A Prospective Study of Microvascular Decompression for Trigeminal Neuralgia

Transcription

1 Acta Neurochir (Wien) (1997) 139: Acta Neuroehirurgiea 9 Springer-Verlag 1997 Printed in Austria A Prospective Study of Microvascular Decompression for Trigeminal Neuralgia H. Sletteb01 and P. K. Eide 2 1 Department of Neurosurgery, The National Hospital, University of Oslo and 2 Department of Neurosurgery, Ullev~l Hospital, University of Oslo, Oslo, Norway Summary In a prospective study of 25 patients with trigeminal neuralgia (TN), we examined the results of microvascular decompression (MVD). Initial pain relief was complete in 22 patients and partial in one. There were two primary failures. After a median observation time of 38 months, 20 of the 22 patients still were completely free of pain, and one patient reported then 50% pain relief. A vascular compression of the trigeminal root was found intra-operatively in 23 patients. No serious complications occurred. Minor but bothersome dyaesthesias were reported by two patients (8%). The results were satisfactory when compared to other MVD studies. Keywords: Trigeminat neuralgia; microvascular decompression; long-term follow-up. Introduction In 1927 the Norwegian neurosurgeon Vilhelm Magnus described a patient with severe trigeminal neuralgia (TN) secondary to "pressure from an inter- nal carotid artery aneurysm on the surface of the Gas- serian ganglion" [11]. To our knowledge, this is the first report of a vascular aetiology of TN. Later, in 1934, Dandy [5] suggested a vascular aetiology in at least 45% of patients with TN. Gardner [8] was the first to relieve the vascular compression surgically, and later Jannetta developed and refined the method called microvascular decompression (MVD). Jannetta found vascular compressions of the trigeminal root in more than 90% of the patients with TN [9]. Pain relief 10 years after MVD may be expected in 70-80% of the patients [4, 20]. Nevertheless, objections against MVD have been raised due to higher morbidity and mortality when compared to percutaneous procedures and controversy with regard to the role of vascular compression in the aetiology of TN [1, 18]. These objections have limited the use of MVD in many neu- rosurgical departments. Percutaneous procedures have been preferred in spite of a higher recurrence rate. With this background, the present prospective study was undertaken to further evaluate the efficacy of MVD for TN when taking into account the compli- cations. Patients and Methods This prospective study was performed during the 5-year period from 1989 to 1994, and includes our 25 first patients undergoing MVD. The following data were recorded in the research protocol: demographic data, medication before and after surgery, previous surgical treatment, pain characteristics, pre-operative radiological findings, postoperative complications, postoperative pain relief. Exclusion criteria were: multiple sclerosis, poor general health or age above 68 years. All the patients had typical TN, not sufficiently relieved by carbamazepine or phenytoin. In 23 patients the pain syndrome was characterized by unilateral intermittent pain, often triggered by non-painful stimulation, and with "pain-free periods. Two of these patients also had continuous background pain. In all these patients TN was to some degree reduced by carbamazepine. The two patients who bad failed to respond to MVD bad continuous pain with a dysaesthetic quality in addition to intermittent pain. In both patients the pain was resistant to carbamazepine. Pathological pain including allodynia and wind-up like pain [6], could be evoked by non-painful stimulation in the affected trigeminal skin area of both these two patients. Demographic data are presented in Table 1. In 17 of 25 patients TN could be provoked by movement (e. g., flexion or rotation of the head, or by stamping tbe foot on the floor), whereas the pain disappeared when the patient rested in the supine position. Prior to MVD, 13 patients had been treated by various surgical methods (Table 1). Exploration of the posterior fossa was performed through a small suboccipital retromastoid craniectomy with the patient in the lateral decubitus position, as described by Jannetta [9]. A Iateral supracerebellar route was chosen [14] and the petrosal vein was sacrificed. Compressing vessels were retracted from the nerve root

