Abstract

Background: This report presents a rare case of trigeminal neuralgia (TN) caused by a radicular arteriovenous fistula (AVF).

Case Description: A 58-year-old woman presented with severe pain in the right lower jaw, typical of TN. Magnetic resonance imaging showed a vascular signal near the trigeminal nerve. Direct surgery revealed tortuous vessels on the dorsal surface of the nerve, with no offending vessels identified at the root entry zone. Digital subtraction angiography (DSA) confirmed a radicular AVF fed by the trigeminocerebellar artery, with venous drainage into the superior petrosal sinus through the petrosal vein. Endovascular embolization with n-butyl cyanoacrylate resulted in complete obliteration of the fistula and symptom resolution. Although a small pontine infarction occurred, no long-term deficits were observed. Follow-up DSA confirmed no recurrence.

Conclusion: To the best of our knowledge, this represents the first documented case of a trigeminal radicular AVF, highlighting the importance of recognizing vascular anomalies and efficacy of endovascular treatment in managing TN.

Keywords: Endovascular therapy, Radicular arteriovenous fistula, Trigeminal nerve, Trigeminal neuralgia

INTRODUCTION

This study reports a case of trigeminal neuralgia (TN) wherein direct surgery revealed an abnormal vascular lesion. Digital subtraction angiography (DSA) confirmed the presence of an arteriovenous fistula (AVF) on the trigeminal nerve surface. The patient underwent successful endovascular treatment, leading to the resolution of AVF symptoms and complete obliteration. To the best of our knowledge, no previously reported cases were diagnosed with trigeminal radicular AVF; this report is the first documented case of this condition.

CASE PRESENTATION

A 58-year-old woman with no significant medical history presented with severe pain in the right lower jaw that had developed approximately 1 month earlier, triggered by activities such as eating and speaking. Despite treatment with carbamazepine, the symptoms persisted and progressively worsened, leading to a referral to our department. At admission, the patient exhibited symptoms but had no focal neurological deficits. A constructive interference in steady-state image of 3-Tesla magnetic resonance imaging (MRI) showed no significant abnormalities, while a source image of high-resolutional three-dimensional computed tomography (CT) angiography demonstrated a vascular signal near the right trigeminal nerve, which was initially suspected to be caused by the artery offending the root entry zone. However, the volume-rendered image of the 3D CT angiography revealed no findings suggestive of arteriovenous shunt disease [ Figure 1 ]. Considering the characteristic presentation of TN, endoscopic microvascular decompression was performed. Intraoperatively, no offending vessels were identified at the root entry zone of the trigeminal nerve. Instead, multiple small tortuous vessels were observed along its dorsal surface. Intraoperative indocyanine green video angiography revealed the presence of fine vascular networks and early filling of the petrosal vein (PV), which are findings not normally observed. No abnormal vessels were observed in the surrounding dura mater [ Figure 2 and Video 1 ].

Figure 1:

Preoperative images of endoscopic microvascular decompression. (a) A CISS image using 3-Tesla MRI showed no significant abnormalities in the right trigeminal nerve root entry zone. (b) The source image of three-dimensional computed tomography angiography image revealed a vascular shadow in this area, (red arrowhead) (c) but the volume-rendered image did not indicate arteriovenous shunting disease. CISS: Constructive interference in steady state, MRI: Magnetic resonance imaging.

Figure 2:

Intraoperative images of endoscopic microvascular decompression. (a) Low magnification visualized the petrosal vein (asterisk) and trigeminal nerve (white arrow), but revealed no evidence of dural arteriovenous fistula. (b) High magnification showed an abnormal reticular cluster of minute blood vessels on the dorsal surface of the right trigeminal nerve (white arrow), with a red vein (white arrowhead) running centrally from the ventral aspect toward the petrosal vein (asterisk). (c) Indocyanine green video angiography visualized abnormal microvessels on the dorsal surface of the trigeminal nerve (white arrow), including a vein (white arrowhead) crossing it and the petrosal vein (asterisk), with no such findings on the dural surface. T: Tentorium, PD: Posterior fossa dura.

