Last Updated on December 5, 2023
Anterior spinal artery syndrome is caused by ischemia of the anterior 2/3 of the spinal cord that results in characteristic motor paralysis below the level of the lesion along with the loss of pain and temperature at and below the level of the lesion.
The motor paralysis may vary in severity depending on the level affected.
Anterior spinal artery syndrome is caused by ischemia in the region of the spinal cord that is supplied by the anterior spinal artery. This artery supplies blood to the anterior two-thirds of the spinal cord.
Aortic surgery is the major cause of anterior spinal artery syndrome.
The anterior spinal artery supplies the ventral two-thirds of the spinal cord and medulla. Infarction or blockage of this artery jeopardizes the supply to the cord and results in symptoms of weakness and loss of pain and temperature sensation below the level of injury.
Anterior spinal cord syndrome is a rare condition but is the most common of all spinal cord infarctions described in some studies in up to 87.2% of the cases.
Relevant Anatomy
The spinal cord is supplied by the anterior spinal artery and two posterior spinal arteries. Thus anterior spinal artery is anterior to the cord and posterior spinal arteries lie posterior to the cord.
The anterior spinal arteries provide the blood to the anterior two-thirds of the spinal cord and the posterior spinal arteries to the posterior one-third.
It is formed by branches given off by vertebral arteries at the level of the foramen magnum in the skull. The anterior spinal artery is located within the anterior median sulcus up to the conus medullaris and is composed of multiple anastomotic networks.
It varies in calbre along the course which is smallest in the thoracic region and largest in the lumbar region.
At each level, it gives off branches (small sulcal and penetrating arteries) to supply the anterior two-thirds of the spinal cord. The rest of the cord and meninges are supposed by other vessels.
[Read about the blood supply of the spinal cord]
It also receives connections from radiculomedullary arteries and these are more readily appreciated in the cervical region. In the thoracic and lumbar region, the connections are from intercostal arteries which gives these radicomedullary branches.
The spinal cord has, on average, from 7 to 8 radiculomedullary arteries. The largest of all radiculomedullary arteries is called the great anterior radiculomedullary artery or artery of Adamkiwiecz. This is the most common occluded radicomedullary vessel in anterior spinal artery syndrome.
The spinal cord can be majorly divided into
- Posterior part
- Supplied by the two posterior spinal arteries
- Contains the fasciculus gracilis and cuneatus
- Responsible for proprioception, vibration sense, and fine touch
- Not affected by anterior cord syndrome
- Anterolateral part
- Contains the spinothalamic and spinocerebellar tracts
- Transmit pain and temperature sensation from extremities to the brain
- Supply is in the watershed zone and the levels may not exactly correlate with the level of insult
- Anteromedial part
- Corticospinal and corticobulbar tracts
- Transmits motor system messages from the brain to extremities
- Supplied by anterior spinal artery
- Completely affected in anterior cord syndrome
- Lateral horns
- Only between T1-12 levels
- Harbor cell bodies of the sympathetic system
- Supplied by anterior spinal artery
- Involvement of these levels leads to sympathetic dysfunction
Pathophysiology of Anterior Spinal Artery Syndrome
From anatomy, we know that the anterior spinal artery is the main source of supply to (along with a few radicular contributions)
- Bilateral anterior and lateral horns
- Bilateral spinothalamic tracts and corticospinal tracts
Ischemia of the anterior spinal artery would therefore lead to symptoms and signs of the dysfunction of these parts. The severity of the symptoms increases as the location of ischemia becomes higher.
Autonomic symptoms are only present if the level is between T1 and T12. The following functions remain preserved (the dorsal column of the spinal cord is preserved)
- Proprioception
- Sense of vibration
- Fine touch
- Two-point discrimination
When the flow stops in the artery, many cellular changes take place. decrease in oxygen supply to the cells results in inflammation and activation of astrocytes and microglia. There is disruption of the brain blood barrier as well which causes ionic pump failure and depolarization.
There is an increased level of calcium and glutamate in the cells. This activates free radical formation, cellular edema, receptor activation, and mitochondrial activity change, ultimately leading to cell death.
Risk Factors
The presence of the following risk factors is associated with anterior cord syndrome.
- High blood pressure or hypertension
- Diabetes
- Deranged lipid levels or dyslipidemia
- Smoking
- History of ischemic cerebrovascular accidents in the patient or family
Causes
The anterior spinal artery syndrome occurs when there is decreased perfusion or occlusion of the anterior spinal artery or any major radiculomedullary branches like the artery of Adamkiweicz.
