of the spinal cord leading to obstruction of the central canal (e.g., tumor, prior trauma, demyelination, hemorrhage).
Subacute Combined Degeneration
Selective involvement of the dorsal columns and corticospinal tracts together occurs in subacute combined degeneration (Fig. 5–4D). Subacute combined degeneration is most commonly caused by vitamin B12 deficiency, but can also be caused by copper deficiency. Vitamin B12 deficiency can be caused by malabsorption (e.g., pernicious anemia, small intestine pathology or surgery, gastric bypass) or a vegetarian or vegan diet. Copper deficiency can occur in the setting of excess zinc ingestion (which can be caused by zinc-containing denture creams), after gastric bypass surgery, or due to malabsorption. Both vitamin B12 deficiency and copper deficiency can result in concurrent myelopathy and neuropathy (myeloneuropathy), which can cause mixed upper and lower motor neuron features on examination (e.g., absent ankle reflexes and brisk knee reflexes, or areflexia with Babinski signs).
The dorsal columns and corticospinal tracts are also selectively affected in the vacuolar myelopathy of AIDS (see “HIV-associated vacuolar myelopathy” in Ch. 20).
Involvement of the dorsal columns and dorsal roots together is seen in tabes dorsalis in syphilis (see Ch. 20).