=Acta Neurochirurgica
Acta Neurochir (Wien) (1992): 116:171 - 175
9 Springer-Verlag 1992 Printed in Austria
Indications for Neurosurgical Treatment of Chronic Pain* J. M. Gybels Department of Neurosurgery, University Hospital, Leuven Belgium
Summary Guidelines are presented for the neurosurgical treatment of chronic pain. In these guidelines a distinction is made between the pain of cancer and neurogenic pain. In cancer pain the survival time and the location of the lesion are the important guidelines. Possible procedures are: opioids via CSF route, lesions in nociceptive pathways and PV-PAG stimulation of the thalamus. In neurogenic pain, neurostimulation procedures, tailored to the location of the pain are procedures of first choice. There are however specific indications for other procedures depending on the aetiology of the pain. Causalgia and reflex sympathetic dystrophy: sympathetic blocade; Tic douloureux: radio-frequency lesion, glycerol, balloon inflation of the ganglion of Gasser, and microvascular decompression; Plexus avulsion: dorsal root entry zone lesion (D.R.E.Z.). There is a need for controlled prospective neurosurgical trials in which as a minimal rule an independent party should evaluate the results of the surgical procedure.
Keywords: Neurosurgical indications; cancer pain; neurogenic pain.
Introduction Surgical indications do not predict therapeutic outcome as well as they should, and pain-relieving surgical procedures tend to be used when all other treatment modalities have failed. Therefore, to give well-founded guidelines for the use of neurosurgical techniques in pain control is no easy task. We can only go by available data, but which data? The data I have used for this papper are those we have collected with Sweet after an extensive search of the literature for a recent monograph on the neurosurgical treatment of persistent pain 6. In spite of this extensive search of the literature there remain difficulties in giving clear answers as to which patient should be considered for surgery because the * Invited Lecture, presented at the European Congress of Neurosurgery, Moscow, June 23-29, 1991.
results in the literature may refer to outdated interventions. In recent years there has indeed been a clear shift away from placing irreversible lesions in the nociceptive pathways towards reversible electrical stimulation in pain modulatory pathways and the intraspinal and intraventricular infusion of opioids. Lord Kelvin stated at the end of this century: "When you can measure what you are speaking about and express it in numbers, you know something about it: when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the stage of science". In the clinical data Sweet and myself collected, we have, to paraphrase Kelvin, not advanced to the stage of science but to the beginning of knowledge. Clinicians should not be ashamed of this state of affairs, but what we have to do in the future is to produce better data. I want to emphasize that the guidelines for surgical intervention which I will formulate here, do not have the force of law, and may vary according to circumstances, of which surgical expertise for a given procedure, "craftmanship", is of major importance.
Neurosurgical Indications in Cancer Pain Surgical indications are not always specific for a given pain syndrome, but is is traditional and it makes sense to make a distinction between pain in cancer and neurogenic pain. In cancer pain the survival time and the location of the pain are important guidelines. It seems fair to propose then when estimated survival is limited to 1-2 months, no ablative or stimulation procedures are indicated, but the administration of opioids via the cere-
172
J . M . Gybels: Indications for Neurosurgical Treatment of Chronic Pain
Table 1. Intraspinal and Intraventricular Administration of Opioids
(N) Mean
Success Toler. foll.up (month) % %
Intraspinal bolus* morphine 818 Continuous intraspinal morphine 129 Intraventricular morphine 281
1.5 2.5 9
71 81 90
Resp. Side dept. effect % %
occurs 0 11 0 5 4
rare 0 10
* 83% epidural and 17% intrathecal. From Gybels 5. With permission of the publisher.
