Type:
Educational Exhibit
Keywords:
Neuroradiology brain, MR, Diagnostic procedure, Normal variants, Education and training
Authors:
L. A. Abd El-Gawad
DOI:
10.26044/ecr2023/C-21767
Background
The CPA is a triangular shaped space filled with cerebrospinal fluid that lies anterolaterally to the junction of the pons and cerebellum. It contains cranial nerves [facial nerve VII and vestibulocochlear nerve VIII] and the AICA.
The IAC, which is a nerve canal surrounded by bone, rises anterolaterally from the CPA to reach the peripheral cochleovestibular organs. The IAC contains cranial nerves VII and VIII, which are responsible for facial muscle movement, hearing and balance.
The AICA usually arises from the basilar artery and courses through the CPA posterolaterally to supply the anterior to middle parts of the cerebellum and inferolateral pons. It branches into the labyrinthine artery, which supplies the labyrinth, cochlea and vestibular organs. The anatomical shape and location of the AICA is variable in the CPA and IAC.
There is no clear etiology of AICA loop formation and anatomical variances seen in AICA positions. Hypotheses include senile elongation of the artery, arteriosclerosis and arachnoid adhesions between nerves and vessels.
The relationship between vascular compression of the vestibulocochlear nerve and audio-vestibular symptoms, such as sensorineural hearing loss, tinnitus and vertigo, remains elusive. Physical examination with detailed medical history has to be performed.
The anatomic location of the AICA loop may help prognosticate hearing outcomes in idiopathic sudden sensorineural hearing loss [ISSNHL] patients and can also be considered in tinnitus etiology.
The knowledge of the AICA/PICA course and branching patterns would be useful not only to decide the appropriate decompression site but also to avoid intraoperative vascular injury leading to massive hemorrhage.