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Introduction

Trigeminal neuralgia (TGN) is a transient, recurrent and intense pain in the area on the face where the trigeminal (TG) nerve is distributed (1–3). Previous studies have demonstrated that 80–90% of primary TGN cases are induced by vascular compression of the TG nerve at the root entry zone (REZ) (1,4). Superior cerebellar artery (SCA) and the anterior inferior cerebellar artery (AICA) are the predominant vessels responsible for the compression, followed by venous vessels (5,6). Brain arteriovenous malformations (bAVMs) often manifest as cerebral hemorrhage, particularly in young patients; therefore, patients with unruptured bAVMs have a 2–4% risk of rupture and bleeding each year, and each bleeding event is associated with an ~18% risk of mortality (7,8). In addition, bAVMs also manifest as chronic headaches, epilepsy and neurological deficits (8–11). However, there have been relatively few reports of cases of TGN caused by bAVM (4,12). The present case report describes a case of TGN caused by bAVMs in the cerebellopontine angle (CPA). Facial pain was successfully relieved after the patient received partial embolization treatment, which may be associated with the blockade of the pulsatile compression of the feeding arteries, the arterialized draining veins or the malformed niduses. Therefore, TGN caused by bAVMs is a vascular nerve compression disease. In the present case study and review, the underlying mechanism and treatment strategy of TGN caused by bAVMs were discussed in the context of present case, and a literature review was carried out.

Case report

A 32-year-old male was admitted to the First Hospital of Jilin University (Changchun, China) on December 6, 2014, suffering from recurrent pain in his right cheek for two years, which had increased in severity over the previous 6 months. The patient reported that the pain began three years previously as a stabbing-like, intense pain that occurred suddenly on the right lower lip and mandible without any prior signs; each episode of pain lasted for 10–30 sec. The first period of pain lasted ~1 week and was self-relieved without medication. The pain recurred following a period of 6 months, and the duration of each episode of pain extended to 2–3 min. The patient was administered 800 mg oral carbamazepine (Novartis, Basel, Switzerland) daily, which was effective at relieving the pain on the right side of the face of the patient. In the 6 months prior to hospital admission, the frequency of the pain in the right cheek of the patient increased. The pain occurred >6 times every day and each episode lasted 10–30 min, and daily oral administration of 1,200 mg carbamazepine was not effective at controlling the pain. Clinical examination demonstrated that no significant trigger point could be palpated and there were no abnormalities in corneal reflexes or facial sensation. Subsequent magnetic resonance imaging (MRI) demonstrated the presence of flow-void signals in the abnormal vessels in the right CPA (Fig. 1). Digital subtraction angiography (DSA) further confirmed the diagnosis of bAVMs, and demonstrated that the malformed niduses were fed by the right SCA and the AICA, and drained into the adjacent venous sinuses on the same side (Fig. 2). Although the patient only exhibited symptoms of TGN, the patient was treated with interventional embolization, due to the risk that the bAVMs may bleed in the future. Embolization was conducted under general anesthesia with intravenous 0.05–0.1 mg/kg midazolam (Nhwa, Jiangsu, China), 1.0–1.5 µg/kg remifentanil (Renfu, Yichang, China), 0.2–0.3 mg/kg etomidate (Nhwa), 0.6 mg/kg rocuronium (Organon, Brussels, Belgium), and was maintained with 0.6 mg/kg propofol (Nhwa), 5–10 mg/(kg/h) and 0.1–0.2 µg/(kg/min) remifentanil (Renfu, Yichang, China). Following arterial puncture and sheath insertion in the femoral artery using the Seldinger technique (13), a 6F-guiding catheter (Cordis Co., Miami, FL, USA) was inserted into the left vertebral artery. Under the guidance of a Mirage micro-wire (ev3, Irvine, California, USA), a Marathon micro-catheter was inserted into the bAVMs. The micro-catheter entered the bAVMs via the right AICA and onyx-18 glue (ev3) was slowly injected. Onyx-18 glue diffused well in the bAVMs and embolized the majority of the malformations. Angiography was conducted immediately following surgery, which demonstrated that the majority of the bAVMs had disappeared and the draining veins were patent (Fig. 2). There were no complications following the surgical procedure and the pain in the right cheek of the patient was completely relieved one week following the surgical procedure. The patient was satisfied with the outcome of the embolization surgery. Post-surgical follow-ups were conducted for a period of two years via telephone. The patient experienced no further pain in his right cheek, and thus chose not to return to the hospital for a follow-up reexamination. The present study was approved by the Ethics Committee of the First Hospital of Jilin University and patient informed consent was obtained prior to the study.