bro-spinal fluid route and percutaneous neurolytic procedures. Table I summarizes the results of intraspina115 and intraventricular 9 administration of opioids. As can be seen, success rate is important and there are few complications. The method is reversible and relatively comfortable for the patient and his relatives. Most authors are of the opinion that the intraspinal administration of morphine is indicated for intractable cancer pain limited to the lower part of the body, but that after failure of intraspinal analgesia and also for either diffuse pains or those above the diaphragm, the intraventricular route is indicated. Tentatively we can say the treatment seems ecouraging enough so that one should promptly resort to a trial of it for cancer pain. The relative values of continuous infusion pumps versus intermittent, often patient-controlled devices are still under assessment. When survival time is estimated to be 2-5 months, there seems to be room for percutaneous neurolytic procedures and intraspinal and intraventricular infusion of opioids is currently very popular. In case of failure of these strategies, ablative procedures should be considered. We have ablative procedures available which are tailored to the location of the pain syndrome. In Table 2 we have summarized the results of the different interventions, indicating the initiator of the procedure, the number of cases taken into consideration for analysis and the percent of sucess at latest followup. The choice of clinical data always contains an element of subjectivity which is difficult to avoid; in our choice of the data 6 we have been guided by the degree of critical assessment of the authors, the availability of thoughtful reviews, the reputation of the authors and our own long-term experience. In case of unilateral pain in the extremities and the trunk anterolateral cordotomy is available. The data of open anterolateral cordotomy given in Table 2 have been derived from a few representive examples of big
Table 2. Ablative Procedures and Results Intervention
Open anterolateral cordotomy Spiller and Martin, 1912 Percutan. anterolateral cordotomy MuUan, 1963 Selective posterior rhizotomy Sindou, 1972 Stereotactic mesencephalotomy Wycis and Spiegel, 1962 Commissural myelotomy Armour, 1927 Stereotactic C1 central myelotomy Hitchcock, 1970 DREZ Nashold and Ostdahl, 1979
N
% Success at latest folk-up
542
69
3357
85
80
69
270
86
235
63
114
71
357
53
series which allow one to trace a general trend. Although cordotomy is now carried out less often than formerly, its capability of producing a completely painfree state in the appropriately selected and fortunate case should not be f o r g o t t e n - t h e more unilateral the pain the more likely is a gratifying result. Percutaneous anterolateral cordotomy is not an easy procedure and requires continuing practise in order to maintain consistently good results but for the neurosurgeon experienced in its use it is a significant improvement over the open operation. Pancoast syndrome pain is a good canditate for selective posterior rhizotomy. Preservation of the lemniscal fibers in this intervention allows more extensive rhizotomies which significantly less impairment of functional capacity of the limb then is the case with posterior rhizotomies and moreover the substrate for a subsequent electrostimulation procedure remains intact.
173
J. M. Gybels: Indications for Neurosurgical Treatment of Chronic Pain
In unilateral cephalofacial cancer pain stereotactic mesencephalotomy may be a possibility. Percutaneous rhizotomy of the fifth and when necessary ninth and tenth cranial nerves is probably the initial step for management of pain of these difficult neoplasms while extensive open rhizotomies of cranical nerves and cervical roots are now very rarely done. In bilateral pain of the lower part of the body commissural myelotomy and stereotactic C 1 central myelotomy probably find their sole and since the introduction of intrathecal opioids, indeed exceptional indication. The C 1 central myelotomy differs from comrnissural myelotomy in three important respects: 1) the larger spatial and especially lateral extension of the lesion; 2) its location is limited to a single level in the spinal cord not determined by the metameric distribution of the pain and 3) by the minimal injury to the dorsal columns. Finally, in diffuse pain, such as in case of multiple metastasis, pituitary destruction4 has its indication. The pain relief obtained in reputable centers by intrasellar alcohol injection, the relatively low stress of the procedure and the low complication rate suggest that this procedure is underutilized in the treatment of severe, diffuse cancer pain. The procedure is also an example of the complexities of the pain suppressive mechanisms of which we have become aware only following critical observations in man. When survival time is estimated to be more than 5 months ablative procedures have thier greatest utility; alternative procedures in this situation are administration of opioids via the cerebrospinal fluid route and stimulation of the periaqueductal periventricular gray 12 matter. The target for stimulation in nociceptive cancer pain is the PV-PAG area of the thalamus. The crucial point in the technique is to reach the correct target; for there are many indications, and the region in the mediodiencephalic mesencephalic junction zone, from which stimulation-produced relief can be obtained, is small indeed. The possibility of activating more or less selectively pain inhibitory pathways without destruction of nervous tissue has tremendous appeal: indeed, unwanted side effects which are a burden with destructive procedures, can be avoided, the effects of electrical stimulation are reversible and, before implanting a stimulating device usually a temporary test-stimulation can be performed. Neurostimulation techniques are not used much in
cancer pain, but as we will see, they are first choice procedures in neurogenic pain. Out of a total of 1534 patients with thalamic stimulation from 27 studies 101 cases were cancer pain patients.
