The spinal cord is the primary communication highway between the brain and the rest of the body. Spinal arteries are specialized blood vessels that deliver a constant supply of oxygen and nutrients, ensuring its proper operation.
Spinal Artery Anatomy and Role
The spinal cord receives its blood supply from a network of arteries. This supply originates primarily from the vertebral arteries, major arteries in the neck that also provide blood to the brain. At the superior aspect of the spinal cord, the vertebral arteries give rise to three main longitudinal arteries: a single anterior spinal artery and a pair of posterior spinal arteries.
The anterior spinal artery, formed by the fusion of two branches from the vertebral arteries, travels down the front of the spinal cord along its anterior median fissure. It is the predominant supplier, delivering blood to the anterior two-thirds of the spinal cord, including areas responsible for motor neurons and pain and temperature sensation. The paired posterior spinal arteries, originating from the vertebral arteries, run along each side of the posterior surface of the spinal cord. These arteries primarily supply the posterior one-third of the spinal cord, which includes regions involved in processing sensory information like proprioception and fine touch.
Reinforcing these main longitudinal arteries are segmental medullary arteries, also known as radicular arteries, that enter the spinal canal at various levels along the spine. These feeder arteries originate from various sources, including branches of the vertebral, ascending cervical, deep cervical, intercostal, lumbar, and sacral arteries. The largest of these, the artery of Adamkiewicz, arises from the lower thoracic or upper lumbar arteries (between T9 and L2) and provides a significant blood supply to the lower two-thirds of the spinal cord. This network ensures the spinal cord receives an adequate blood supply, necessary for maintaining its health and supporting its functions, including motor control, sensation, and reflex responses.
Common Issues Affecting Spinal Arteries
Problems with spinal arteries can have consequences due to the spinal cord’s reliance on a constant blood supply. Spinal cord ischemia, also known as a spinal stroke or spinal infarction, occurs when blood flow to the spinal cord is blocked, depriving it of oxygen and nutrients. This can lead to tissue damage and cell death within the spinal cord. Spinal cord ischemia can result from various factors, including the buildup of plaque in arteries (atherosclerosis), blood clots (embolism), or inflammation of blood vessels (vasculitis). It can also occur as a complication of spinal surgery or other procedures involving the aorta, which can disrupt blood flow to the spinal cord.
Another type of problem involves abnormal connections between arteries and veins. Spinal arteriovenous malformations (AVMs) are tangles of blood vessels that form on, in, or near the spinal cord, creating irregular connections between arteries and veins that bypass the normal capillary network. This rerouting of blood means that the surrounding spinal cord tissue may not receive enough oxygen, leading to weakening or death of cells. These malformations can also enlarge over time, pressing on the spinal cord, or they may rupture, causing bleeding (hemorrhage) within the spinal cord.
Spinal arteriovenous fistulas (AVFs) are similar to AVMs but involve a direct, abnormal connection between a single artery and a single vein, bypassing the capillaries. This can lead to high-pressure arterial blood flowing directly into veins, causing the veins to swell and become congested. This increased venous pressure can lead to blood pooling and reduced oxygen delivery to spinal cord tissues.
Other issues include dissections, which are tears in the wall of a spinal artery, allowing blood to leak between the layers of the arterial wall. This can narrow or block the artery, reducing blood flow to the spinal cord and potentially leading to ischemia. These can be caused by trauma or occur spontaneously due to underlying conditions like atherosclerosis or connective tissue disorders. External compression of spinal arteries from conditions like tumors, herniated discs, or bone spurs can also reduce blood flow, impacting the spinal cord’s function.
Recognizing and Diagnosing Spinal Artery Problems
Recognizing problems with spinal arteries involves observing a sudden onset of neurological symptoms, which can vary depending on the affected area. Common indicators include sudden weakness or paralysis in the limbs, ranging from mild to complete inability to move. Sensory changes are also reported, such as numbness, tingling, or a loss of the ability to feel pain and temperature, while the sense of touch or vibration might be preserved. Patients may also experience back pain that can radiate into the arms or legs, and some may have difficulty controlling their bladder or bowel functions.
When a spinal artery problem is suspected, medical professionals begin with a thorough neurological examination to assess reflexes, muscle strength, and sensory responses. Imaging techniques are then employed to visualize the spinal cord and its blood vessels. Magnetic Resonance Imaging (MRI) of the spine is a primary diagnostic tool, as it can reveal areas of tissue damage, swelling, or abnormal signals within the spinal cord that suggest ischemia or other lesions. MRI can also help rule out other conditions that might cause similar symptoms, such as tumors or disc herniations.
Magnetic Resonance Angiography (MRA) is a specialized MRI technique that focuses on visualizing blood flow within the arteries and veins, helping to identify vascular malformations, blockages, or dissections. Computed Tomography (CT) scans can also be used to quickly identify large vessel issues like aortic dissections that might be affecting spinal cord blood supply. Conventional angiography, which involves injecting contrast dye directly into blood vessels, remains the gold standard for detailed visualization of spinal vascular anatomy, but non-invasive methods like MRA and CTA are used for initial assessment.
Managing Spinal Artery Conditions
Managing conditions affecting spinal arteries requires individualized approaches. For acute spinal cord ischemia, or spinal stroke, immediate supportive care focuses on maintaining blood pressure and oxygenation to the spinal cord. Strategies may include blood pressure management and the use of antiplatelet medications like aspirin to prevent further clotting. Addressing the underlying cause, such as an aortic dissection or severe hypotension, is also a priority to minimize further damage.
For structural issues like arteriovenous malformations (AVMs) or fistulas (AVFs), or external compression, interventional or surgical options are considered. Endovascular embolization is a procedure where a catheter is guided into the affected artery, and a gluelike substance or small particles are injected to block abnormal vessels and reduce blood flow to the malformation. This can help shrink the AVM or AVF and lower the risk of bleeding. Surgical repair, which involves directly ligating or resecting the abnormal vessels, may also be performed. Radiosurgery, which uses focused radiation to destroy the abnormal blood vessels over time, may be an option for smaller, unruptured AVMs.
Rehabilitation plays a role in recovery from spinal artery conditions. Physical therapy helps regain muscle strength and improve mobility, especially for individuals experiencing weakness or paralysis. Occupational therapy helps patients adapt to new ways of performing daily activities, while speech therapy may be necessary if communication or swallowing is affected. Long-term management also involves addressing risk factors for vascular disease, such as high blood pressure or high cholesterol, through lifestyle modifications and medication to help prevent future complications.