2024 Volume 11 Pages 285-290
Trigeminal neuralgia (TN) associated with a primitive trigeminal artery variant (PTAV) is a rare condition that causes severe facial pain. We report the case of an 81-year-old woman presenting with right facial pain. Brain magnetic resonance imaging revealed an aberrant artery originating from the cavernous portion of the right internal carotid artery (ICA), coursing laterally around the posterior clinoid process and running toward the anterior inferior cerebellar artery (AICA) territory, suggesting a PTAV. Although the pain subsided with carbamazepine, liver dysfunction developed; microvascular decompression was performed. Transposition of the PTAV in a lateral direction revealed a marked indentation at the root of the right trigeminal nerve. The PTAV was surgically transposed laterally and fixed to the pyramidal bone surface using a Teflon sling, whereas the proximal part was fixed downward to the brainstem. There was immediate facial pain relief, following surgery. We reviewed 27 cases of TN associated with PTA or PTAV reported in the literature, which showed that the average age of onset was similar to our case, at 56.5 years, with a male-to-female ratio of 1:2.85. The proportion of patients with PTAV with V2 region affected was highest (91.3%), with PTAV (AICA) being the most common aberrant blood vessel (40.7%).
In cases of TN associated with PTA or PTAV, it is crucial to identify blood vessels that are compressing or contacting the nerve and transpose these arteries from the nerve. It is also critical to plan movement direction in order to prevent ischemia of perforators to the brainstem or internal auditory artery.
Primitive vascular anastomoses exist between the internal carotid and the vertebrobasilar arteries during the embryonic stage, and as the posterior communicating and vertebral arteries develop, these anastomoses regress but, in rare cases, persist into adulthood.1) Primitive trigeminal artery (PTA) is the most common carotid-basilar anastomosis.1,2) It has a variant, PTAV, which anastomoses to the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery, which perfuse the cerebellar cortex in addition to the basilar artery (BA).1) The frequency of coexistence of persistent PTA with other vascular abnormalities is as high as 25% and the incidence of aneurysm complication is 14%.3-5) Although this has been reported to cause trigeminal neuralgia (TN), it is extremely rare.6) We report the case of an 81-year-old woman with TN associated with a persistent PTAV and a review of the literature regarding its clinical, radiological, and surgical features.
An 81-year-old woman presented to our hospital with a history of pain on her right face for 4 years. She was referred to the Department of Oral and Maxillofacial Surgery of our hospital, where she was conservatively treated with carbamazepine. Although the pain subsided, liver dysfunction was detected, and she was referred to the Department of Neurosurgery for plausible surgery. Her facial pain was intense and lasted up to 5 min, caused by a lesion on the second branch of the right trigeminal nerve. The lancinating pain was triggered by the slightest touch on the face. Magnetic resonance imaging (MRI) revealed an artery originating from the cavernous portion of the right internal carotid artery (ICA), coursing laterally around the posterior clinoid process and running toward the territory of the AICA, suggesting a PTAV (Fig. 1). Constructive interference in steady state image revealed that the right trigeminal nerve was compressed by the PTAV. The patient's medical history was unremarkable. Microvascular decompression for the right trigeminal nerve was planned.
Magnetic resonance imaging (MRI) and MR angiography of the brain.
Brain MRI at onset shows a low-intensity spot compressing the right trigeminal nerve laterally in the cisternal portion (A, dotted circle) and an aberrant artery arising directly from the cavernous portion of the right internal carotid artery perfusing the anterior cerebellar artery territory not connected to the basilar artery in MR angiography (B, C, arrows).
The patient was placed in the supine lateral position, and a lateral suboccipital craniotomy was performed with an exoscope under general anesthesia. After retracting the right cerebellar hemisphere and opening the right horizontal fissure of the cerebellum,7) cisternal portion of right trigeminal nerve and its surrounding structure was exposed (Fig. 2). It was found that root entry zone of the right trigeminal nerve was compressed by the PTAV from lateral to medial direction (Fig. 2A). As the PTAV was transposed in a lateral direction, a marked indentation was observed at the root of the right trigeminal nerve. The PTAV was transposed laterally and fixed to the surface of the pyramidal bone with a Teflon sling (Fig. 2B). Following the maneuver of this transposition, a new vascular contact was detected in the center of the trigeminal nerve, which was attached downward to the brainstem (Fig. 2C). Auditory brainstem response (ABR) monitoring was started as soon as surgery began to prevent hearing impairment. The baseline wave V latency was 6.4 ms, and even at maximum delay, it was 6.9 ms; thus, no postoperative hearing disturbance occurred.
