Cerebellar infarction in the territory of the anterior and inferior cerebellar artery. A clinicopathological study of 20 cases.

Clinicopathological reports on infarction in the territory of the anterior inferior cerebellar artery (AICA) are rare. In the present series cerebellar infarcts involved only the AICA territory in 13 cases. They were bilateral in 3 cases. In these pontocerebellar infarcts the middle cerebellar peduncle was the core of the affected territory. It was seldom selectively affected. In a few cases, the infarction extended to the flocculus. Next most frequently involved was a thin band of tissue in the adjacent cerebellar white matter, comprising laterally the neighbouring cerebellar lobules. The largest infarcts extended to the anterior and inferior aspects of the cerebellum. In these cases, the posterior inferior cerebellar artery (PICA) was hypoplastic. In most infarcts, the inferolateral pontine territory was involved, the infarction sometimes extending up to the middle third of the lateral pons and down to the superior part of the lateral medulla. No brainstem compression or tonsillar herniation were observed with infarcts affecting the AICA territory alone. Clinically, involvement of several cranial nerves (facial palsy, multimodal trigeminal sensory impairment, deafness, sometimes with tinnitus, a vestibular syndrome, or lateral gaze palsy) was constant. Cerebellar signs and motor weakness occurred frequently. Contralateral pain and temperature sensory loss was present at times. Horner's syndrome or skew deviation was rare. Study of the arteries showed that arterial occlusion was mainly due to thrombosis superimposed on atheromatous stenosis. In 7 cases, the infarction also involved the PICA territory or the PICA and the superior cerebellar artery territories. These extensive infarcts were often associated with tonsillar herniation and massive paramedian brainstem infarction. The cases in which the territories of the three cerebellar arteries were affected presented in deep coma, together with tetraplegia in some patients. Those in which PICA and AICA territories were involved together presented with similar clinical features as in the cases in which only the AICA territory was involved.