2 422 H. SlettebO and P. K. Eide: Microvascular Decompression for Trigeminal Neuralgia Table 1. Patients Feature ~ca Total 25 Sex (male/female) 12/13 Affected side (right/left) 18/7 Age at surgery (years) median 53 ranges Duration of symptoms (years) median 7 ranges 1-24 Follow-up period (months) median 38 ranges 7-66 Previous surgical treatment PRGR a 12 exeresis l alcohol injection 1 ~,v~,~ Fig. 1. The most common intra-operative finding: the right superior cerebellar artery (SCA) in contact with the nerve root. A Teflon prosthesis measuring about cm 2 inserted under the vessels and upon the nerve root a Percutaneous retrogasserian glycerol rhizotomy. and a Teflon prosthesis measuring about cm 3 was inserted under the vessels and upon the nerve root (Fig. 1). The tentorium was split in one patient to allow upward extension of the basilar artery. The degree of pain relief was rated as 100% pain relief, more than 50% pain relief and less than 50% pain relief. The patients were foitowed post-operatively by personal contact or by telephone. A disinterested third party interview was performed at the end of the observation period. The median follow-up period was 38 months. The patients were contacted by telephone and the answers were confirmed by a standard questionnaire mailed to the patients. Results Operative Findings The trigeminal root was compressed by the superi- or cerebellar artery in 20 patients and in four of these an additional vessel, a vein, was in close contact with the nerve root. The nerve root was compressed by the anterior inferior cerebellar artery in one patient, by the basilar artery in one patient, and by a vein in one patient. No compressing vessels were found in two of the patients. Conventional magnetic resonance imaging (MRI) was performed pre-operatively in 22 of the patients, and computerized tomography (CT) scanning in the other three. MRI revealed no neurovascular contacts in 15 of 22 patients. However, in five patients a tortuous superior cerebemar artery was demonstrated, arid in all these patients this artery was found to compress the nerve root. A tortuous basilar artery was identified pre-operatively in two patients. In one of these we Fig. 2. Magnetic resonance imaging in a 6g-year-old woman with left trigeminal neuralgia showing compression of the left trigeminal nerve by the basilar artery found the nerve root severely compressed by the bas- ilar artery (Fig. 2). Pain Relief Two of 25 patients reported no pain relief after MVD. Total relief of pain was reported by 23 patients, immediately after surgery in 21, after a few days in one, and after two weeks in one patient. More than 50% recurrence of pain was reported one year after surgery in one patient. Less than 50% recurrence of pain occurred in two patients, after six weeks in one patient and after two years in the other. One of these patients received PRGR after 18 months, and was free of pain thereafter. The resutts after a median foliow-up time of 38 months axe presented in Table 2, and a verbal descrip- tion of the severity of TN pre-and post-operatively is presented in Table 3. It should be noted that all the 23

3 H. Slettebo and P. K. Eide: Microvascular Decompression for Trigeminal Neuralgia 423 Table 2. Pain Relief at A Median Follow-up Time oj" 38 Months After MVD Pain relief Total (100%) relief of pain 20 > 50% relief of pain 1 < 50% relief of pain 2 No pain relief 2 Table 3. Verbal Description of Pain Table 4. Influence of Previous PRGR PRGR No PRGR n=12 n=13 Primary failures 2 0 Observation time (months) mean Recurrences major I 1 minor 0 [ No pain at follow-up 9 l 1 Description Before surgery horrible 4 excruciating 21 Result at best no pain 21 discomforting 1 distressing 1 horrible 1 excruciating i Current results no pain 20 discomforting 2 excruciating 3 patients who reported pain relief answered positively to the present question: "considering the overall pain relief you have received from the treatment, and considering the operation, hospitalization, discomfort, and expense involved, would you go through it all again for the results you have obtained?" The two patients that failed to respond to MVD answered "No" to this question. Long-term pain relief was compared with the operative findings. In the 20 patients with total pain relief, the trigeminal root was compressed by an artery in 18 patients, by a vein in one patient and by fibrotic adhesions in one patient. In the two patients with no pain relief, the nerve root was compressed by an artery in one patient whereas no vascular compression was found in the other patient. In all the 3 patients with partial pain relief, an artery was compressing the nerve, though the compression was at a distance from the root entry zone in one of the patients with less than 50% pain relief. The influence of previous PRGR treatment can be gleaned from Table 4. In 12 patients PRGR had been performed with particularly