Medullary arteries are blood vessels that deliver oxygenated blood and nutrients to specific tissues, supporting their normal function. Their proper functioning is necessary for the health of the tissues they supply.
Anatomical Location and Structure
Medullary arteries are associated with the spinal cord, serving as branches that reinforce its blood supply. These vessels originate from larger arteries, such as the aorta or intercostal arteries. They travel through the intervertebral foramina, openings between the vertebrae, to reach the spinal cord.
These arteries are small, penetrating vessels that connect with the main longitudinal arteries of the spinal cord: the single anterior spinal artery and the paired posterior spinal arteries. While many radicular arteries supply nerve roots, medullary arteries directly contribute to the spinal cord’s arterial network. There are 4-9 medullary spinal arteries, found mostly in the lower cervical, lower thoracic, and upper lumbar regions.
Role in Spinal Cord Blood Supply
Medullary arteries provide blood, oxygen, and nutrients to the spinal cord. This continuous supply is necessary for the spinal cord’s proper functioning, as it transmits signals between the brain and the rest of the body, controlling movement, sensation, and reflex responses. Without adequate blood flow, nerve cells in the spinal cord can suffer damage due to insufficient oxygen.
The spinal cord’s blood supply system includes “watershed areas,” which are regions that receive blood from the farthest reaches of two different arterial supplies. These zones, often located in the mid-thoracic spinal cord (T4-T6) and in the central and peripheral gray matter, are more susceptible to injury if blood flow is reduced because they have fewer overlapping arterial feeders. Damage to a dominant medullary artery, such as the artery of Adamkiewicz, which arises between T9 and L2, can cause paralysis due to spinal cord infarction, particularly in the lumbosacral segments.
Common Conditions Affecting Medullary Arteries
Several conditions can affect medullary arteries, potentially disrupting the blood supply to the spinal cord. Atherosclerosis involves the buildup of plaque within artery walls, leading to narrowing and hardening of the vessels. This plaque can restrict blood flow, reducing oxygen and nutrients reaching the spinal cord.
Arteriovenous malformations (AVMs) are abnormal tangles of blood vessels where arteries connect directly to veins, bypassing the normal capillary network. In the spinal cord, AVMs can create an enlarged mass of vessels with abnormal blood flow, which may prevent surrounding tissues from receiving sufficient oxygen. These malformed vessels are often thin and weak, increasing the risk of rupture and bleeding.
Aneurysms, which are balloon-like bulges in the wall of a blood vessel, can also affect medullary arteries. These weakened areas can burst, leading to hemorrhage. Embolisms or thromboses can cause blockage of these arteries. An embolism occurs when a blood clot or other material travels through the bloodstream and lodges in a vessel, while thrombosis refers to the formation of a blood clot within the artery itself.
Signs of Impaired Blood Flow
Impaired blood flow to the spinal cord due to issues with medullary arteries can manifest through sudden signs and symptoms. Individuals may experience sudden weakness or paralysis in the limbs, affecting their ability to move or control parts of their body. The extent of weakness or paralysis depends on which segments of the spinal cord are affected.
Sensory changes are common, including numbness, tingling, or an inability to feel heat, cold, or pain in areas below the level of the affected artery. These symptoms arise because the spinal cord’s nerve tissues are deprived of adequate oxygen and nutrients. Problems with bowel and bladder function, as well as changes in reflexes, can occur.
Diagnosing and Managing Medullary Artery Issues
Diagnosing problems with medullary arteries often involves advanced imaging techniques to visualize the blood vessels and assess blood flow. Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA) are frequently used, with MRA specifically focusing on blood vessels to detect narrowing, widening, or blockages. These non-invasive tests use magnetic fields and radio waves to create detailed images without radiation.
Computed Tomography Angiography (CTA) is another diagnostic tool that uses X-rays and a contrast dye to produce images of blood vessels. Conventional angiography, while more invasive, involves inserting a catheter into a blood vessel and injecting contrast material to provide a detailed view of the arterial network, though it is often considered a gold standard for certain diagnoses. These tests help pinpoint the location and nature of the vascular issue.
Management strategies for medullary artery issues depend on the specific condition and its severity. Medical management may involve controlling underlying risk factors such as high blood pressure, high cholesterol, and diabetes through lifestyle changes and medications like statins or anticoagulants. For conditions like arteriovenous malformations or stenosis, surgical or endovascular interventions may be considered. Endovascular procedures, such as embolization for AVMs or stenting for narrowed arteries, involve minimally invasive techniques to repair or bypass affected vessels.