Video 1

Following surgery, DSA was performed, revealing a vascular abnormality corresponding to the findings observed during endoscopic microvascular decompression. The right trigeminocerebellar artery (TCA), originating from the basilar artery, was found to run laterally between the right superior cerebellar artery and anterior inferior cerebellar artery (AICA). At the root entry zone of the right trigeminal nerve, this artery formed an AVF with venous drainage into the PV, subsequently draining into the superior petrosal sinus (SPS). In addition, a minor drainage route into the inferior petrosal sinus (IPS) was identified [ Figure 3 ]. Based on these angiographic and intraoperative findings, the lesion was diagnosed as an AVF located on the ventral surface of the right trigeminal nerve.

Figure 3:

(a) Anteroposterior and (b) lateral views of left vertebral artery angiography showed the TCA (red arrowhead in a) branching from the BA between the SCA and AICA. Arteriovenous shunting was observed through an abnormal vascular network, draining from the PV to the SPS, with minor drainage into the IPS. (c) These vascular structures including TCA (red arrowhead) were visualized in the VR and (d) MIP image also shows TCA (red arrowhead). (e) On the MPR image the TCA (red arrowhead) originating from the BA ran along the posterolateral margin of the pons, connecting the trigeminal root to fine abnormal vascular network on its surface, draining from the PV into the SPS. (f) The magnified view highlights the position of the trigeminal nerve with red dotted lines, which overlapped with an abnormal vascular network fed by the TCA (red arrowhead). AICA: Anterior inferior cerebellar artery, IPS: Inferior petrosal sinus, MIP: Maximum intensity projection, MPR: Multiplanar reconstruction, PV: Petrosal vein, SCA: Superior cerebellar artery, SPS: Superior petrosal sinus, TCA: Trigeminocerebellar artery, VR: Volume rendering.

Endovascular treatment was performed under general anesthesia 2 days post-surgery. A 5Fr guiding sheath (Fubuki; Asahi Intecc, Aichi, Japan) was inserted into the left vertebral artery by the right transfemoral approach, distal access catheter (Vecta46; Stryker, Kalamazoo, MI, USA) was advanced, and microcatheter system comprising a DeFrictor Nano (Medico’s Hirata Inc., Osaka, Japan) and Chikai X10 (Asahi Intecc) was used to access the feeder vessel. The vascular architecture of the fistula was mapped through superselective injection [ Figures 4a and b ], after which the microcatheter was advanced proximally to the fistulous segment [ Figures 4c and d ]. Embolization was performed using the continuous column method employing 0.78 mL of 15% n-butyl cyanoacrylate (NBCA) diluted with lipiodol. The NBCA successfully penetrated the fistula, reaching the PV at its confluence with the SPS. Post-embolization DSA revealed residual flow from the subarcuate artery, which branched distally from the right AICA and drained into the IPS [ Figures 4e and f ]. Using the same catheter system, the right AICA was accessed and advanced to the origin of the subarcuate artery. During superselective injection, slight extravasation was observed [ Figures 4g and h ]. The microcatheter was retracted by approximately 2 mm, and an additional 0.29 mL of 15% NBCA was used for embolization. The normal branches of the AICA were preserved, though a minimal residual AVF remained [ Figures 4i and j and Video 2 ].

Figure 4:

Superselective angiography. (a and b) Anteroposterior and lateral views demonstrate a feeder from the TCA, forming an arteriovenous fistula AVF through a fine abnormal reticular network, draining into the PV and SPS. (c and d) Enlarged anteroposterior and lateral views of the embolization site. (e and f) Anteroposterior and lateral views of the left vertebral artery angiography reveals residual AVF from the AICA, draining into the IPS. (g and h) Angiography via a microcatheter guided into the subarcuate artery through the trunk of the AICA shows extravasation. (i and j) Final anteroposterior and lateral views of left vertebral artery angiography after embolization demonstrates near-complete obliteration of the AVF. AICA: Anterior inferior cerebellar artery, AVF: Arteriovenous fistula, IPS: Inferior petrosal sinus, PV: Petrosal vein, SPS: Superior petrosal sinus, TCA: Trigeminocerebellar artery.

