Spinal Cord Hemorrhage

Hemorrhage affecting the spinal cord is rare. Spinal cord hemorrhage can be divided based on etiology, into two types: (1) traumatic and (2) non-traumatic. It can also be divided based on the compartment into which the hemorrhage occurs, namely: (1) intramedullary (including hematomyelia), (2) subarachnoid (SAH), (3) subdural (SDH), and/or (4) epidural (EDH). ^[1] Spinal cord hemorrhage is most commonly caused by trauma, vascular malformations, or bleeding diatheses. Spinal cord hemorrhage usually presents as sudden, painful myelopathy, which may reflect the anatomic level of the hemorrhage. ^[2]

For perfusion, three longitudinal vessels form an anastomotic network that supplies the spinal cord: two posterior spinal arteries, and the anterior spinal artery. Blood flows from the anterior spinal artery into medullary branches of the intradural vertebral arteries, and subsequently into segmental radiculomedullary arteries. The blood flow to the posterior spinal arteries originates from intradural vertebral arteries, which are from medullary segments of the posterior inferior cerebellar arteries and segmental radiculopial arteries. Blood flow to the lower portion of the spinal cord (T8–L3) is supplied by a large radicular artery with somewhat variable positioning, termed the Artery of Adamkiewicz. ^[1]

Vascular supply and venous drainage of the spinal cord

The cross-sectional blood supply of the spinal cord can be divided into (1) central and (2) peripheral systems, which supply the grey and white matter, respectively (with some degree of overlap). The central perfusion region receives blood supply from the anterior spinal artery, which forms the central sulcus artery and courses into the ventral median sulcus and supplies the grey matter of spinal cord. The posterior spinal arteries give rise to the “vasocorona,” which eventually branches into peripheral arteries and mainly supplies the white matter of the spinal cord. ^[1]

Anterior and posterior median spinal veins drain the anterior and posterior regions of the spinal cord, respectively. The pial surface and superficial regions of the spinal cord are drained by radial veins and the coronal venous plexus. ^{[1, 3, 4]}

The most common cause of spinal cord hemorrhage is traumatic injury. With trauma, shear forces acting upon the spinal cord and surrounding structures may lead to hemorrhage and vascular damage. These may in turn cause additional injury through edema and infarction. Autopsy studies demonstrate the hemorrhagic necrosis of the spinal cord that is caused by trauma. In non-traumatic cases, vascular malformations and coagulopathies are the most common etiologies, in almost equal proportions.

Hematomyelia is defined as the presence of a well-defined focus of hemorrhage within the spinal cord itself. Trauma is the leading cause of hematomyelia. Hematomyelia more commonly involves the cervical rather than thoracic or lumbar spinal cord. In hematomyelia, blood tends to dissect longitudinally above and below the hemorrhage, disrupting grey matter more than white matter. The most common location is within the central grey matter of the spinal cord, centered at the point of mechanical impact.  Ischemia results from mass effect and disruption of blood flow, which may cause infarction of the spinal cord. Such infarction also usually involves the grey matter to greater extent than the white matter. ^{[1, 5, 6]}  

Hematomyelia can also be spontaneous, and has been reported in patients with hereditary coagulation disorders and/or patients on antiplatelet and anti-coagulation therapies. Intramedullary spinal cord tumors, both primary CNS and metastatic (especially renal cell carcinoma), can also bleed and lead to hematomyelia. ^{[7, 8]} The causes for bleeding within the spinal cord are summarized in Table 1. 

Table 1. Summary of intramedullary spinal cord hemorrhage etiologies, with history and associated clues, common imaging findings, and representative management. Adapted from Leep, Hunderfund, & Wijdicks (2009). (Open Table in a new window)

Hemorrhage due to a vascular malformation (such as arteriovenous malformation [AVM], cavernoma, or spinal arteriovenous fistulas [AVF]), is the second most common cause of intramedullary spinal cord hemorrhage. Vascular malformations can also lead to spinal subarachnoid hemorrhage (SAH). A small percentage of spinal AVMs are associated with Osler-Webber-Rendu disease. 

Spinal cavernomas are much less common than cranial cavernomas. Up to 45% of patients with a spinal cavernoma will have at least one cranial cavernoma. ^[1] Spinal AVFs often arise from the posterior aspect of the spinal cord, and most commonly occur in the thoracic region. AVFs may cause venous congestion, with lack of adequate drainage of the spinal cord. The subsequent congestive ischemia usually involves the posterior sensory elements of the spinal cord, but can progress to paralysis. Spinal AVFs do not typically bleed, but hemorrhages due to AVFs (when they do occur) are intramedullary in most cases.

