Trauma: The most likely cause of a prevertebral hematoma at T10-T12 is trauma, which could be due to a fall, motor vehicle accident, or any other form of physical injury that affects the spinal region. This is because trauma can directly cause damage to the blood vessels in the prevertebral space, leading to bleeding.

Vascular Malformation or Aneurysm: Abnormalities in blood vessels, such as malformations or aneurysms, can rupture and cause a hematoma. These conditions may be congenital or acquired.
Tumor: Certain tumors, either benign or malignant, can erode into nearby blood vessels, leading to bleeding into the prevertebral space.
Infection: Infections like abscesses or osteomyelitis in the spine can cause erosion of blood vessels, resulting in hematoma formation.
Anticoagulation Therapy: Patients on anticoagulant medications are at a higher risk of developing hematomas due to the increased risk of bleeding.

Aortic Dissection: Although less common, an aortic dissection can extend into the prevertebral space and cause a hematoma. This condition is life-threatening and requires immediate medical attention.
Spinal Epidural Hematoma: While this condition is more commonly associated with the epidural space, it can sometimes be confused with or extend into the prevertebral space, and it is a medical emergency.
Hemorrhagic Transformation of a Spinal Cord Infarct: In rare cases, a spinal cord infarct can undergo hemorrhagic transformation, leading to a hematoma in the prevertebral space.

Bleeding Disorders: Inherited or acquired bleeding disorders, such as hemophilia, can increase the risk of developing a hematoma, including in the prevertebral space.
Vasculitis: Inflammation of blood vessels due to vasculitis can lead to weakening of the vessel walls and subsequent rupture, causing a hematoma.
Prevertebral Abscess Rupture: A prevertebral abscess that ruptures can cause a hematoma, although this would typically be accompanied by signs of infection.