Figure 1. (A) T2-weighted axial MRI and (B) T1-weighted axial MRI showing flow-void signals (arrows) of abnormal vessels in the right cerebellopontine angle prior to the surgical procedure. MRI, magnetic resonance imaging.

Figure 2. (A and B) Lateral views of DSA prior to embolization shows the bAVMs, which are associated with the right superior cerebellar and the right anterior inferior cerebellar, and draining rapidly into the adjacent venous sinuses on the same side. (C and D) Lateral views of the DSA following embolization show that the majority of the bAVMs were embolized. DSA, digital subtraction angiography; bAVMs, brain arteriovenous malformations.

Literature review

A total of 29 studies (4,12,14–40) which reported TGN caused by bAVMs were retrieved from the PubMed database, the majority of which were clinical reports that described individual cases. We searched the PubMed database up to 2015 using the key words ‘AVM’, ‘bAVM’, ‘arteriovenous malformation’, ‘cerebral arteriovenous malformation’, ‘brain arteriovenous malformation’, ‘Cerebral vascular malformation’ in combination with ‘trigeminal neuralgia’ and ‘TGN’. Abstracts were reviewed to identify relevant literature, only the TGN caused by bAVM related literatures were enrolled.

A total of 40 patients with TGN caused by bAVMs were reported in these 29 studies (Table I; 4,12,14-40). Excluding two patients for whom the information was incomplete (27,33), there were 24 male and 14 female patients (male:female ratio, ~1.71) aged between 23 and 69 years with a mean age of 46.8±14.7 years. These patients presented with bAVMs located in the CPA (n=19)(12,16,17,20,23,27–33,36,38), cerebellar hemisphere (n=8)(15,18,21,26,34,35,40), the TG nerve (n=7)(22,25,39), the cerebellar vermis (n=3)(4,14,24), the pontine (n=1)(37), the septum pellucidum (n=1)(19) and both the cerebellar hemisphere and cerebellar vermis (n=1)(38) (Fig. 3). Five of these patients had a confirmed history of repeated hemorrhage (19,29,32,33,35). The majority of these patients suffered from TGN on the same side as the bAVM lesions; however, one patient suffered from TGN on the contralateral side of the bAVMs lesions (40), and two patients suffered from coexistent TGN and hemifacial spasm on the same side (14,16). In terms of treatment, 2 patients received drug therapy (17) and 1 patient was without mention of treatment (12). The other 37 patients received non-drug treatment (4,14–40), 11 patients received surgical resection alone (19,25,27–30,32), 2 patients received surgical resection following partial embolization (23,26), 1 patient received surgical resection following destructive neurosurgical manipulation of the TG nerve(31), 3 patients received surgical resection of bAVMs combined with microvascular decompression (MVD; 14,15,18,20,24), 5 patients received an interventional embolization treatment, 2 patients received radiotherapy following embolization (4,21), 6 patients received MVD treatment alone (37–39), 2 patients received radiotherapy following MVD (36,40), 4 patients received destructive neurosurgical manipulation of the TG nerve (16,17,33,38), and 1 patient received stereotactic radiotherapy (SRS; 22) (Fig. 4).

Figure 3. Respective locations of the bAVMs in patients with trigeminal neuralgia caused by bAVMs as reported in previous studies (n=40). bAVMs, brain arteriovenous malformations.

Figure 4. Non-drug treatment methods used for patients with trigeminal neuralgia caused by brain arteriovenous malformations, as reported in previous studies (n=37). MVD, microvascular decompression; SRS, stereotactic radiotherapy.

Table I. Literature review of patients with trigeminal neuralgia caused by bAVMs.

