Unveiling a rare cause of trigeminal neuralgia: Arteriovenous malformation diagnosed via MRI

Abstract

Trigeminal neuralgia is a debilitating condition that often presents secondary to neurovascular compression of the trigeminal nerve. However, arteriovenous malformations (AVMs) involving the trigeminal nerve are exceedingly rare and represent a unique diagnostic challenge. This report describes the case of a 54-year-old man presenting with severe, paroxysmal facial pain consistent with trigeminal neuralgia as the first manifestation of a cranial nerve V AVM. Radiological evaluation, including advanced magnetic resonance imaging (MRI), was pivotal in identifying the AVM. This case highlights the importance of comprehensive imaging in patients with atypical neuralgia to exclude rare but significant causes like AVMs.

Introduction

Trigeminal neuralgia (TGN), also known as tic douloureux, is a neurological condition involving sudden, intense pain on 1 side of the face. The pain occurs in brief, intense spasms lasting from a few seconds to a few minutes and affects one or more branches of the trigeminal nerve [1].

TGN affects about 4.3 out of every 100,000 people annually. Most cases are unilateral, affecting the right side of the face more often (at a ratio of 1.5:1), while approximately 3% are bilateral. The condition typically peaks between the ages of 60 and 70, and its prevalence increases with age [2].

Most primary TGN cases (80%-90%) result from vascular compression at the root entry zone (REZ), typically by the superior or anterior inferior cerebellar arteries. This compression occurs at the cisternal portion of the trigeminal nerve at its transition zone. Additional causes include compression by cerebellopontine angle tumors or cysts, perineural spread of tumors, and multiple sclerosis [1].

Although arteriovenous malformations (AVMs) are most often linked to cerebral hemorrhages, particularly in younger patients, they may also manifest as chronic headaches, epilepsy, and other neurological deficits. The annual risk of rupture and bleeding in unruptured AVMs is 2%-4%, with each bleeding event carrying an 18% mortality risk. However, TGN resulting from AVMs is relatively underreported, highlighting an intriguing but less recognized manifestation of these vascular malformations [3,4]. Understanding this rare connection provides valuable insight into the broader range of neurological complications that AVMs can cause.

This case report emphasizes the importance of clinicians considering AVMs as a potential cause in patients with TGN, even in the absence of typical hemorrhagic symptoms, and discussing the mechanism, imaging, and management.

Case report

A 54-year-old man with a history of active smoking, ischemic heart disease, and anticoagulant treatment presented with hemicranial headaches that had lasted a few minutes for 6 months. The headaches were exacerbated by anteflexion and had become more severe. Daily self-medication with analgesics had not been effective in controlling the pain over the previous 2 months.

Given these symptoms, the patient consulted a neurologist. The clinical examination revealed no notable trigger points upon palpation and no abnormalities in corneal reflexes or facial sensation.

Magnetic resonance imaging (MRI) of the brain was requested to further investigate the diagnosis and demonstrated the presence of an angiomatous nidus containing the cisternal portion of the right trigeminal nerve. The AVM was Spetzler-Martin grade II, measuring 1 cm and supplied by the superior cerebellar artery and anterior inferior cerebellar artery (AICA), with deep venous drainage (Fig. 1). The nidus appeared hypointense (flow void) on all conventional MRI sequences, including T1, T2, and FLAIR-weighted images, consistent with its high-flow vascular nature. Advanced MRI sequences, including 3D constructive interference in steady state (CISS), were used to better delineate the trigeminal nerve and adjacent vascular structures.

Fig. 1.

CISS weighted axial MRI (A); T2FLAIR weighted Axial MRI (B) and T1- weighted sagittal MRI (C) showing flow-void signals (arrows) of abnormal vessels in the right cerebellopontine angle, encompassing the cisternal portion of the right trigeminal nerve.

The contrast-enhanced study does not clearly show the nidus (Fig. 2), but reveals that it is primarily supplied by the dilated superior cerebellar artery and, incidentally, the moderately dilated AICA (Fig. 3). Drainage occurs via a single venous collector that connects to the basal vein of Rosenthal and then to the vein of Galen (Fig. 3).

Fig. 2.

Contrast-enhanced T1-weighted showing a signal abnormality at the level of the right ponto-cerebellar angle (PCA) and along the trajectory of the trigeminal nerve. (arrow).

Fig. 3.

Coronal 3DTOF MRI (D) and (E) : dilated superior cerebellar artery and dilated AICA (F); Axial 3DTOF MRI (G) : showing a dilated and arterialized single venous collector (red vein) for drainage which joins the basal vein of Rosenthal (arrows).

To further characterize the vascular architecture and flow dynamics, a 3D time-of-flight (TOF) MRI was performed. This non-invasive imaging technique provides detailed visualization of cerebral blood vessels. In our patient, this sequence revealed a dilated right superior cerebellar artery, and flow was identified within the adjacent draining vein. This finding suggests that arterial blood is shunting directly into the venous system, causing early venous opacification—a phenomenon known as the “red vein.” This feature was clinically significant because it indicated the presence of an arteriovenous shunt and helped localize the nidus. Thus, it played a crucial role in both diagnosis and surgical planning (Fig. 3).