Foix-Alajouanine syndrome results from compression of the spinal cord due to increased venous pressure (usually due to AVF; less commonly AVMs) and often involves acute to sub-acute progression of neurological deficits from spastic paraplegia to flaccid paralysis, loss of sphincter tone, and ascending sensory loss. ^[9]  

Spinal subarachnoid hemorrhage (SAH) may cause symptoms due to blood in the subarachnoid space, or blood dissecting into the spinal cord or along nerve root sheaths. Causes of spinal cord SAH include vascular malformations and spinal aneurysms, however, hemorrhagic spinal tumors, and rarely, extension of cranial SAH, may present as spinal SAH. Spinal aneurysms are usually located in the cervical and thoracic regions and are most often dissecting or fusiform in morphology. It is also possible for a blood clot to form in the spinal subarachnoid space, forming a subarachnoid space hematoma. This is recognized as a separate entity and usually presents with gradual compression of the spinal cord rather than acute pain and paralysis. The cause for this is also different from SAH, and is usually associated with procedures such as lumbar puncture or epidural anesthesia, especially in patients on anticoagulation therapy. ^{[1, 10]}

Spinal epidural hemorrhage (EDH) is usually due to trauma or iatrogenic etiologies including spinal surgeries, obstetrical birth trauma, lumbar puncture, spinal manipulations, and epidural procedures. The epidural space is the most common compartment for bleeding affecting the spinal cord. ^[1]  

Spinal subdural hemorrhage (SDH) occurs less commonly than spinal EDH, however, it presents similarly and is also usually due to trauma, or iatrogenic due to surgical procedures or anticoagulation. ^{[11, 12]}

Spinal SDH and EDH may cause symptoms and signs of spinal cord compression, corresponding (or caudal) to the level of the hematoma. The timing of symptom onset and progression may vary based on the rate of hematoma expansion. Unlike cranial hematomas, the vascular source for both spinal SDH and EDH is usually venous.   

Symptoms may develop more slowly in cases of spinal SDH due to a slower rate of bleeding. ^{[13, 14]} Otherwise, the features distinguishing EDH from SDH include the evidence from imaging studies, usually MRI. Epidural hematomas are generally located dorsally, due to the firm adherence of the thecal sac to the posterior longitudinal ligament at the ventral aspect of spinal canal. They usually have characteristic biconvex shape on imaging, with tapering superior and inferior boarders in sagittal view. Spinal SDHs, on the other hand, are often located ventral to the spinal cord.

Intrasyringal hemorrhage may rarely occur in patients with pre-existing syringomyelia. Conditions known to predispose to syrinx formation include Arnold-Chiari malformation, meningitis, trauma, scoliosis and trauma. In rare cases, such a hemorrhage may occur spontaneously. ^[2]

Frequency

Spontaneous spinal EDH has an incidence of 0.1 per 100,000 person-years. Spinal EDH occurs at least 4 times more commonly than spinal subdural hemorrhage. Spinal SAH accounts for less than 1% of all CNS subarachnoid hemorrhages. Minor trauma is a possible causative factor for most of these cases. ^[15]

Otherwise, the precise frequencies and breakdown of spinal cord hemorrhages by type and/or cause are difficult to find in the literature. As mentioned, the most common etiology is trauma, followed by iatrogenic, neoplastic, and vascular malformation causes. ^[1]

Mortality/Morbidity

Hemorrhage of the spinal cord can lead to irreversible myelopathy (including conus medullaris and cauda equina syndromes) and/or radiculopathy, depending on the location and the extent of the hemorrhage. The presence of intramedullary hemorrhage and extended segments of edema have been associated with clinically complete spinal cord injury. Prognosis may often be poor due to the added effect of reduced perfusion, edema, and secondary injury. ^{[16, 17]}

Sex- and age-related characteristics

The incidence of hematomyelia, spinal SAH, and spinal EDH is higher in males than in females. Spinal SDH is more common in women, with a female-to-male ratio of 2:1. ^{[18, 19]}

Spinal EDH has a bimodal distribution, with peaks during childhood and the fifth and sixth decades of life. Spinal EDH is most common in the cervical region in children and in the thoracic and lumbar regions in adults. Spinal SDH predominates in the sixth decade. ^{[20, 21, 22]}

Prognosis varies but generally is correlated with severity of deficit, particularly the “completeness” of the spinal cord injury. The clinical outcome of spinal cord hemorrhage also depends on the type (i.e., the compartment and level involved) and acuity of the symptoms. ^[27] Several studies have reported that more extensive and acute hemorrhages result in higher morbidity and mortality even with prompt intervention. Similarly, intramedullary and subarachnoid spinal hemorrhages are associated with higher morbidity and mortality. ^{[2, 26, 28, 29, 30]} Prompt diagnosis and intervention is advocated if possible, in an effort to improve outcome regardless of hemorrhage etiology. ^{[1, 9, 16, 24, 28]}