Blood supply of cochlea

Arterial supply:

The blood supply to the cochlea is highly complex. The labyrinthine artery which is an end artery supplies the inner ear. This is a branch of anterior inferior cerebellar branch of internal carotid artery. The inner ear blood supply is devoid of collaterals and hence is higly vulnerable to ischemic effects. The common cochlear branch of the vestibulo cochlear artery supplies the cochlea. The common cochlear artery gives rise to two branches:

1. Main cochlear artery that supplies the modiolus in the upper basal, middle and apical areas of the cochlea
2. The cochlear ramus branch supplying about 1/4 of the basal coil and modiolus of cochlea.

Inside the modiolus the artery branches to form an external radiating arteriole and an internal radiating arteriole.

The external radiating arteriole travels within the interscalar septum to reach the lateral wall of the cochlear coil. As soon as it reaches the lateral wall it branches to give rise to 4 vessels forming a capillary network. These vessels are:

1. Vessels of the scala vestibuli
2. Vessels of spiral ligament
3. Vessels of scala tympani
4. One branch contributing to the capillary network in the scala vestibule.

The internal radiating arteriole supplies the medial wall of the cochlear coil.

The arteries supplying the inner ear should pulsate less because pulsations are sufficient to cause excitation of the cochlea. In order to reduce the intensity of arterial pulsations the labyrinthine artery consists of many parallel arteries which ensure adequate blood supply to the inner ear without intense pulsations.

Venous drainage:

The primary venous drainage of inner ear is via:

Vein of the cochlea

Vein of the vestibular aqueducts.

The cochlea is primarily drained by anterior and posterior spiral veins. The anterior spiral vein drains the supero lateral (scala vestibuli and osseous spiral lamina). The posterior spiral vein drains the inferior aspect of the cochlea (spiral ganglion, scala media and scala tympani). Ultimately the cochlear vein and the vein of the vestibulat aqueduct drain via the inferior petrosal sinus.