Video 2

Postoperative plain head CT revealed contrast extravasation, minimal subarachnoid hemorrhage, and a cast of NBCA at the root entry zone of the right trigeminal nerve [ Figure 5a ]. However, the patient recovered well from general anesthesia, exhibiting clear consciousness and no motor or sensory deficits in the limbs. No signs of facial paralysis or hearing impairment were observed. Mild numbness on the right side of the face and slight dysarthria were noted; however, TN resolved the following day, while mild unsteadiness during walking suggestive of slight ataxia was observed. A diffusion MRI was performed the next day [ Figure 5b ], and revealed a small acute cerebral infarction on the right margin of the pons, likely due to partial compromise of the normal TCA perfusion.

Figure 5:

A postoperative plain CT (a) revealed contrast extravasation, minimal subarachnoid hemorrhage, and a cast of NBCA at the root entry zone of the right trigeminal nerve. A diffusion image of the MRI on the next day (b) showed a small acute cerebral infarction on the right margin of the pons. Left vertebral artery angiography performed 3 months after endovascular treatment (c: Anteroposterior view, d: Lateral view) confirmed complete obliteration of the arteriovenous fistula. CT: Computed tomography, MRI: Magnetic resonance imaging, NBCA: n-Butyl cyanoacrylate.

The patient was discharged 10 days after the procedure and regained the ability to walk independently showing no neurological deficits or signs of TN. At the 3-month follow-up, the patient had no recurrence of TN or neurological deficits. DSA confirmed the sustained, complete obliteration of the AVF [ Figures 5c and d ]. Further clinical observation and annual MRI examination will be continued.

DISCUSSION

Vascular lesions associated with TN

TN is commonly caused by neurovascular compression at the root entry zone, often involving the superior cerebellar artery. However, other etiologies, such as brain tumors (e.g., meningiomas, schwannomas, and epidermoid cysts)[ 8 ] and vascular abnormalities,[ 1 , 2 , 4 , 5 , 7 ] can also lead to TN. These lesions may compress or irritate the trigeminal nerve, causing paroxysmal pain; an MRI is critical for distinguishing such structural causes. In addition to tumors, vascular lesions, including arteriovenous malformations (AVMs) and fistulas, may contribute to TN symptoms by affecting the nerve through altered hemodynamics, causing irritation or compression. Recognizing these rare causes is crucial for accurate diagnosis and management, as treatment approaches vary depending on the underlying pathology. In the present case, TN was attributed to a previously unrecognized AVF located on the trigeminal nerve surface. An enlarged red vein running near the trigeminal nerve and its root entry zone is considered a possible cause; in addition, relative nerve ischemia due to an arteriovenous shunt cannot be ruled out. The utilized DSA provided critical information regarding vascular anatomy and guided endovascular treatment, engendering complete AVF symptom resolution and obliteration. In this case, had the vascular lesion been identified before the endoscopic surgery, direct microsurgery might have been a viable option to treat the lesion. However, the lesion was ultimately found to be located on the ventral surface of the trigeminal nerve, making it difficult to address through a posterior approach. Although direct surgery through an anterior transpetrosal route remained a potential alternative, endovascular treatment was deemed appropriate given the prior craniotomy, the minimally invasive nature of the preceding endoscopic procedure, and the DSA findings, which confirmed the feasibility of endovascular intervention. With regard to the therapeutic strategy for liquid embolization, in the present case, the feeder vessel was too small in diameter to allow for the plug-and-push technique using Onyx. Therefore, we preferred very diluted NBCA, which was more suitable for achieving penetration from the shunt point to the foot of the draining vein through a simple push technique.

AVF classification

Based on intraoperative and angiographic findings, the lesion was classified as a radicular AVF rather than a dural AVF. Direct surgery revealed no abnormal vessels in the adjacent dura mater, thereby excluding the possibility of a dural AVF. Instead, multiple small, tortuous vessels were identified along the dorsal surface of the right TN, indicating that the vascular anomaly responsible for these vessels was located on the ventral aspect of the nerve root. To the best of our knowledge, while the concept of radicular AVF has gained increasing recognition in recent years,[ 3 , 6 ] particularly at the craniocervical junction, no previous reports have documented such a lesion on the surface of an intracranial nerve.