Intraoperative images of the position of the trigeminal nerve.
Intraoperative photographs showing the artery (blue arrow) compressing the trigeminal nerve from lateral to medial (A). After dissecting the surrounding arachnoid membrane, the artery was transposed to the lateral side and fixed to the surface of the petrous bone with fibrin glue and Teflon sling (B, red arrow). A new vascular contact was detected in the center of the trigeminal nerve (B, blue arrow) and the proximal part of the artery was fixed downward toward the brainstem (C, red arrow).
The patient's right facial pain was completely relieved immediately following surgery, and there were no postoperative neurological impairments. A postoperative MRI confirmed the laterally transposed PTAV (Fig. 3).
Postoperative magnetic resonance imaging (MRI).
Postoperative MRI shows a low-intensity spot moving medially from the trigeminal nerve (A, dotted circle). MR angiography shows medial transposition of the proximal part (B, yellow arrow) and lateral transposition of the peripheral part of the artery (red arrow).
This case report was conducted in accordance with the principles of the Declaration of Helsinki, and the corresponding author explained to the patient the significance of submitting this case to a medical journal as an academic paper; a written informed consent was obtained from the patient in this study.
PTAV was first reported in 1973 by Teal et al.8) as a "variant of primitive trigeminal artery" and this abnormal artery was later reported to cause TN.6) We reviewed 26 previously reported cases of TN and the present case associating PTA and PTAV (Table 1).6,9-25) In general, TN often occurs after the age of 50, with a male-to-female ratio ranging from 3.4 to 5.9, being more common in women. The pain predominantly affects the V2 (maxillary) and V3 (mandibular) branches of the trigeminal nerve, accounting for 80% of all cases, with the most common offending vessel being the SCA in approximately 75% of cases.26-28) In the 27 cases we reviewed, the average age was 56.5 years, consistent with that reported for TN. The male-to-female ratio was higher at 1:2.85, and of the 23 cases with a description of the pain area, 3 (13.0%) were in V1, 21 (91.3%) in V2, and 10 (43.5%) in V3 regions. PTAV (AICA) was the most common offending vessel with a 40.7% frequency. In TN involving PTAV, there was a strong tendency to have greater pain in the V2 region. It remains unclear why TN involving PTA or PTAV is more prevalent in women compared with normal TN. The large number of PTAVs circulating in this area suggested that the route of this artery in the rostral direction was related to its proximity to the trigeminal nerve. Adams et al.29) reported that the intracisternal trigeminal nerve topography has the first branch adjacent to the motor root and the third branch in the direction of the auditory nerve. TN involving PTA or PTAV is frequently found in the area of the second branch; thus, it is possible that the aberrant artery, which runs a long distance close to the trigeminal nerve, compresses the trigeminal nerve from above rather than from the side or that the trigeminal nerve is compressed by multiple arteries or branches.
Summary of the 26 patients with trigeminal neuralgia associated with PTA or PTAV
| No. | Age at onset | Age at operation |
Sex | Site of pain | Offending vessels | Literature |
|---|---|---|---|---|---|---|
| average | 56.5 | 63.1 | ||||
| PTA/PTAV: nd, not described |
||||||
| 1 | 71 | 71 | F | V3 | PTAV (SCA) | Satoh T et al., 2023 |
| 2 | 58 | 63 | F | V1 + 2 | PTA | Fu C et al., 2015 |
| 3 | 40 | 55 | M | nd | PTA, SCA | Sadashiva N et al., 2021 |
| 4 | 63 | 65 | M | V2 | PTAV | Sano K et al., 2020 |
| 5 | 41 | 51 | F | V2 | PTAV (AICA, SCA) | Tamura Y et al., 2003 |
| 6 | 55 | 65 | M | V2 | PTAV, SCA | Miki K et al., 2019 |
| 7 | 57 | 66 | M | nd | PTA | Park CK et al., 2014 |
| 8 | 62 | 62 | F | V1 + 2 | SCA | Kato N et al., 2011 |
| 9 | 28 | 31 | M | V2 | PTAV (AICA), SCA | Yamada Y et al., 2006 |
| 10 | 68 | 69 | F | V2 | BA, VA | Fukuda M et al., 1998 |
| 11 | 45 | nd | F | V2 + 3 | PTA, PTAV (AICA, PICA) | Son B et al., 2013 |