poor,results: 5 primary failures and 6 recurrences within 2 years. At follow- up after MVD, 9 of these 12 patients were free of pain while 11 of 13 patients not previously treated with PRGR, were painfree. Thus, the results of MVD were not significantly impaired by previous PRGR treatment (P > 0.25, Chi square test). Complications Serious complications were not observed in any of the patients after MVD. Minor, but bothersome complications were recorded in only two patients. Both reported numbness and reduced sensation in the face, and one of these two patients also reported dizziness and anosmia. Another patient reported non-bothersome reduction in facial sensation occurring abruptly on the 14th postoperative day. In one of the two patients with bothersome complications, a vein adjacent to the nerve root was coagulated during surgery. In the other one a small branch from a tortuous superior cerebellear artery was torn, resulting in a minor bleeding. Non-bothersome numbness in the skin surrounding the surgical incision was reported by four patients. When taking into account the relief of pain obtained by MVD, however, all these patients considered the complications as minimal. It should be noted that dysaesthetic numbness in the trigeminal area was present in five patients before MVD due to previous PRGR or local alcohol injection. Discussion In this prospective study of 25 patients with TN, successful outcome of MVD was found in 21 patients. Few and only minor complications occurred. Our results are comparable to various recently reported long-term studies. Several studies, including a total of more than 2500 patients, have reported pain relief after 5-10 years in 70-80% of the patients [4,

4 424 H. Slettebr and P. K. Eide: Microvascular Decompression for Trigeminal Neuralgia 20]. Sweet compared the results of 13 studies including 1375 patients, and found that recurrence of pain immediately after surgery was 7% and 14% at followup [18], It should be noted that the great majority of recurrences of TN takes place within the first months after MVD [4, 13, 16]. After PRGR, major recurrences occur in at least 30% within 3-4 years, and in about 25% after radiofrequency rhizotomy [18]. Vascular compression of the trigeminal root was found in 92% of our patients, which is in line with the findings of Jannetta [9], and several other authors [2, 10, 16]. The literature is, however, variable with regard to the frequency of vascular compression in patients with "idiopathic" TN [ 1, 18]. In our material conventional MRI detected only 1/3 of the vascular compressions. Some recent results indicate that more sophisticated MRI techniques may reveal vascular compression in a larger proportion of the patients [7, 12, 21]. Our clinical data indicate that the pathogenesis of TN involves a mechanical component. In 17 of 25 patients TN could be provoked by movement (e. g., flexion or rotation of the head, or by stamping the foot on the floor), whereas the pain disappeared when the patient rested in the supine position. In all these 17 patients a vascular compression was found. The two patients who failed to respond to MVD both reported continuous dysaesthesia pain before surgery. This type of pain failed to respond to carbamazepine. No vascular compression was found in one of the patients. Furthermore, somatosensory testing demonstrated pathologically evoked pain in both patients, possibly related to a central sensitization to pain [6]. In our opinion, MVD should not be recommended in patients with continuous dyseasthesia pain in the trigeminal area. This opinion is supported by the observations of others that continuous background pain responds markedly less to MVD than paroxysmal pain [19]. A major objection against MVD is the higher morbidity and mortality compared to percutaneous procedures [18]. We recorded no serious complications, and minor but bothersome complications in only two of 25 patients. In comparison, long-lasting and troublesome reduction in facial sensation may occur in up to 1/3 of patients treated by PRGR [15, 171. This method also has a much higher rate of recurrence ~15, 18]. In the present study 12 patients had been previously treated by PRGR. The results of MVD were not impaired by previous PRGR treatment. Others, on the other hand, have reported that percutaneous rhizotomy prior to MVD influences negatively the results of MVD [3]. In conclusion, this study shows that MVD provided a high rate of success with a minor risk of complications, and gives support to the hypothesis that in most cases TN is caused by a neurovascular compression. The outcome after MVD was not affected by previous