”PTFE Sleeve Graft” Technique to Remove Neurovascular Conflict in Micro Vascular Decompression for Trigeminal Neuralgia
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.355155
Source of Support: None, Conflict of Interest: None
Keywords: Cranial nerve compression syndrome, microvascular decompression, sleeve graft, Teflon, trigeminal neuralgia
Trigeminal neuralgia, also known as tic douloureux, is a highly morbid condition presenting as shooting crippling facial pain. It has an incidence of 4.5 per 100,000 population. It is a commonly misdiagnosed condition, with most patients presenting with emaciation and multiple dental extractions. It may be associated with arterial hypertension. Trigeminal neuralgia can be due to various causes, including vascular compression, cerebellopontine angle tumors, tuberculomas, abscess, and vascular malformations. Vascular compression of the trigeminal root entry zone has been found to be the most common cause with a reported incidence as high as 96%.
Initially, these patients are managed by medical treatment using drugs such as carbamazepine, gabapentin, and lamotrigine. Patients who do not respond to the medical line of treatment can be treated by surgery (microvascular decompression), percutaneous ablative procedures, or gamma knife. Percutaneous ablative procedures and gamma knife are associated with a high recurrence rate., Microvascular decompression (MVD) of the trigeminal nerve has the least long-term recurrence and most success rates.
Dr. Janneta initially introduced MVD and popularized the technique. He placed a muscle patch between the nerve and artery. Muscle patch was associated with a high recurrence rate due to resorption. This led to research into various other graft materials to replace muscle in MVD to improve the success rates. Most commonly used graft materials include Teflon, cotton, gelfoam, Silastic graft, fenestrated aneurysm clips, vascular tape, and titanium plates.,,,,,, Of all these, Teflon is the most commonly used material for this purpose.
Neurosurgeons have tried various shapes and techniques to use Teflon (PTFE) to achieve maximum results. The most commonly used shapes are Teflon felt, puff, and ring grafts., These puff or felt grafts can slip due to various reasons and may cause a recurrence of symptoms and other graft-related complications, including arachnoiditis or granuloma formation. In this study, we are reporting a single institutional series of 376 patients in whom we used the novel technique of a PTFE “sleeve” shaped PTFE graft for MVD in cases of trigeminal neuralgia, and we aim to study the efficacy and complications of the same.
It is a single institutional observational prospective study wherein 376 patients underwent MVD for trigeminal neuralgia using the “sleeve graft” technique with a Teflon graft over a period of 18 years at our institution from 2002 to 2020. The clinical and demographic details were obtained. All these cases had a classical history of neurovascular compression syndrome of the fifth cranial nerve with no other nerve compression syndrome present simultaneously.
We considered MVD only in patients who (1) had received medical treatment in full doses for at least 6 months with no significant relief in pain, (2) had radiological confirmation of the neurovascular conflict, (3) no history of any concomitant cranial nerve compression syndrome, (4) cutaneous sensations present over trigeminal nerve distribution.
The diagnosis was confirmed based on the clinical symptomatology and radiological correlation on magnetic resonance imaging of the brain with three-dimensional constructive interference in steady state or fast imaging with steady-state free precession sequences. The severity of pain was recorded using the Barrow Neurological Institute (BNI) pain intensity score (I–V) pre-operatively.
The neurovascular conflict was classified into four categories, as mentioned by Haidar et al. Simple contact: The conflict is caused by an arterial loop and there is a single point of contact with the nerve. Multiple contacts: The conflict includes different points of contact by several arterial loops. Nutcracker type of contact: The conflict includes one or more offending vessels above and below, with the nerve entangled between them. Vein contact: The most common offending vein is the Dandy vein or an inconstant and aberrant petrous vein.
