The snake-head sign on MRI in craniocervical junction dural arteriovenous fistulas: a novel imaging feature and a hypothesis of venous remodeling and congestion
- 1Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College
- 2Department of Neurology, Linyi Shangcheng Hospital
Abstract
Background: Craniocervical junction (CCJ)-region dural arteriovenous fistulas (dAVFs) are rare but potentially reversible causes of venous congestive myelopathy, often difficult to recognize due to non-specific presentation. We observed a characteristic pattern of intramedullary T2 hyperintensity on sagittal MRI, involving the medulla and upper cervical cord with a rostral end divided into ventral and dorsal limbs, which we termed the “snake-head sign.” This study aimed to characterize the prevalence of this feature among reported CCJ-region dAVF cases and explore its clinical and anatomical correlates.
Methods: We retrospectively reviewed published cases of CCJ-region or adjacent dAVFs reported between 1996 and 2026 that included retrievable sagittal T2-weighted or FLAIR images. The presence of the snake-head sign was assessed, and clinical, angiographic, and treatment-related variables were extracted, including fistula location, feeding artery, draining vein direction, treatment modality, and outcome. Associations with the sign were evaluated using univariate analyses. Given the retrospective, literature-based design and limited sample size, findings were considered hypothesis-generating.
Results: Among 64 reported cases, the snake-head sign was identified in 31 (48.4%). No significant associations were found between the sign and age, sex, symptom duration, feeding artery, treatment modality, or outcome. However, a non-significant trend was observed for venous drainage configuration: cases with cranial convergence of the draining vein toward the CCJ more frequently demonstrated the sign, whereas purely caudal drainage patterns showed it less often. Fistulas at lower cervical nerve-root sleeves, requiring a longer cranial venous course, also showed higher sign frequency. These findings suggest the sign may reflect venous outflow geometry rather than arterial source or fistula location.
Conclusion: The snake-head sign is a recognizable MRI feature present in roughly half of reported CCJ-region dAVF cases. Its identification may raise clinical suspicion for CCJ-related dAVF, particularly in unexplained venous congestive myelopathy. The trend toward a higher frequency of the sign in cases with cranially convergent venous drainage raises the hypothesis that it reflects concentrated venous congestion at this anatomical transition zone. Prospective multicenter studies with standardized imaging review and angiographic correlation are needed to confirm its diagnostic value and clarify the underlying mechanism.
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BibTeX
@article{shen2026snakehead,
title = {{The snake-head sign on MRI in craniocervical junction dural arteriovenous fistulas: a novel imaging feature and a hypothesis of venous remodeling and congestion}},
author = {Dongchao Shen and Xinghua Chen and Zhe Zhang and Yanying Wang and Chang Geng and Hongzhi Guan},
journal = {Frontiers in Neurology},
year = {2026},
month = oct,
doi = {10.3389/fneur.2026.1972107},
url = {https://www.frontiersin.org/articles/10.3389/fneur.2026.1972107/full},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The snake-head sign on MRI in craniocervical junction dural arteriovenous fistulas: a novel imaging feature and a hypothesis of venous remodeling and congestion
AU - Dongchao Shen
AU - Xinghua Chen
AU - Zhe Zhang
AU - Yanying Wang
AU - Chang Geng
AU - Hongzhi Guan
PY - 2026
DA - 2026/10/16
JO - Frontiers in Neurology
DO - 10.3389/fneur.2026.1972107
UR - https://www.frontiersin.org/articles/10.3389/fneur.2026.1972107/full
AB - Background: Craniocervical junction (CCJ)-region dural arteriovenous fistulas (dAVFs) are rare but potentially reversible causes of venous congestive myelopathy, often difficult to recognize due to non-specific presentation. We observed a characteristic pattern of intramedullary T2 hyperintensity on sagittal MRI, involving the medulla and upper cervical cord with a rostral end divided into ventral and dorsal limbs, which we termed the “snake-head sign.” This study aimed to characterize the prevalence of this feature among reported CCJ-region dAVF cases and explore its clinical and anatomical correlates. Methods: We retrospectively reviewed published cases of CCJ-region or adjacent dAVFs reported between 1996 and 2026 that included retrievable sagittal T2-weighted or FLAIR images. The presence of the snake-head sign was assessed, and clinical, angiographic, and treatment-related variables were extracted, including fistula location, feeding artery, draining vein direction, treatment modality, and outcome. Associations with the sign were evaluated using univariate analyses. Given the retrospective, literature-based design and limited sample size, findings were considered hypothesis-generating. Results: Among 64 reported cases, the snake-head sign was identified in 31 (48.4%). No significant associations were found between the sign and age, sex, symptom duration, feeding artery, treatment modality, or outcome. However, a non-significant trend was observed for venous drainage configuration: cases with cranial convergence of the draining vein toward the CCJ more frequently demonstrated the sign, whereas purely caudal drainage patterns showed it less often. Fistulas at lower cervical nerve-root sleeves, requiring a longer cranial venous course, also showed higher sign frequency. These findings suggest the sign may reflect venous outflow geometry rather than arterial source or fistula location. Conclusion: The snake-head sign is a recognizable MRI feature present in roughly half of reported CCJ-region dAVF cases. Its identification may raise clinical suspicion for CCJ-related dAVF, particularly in unexplained venous congestive myelopathy. The trend toward a higher frequency of the sign in cases with cranially convergent venous drainage raises the hypothesis that it reflects concentrated venous congestion at this anatomical transition zone. Prospective multicenter studies with standardized imaging review and angiographic correlation are needed to confirm its diagnostic value and clarify the underlying mechanism.
SN - 1664-2295
ER -