Neurosurgical Indications in Neurogenie Pain Neurostimulation procedures are the first choice for neurogenic pain. We will discuss them first and then turn our attention to causalgia and reflex sympathetic dystrophy, tic douloureux, plexus avulsion and spasms of neural origin. Table 3 summarizes according to pathology the data of dorsal column stimulation (D.C.S.) and PVL-PVM stimulation. The percentages of success contain data from many different authors, short-term and long-term results are lumped together. Spinal cord stimulation for pain is frequently not a single and simple but a time-consuming and rather expensive technique. It is as yet not possible to correlate a particular pain condition with an expected success rate, but spinal cord stimulation is more effective for pain of neurogenic than somatic origin and particularly effective in those cases in which a vascular disorder is present. It has probably been over-used but its reversible character has largely avoided unwanted side effects. There are many clinical indications that deep brain stimulation can be very valuable for treating persistent neurogenic pain even in those conditions in which alternative treatments have failed. As in so many other methods of treatment for chronic pain, it remains difficult to evaluate the percentage of truly successful cases. Deep brain stimulation is not an established rou-
Table 3. Results of Dorsal Column (D.C.S.) and VPL-VPM (D.B.S.) Stimulation in Neurogenic, Low Back and Limb Ischaemia Pain (N)
Amputation/phantom limb 103 Brachial plexus avulsion 20 Thalamic pain Anaesthesis dolorosa Paraplegic pain 21 Post-cordotomy pain 19 Spinal cord/periph, nerve 21 Post-herpetic neuralgia 8 Causalgia Low back pain 487 Severe limb ischaemia 2l
D.C.S. (N) % Success
D.B.S. % Success
33 20
67 55 27 42 34 85 72 57 69 79
33 58 38 25 58 71
87 65 70 106 32 20 69 47 26 254
From Gybels 5. With permission of the publisher.
174
J.M. Gybels: Indications for NeurosurgicalTreatment of Chronic Pain
Table4. Results of Three Currently Used Procedures in Trigeminal Neuralgia
Trigem. thermal rhizotomy Trigem. glycerolrhizotomy Microvasc. decompressionin posterior fossa
(N)
Follow-up % Success
:t: 8000 2019 1232
6m.-16y. 84 2 m.- 8 y. 82 av. 46m. 77.5
m : months, y : years. From Gybelss. With permission of the publisher. tine method and is mostly performed by those neurosurgeons who have a major interest in pain and its physiopathology; in their hands it is a very safe method. It is obvious that knowledge of how electrical stimulation of the brain has a suppressive effect on chronic pain remains fragmentary and that in explaining it one is on less firm ground than was initially thought. In those conditions in which pain is due to an injury of a peripheral nerve rather favourable results are reported with peripheral nerve stimulation. In a total of 335 cases success was obtained in 51%. Long-term results are best in peripheral neurogenic pain of the upper extremities. It is not rare that as time passes, one has to stimulate less and less to obtain the same painsuppressive effect. In causalgia and reflex sympathetic dystrophy, sympathetic blockade, followed eventually by sympathectomy is the rule. It should however be remembered that many patients with nerve injury are not relieved of their pain with sympathetic blockade and that surgery of the peripheral nerve occasionaly may provide excellent pain relief3. However, I do not know of any guidelines predicting which patient will be helped by peripheral nerve surgery and who will not. It seems that the longer those pains have been left untreated by sympathetic blockade the less likely they are to respond to it. The increasing knowledge of sympathetic blocking pharmaceuticals and new methods of applying them either by mouth or intravenous regional injections in the limbs have decreased in an important manner the need for operative sympathectomy. One also has the impression that the ease of excecution of percutaneous approaches to the sympathetic system has led to a somewhat cavalier assessment of the completeness of sympathetic denervation they achieve. Tic douloureux, not well managed by drugs, is a straightforward surgical indications but there is no unanimity as to the type of intervention. As can be seen in Table 4 a great number of data are available. Our intensive search 6 confirms numerous lines of evidence
