Trigeminal neuralgia caused by dolichoectatic vertebral artery: Reports of two cases

1 Introduction

Trigeminal neuralgia (TN), also known as tic douloureux, is a widely known clinical entity that presents as paroxysmal hemifacial pain induced by several causes and sudden attacks of severe facial pain due to the involvement of the fifth cranial nerve [1]. TN is chronic, neuropathic pain that is usually clinically presented as sudden, intense pain and aching sensations between attacks [2]. Among all anatomical possibilities and variants that lead to TN, vertebrobasilar dolichoectasia is the most unusual cause of TN and accounts for up to 7% of all TN cases [3]. The most common cause of TN is trigeminal nerve compression by the superior cerebellar artery (SCA) in almost 80% of all TN cases, followed by the anterior inferior cerebellar artery (AICA) and, less commonly posterior inferior cerebellar artery (PICA) or primitive trigeminal arteries [4].

Although rare, dolichoectasia of the vertebrobasilar artery with compression of the trigeminal nerve is a well-known entity of TN, and many cases have already been described and surgically treated with a good outcome [5]. Neurovascular theory in the development of trigeminal pain and surgical microvascular decompression (MVD) was first introduced and performed by Jannetta [6].

When conservative possibilities are exhausted, the final decision for a surgical treatment is usually made after magnetic resonance imaging (MRI) in a steady state gradient echo sequence, which remains the gold standard in radiologic evaluation of TN.

The authors present the two cases of TN secondary to the dolichoectatic vertebrobasilar artery and its surgical treatment.

2 Case reports

Case 1: An 82-year-old female patient suffered from the right-sided TN for the last 2 years. She primarily underwent conservative treatment; several therapeutics were introduced, but symptoms were refractory regardless of treatment. Mastication and speech were thoroughly compromised, and the patient lost a large proportion of her body weight. Also, significant physical and cognitive decline were noted. Symptoms were mainly presented along the maxillary and mandibular branches of the right-sided trigeminal nerve.

Due to clinical and neurological decline and unbearable pain, refractory to therapeutics, the patient underwent an MRI scan, including three-dimensional (3-D) constructive interference in steady state mode (CISS), which revealed a dolichoectatic vertebrobasilar artery (VA) with concomitant compression of the right-sided trigeminal nerve by the ipsilateral VA (Figure 1).

Figure 1

Axial MRI CISS (a) revealed a dolichoectatic vertebral artery; the left-sided vertebral artery (LVA) is tortuous and completely removed to the opposite site and has a dominant blood supply (down arrow). The left arrow points to a narrower artery that is the right-sided vertebral artery (RVA). The trigeminal nerve (right arrow) is clearly compressed by the RVA. Coronal MRI CISS (b) image revealed neurovascular conflict between the RVA (left arrow) and trigeminal nerve (right arrows).

Preoperative evaluation revealed completely normal laboratory findings.

The patient underwent surgical treatment under general anesthesia and usual fashion; the right-sided retromastoid craniotomy was performed. Microvascular decompression of the trigeminal nerve using Teflon^® felts was performed.

The trigeminal nerve was largely compressed by the ipsilateral vertebral artery; also posterior inferior cerebellar artery (PICA) and Dandy’s vein (DV) were recognized at the same site. The fifth nerve was decompressed in a 360° manner, and Teflon felt was put between the nerve and the ipsilateral VA and the nerve and DV (Figure 2). When felt was in situ, the authors used the fibrin glue to achieve better adherence. The wound was closed in a usual fashion; no postoperative cerebrospinal fluid (CSF) leak was noted. The patient recovered well postoperatively and had no facial pain afterwards.

Figure 2

(a) Intraoperative image before MVD in an 82-year-old female patient: Right arrow depicts the right-sided TN and down arrow depicts RVA. (b) Intraoperative image after MVD: Right and down arrow depict Teflon^® felts, up arrow depicts TN, and star depicts Dandy’s vein. Note that TN was decompressed in a 360° manner.

Several days after hospital discharge, the patient suffered from pneumonia; she was treated by a pulmonologist in her referral institution, and she recovered well. An early follow-up 1 month after surgery revealed completely resolved facial pain.

Case 2: A 68-year-old male patient suffered from left-sided neuralgic pain along the V2 and V3 branches. Symptoms persisted for more than 4 years, and symptoms mainly worsened during chewing. He underwent algologic and maxillofacial conservative treatment, but no regression of symptoms was noted. Radiologic evaluation, i.e., MR CISS sequences, revealed significant compression of the left TN by the dolichoectatic vertebral artery (Figure 3). The patient was treated conservatively for arterial hypertension, dyslipidemia and type II diabetes; the patient had no drug allergies. Preoperative evaluation confirmed normal values of laboratory findings. The patient underwent surgical treatment under general anesthesia. The left-sided retrosigmoid suboccipital osteoplastic craniotomy was performed. When neurovascular conflict was presented, the authors performed microvascular decompression using Teflon^® felt (Figure 4). The authors found no other vessel or arachnoid with significant compromise of the trigeminal nerve. They used fibrin glue to achieve better adherence of the inlay.