In this case, the arterial feeder originated primarily from the right TCA, a branch of the basilar artery, with additional contribution from the right subarcuate artery. It formed a direct arteriovenous shunt on the surface of the trigeminal nerve, with venous drainage primarily into the SPS through the PV and minor outflow into the IPS. Therefore, this case was diagnosed as a rare AVF case, specifically involving the TN. This diagnosis was further supported by the absence of a nidus, eliminating an AVM,[ 4 ] and its distinction from dural AVFs,[ 1 , 2 , 5 ] which are typically located in the dural venous sinuses or adjacent dura. While complications such as minor extravasation and a small acute infarction occurred, the symptoms resolved completely with appropriate treatment. Endovascular embolization using NBCA significantly reduced the abnormal shunt, and follow-up angiography confirmed complete obliteration.

The etiology of intracranial shunt diseases remains unclear. Dural arteriovenous fistulas are generally considered acquired lesions and have been reported in some cases to be associated with sinus thrombosis and altered venous hemodynamics. In contrast, AVMs and pial AVFs within the dura are typically regarded as congenital or embryologic in origin. The present case of radicular AVF, an intradural shunt lesion, appears more closely related to AVM/pAVF-type pathology. Nonetheless, no genetic factors have been identified based on systemic findings or family history in this case; consequently, its etiology remains undetermined.

CONCLUSION

This report is the first to describe a rare case of AVF-derived TN, as supported by our intraoperative and DSA findings. Endovascular embolization with NBCA was determined to completely resolve fistula symptoms and obliterate it, despite minor complications. This highlights the importance of recognizing vascular anomalies, including radicular AVFs in the differential diagnosis of TN, as well as potential efficacy of endovascular treatment for such rare lesions.

Ethical approval:

Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Videos available on:

https://doi.org/10.25259/SNI_364_2025

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

References

1. Dai X, Xu D, Chen K, Cai Y, Mei Z, Wu J. Dural arteriovenous fistula presenting as trigeminal neuralgia: Case report and literature review. Heliyon. 2024. 10: e30000

2. Ghodasara S, Balasubramanian R, Poyyamoli S. A rare case of right trigeminal neuralgia due to dural arteriovenous fistula. Asian J Neurosurg. 2021. 16: 174-7

3. Hiramatsu M, Sugiu K, Ishiguro T, Kiyosue H, Sato K, Takai K. Angioarchitecture of arteriovenous fistulas at the craniocervical junction: A multicenter cohort study of 54 patients. J Neurosurg. 2018. 128: 1839-49

4. Nagai A, Endo H, Sato K, Kawaguchi T, Uchida H, Omodaka S. Arteriovenous malformation of the trigeminal nerve root presented with venous congestive edema of the medulla oblongata and upper cervical cord: Illustrative case. J Neurosurg Case Lessons. 2021. 2: CASE21402

5. Saglam M, Anagnostakou V, Kocer N, Islak C, Kizilkilic O. Teaching neuroimages: A rare cause of trigeminal neuralgia: Dysplastic venous aneurysm of dural arteriovenous fistula. Neurology. 2015. 84: e128-9

6. Wada K, Tanei T, Hattori K, Hatano H, Fujitani S, Ito R. Unique vascular structures of a radicular arteriovenous fistula at the craniocervical junction along the first cervical spinal nerve: A case report. Surg Neurol Int. 2023. 14: 85

7. Wang S, Mo J, Gai S, Ou C, Chen Y. Trigeminal neuralgia associated with cerebellar pial arteriovenous fistula: A case report. Medicine (Baltimore). 2020. 99: e18873

8. Zhang YQ, Yu F, Zhao ZY, Men XZ, Shi W. Surgical treatment of secondary trigeminal neuralgia induced by cerebellopontine angle tumors: A single-center experience. World Neurosurg. 2020. 141: e508-13