Major reported causes of anterior spinal artery syndrome are
- Aortic conditions
- Iatrogenic injuries during surgery (most common cause)
- Aortic dissection
- Atherosclerosis
- Cardiac arrest
- Embolic phenomenon
- Cardiac emboli as in infectious endocarditis
- During digital subtraction angiography
- Vasculitis
- Vertebral fracture resulting in anterior cord impingement by a fracture fragment.
- Hypovolemic shock
- Shock: hypotension leads to ASAS
- Arteriovenous malformations
- Thrombosis
- Hypercoagulable state
- Sickle cell disease
- Cocaine use
Presentation of Anterior Spinal Artery Syndrome
- Acute back pain at the injury level
- Flaccid paraplegia or quadriplegia (depending on the level involved)
- Flaccidity due to spinal shock, later it would become spastic
- Loss of pain and temperature sensation below the level of injury
- Autonomic dysfunction if there is the involvement of the sympathetic system (Between T1-12 levels)
- Hypotension
- bradycardia
- Poor temperature regulation
- Preservation of dorsal column functions
- vibration, fine touch, proprioreception
- Respiratory failure in high lesions involving phrenic nerve
- Spasticity or increased muscle tone in paralyzed limbs
- Hyperreflexia
- Babinski sign
- Neurogenic bladder/bowel and sexual dysfunction
Differential Diagnoses
- Other cord syndromes
- Central cord syndrome
- Dorsal cord syndrome
- Brown-Sequard syndrome
- Conus medullaris syndrome
- Cauda equina syndrome
- Transverse myelitis
- Guillain-Barre syndrome
- Multiple sclerosis
- Spinal space-occupying lesions
- Spinal epidural abscess
- Epidural hematoma
- Malignancy
- Disc herniation
- Meningitis/encephalitis
Diagnostic Work-Up
MRI
- Thin “pencil-like” hyperintense region extending vertically and including many levels in sagittal views.
- “Owl’s eyes”- Bright dots at each anterior horn in axial view
Other Investigations
These are not necessary for diagnosis but are done to find out probable causes
- CSF analysis
- Multiple sclerosis
- Inflammatory causes
- Infection, or inflammatory disease
- Echocardiogram – for cardiac causes
- Lab studies
- Hypercoagulation profile
- Atherosclerosis
- Infection
- Drugs
Treatment
There is no effective treatment to stop or reverse anterior spinal artery syndrome.
usually, the supportive treatment is undertaken
- IV fluids
- Artificial ventilation in c/o respiratory failure
- Bladder-bowel care
- Prevention of bed sores
- Prevention of gastrointestinal stress ulcers
- Deep vein thrombosis prophylaxis
Surviving patients would later require physical and occupational therapy along with psychological therapy.
Complications of Anterior Spinal Artery Syndrome
Acute
- Infection
- Electrolyte imbalances
- Renal failure
Late
- Spasticity and permanent neurologic deficit
- Deep venous thrombosis
- Pulmonary embolism
- Pressure ulcers
- Autonomic dysfunction
- Neurogenic bowel/bladder
- Sexual dysfunction
- Chronic neuropathic pain
- Depression
Prognosis
The prognosis of anterior spinal artery syndrome is poor. The condition has a mortality rate as high as 20% in the acute period. Causes like disc herniation have a better lookout.
Most of the people who survive have varying degrees of neurologic deficits, both motor and sensory.
The following patients have shown a worse prognosis
- Due to aortic dissection
- Severe symptoms
- No improvement in the first 24 hours
- Old age
- Female gender
References
- Bredow J, Oppermann J, Keller K, Beyer F, Boese CK, Zarghooni K, Sobottke R, Eysel P, Siewe J. Anterior spinal artery syndrome: reversible paraplegia after minimally invasive spine surgery. Case Rep Orthop. 2014;2014:205732. [Link]
- Hanson SR, Romi F, Rekand T, Naess H. Long-term outcome after spinal cord infarctions. Acta Neurol Scand. 2015 Apr;131(4):253-7. [Link]
- Romi F, Naess H. Spinal Cord Infarction in Clinical Neurology: A Review of Characteristics and Long-Term Prognosis in Comparison to Cerebral Infarction. Eur Neurol. 2016;76(3-4):95-98. [Link]