Table I.

Literature review of patients with trigeminal neuralgia caused by bAVMs.

				History of drug therapy		Non-drug therapy
Author	Gender/age	bAVMs location	Compressing vessels	Drugs	Therapeutic effects	Treatment methods	Complications	Therapeutic effects	Notes	Refs.
Kikuchi et al	Male/45	CPA	Feeding arteries	Not mentioned	Not mentioned	Resection of bAVMs	Not mentioned	Immediate complete relief	The patient had a history of SAH 15 years prior	(29)
Figueiredo et al	Male/18	CPA	Not mentioned	Not mentioned	Poor	Resection of bAVMs	Transient numbness in V3	Immediate complete relief		(30)
Kawano et al	Male/48	CPA	Malformed niduses and draining veins	Not mentioned	Pain aggravated after 2 years	Glycerol rhizolysis was performed on either side of the semilunar ganglion of the TG nerve, and shown to be ineffective; subsequent resection of the bAVM was performed	Not mentioned	Immediate complete relief		(31,32)
Kawano et al	Female/61	CPA	Not mentioned	Not mentioned	Not mentioned	Resection of bAVMs	Not mentioned	Not mentioned	The patient had a history of hemorrhage in the left CPA 10 days prior to admission to the hospital	(20)
Johnson and Salmon	N/A	CPA	Not mentioned	Not mentioned	Not mentioned	Resection of the TG nerve	Not mentioned	Pain relief	The patient had a history of SAH and multiple events of transient loss of consciousness	(33)
Niwa et al	Female/44	Cerebellar hemisphere	Feeding arteries and draining veins	Not mentioned	Not mentioned	Resection of bAVMs and MVD	Not mentioned	Immediate complete relief		(34)
Nishizawa et al	Male/42	Cerebellar hemisphere	Feeding arteries	Not mentioned	Not mentioned	TGN recurred 6 months after TG nerve was blocked. Resection of the bAVMs and MVD was subsequently performed	Not mentioned	Immediate complete relief	The patient had a history of SAH 10 years prior	(35)
Edwards et al	Male/38	Intrinsic TG nerve	Draining veins, malformed niduses, and feeding arteries	Carbamazepine	Poor	Resection of the bAVMs and MVD	Mild V1 hypesthesia	Immediate relief		(25)
	Female/55	Intrinsic TG nerve	Draining veins and malformed niduses	Carbamazepine	Poor	Resection of bAVMs	Mild V1–3 hypesthesia and corneal areflexia	Immediate relief
	Female/46	Intrinsic TG nerve	Draining veins and malformed niduses	Carbamazepine	Poor	Resection of bAVMs	Mild V1 & V2 hypesthesia and occasional mild dysesthesia	Immediate relief
	Female/35	Intrinsic TG nerve	Draining veins and malformed niduses	Carbamazepine	Poor	Resection of bAVMs	None	Immediate relief	TGN recurred 4 years later; the be relieved by drugs
	Female/36	Intrinsic TG nerve	Draining veins and malformed niduses	Carbamazepine	Poor	Resection of bAVMs	Small pontine hematoma, transient ataxia, VII weakness, nausea, vomiting, permanent V2 & V3 anesthesia, V1 hypesthesia, and corneal areflexia	Immediate relief
Mineura et al	Male/21	Cerebellar hemisphere	Draining veins	Not mentioned	Not mentioned	Embolization and resection of bAVMs	Mild cerebellar ataxia	Complete relief		(26)
Nomura et al	N/A	CPA	Not mentioned	Not mentioned	Not mentioned	Resection of bAVMs	Not mentioned	Complete relief		(27)
	Male/44	CPA	Malformed niduses	Not mentioned	Not mentioned	Resection of bAVMs	Not mentioned	Complete relief
Mendelowitsch et al	Female/47	CPA	Feeding arteries	Not mentioned	Poor	Resection of bAVMs	Pulmonary embolism	Complete relief		(28)
Anderson et al	Female/39	Intrinsic TG nerve	Not mentioned	Not mentioned	Poor	SRS	Not mentioned	Complete relief		(22)
Wanke et al	Male/56	CPA	Not mentioned	Carbamazepine	Poor	Embolization and resection of bAVMs	Hydrocephalus and SAH occurred after embolization. Surgical resection was subsequently performed. Paresis of the III, VII and XII cranial nerves occurred, and the trigeminal neural sensation was reduced. Every function except the trigeminal neural sensation recovered after 3 months	Complete relief following resection		(23)