| 12 | nd | 52 | F | V2 + 3 | PTA | Kempe LG et al., 1969 |
| 13 | 77 | 86 | F | V2 + 3 | PTAV (AICA) | Kawahara I et al., 2011 |
| 14 | 54 | 61 | F | nd | PTAV (PICA) | Lee SH et al., 2011 |
| 15 | 70 | 74 | F | V2 + 3 | PTA | Tokimura H et al., 1990 |
| 16 | 44 | 48 | M | V2 + 3 | PTAV (AICA), SCA | |
| 17 | nd | 53 | M | nd | PTA | Kono K et al., 2013 |
| 18 | nd | 75 | F | V2 + 3 | PTAV (AICA) | Morita A et al., 1989 |
| 19 | nd | 77 | F | V2 | PTAV (SCA) | |
| 20 | nd | 53 | F | V2 | PTAV (PICA), AICA, SCA | |
| 21 | nd | 54 | F | V2 + 3 | PTAV (AICA), SCA | |
| 22 | nd | 74 | F | V2 + 3 | PTA, AICA, SCA | |
| 23 | nd | 56 | F | V2 | PTAV (AICA) | |
| 24 | nd | 69 | F | V1 + 2 | PTAV (AICA) | |
| 25 | nd | 67 | F | V2 + 3 | PTAV (AICA) | |
| 26 | 51 | nd | F | nd | PTA | Pereira LP et al., 2009 |
| 27 | 77 | 81 | F | V2 | PTAV (AICA) | Present case |
Morita et al.6) reported that, anatomically, the PTA runs medially into the posterior cranial fossa and connects to the BA, so it is less likely to compress the root entry zone, and the PTA variant is more likely to cause TN. Of the 62 patients with PTAV reported by Tsukamoto et al.,30) the AICA region was perfused in 65% of patients, whereas the SCA region was perfused in 18% cases. PTAV (AICA) is the most common because after branching from the internal carotid artery, the artery exits from the lateral side of the posterior clinoid process into the prepontine cistern, turns outward, and perfuses the AICA region and its long course intersects with the trigeminal nerve. The persistent PTA directly transmits blood flow from the internal carotid artery to the posterior fossa. Due to hemodynamic stress, the blood vessels in the posterior fossa can dilate and become tortuous. This hemodynamic stress and resultant vascular changes can lead to neurovascular compression of the trigeminal nerve, contributing to TN. Multiple blood vessels, not just the PTA or PTAVs, can be responsible for this condition.24) In 40% of the PTA-related TN cases we reviewed, multiple offending arteries were identified. In this case, the only offending artery was the PTAV, which anastomoses to the anterior inferior cerebellar artery, but the tortuosity was strong, and new contacts occurred when the position of the blood vessel changed. Moreover, during the surgery, it is important not to overlook any blood vessel that is compressing or is in contact with the nerve. Most PTAs and PTAVs have perforators that branch into the brainstem, and care must be taken when transposing them. The PTAV, which perfuses the AICA region, also branches to the internal auditory artery.23) In our case, the trigeminal nerve was difficult to move since it crossed from cranial to caudal; therefore, we adopted measures such as shifting the blood vessels dorsally (toward the brainstem) while considering the brainstem and the internal auditory artery. Thus, it was crucial to have continuous ABR monitoring in order to ensure auditory function preservation and to promptly detect any signs of neural compromise.
We have described our experience of a rare case of TN in which the PTAV, a persistent primitive artery, was involved. In cases of TN involving the PTA or PTAV, it is important not to overlook any blood vessel that is compressing or contacting the nerve. In such cases, these vessels should be moved away from the nerve. Thus, complications in microvascular decompression, a form of functional neurosurgery, need to be avoided diligently, and it is important to devise the direction of movement in order not to cause ischemia of perforators to the brainstem or internal auditory artery.
We would like thank Professor Takamitsu Fujimaki of Saitama Medical University for his very valuable comments and Editage (www.editage.jp) for English language editing.
PTA, primitive trigeminal artery; PTAV, primitive trigeminal artery variant; TN, trigeminal neuralgia; ICA, internal carotid artery; AICA, anterior inferior cerebellar artery; SCA, superior cerebellar artery; BA, basilar artery; MRI, magnetic resonance imaging
The authors declare no conflicts of interest.