Due to the risk of future hemorrhage from the brain AVM, the patient underwent interventional embolization under general anesthesia. Immediate postoperative angiography revealed successful obliteration of most of the AVMs, while preserving the patency of the draining veins. The postoperative course was uneventful, and the pain in the patient’s right cheek resolved completely within 1 week. The patient was satisfied with the embolization outcome. Follow-up care was provided for a period of time. Unfortunately, the patient was subsequently lost to follow-up.

Discussion

The trigeminal nerve root entry zone (REZ), where the nerve exits the brainstem, marks the transition between central and peripheral myelination. This approximately 2 mm zone involves a shift from oligodendrocyte to Schwann cell myelin insulation and is located in the proximal cisternal segment. This transition zone is particularly vulnerable to injury, although the exact mechanisms remain unclear. In our patient, the dilated appearance of the right trigeminal nerve, perineural infiltration, and mild contrast enhancement following gadolinium injection (Fig. 2) suggest early demyelination or irritation in this fragile region, which may explain the patient’s right facial pain [1].

TGN caused by brain arteriovenous malformations (AVM) is extremely rare, accounting for only 0.22%-1.78% of primary TGN cases [5,6]. AVMs are usually found in the posterior fossa on the same side of the brain and can cause TGN by compressing the nerve directly or by dilating the arteries that feed it. Mori et al. classified TGN cases associated with AVMs into 4 groups based on AVM location : intrinsic to the trigeminal nerve, cerebellopontine angle, distant, and dural (petrotentorial) [7]. In our case, the AVM was located in the cerebellopontine cistern, adjacent to the cisternal segment of the trigeminal nerve, placing it in the cerebellopontine angle category.

This anatomical configuration supports a mechanism of neurovascular compression, consistent with the patient’s facial pain and imaging findings. The rarity of this presentation underscores the importance of considering vascular causes in cases of atypical TGN, particularly when conventional imaging reveals adjacent vascular anomalies.

TGN caused by vascular compression is most commonly due to compression by the superior cerebellar artery, though compression by the anterior inferior cerebellar artery (AICA) has also been reported. Imaging plays a pivotal role in diagnosing TGN secondary to arteriovenous malformations, providing critical insights into the neurovascular anatomy and pathology. Advanced MRI techniques, such as 3D-CISS, TOF, and MR angiography, enable precise visualization of the trigeminal nerve and its relationship with adjacent vessels [5].

In our case, an MRI clearly demonstrated an AVM in the right cerebellopontine angle, which was causing pulsatile compression of the nerve. TOF angiography detailed the AVM's arterial and venous components. Digital subtraction angiography (DSA) complemented these findings by providing dynamic visualization of the AVM. This visualization identified the feeding arteries, nidus, and draining veins, essential for confirming the diagnosis and planning treatment. Combining MRI and DSA ensures a comprehensive assessment, distinguishing AVMs from other potential causes of TGN, such as vascular loops, tumors, or inflammatory lesions [5,6].

Because this condition is rare, there is no established consensus on the most effective management approach. Treatment should be personalized based on factors such as AVM characteristics, patient risk factors, and care goals. While medical management is typically initial, secondary TGN often does not respond well to medication. In some reports, symptom resolution has been achieved following palliative embolization of cerebellopontine angle AVMs [11].

Several treatment methods have been described for this condition, including:

• •Embolization: Minimally invasive; can provide temporary relief by reducing vessel pulsatility but carries risks such as ischemia and incomplete obliteration [4,8].
• •Radiotherapy: Minimally invasive; delayed response, may not immediately alleviate symptoms [9].
• •Surgical resection: Definitive treatment for cases with prior hemorrhage, addressing compression and bleeding risks [10].
• •Microvascular decompression (MVD): Effectively relieves symptoms when compression involves feeding arteries or draining veins [10].
• •Radiosurgery: Option for small, deep AVMs [9].
• •Craniotomy for AVM resection, with or without MVD: Definitive treatment but higher morbidity and mortality risk [10].

Prognosis largely depends on complete obliteration of the AVM and absence of treatment complications. Successful intervention results in significant symptom relief and improved quality of life. Incomplete obliteration or complex vascular anatomy may lead to persistent or recurrent symptoms. Neurological deficits or hemorrhagic events related to treatment can affect outcomes. Close clinical and imaging follow-up is essential. Due to rarity, further studies are needed to better understand long-term prognosis and optimize management strategies [3,4,8].

Conclusion

Management of TGN caused by arteriovenous malformations must be tailored to each patient. In this case, partial embolization effectively relieved symptoms by reducing pulsatile compression on the trigeminal nerve [4,8]. This outcome underscores the importance of endovascular intervention in select cases, particularly when complete resection poses high risk. However, the presence of deep venous drainage, as observed in this patient, poses challenges to surgical accessibility and limits complete resection. AVMs with deep venous drainage are associated with higher procedural risk and lower obliteration rates, highlighting the need for a multidisciplinary approach to optimize outcomes while minimizing morbidity [3,10].

Patient consent

Written informed consent was obtained from the patient for the publication of this case report.