Anterior inferior cerebellar artery

The anterior inferior cerebellar artery (AICA) is one of the three principal paired arteries supplying the cerebellum. It most commonly arises from the lateral aspect of the lower or middle third of the basilar artery, near the pontomedullary region, although its exact level of origin is variable.

From its origin, the AICA courses posterolaterally around the pons, passing through the prepontine region into the cerebellopontine angle, where it has an important relationship with the facial (CN VII) and vestibulocochlear (CN VIII) nerves. It then continues over the anterior aspect of the cerebellum and commonly divides into superior and inferior trunks.

Subdivision of anterior inferior cerebellar artery

More detailed descriptions divide its course into anterior pontine, lateral pontine, flocculopeduncular, and cortical segments.

Vascular distribution of anterior inferior cerebellar artery

The amount of tissue supplied by the AICA is variable, depending upon whether the PICA is more or less dominant, but Its usual distribution includes the anteroinferior surface of the cerebellum, flocculus, middle cerebellar peduncle, and inferolateral pons, as well as branches to the choroid plexus.

The labyrinthine (internal auditory) artery most commonly arises from the AICA, although it may arise directly from the basilar artery. It accompanies CN VII and VIII into the internal auditory meatus and supplies the inner ear, including the cochlear and vestibular apparatus.

Clinical correlate

Occlusion of the anterior inferior cerebellar artery (AICA) may produce lateral pontine syndrome:

• Involvement of the spinal trigeminal system and spinothalamic tract produces the characteristic crossed sensory deficit, i.e. ipsilateral loss of pain and temperature sensation from the face with contralateral loss from the body.

• Involvement of the facial nerve nucleus or fibres causes ipsilateral facial paralysis, while involvement of vestibulocochlear structures or the labyrinthine artery may cause vertigo and ipsilateral sensorineural hearing loss.

• Damage to descending sympathetic fibres may produce ipsilateral Horner syndrome,

• While involvement of the middle cerebellar peduncle and related pathways causes ipsilateral ataxia.

Distinction of AICA syndrome from smaller lateral pontine arteries' involvement and PICA syndrome

AICA infarction can overlap clinically with infarction of the smaller lateral pontine branches of the basilar artery. However, prominent CN VII and VIII deficits together with cerebellar signs favour AICA involvement.

This also helps distinguish AICA-related lateral pontine syndrome from PICA-related lateral medullary (Wallenberg) syndrome, in which dysphagia and hoarseness due to nucleus ambiguus involvement are characteristic rather than facial paralysis.