that the mechanism responsible for essential trigeminal neuralgia is often mysteriously labile. The peculiar propensity for the pain in this nonlethal disorder to stop on minimal and even presumably unrelated manoeuvers demands an unusually conservative surgical approach in the first instance because of the amazing likelihood of its succees. It is crucial to recognize that the debate as to the cause or causes of the disorder need not be resolved in order logically to lead to this decision. It is immaterial whether the cause is abnormal myelination of sensory trigeminal fibers or extensive pressure against them, or both or neither. We conclude from an analysis of the available results that performance of a conservatice percutaneous lesion represents the best tactic as the first invasive procedure. Specifically, we mean R F lesion 14, glycerol in small amounts 7, or balloon inflation 1~ in Meckel's cave for less than a minute. These procedures correctly performed are likely to be virtually free of dysaesthesias or corneal anaesthesia as well as the many minor and major complications which may follow open operation in the posterior fossa 8. Not everybody will agree with this conclusion as has been clearly demonstrated in the many letters to the editor which followed Adams' scholarly article 1 regarding the role of microvascular compression in tic douloureux. It seems then that the present technique of Nashold and colleagues ~ is of proven efficacy with a low rate of complications for pain related to avulsion of sensory rootlets from the cord. For treatment of the neurogenic pains of traumatic paraplegia the rostral "boundary or end zone" pains are more likely to be relieved than the more diffuse, more caudal pains. However, the low rate of neural complications makes such cases suitable for critical evaluation of the operation. For other types of pain the use of the operation is in the exploratory phase with the exception of the pains related to lumbar arachnoiditis and other causes of failure of lumbosacral surgery for pain. In this group the procedure appears proven to be of no value. It is worthwhile here to draw attention to one of the postmortem studies of D R E Z lesions published to-day. This is the case of Richter and Schachenmayr 13. The histological sections following death on the 5 th postoperative day revealed that almost the entire posterior horn was replaced by a pseudocyst which was described by the pathologist as due to the original root avulsion. There was a complete absence of any tissue for virtually the entire extent of the posterior horn. Clearly in this patient no irritative focus in the posterior horn was causing the pain. This
J. M. Gybels: Indications for Neurosurgical Treatment of Chronic Pain important case is a lesson in humility and also strongly suggests that we should be looking elsewhere as well in the CNS for the pathophysiological process in plexus avulsion pain. The intraspinaI administration of morphine in neurogenic pain is not well explored and remains controversial, but a few of us are finding long sustained pain relief in some patients whose lasting intense pain is unrelated to cancer. I myself have seen some excellent long-term pain relief with continuous intrathecal Baclofen administration in some patients with p a i n f u l spasms due to spinal cord lesions.
175 rosurgical pain research has been the rarity of wellcontrolled research to evaluate ist operative procedures, although there is good evidence that surgery can act as a powerful placebo 2. The more subjective the outcome may be, the greater is the rationale of a double-blind trial. The question is: can it be done? Certainly a first and easy to realize step could be that patients, in whom surgery is performed, are assessed by independent observers.
Acknowledgements The author thanks Mrs. M. Feytons-Heerenand Mr. P. De Sutter for expert technical assistance. Part of the work was supported by the F.G.W.O. of Belgium (grant 3.0031.87).