These patients underwent MVD using the “sleeve graft” technique. Post-operatively, patients were examined and their pain level was recorded according to the BNI pain intensity score. They were ambulated the next day and discharged within one to two days. The outcome of MVD was assessed at the time of discharge and after 5 years of follow-up:
MVD was done using the standard technique under general anesthesia. With the patient in the lateral position, suboccipital retro-mastoid craniotomy was done (1.5 × 1.5 cm). Dura was incised and retracted. The cerebellar hemisphere was retracted inferiorly after opening the arachnoid and draining cerebrospinal fluid. The trigeminal nerve along with indenting vessels were identified; 360 degrees of the nerve was dissected free of all neurovascular conflicts and surrounding arachnoid along the cisternal portion of the nerve. A sleeve-shaped Teflon (PTFE) graft was harvested from the vascular tube graft [Figure 1], which is commonly used by vascular surgeons to repair vessels. This tube graft has a memory fold. The dimensions of the graft were customized according to the length of the cisternal portion of the nerve and neurovascular conflicts present. The split PTFE graft was then wrapped around the nerve, keeping the offending vessels away from the nerve using the memory fold. It formed a “sleeve” around the nerve and protecting it from any neurovascular conflict from all sides. [Figure 2] Nerve in the sleeve graft was examined all around for any residual contact with vessel, and arachnoid loculations around the nerve were opened. Dura was then closed in a water-tight fashion and bone was replaced in position and fixed using threads/titanium plates and screws.
In this study, 376 cases of medically refractory trigeminal nerve compression syndrome were assessed. All the patients had pure trigeminal neuralgias with no concurrent other cranial nerve compression syndromes. The demographic and clinical profiles of the patients have been illustrated in [Table 1]. The patients in the study were between the age group of 23 and 76 years. The average age of patients was 57 years. Females were more affected than males in a ratio of 1.19:1. In total, 198 patients (52.7%) underwent MVD with no prior intervention, 158 (36.7%) underwent MVD following percutaneous ablative procedure, 13 (3.5%) were “Revision MVD” previously done at other centers, and four (1.1%) were post gamma knife failure. The majority of the patients (70.2%) had symptoms for 1–2 years. Further, 59.8% (n = 225) of the patients had trigeminal neuralgia lateralized to the right side and 40.2% (n = 151) patients had on the left side. Most patients had pain in V2 and V3 distribution (40.4%), while 10.9% had involvement of only V1 division, 4.5% in V2, 8.5% in V3, 27.4% in V1 and V2 distribution, and 8.2% patients had pain in all three divisions (V1, V2, and V3). The compressing vessels included the superior cerebellar artery (58.7%), anterior inferior cerebellar artery (29.8%), posterior inferior cerebellar artery (9%), and dolichoectatic basilar artery (2.4%). Moreover, 151 patients (40.2%) had type 1 conflict, 116 (30.9%) had type 2 conflict, and 109 (29%) patients had type 3 conflict; no patient had type 4 conflict. Pre-op BNI pain intensity score was V in 315 patients (83.8%) and IV in 61 patients (16.2%).
All these patients underwent microvascular decompression of the trigeminal nerve using the “sleeve graft” technique. Outcome of these patients is illustrated in [Table 2]. 363 (96.5%) patients had complete recovery from symptoms while 13 (3.5%) had partial recovery at the time of discharge. Out of 13, all patients had pre-op BNI pain intensity of V and post-op BNI pain intensity was II in 11 and III in 2. Complications included hearing loss (n = 1), temporary hypoesthesia (n = 45), and permanent hypoesthesia (n = 7). After 5 years of follow-up, 368 patients (97.8%) had complete recovery and eight (2.2%) had partial recovery. There was no incidence of graft displacement, local arachnoiditis, or recurrence on follow-up.
Trigeminal neuralgia is reported to be one of the worst pains that afflict humankind. Gardner postulated that it arises due to short-circuiting between the demyelinated axons of the trigeminal nerve leading to ephaptic transmission and thereby causing paroxysms of pain. Trigeminal neuralgia can be primary or secondary depending on the antecedent cause. Most primary cases are caused due to vascular compression of the nerve at the root entry zone, resulting in demyelination of axons and ephaptic transmission. Dandy, in 1932, first proposed vascular compression as a cause of trigeminal neuralgia.
