Neuro‐Image of a Ring‐Liked Sign in Serpentine Aneurysm

A 39-year-old woman was admitted to the emergency department with new-onset headache and repeated vomiting for 8 hours. On admission, she had a blood pressure of 175/98mmHg and physical examination revealed a stiff neck. Emergency computed tomography (CT) revealed an uneven density mass accompanied by a subarachnoid hemorrhage (Fig 1A). Computed tomography angiography (CTA) revealed a ring-like abnormal vascular structure, indicating a large thrombosed aneurysm (Fig 1B). Magnetic resonance imaging (MRI) revealed blood flow voids between the aneurysm wall and thrombus (Fig S1). Digital subtraction angiography (DSA) showed separated inflow and outflow tracts, and the distal tissues supplied by the outflow tract, which was confirmed as a serpentine aneurysm (Fig 1C, Video S1). Subsequently, the patient underwent a direct surgical clipping. During clipping, old and fresh thrombi were found to coexist in the aneurysm cavity and were adhered to the anteroinferior wall. Intraoperative ultrasonic Doppler and indocyanine green video angiography revealed good patency of the parent artery. Repeat vascular evaluation at the 3-month follow-up demonstrates that a fusiform aneurysm had appeared in situ (Fig S2); however, the patient refused further treatment. A serpentine aneurysm is a rare form of intracranial aneurysm characterized by unique pathologic and radiologic features, which presents with eccentric and twisted vascular channels and resembles a serpentine shape.1, 2 The formation of these serpentine channels is a result of the Coanda effect, in which the jet flow of blood is directed toward one wall instead of the central portion of the aneurysm.3 Pathologic findings often reveal large globular masses containing a main irregular serpentine channel, with or without multiple small channels, coursing through a partially thrombosed aneurysm.1, 2 Serpentine aneurysm commonly presents with symptoms such as headaches, altered consciousness, hemiplegia, and seizures after rupturing.4 Contrary to previous studies, our case demonstrated the formation of a ring-like vessel structure, instead of a typical serpentine channel. Although similar imaging techniques have been reported,1 the precise mechanisms underpinning the formation of this structure remain elusive. The MRI and DSA analysis of this patient revealed that the main blood flow channel encircled the thrombus rather than traversing through it. This distinct pattern of blood flow may lead to unique hemodynamic changes, possibly contributing to formation of distinctive channels. The ring-like sign appears to be a vivid depiction of the blood flow condition, which could also be a reminder of the serpentine channels and may also serve as a diagnostic indicator of a serpentine aneurysm. We thank Wiley Editing Services for English language and figures editing. L.W. and C.H.W. contributed to the conception and design of the study. C.H.W. and Z.F.S. contributed to the acquisition and analysis of data. L.W. and Y.H. contributed to drafting the text and preparing the figures. Nothing to report. The data that support the findings of this study are available from the corresponding author upon reasonable request. Figure S1. Magnetic resonance imaging revealed a space-occupying lesion with heterogeneous signal intensity and blood flow voids between the aneurysm wall and the thrombus. Figure S2. Computed tomographic angiography image showing a fusiform aneurysm that has developed in situ 3 months after clipping (indicated by an arrow). Video S1. Digital subtraction angiography video showing a serpentine aneurysm. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.