Athanasiou et al	Male/56	Cerebellar vermis	Feeding arteries	Carbamazepine	Little effect	Embolization	None	Complete relief		(24)
García-Pastor et al	Male/57	CPA	Malformed niduses	Not mentioned	Poor	The effect of radiofrequency thermocoagulation of the TG nerve was poor; micro-balloon compression of the TG nerve was subsequently performed.	Not mentioned	Complete relief		(38)
	Male/68	CPA	Malformed niduses	Not mentioned	Poor	MVD	Not mentioned	Complete relief
	Male/40	Cerebellar hemisphere and vermis	Feeding arteries	Not mentioned	Poor	MVD	Not mentioned	Complete relief
	Male/54	CPA	Malformed niduses	Not mentioned	Poor	MVD	Not mentioned	Complete relief
Levitt et al	Female/13	Cerebellar hemisphere	Not mentioned	Carbamazepine	Poor	Multiple embolization treatments of bAVMs had no effect; the artery of the foramen rotundum (the blood-supplying artery of the TG nerve V2 branch) was subsequently embolized, following which the pain was relieved	A small area of hypesthesia on the left cheek	Immediate relief following embolization of the artery of the foramen rotundum		(18)
Talanov et al	Male/16	Septum pellucidum	Draining veins	Not mentioned		Resection of bAVMs	None	Not mentioned	Pain on the left side of the TG nerve combined with hemorrhage	(19)
Simon et al	Male/72	CPA	Not mentioned	Carbamazepine	The pain increased after 1 year	Embolization	None	Immediate complete relief. The pain recurred 17 months later; but was relieved following secondary embolization		(20)
Lesley	Male/55	Cerebellar hemisphere	Feeding arteries and draining veins	No history of drug therapy		Staged embolization and SRS	None	Complete relief		(21)
Ferroli et al	Female/52	Pontine	Draining veins	Carbamazepine	Poor	MVD	None	50% free after 1 month		(37)
	Male/38	Cerebellar hemisphere	Feeding arteries and draining veins	Not mentioned	Poor	Radiofrequency thermocoagulation of TG nerve was poor; MVD was subsequently performed	Not mentioned	Complete relief
Karibe et al	Male/55	Intrinsic TG nerve	Feeding arteries	Carbamazepine	Little effect	MVD	None complete relief	Immediate and		(39)
Sato et al	Female/49	Cerebellar hemisphere	Draining veins	Not mentioned	Not mentioned	MVD + SRS	None	Complete relief after 1 year. The size of the bAVMs was reduced	The patient had pain on the contralateral TG nerve	(40)
Mori et al	Male/69	Cerebellar vermis	Feeding arteries	Carbamazepine	The pain was relieved for 5 years, then gradually reappeared	Embolization and SRS	Temporary truncal ataxia following embolization	Partial relief was achieved following embolization. Complete pain relief was achieved following subsequent radiotherapy		(4)
Yip et al	Female/64	CPA	Malformed niduses	Carbamazepine	Poor	Not mentioned				(12)
Dou et al	Female/24	Cerebellar vermis	Not mentioned	Carbamazepine	Poor	Embolization	None	HFS and TNG was completely relieved	Combined with HFS	(14)
Kono et al	Male/53	Cerebellar hemisphere	Feeding arteries	Anti-TN medication	The pain increased gradually	Embolization	None	The pain was completely relieved after 1 month		(15)
Son et al	Male/42	CPA	Not mentioned	Non-specific	Poor	Radiofrequency thermocoagulation of TG nerve and injection of carnitine	None	The pain was relieved; carnitine was regularly injected to relieve facial spasm (every 3–4 months)	Combined with facial spasm	(16)
Machet et al	Male/61	CPA	Not mentioned	Oxcarbazepine	Follow-up was conducted for 10 months; the pain was relieved	None	Not mentioned			(17)
Sumioka et al	Male/66	CPA	Feeding arteries and malformed niduses	Not mentioned		MVD + SRS	Not mentioned	Immediate complete relief. MRI showed that the bAVMs disappeared		(36)
	Female/64	CPA	Not mentioned	Carbamazepine	Follow-up was conducted for 18 months; the pain was relieved	None	Not mentioned
	Male/50	CPA	Not mentioned	Carbamazepine	The pain was partially relieved	Micro-balloon compression of the TG nerve	Not mentioned	Pain partially disappeared