With the advances in technology, it is possible to identify neurovascular conflicts using magnetic resonance imaging. Among various available therapeutic modalities, the first line of treatment is medical management using drugs such as carbamazepine, which is the drug of choice in such cases. Other drugs that have shown good response include oxcarbazepine, phenytoin, gabapentin, and lamotrigine. Patients who do not respond to medical management can undergo percutaneous ablative procedures, stereotactic radiosurgery, or microvascular decompression. There have been various studies wherein the efficacy of MVD has been found to be around 70%–90%, as reported by various studies.,,,,, Percutaneous ablative procedures are easy to perform and can be done as a daycare procedure although, they are associated with a higher recurrence rate. In a comparative study done by Meglio et al., it was seen that microvascular decompression is the most effective treatment with the least complication rates for trigeminal neuralgia particularly those with neurovascular conflict. In another study by Sharma et al., it was observed that microvascular decompression is more efficacious than gamma knife therapy as the first line of treatment while complication rate was lower with surgery, including facial numbness and dysesthetic pain.
In microvascular decompression, it has been observed that recurrence rates of symptoms after MVD range from 3% to 47% depending on the duration of follow-up. Failure of MVD is associated with recurrent vascular compression, formation of adhesions around the nerve, resorption of the graft, slippage of the graft, or development of graft granuloma., This led to research into various graft materials available so as to increase the efficacy of the procedure while reducing the complication rate at the same time. Autologous muscle grafts are associated with a high rate of resorption leading to recurrence of symptoms. A polytetrafluoroethylene (PTFE) or a Teflon graft is the material of choice for MVD because it is inert, well-tolerated in the nervous system, resistant to resorption, and has a lower complication rate than other materials.,, However, it is not that inert and can form a granuloma.,
Teflon graft is generally used by making a puff, felt, or ring around the offending vessel or nerve or as an interposition graft. Teflon felt can slip due to pulsations of the brain, cerebrospinal fluid flow, or arterial pulsations. This results in failure of treatment and recurrence of symptoms. To avoid graft slippage, some surgeons have tried various techniques such as anchoring the graft using stitches or glue and transposition of the offending artery., Recently, in a study published by Bishnoi et al., they used a ring graft around the trigeminal nerve to prevent graft migration as well as protecting the nerve circumferentially from multiple vessels.
In our technique, we use a sleeve-shaped graft of Teflon that is acquired from the shavings of PTFE graft used by vascular surgeons. These PTFE grafts have a memory fold and a smooth internal surface, which possibly reduces the incidence of granuloma formation or local reactionary arachnoiditis. The graft is cut into size customized according to the cisternal length of the nerve while keeping in mind the location of neurovascular conflicts. After the dissection, graft is placed around the nerve using the memory fold property of the graft. The complete encirclement of the nerve gives the advantage of minimal chance of graft migration and also takes care of multiple neurovascular conflicts. With a full “sleeve graft” in place, any future possibility of compression by a new vessel is also taken care of, reducing the incidence of recurrence. This puts an advantage over the “ring graft” technique, wherein the graft is placed circumferentially only around the established neurovascular conflict leaving the rest of the cisternal length of the nerve bare. During the entire 18 years, there has been no incidence of any granuloma formation, graft displacement, or recurrence.
The limitation of our study is that there was a very small sample size. Long-term follow-up studies with a larger sample size need to be done to look for long-term efficacy and complications associated with the technique.
PTFE “sleeve graft” technique is an efficacious alternate technique associated with very low complication and recurrence rates for micro vascular decompression (MVD) in cases of trigeminal neuralgia as compared to published world literature.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2]
[Table 1], [Table 2]