2023 ARRS ANNUAL MEETING - ABSTRACTS

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E2074. Closing the (Vascular) Loop: What Matters in Neurovascular Conflicts
Authors
  1. Gaby Abou Karam; Yale School of Medicine
  2. Sam Payabvash; Yale School of Medicine
Background
We frequently encounter vascular loops in the posterior fossa especially due to the widespread use of high-resolution 3D imaging of the posterior fossa. Radiologists often detect and report these loops but sometimes hesitate if there is a neurovascular conflict that would be clinically significant. Many patients also are surgically treated and will present for recurrence of symptoms. The post operative imaging can also be sometimes challenging to understand and interpret. This exhibit is based on the experience of a dedicated multidisciplinary team in a large tertiary care center specialized in treating patients presenting with neurovascular conflicts.

Educational Goals / Teaching Points
The role of this exhibit is to familiarize the radiologist with the different neurovascular conflicts in the posterior fossa. - Cranial nerves anatomy in the posterior fossa - Understand the importance of imaging techniques in neurovascular conflicts - Understand what to look for in the most commonly encountered neurovascular conflict involving the trigeminal nerve, common clinical presentation, additional findings associated with trigeminal neuralgia (such as absent Meckel's cave) - Understand what to look for in a facial nerve conflict, common patient presentation and how to approach commonly encountered imaging finding (anterior inferior cerebellar artery (AICA) loop going into the internal auditory canal (IAC)) - Understand what to look for in a facial nerve conflict, common patient presentation and how to approach commonly encountered imaging finding - Familiarize the radiologist with post-surgical appearance status post microvascular decompression or gamma knife radio surgery

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
A brief review of the anatomy of the nerves will be discussed first. The key technique is obtaining a 3D T2 weighted sequence of the posterior fossa in addition to a post contrast T1 thin slices. The most common neurovascular (NV) conflict is involvement of the trigeminal nerve. Patients usually present with hemifacial pain. The involvement is usually at the root entry zone (REZ). The vessel causing the NV conflict is commonly the superior cerebellar artery. Sometimes a vein is the culprit. Another area of involvement is Meckel’s cave. Some patients have an absent Meckel’s cave. The second most common neurovascular conflict is involvement of the facial nerve. Patients usually present with hemifacial spasm. The involvement is usually at the REZ. The vessel causing the NV conflict is commonly the AICA or less common the ipsilateral intracranial vertebral artery. A commonly encountered vascular loop is the AICA going into the IAC. Radiologists sometimes describe this entity but it appears to be of no clinical significance most of the time. The least common neurovascular conflict is involvement of the hypoglossal nerve. Patients usually present with electrical stabbing throat pain. The involvement is usually at the REZ. The vessel causing the NV conflict is commonly the ipsilateral intracranial vertebral artery.

Conclusion
At the end of this exhibit, the radiologist should become more familiar with the different types of neurovascular conflicts.