Figure 3

Axial (a) MRI CISS sequence of the left-sided neurovascular conflict between LVA (right arrow) and the trigeminal nerve (left arrow). Coronal (b) MRI CISS image revealed neurovascular conflict between LVA (down arrow) and the left-sided TN (up arrow).

Figure 4

(a) Intraoperative image before MVD in a 68-year-old male patient: Right arrow depicts TN and up arrow depicts LVA. (b) Intraoperative image after MVD: Down arrow depicts decompressed TN, up arrow depicts LVA, and left arrow depicts Teflon^® felt.

Surgery and postsurgical treatment at our department went uneventfully. The patient confirmed a complete pain resolution, and no postsurgical complications were noted. The same patient underwent the contralateral MVD in general anesthesia over a time span of 3 months.

3 Discussion

With an incidence of only around 0.05%, TN secondary to VBD is a very uncommon disorder [7]. The term dolichoectasia originates from the Greek language, which means distension and elongation; therefore, VBD is a vascular disorder characterized by a dilated, elongated, and tortuous vertebrobasilar system that potentially causes paroxysmal hemifacial pain as a consequence of compression of the trigeminal or facial nerves. Besides the nerve compression, VBD can rarely result in an ischemic event [8].

The most accepted mechanism for TN is vascular compression in the root entry zone (REZ), a particular area of the cisternal segment of the nerve. Continuous, pulsating pressure is common in REZ, which can cause focal demyelination of the nerve and concomitant short-circuiting of impulses at demyelinated areas of the nerves, both resulting in pain [9].

TN is diagnosed clinically, and VBD as etiology is confirmed with radiological imaging. MRI is regarded as the gold standard in radiologic diagnosis. Detailed MRI scans of the brain are crucial for determining the presence of a trigeminal neurovascular conflict, the degree of compression, and visualization of vascular structures. CISS are crucial in identifying the nerves – the CISS sequence offers a clear contrast between cerebrospinal fluid and cranial nerves, and it is used to identify cranial nerves that appear dark gray. The CISS sequence uses a powerful T2-weighted three-dimensional gradient echo technique to create high-resolution isotropic pictures. For improved nerve delineation, the Fast Imaging Employing Steady-state Acquisition (FIESTA) sequence is also utilized [9]. Surgery is the best known and commonly accepted treatment of TN secondary to VBD. Utilization of a surgical microscope led to conventional MVD surgery to demonstrate that TN can result from artery or vein compression, which was introduced by Jannetta. Jannetta later selected the posterior fossa, i.e., retrosigmoid approach, after honing his surgical technique over time. Teflon paddings were utilized to decompress the trigeminal nerve and the culprit vessel. Teflon was swiftly accepted as the material, which was easy to work with and left little arachnoid scarring. Based on Jannetta’s 30 years of experience, he reported that 82% of nearly 1,200 patients experienced complete pain alleviation [10]. The turning point in making MVD surgery the preferred surgical treatment for TN was its durability and longevity [11]. Accordingly, the surgical approach is used regardless of arterial diameter. Moreover, due to the larger caliber of the VA, the Teflon felt does not present a risk of compression or occlusion of the VA. Meanwhile, the other opportunities emerged as a possibility in the treatment of TN, such as Gamma knife (GK or rhizotomies. In 2019. Lakshman et al. published an article that described the efficacy of GK in the treatment of TN caused by VBD, in which the patient experienced an immediate pain relief with no concomitant complications [9]. Surgical treatment in the form of MVD could be considered the best explored and applied treatment for TN. GK treatment remains the second most applied procedure. In comparison to all other types of TN treatment, the surgical one needs general anesthesia and postoperative hospitalization to avoid some potential risks and complications. From our experience, the most presented symptom in surgically treated patients was headache due to excessive operative CSF evacuation. The other described complications comprise intracranial bleeding, injuries of the trigeminal or the facial nerve with hemifacial spasm and facial nerve palsy or hearing loss and double vision [12]. In the presented cases, the authors did not experience any significant complications besides headache, and it was mostly pronounced on the first postoperative day. Both patients experienced complete pain relief with complete exclusion of preoperative medication, and no CSF leak was noted in either patient. According to established TN treatment guidelines from 2021, MVD has a strong recommendation over GK treatment, but a weak one compared to percutaneous neuroablative procedures. These types, such as balloon compression, glycerol rhizolysis, or radiofrequency thermocoagulation, have a median of 3 to 4 years of pain relief and repetitive procedures are needed. These procedures could not be considered and defined as an option in VBD [13].

The authors advocate surgical treatment as the method of choice. Moreover, some points should be emphasized to avoid any bias toward surgical treatment: (a) the closest and the only one GK option in the Republic of Croatia is 250 miles away; therefore, some patients cannot afford it; (b) authors’ surgical experience and good postoperative outcome; and (c) thorough maxillofacial and algology treatment before suggestion of surgical treatment to our patients, especially if these treatments fail. In conclusion, the effects of MVD in TN are already known and established. There are no significant gaps to fill regarding surgical options; nevertheless, some new surgical materials should be explored to confirm their durability and usability.