Anterior spinal artery syndrome

Overview

Anterior Spinal Artery Syndrome (ASAS), also known as anterior cord syndrome, is a rare but serious neurological condition caused by decreased blood flow through the anterior spinal artery, which supplies the front two-thirds of the spinal cord. This leads to sudden loss of motor function and pain/temperature sensation below the level of the injury, while preserving light touch and proprioception (position sense), which are supplied by the posterior spinal arteries.

ASAS typically presents as an acute spinal cord infarction and is considered a spinal cord stroke. It is a medical emergency requiring immediate evaluation and management.

Causes

Anterior spinal artery syndrome results from ischemia or infarction in the anterior spinal cord. Common causes include:

• Arteriosclerosis or atherosclerosis of the supplying arteries

• Aortic surgery or dissection, especially involving the thoracoabdominal aorta

• Hypotension or shock (e.g., after cardiac arrest)

• Embolism or thrombosis involving the anterior spinal artery

• Spinal trauma (fractures or dislocations)

• Vasculitis or inflammatory vascular diseases

• Epidural or spinal anesthesia complications

• Intervertebral disc herniation or mass lesions compressing spinal arteries

Symptoms

The symptoms of ASAS appear suddenly and reflect the areas of the spinal cord deprived of oxygen:

Motor and Sensory Deficits:

• Acute flaccid paralysis or weakness of both legs (paraplegia) or all four limbs (quadriplegia) depending on the level of involvement

• Loss of pain and temperature sensation below the level of the lesion

• Preservation of light touch, vibration, and position sense (posterior column functions)

Autonomic Dysfunction:

• Urinary retention or incontinence

• Bowel dysfunction

• Hypotension or sexual dysfunction in some cases

Additional Signs:

• Back or neck pain at the onset (especially if vascular compromise is sudden)

• Muscle tone may be flaccid acutely, followed by spasticity over time

Diagnosis

Diagnosis of anterior spinal artery syndrome is based on clinical presentation and confirmed by imaging and diagnostic studies:

• Neurological examination: Demonstrates motor loss and dissociated sensory loss (pain/temp affected; touch/proprioception spared)

• MRI of the spine: Confirms spinal cord infarction and rules out compressive causes (e.g., herniated disc, tumor)

• Spinal angiography: May help visualize vascular compromise

• Blood tests and vascular studies: To assess for clotting disorders, atherosclerosis, or vasculitis

• CT angiography or echocardiogram: To identify embolic sources (e.g., aortic dissection, cardiac thrombus)

Treatment

There is no specific cure for ASAS; treatment is aimed at stabilizing the patient, restoring spinal cord perfusion (if possible), and managing symptoms. Key aspects include:

Acute Management:

• Identify and treat underlying cause: Such as aortic dissection, hypotension, or embolism

• Supportive care: Including intravenous fluids, oxygen, and blood pressure management to optimize spinal perfusion

• Antithrombotic therapy: If an embolic or thrombotic cause is identified

Rehabilitation and Long-Term Management:

• Physical and occupational therapy: To improve mobility and function

• Bladder and bowel management

• Assistive devices: Such as braces or wheelchairs if motor function is impaired

• Pain management and spasticity control

Prognosis

The prognosis of anterior spinal artery syndrome depends on the level and severity of the lesion, the speed of diagnosis and intervention, and the extent of spinal cord ischemia. In general:

• Motor recovery is often limited, especially if paralysis is complete at onset

• Some patients regain partial function with rehabilitation

• Sensory and autonomic deficits may persist long-term

• Prompt diagnosis and treatment of reversible causes (e.g., hypotension, embolism) improve outcomes

Unfortunately, many patients with ASAS are left with significant disability. Lifelong follow-up and multidisciplinary care are often required.