[i] TGN, trigeminal neuralgia; CPA, cerebellopontine angle; N/A, not available; bAVMs, brain arteriovenous malformations; TG nerve, trigeminal nerve; MVD, microvascular decompression; SRS, stereotactic radiotherapy; HFS, hemifacial spasm; SAH, subarachnoid hemorrhage.

Discussion

TGN is one of the most common symptoms of neurovascular compression, and is a demyelinating lesion of the sensory fibers of the TG nerve caused by compression of the TG nerve at REZ by the SCA and the AICA (1–4). However, TGN caused by bAVMs remains rare, accounting for 0.22–1.78% of primary TGN cases (12,16,38). The present case study described a case of TGN caused by bAVMs in a middle-aged male patient suffering from recurrent pain in the right cheek. MRI and DSA analyses demonstrated bAVMs in the CPA of the posterior fossa on the affected side. As it remains difficult to distinguishing the symptoms of TGN caused by bAVMs, particularly TGN induced by insignificant bAVMs, which is usually negative in angiography, the symptoms of primary TGN can be easily misdiagnosed (12,25). However, the majority of patients can be accurately diagnosed through MRI and cerebral angiography (4,20,21,36). Previous studies have demonstrated that combined use of three-dimensional (3D) constructive interference in steady state MRI and 3D time of flight angiography clearly demonstrate the anatomic association between the TG nerve and the surrounding vessels, as well as other neighboring structures (41,42). DSA clearly shows the bAVMs, including the feeding arteries, niduses and draining veins, and determines whether they are associated with aneurysms, which is beneficial for the preoperative evaluation of patients (17). Among the 40 previous case reports (4,12,14–40), 39 patients (97.5%) presented with bAVMs in the posterior fossa. bAVMs located in the posterior fossa are more likely to result in TGN (4,12,14–18,20–40). García-Pastor (38) conducted a study on 375 cases of bAVMs, which demonstrated that 1.3% of the patients with bAVMs developed TGN, whereas 9.8% of the patients with bAVMs in the posterior fossa developed TGN. The majority of the patients suffered from TGN on the same side as the bAVMs, and only one patient suffered from TGN on the contralateral side of the lesions, which was predominantly caused by the compression of the contralateral TG nerve REZ by the arterialized draining veins (40). The aforementioned findings also demonstrated that TGN caused by bAVMs is a symptom of neurovascular compression, caused by the pulsatile compression of vessels. Pulsatile compression of the vessels may be caused by the feeding arteries of bAVMs, arterialized draining veins or malformation niduses (38,40,43). Among the 40 patients evaluated (4,12,14–40), there were 27 patients (4,12,15,19,21,24–29,31,34–40) in whom TGN was demonstrated to originate from vascular compression as determined by angiography or during the surgical procedure. Of these 27 patients, TGN was caused by compression by the feeding arteries of bAVMs (n=8)(4,15,24,28,29,35,38,39), the draining venous system (n=4)(19,26,37,40), malformation niduses (n=5)(12,27,38), simultaneous compression by the feeding arteries and the draining venous system (n=3)(21,34,38), simultaneous compression by the feeding arteries and the malformation niduses (n=1)(36), the simultaneous compression by the draining venous system and the malformation niduses (n=5)(25,31) and simultaneous compression by the feeding arteries, the draining venous system and the malformation niduses (n=1) (25). Since the origin of vascular compression could not be confirmed by image analysis in certain patients, and these patients had also received drug therapy, interventional embolization, and destructive neurosurgical manipulation of the TG nerve, the incidence of TGN originating from vascular compression may be even higher.