PRGR. PRGR is a simple and safe method, but recurrences and dysaestesias are more frequent than after MVD [15]. Therefore, in patients below 65 years of age we recommend MVD as the primary surgical procedure if medical treatment fails. If the patient hesitates to accept the small, but definite risk associated with MVD, we perform a PRGR. MVD should be considered if pain recurs after a single PRGR since failures are common after repeated PRGRs [15]. References 1. Adams CBT (1989) Microvascu[ar compression: an alternative view and hypothesis. J Neurosurg 57: Aksik I (1993) Microneural decompression operations in the treatment of some forms of cranial rhizopathy. Acta Neurochir (Wien) 125: Barba D, Alksne JF (t984) Success of microvascu[ar decompression with and without prior surgical therapy for trigeminal neuralgia. J Neurosurg 60: Barker FG, Jannetta PJ, Jho H-D, Blssonette D (1994) Microvascular decompression for typical trigeminal neuralgia: a 20- year experience. J Neurosurg 80: 392A-393A 5. Dandy WE (1934) Concerning the cause of trigeminal neuralgia. Am J Surg 24: Eide PK, J0rum E, Stubhaug A, Bremnes J, Breivik H (1994) Relief of postherpetic neuralgia with the N-methyl-D-aspartic acid receptor antagonist ketamine. A double-blind, cross-over comparison with morphine and placebo. Pain 58: Furuya Y, Ryu H, Uemura K et al (1992) MRI of intracranial neurovascular compression. J Comput Assist Tomogr 16: Gardner WJ, Miklos MV (1959) Response of trigeminal neuralgia to "decompression" of sensory root. JAMA 170: Jannetta PJ (1990) Microvascular decompression of the trigeminal nerve root entry zone. Theoretical considerations, operative anatomy, surgical technique, and results. In: Rovit RL, Murali R, Jannetta PJ (eds) Trigeminal neuralgia. Williams and Wilkins, Baltimore, pp Klun B (1992) Microvascular decompression and partial sensory rhizotomy in the treatment of trigeminal neuralgia: persenal experience with 220 patients. Neurosurgery 30: Magnus V (1927) Aneurysm of the internal carotid artery. JAMA 88: Meaney JFM, Eldridge PR, Dunn LT et al (1995) Demonstration of neurovascular compression in trigeminal neuralgia with

5 H. Slettebo and P. K. Eide: Microvascular Decompression for Trigeminal Neuralgia 425 magnetic resonance imaging. Compmison with surgical findings in 52 consecutive patients. J Neurosurg 83:79% Potlack IF, Jannetta PJ, Bissonette DJ (1988) Bilateral trigeminal neuralgia: a 14-year experience with microvascular decompression. J Neurosurg 68: Sindou M, Mertens ~ (1993) Microsurgical vascular decompression (MVD) in trigeminal and glosso-vago-pharyngeal neuralgias. A twenty year experience. Acta Neurochir (Wien) 58: Sletteb0 H, Hirschberg H, Lindegaard K-F (1993) Long-term results after percutaneous retrogasserian glycerol rhizotomy in patients with trigeminal neuralgia. Acta Neurochir (Wien) 122: Sun T, Saito S, Nakai O, Ando T (1994) Long-term results of microvascular decompression for trigeminai neuralgia with reference to probability of recurrence. Acta Neurochir (Wien) 126: Sweet WH, Polletti CE (1985) Problems with retrogasserian glycerol in the treatment of trigeminal neuralgia. Appl Neurophysiol 48: Sweet WH (1991) Trigeminal neuralgia: problems as to cause and consequent conclusions regm'ding treatment. In: Wilkins RH, Rengachary SS (eds) Neurosurgery update II. Vascular, spinal, pedianic, and functional neurosurgery. McGraw-Hill, New York, pp Szapiro J, Sindou M, Szapiro J (1985) Prognostic factors in microvascular decompression for trigeminal neuralgia. Neurosurgery 17: Taha JM, Tew JM (1996) Comparison of surgical treatments for trigeminal neuralgia: reevaluation of radiofrequency rhizotomy. Neurosurgery 38: Umehara F, Kamishima K, Kashio Net al (1995) Magnetic resonance tomographic angiography: diagnostic value in trigeminal neuralgia. Neuroradiology 37: Comment This is a straightforward manuscript, presenting in a concise manner the experience of the authors in treating 25 patients with trigeminal neuralgia over a five-year period with complete followup on all of their patients. This study is a small study and therefore suffers from lack of numbers in terms of comparable studies that are present in the literature. Its strengths, however, are the clarity with which it is presented and the fact that they have been able to follow all of their patients throughout this period so that none have been lost. This is not often true of patients who have been reported in other studies, particularly where the population may be more mobile. R. Apfelbaum Correspondence: Haldor Sletteb0, M.D., Department of Neurosurgery, Haukeland Hospital, University of Bergen, N-5021 Bergen, Norway.