Anterior spinal branch of vertebral artery

The anterior spinal artery (ASA) is usually formed by the union of descending anterior spinal branches arising from the right and left vertebral arteries near the medulla. It descends along the anterior aspect of the medulla and spinal cord, within or close to the anterior median fissure, and is reinforced along its course by segmental arterial contributions.

Vascular distribution

The anterior spinal artery (ASA) supplies approximately the anterior two-thirds of the spinal cord. In the medulla, the ASA and its roots also give rise to very small perforating (paramedian) medullary arteries, which contribute to the arterial supply of the medial medulla. These perforators form part of the perforating group of medullary arteries and may arise independently or through common stems with anterolateral and, occasionally, lateral arteries.

Clinical correlate (medial medullary syndrome)

Medial medullary syndrome may result from ischemia involving the ASA and its paramedian branches, or from vertebral artery disease that compromises this arterial supply.

The characteristic deficits reflect involvement of three major structures in the medial medulla:

1. Damage to the corticospinal tract within the pyramid, above the pyramidal decussation, causes contralateral weakness or paralysis of the limbs

2. Damage to the medial lemniscus causes contralateral loss of fine/discriminative touch, vibration and conscious proprioception, and

3. Involvement of the hypoglossal nucleus, fascicles or nerve causes ipsilateral tongue weakness, with the tongue deviating toward the side of the lesion due to weakness of the genioglossus.

In contrast to the typical lateral medullary syndrome, the classic medial syndrome prominently affects motor pathways and the hypoglossal nerve, while generally sparing the laterally situated spinothalamic and descending sympathetic pathways.