Currently, the majority of treatments for TGN caused by bAVMs are determined on an individual basis, and there has been no consistent conclusion as to the optimal treatment for TGN caused by bAVMs (14–16). Drug therapy did not yield an ideal therapeutic effect in the majority of cases, and the patients who received drug therapy predominantly proceeded to seek non-drug treatments (4,12,14–16,22,23,25,28,30–32). Non-drug treatments include surgical resection of bAVMs, MVD, SRS, and destructive neurosurgical manipulation of the TG nerve (4,16,33,36,37). Therefore, when selecting a treatment, it is necessary to comprehensively consider whether the patient has a history of hemorrhage, whether the bAVMs are associated with aneurysms and the origin of the compression of the TG nerve.

Theoretically, complete surgical resection is the ideal therapeutic option, as it eliminates the compression on the TG nerve and avoids the potential risk of hemorrhage of bAVMs, which is particularly important for patients with a history of hemorrhage. In addition, the craniotomy for resection of bAVMs may also confirm whether the feeding arteries and the draining veins compress the TG nerve root; if necessary, MVD can be performed simultaneously (44). Among the 40 patients evaluated (4,12,14–40), 42.5% of the patients received surgical resection (n=17), and amongst these 17 patients (19,23,25–32,34,35), 11 patients received surgical resection alone (19,25,27–30,32), 3 patients received surgical resection combined with MVD (25,34,35), and 2 patients received surgical resection due to complications following embolization (23,26), and 1 patient received surgical resection due poor effect after destructive neurosurgical manipulation of the TG nerve (31). The pain caused by TGN was immediately relieved in all the patients who received surgical resection. The longest duration of follow-up visits in these previous studies was 109 months (25). According to the long-term follow-up visits reported, relapsed pain was only reported in one patient at a four-year post-surgical follow-up, and this pain was controlled by 400 mg/day carbamazepine (25). The majority of these lesions were located deep in the posterior fossa adjacent to the brain stem and surrounding important nerves (23,26,27). Furthermore, there were numerous complications during surgical resection, particularly for patients with bAVMs in the TG nerve REZ. Edwards et al (25) reported the treatment of five patients with bAVMs in the TG nerve REZ through surgical resection, and following the surgical procedure, four of these patients experienced varying levels of dysesthesia of the TG nerve, and one patient also experienced weakening of the facial neurological function, short-term ataxia and cerebellar hematoma. Although the remission rate of TNG is very high after surgical resection, there are also many complications. Thus it is a necessary to weigh the benefits and risks before the operation.

It is sometimes difficult to perform complete surgical resection of bAVMs, and this procedure may also be unnecessary for some patients. Among the 40 patients (4,12,14–40) with TGN caused by bAVMs, 55% of patients (n=22)(4,15,19,21,24–26,28,29,33–40) presented with TGN which partially or completely originated from the compression of feeding arteries or the draining veins, which was confirmed by image analysis or during the surgical procedure. Therefore, surgical resection of bAVMs was unnecessary in these patients with TGN with no history of hemorrhage, and MVD surgery would have been sufficient. MVD surgery of the TG nerve is >90% effective and is capable of preserving neurological function relatively well; thus, MVD surgery has become the first choice of surgical treatment for primary TGN (45). Furthermore, bAVMs in the CPA, and even malformed niduses in the TG nerve, may not necessarily result in TGN (39,43,46). Therefore, focusing on complete resection of bAVMs as the predominant therapeutic option may cause further complications. The mid-term results of a multicenter, randomized control study which investigated the treatments of unruptured bAVMs demonstrated that the effects of drug therapies are superior to those of invasive therapies when treating unruptured bAVMs (47). Among the 40 patients evaluated in the present review (4,12,14–40), 27% of patients (n=11) received MVD surgery, with the longest duration of follow-up being 18 months (36). A 100% overall effective rate was achieved and no surgery-associated complications occurred (34–40).

