Anterior Spinal Artery Syndrome¶

Definition¶

Anterior spinal artery syndrome is the clinical manifestation of infarction in the territory of the anterior spinal artery, which supplies the anterior two-thirds of the spinal cord. It produces sudden motor paralysis, loss of pain and temperature sensation, and autonomic dysfunction below the level of the infarct, with characteristic preservation of posterior column function (proprioception, vibration, light touch).

Clinical Features¶

Motor — Bilateral motor paralysis below the infarct level (corticospinal tracts)
Sensory — Loss of pain and temperature sensation bilaterally (spinothalamic tracts)
Preserved — Proprioception, vibration, and light touch (dorsal columns, supplied by posterior spinal arteries)
Autonomic — Bladder and bowel dysfunction
Onset — Typically sudden (minutes to hours)

Imaging Findings¶

MRI¶

T2 hyperintensity in the anterior two-thirds of the cord on axial images
"Owl eyes" sign — bilateral anterior horn hyperintensity
Cord expansion in the acute phase
DWI restricted diffusion
Posterior columns are spared (normal signal)
May span multiple vertebral segments, typically in the thoracolumbar watershed zone (T4–T8)

Owl eyes sign anterior spinal artery syndrome — Anterior spinal cord syndrome. Sagittal T2 showing long-segment cord hyperintensity (A) and axial T2 showing the "owl's eye sign" with bilateral anterior horn involvement (B), characteristic of anterior spinal artery territory infarction. (Source: Harada et al., J Gen Fam Med, 2018. CC BY 4.0)

Clinical Pearl

Anterior spinal artery syndrome must be distinguished from other causes of acute myelopathy — particularly transverse myelitis and cord compression. The key MRI clue is the anterior two-thirds distribution with posterior column sparing. On axial images, this creates a characteristic "pencil-shaped" or crescent-shaped T2 hyperintensity in the anterior cord, distinct from the central cord involvement of transverse myelitis or the dorsal column involvement of B12 deficiency.

Key Points¶

Infarction of the anterior two-thirds of the cord from anterior spinal artery occlusion
Motor paralysis + loss of pain/temperature with preserved proprioception/vibration
"Owl eyes" sign on axial T2 MRI
DWI restricted diffusion is the earliest finding
Thoracolumbar watershed zone is most vulnerable
Distinguish from transverse myelitis by the anterior distribution

References¶

Sandoval JI, De Jesus O. Anterior Spinal Artery Syndrome. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2024 Jun 7. https://www.ncbi.nlm.nih.gov/books/NBK560731/
Vargas MI, Gariani J, Sztajzel R, et al. Spinal cord ischemia: practical imaging tips, pearls, and pitfalls. AJNR Am J Neuroradiol. 2015;36(5):825-830. https://pubmed.ncbi.nlm.nih.gov/25324492/
Yuh WT, Marsh EE 3rd, Wang AK, et al. MR imaging of spinal cord and vertebral body infarction. AJNR Am J Neuroradiol. 1992;13(1):145-154. https://pubmed.ncbi.nlm.nih.gov/1595432/
Yadav N, Pendharkar H, Kulkarni GB. Spinal cord infarction: clinical and radiological features. J Stroke Cerebrovasc Dis. 2018;27(10):2810-2821. https://pubmed.ncbi.nlm.nih.gov/30093205/
Masson C, Pruvo JP, Meder JF, et al. Spinal cord infarction: clinical and magnetic resonance imaging findings and short-term outcome. J Neurol Neurosurg Psychiatry. 2004;75(10):1431-1435. https://pmc.ncbi.nlm.nih.gov/articles/PMC1738740/
Expert Panel on Neurological Imaging; Agarwal V, et al. ACR Appropriateness Criteria® Myelopathy: 2021 Update. J Am Coll Radiol. 2021;18(5S):S73-S82. https://pubmed.ncbi.nlm.nih.gov/33958120/