Interventional embolization can be used to reduce the size of bAVMs by reducing blood supply to bAVMs (4,21,23,26). This procedure is predominantly performed to surgically treat bAVMs or as an adjuvant therapy prior to SRS (4,21,23,26). However, when treating TGN caused by bAVMs, TGN may be effectively relieved following partial embolization of bAVMs due to the change in hemodynamics, which also demonstrates that TGN caused by bAVMs is a symptom of neurovascular compression (20). Due to these characteristics, interventional embolization was performed on the present patient and TGN was completely relieved following successful embolization of the majority of the bAVMs. Post-embolization follow-ups were conducted for two years, and the therapeutic effect of this treatment option remained satisfactory. Among the 40 patients (4,12,14–40) evaluated in the present review, 22.5% of patients (n=9)(4,14,15,18,20,21,23,24,26) underwent interventional embolization and experienced significantly relieved TGN following embolization. Among these 9 patients, 5 patients received an interventional embolization treatment alone (14,15,18,20,24), 2 patients received subsequent SRS (4,21) and 2 patients received secondary surgical resection(23,26). The longest duration of follow-up visits for patients who underwent interventional embolization was six years (4). One patient reported relapsed pain 17 months post-embolization and the pain was subsequently relieved following a secondary embolization (4). The pain relief may be associated with the blocking of the pulsatile compression of the feeding arteries of the bAVMs, the arterialized draining veins or the malformed niduses that compressed the TG nerve following embolization, which appears to have a similar mechanism to the MVD of the TG nerve. However, caution should be taken with this therapeutic option as interventional embolization and the change in hemodynamics following embolization may induce ischemia, hemorrhage or embolization of the venous system (4,23,26). Among the aforementioned eight patients who received embolization, one patient experienced transient ataxia (4), one patient received secondary surgical resection of bAVMs due to subarachnoid hemorrhage and hydrocephalus following the embolization (23), and one patient suffered from severe paresis and sensory disturbance due to the dilated draining veins following embolization, which required surgical resection (26). Furthermore, since the rate of complete embolization is restricted when treating bAVMs with interventional therapy alone, and post-embolization recanalization is relatively common, embolization alone may not result in a long-term therapeutic effect. Simon et al (20) reported the case of a patient with TGN caused by bAVMs whose pain was relieved following embolization; however, the pain recurred 17 months later. It has also been demonstrated that only short-term pain relief was achieved following multiple embolization procedures (18), which may be associated with the recanalization of bAVMs.

SRS is often performed following partial embolization or combined with other treatment methods (4,21,36,40). Among the 40 patients evaluated in the present review (4,12,14–40), there was only one report (22) of the achievement of an effective therapeutic effect of SRS alone. In this case, the bAVMs were located inside the TG nerve and the size of the malformation niduses was ~1.2×0.8×0.9 cm; the TGN was completely relieved following 13 months of SRS (22). Notably, Levitt et al (18) treated a patient with TGN by embolizing the supplying artery of the V2 branch of the TG nerve, an artery of the foramen rotundum, which induced sustained relief from TGN, but resulted in hypoesthesia of the cheeks on the same side. Previous studies have also reported other palliative destructive neurosurgical techniques of the TG nerve root (16,17,33,38), including radiofrequency thermocoagulation, glycerol rhizolysis, balloon compression and resection of the TG nerve; however, these palliative therapies may result in complications, such as facial numbness and weakened corneal reflexes (16,17,33,38). Furthermore, the therapeutic effects of these palliative therapies remain uncertain, and TGN has a relatively high recurrence rate when treated with these therapeutic strategies (16,17,33,38).

In conclusion, surgical resection of the malformed vessels is an ideal therapeutic option in theory, as this approach relieves TGN and eliminates the risk of hemorrhage of bAVMs; whereas MVD surgery is a recommended treatment for patients who cannot receive surgical resection of bAVMs. Good therapeutic outcomes have also been achieved with interventional embolization in certain patients, including the patient described in the present case study. Destructive neurosurgical manipulation of the TG nerve may result in facial numbness and weakened corneal reflexes, and has a high recurrence rate; therefore, this approach is only recommended as an alternative for elderly surgery-intolerant patients.

References