Suggestions for the Improvement of Guidelines It must be clear by now that there are indeed specific indications for neurosurgical techniques in pain control. The most basic rule is that there should be an identified organic cause for the pain syndrome, either nociceptive or neurogenic or both; moreover when for a given pain syndrome several procedures are a possibility, preference should be given to the least invasive, least expensive, with the lowest morbidity and the highest comfort for the patient. On purpose I have not compared neurosurgical treatment with other treatment modalities such as the administration of drugs and cognitive-behavioural multidisciplinary treatment programs. And we have to admit that it is striking that patients I will subject to a surgical procedure in the clinic next door will be managed by pharmacological, psychological and anaesthesiological techniques. The key question is whether long-term results are superior with any one of these management strategies. To improve guidelines for surgical intervention many steps can be taken but I would like to make two suggestions which can be rather easily realized. First, the criteria for "success" are often inadequately specified. However in the last decade a number of reliable measures for assessing chronic pain have been proposed. They have been reviewed recently by Williams 16 and we should be able to give a meaningful number to a given individual result. Current differences of opinion as to the usefulness of a given treatment will be more likely to be resolved when we have firmer facts. Second, in nonsurgical fields, in the evaluation of a given treatment such as drug administration, the crucial role of the controlled prospective randomized trial has received general acceptance, and there are now many textbooks on clinical trials, but there are, however, few references to surgical trials and complex factors that are unique to surgery. One of the deficiencies in neu-
References 1. Adams CBT (1989) Microvascular compression: an alternative view and hypothesis. J Neurosurg 70:1-12 2. Beecher HK (1961) Surgery as placebo. J Am Med Ass 176:
1102-1107 3. Campbell JN, Raja SN, Meyer RA (1988) Painful sequelae of nerve inury. In: Dubner R et al. (eds) Pain research and clinical management, Vol 3. Elsevier, Amsterdam, pp 135-143 4. Greco T, Sbaragli F, Cammilli L (1957) L'alcolizzazionedella ipofisi per via transfenoidale nelle terapia di particoloari tumori maligni. Settim Med 45:355-356 5. GybelsJM (1991) Indications for the use of neurosurgical techniques on pain control. In: Bond MR etal. (eds) Proceedings of the VIth World Congress on pain. Elsevier, Amsterdam, pp 475-482 6. Gybels JM, Sweet WH (1989) Neurosurgical treatment of persistent pain. Karger, Basel 7. H/ikansonS (1981) Trigeminal neuralgia treated by the injection of glycerolinto the trigeminal cistern. Neurosurgery9:638-646 8. Jannetta PJ (1976) Microsurgical approach to the trigeminal nerve for tic douloureux. Prog Neurol Surg 7:180200 9. LeavensME, Hill CS, Cech DA, WeylandJB, Weston JS (1982) Intrathecal and intraventricular morphine for pain in cancer patients: initial study. J Neurosurg 56:241-245 10. Mullan S, Lichtor T (1983) Percutaneous microcompressionof the trigeminal ganglion for trigeminal neuralgia. J Neurosurg 59:1007-1012 11. Nashold BS, Ostdahl RH (1979) Dorsal root entry zone lesions for pain relief. J Neurosurg 51:59-69 12. Richardson DE, Akil H (1977) Long-term results of periventricular gray self-stimulation. Neurosurgery 1:199-202 13. Richter H-P, SchachenmayrW (1984) Is the substantia gelatinosa the target in dorsal root entry zone lesions? An autopsy report. Neurosurgery 15:913-916 14. Sweet WH (1968) Trigeminal neuralgias. In: Alling CC (ed) Facial pain. Lea and Febiger, Philadelphia, pp 89-106 15. Wang JK, Nauss LA, Thomas JE (1979) Pain reliefby intrathecally applied morphine in man. Anesthesiology50:14%151 16. Williams RC (1988) Toward a set of reliable and valid measures for chronicpain assessmentand outcomeresearch. Pain 35: 239251 Correspondence and Reprints: Prof. J. M. Gybels, Department of Neurology and Neurosurgery, UZ Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
Acta Neurochir (Wien) (1992): 116:171 - 175
9 Springer-Verlag 1992 Printed in Austria
Indications for Neurosurgical Treatment of Chronic Pain* J. M. Gybels Department of Neurosurgery, University Hospital, Leuven Belgium
Summary Guidelines are presented for the neurosurgical treatment of chronic pain. In these guidelines a distinction is made between the pain of cancer and neurogenic pain. In cancer pain the survival time and the location of the lesion are the important guidelines. Possible procedures are: opioids via CSF route, lesions in nociceptive pathways and PV-PAG stimulation of the thalamus. In neurogenic pain, neurostimulation procedures, tailored to the location of the pain are procedures of first choice. There are however specific indications for other procedures depending on the aetiology of the pain. Causalgia and reflex sympathetic dystrophy: sympathetic blocade; Tic douloureux: radio-frequency lesion, glycerol, balloon inflation of the ganglion of Gasser, and microvascular decompression; Plexus avulsion: dorsal root entry zone lesion (D.R.E.Z.). There is a need for controlled prospective neurosurgical trials in which as a minimal rule an independent party should evaluate the results of the surgical procedure.
Keywords: Neurosurgical indications; cancer pain; neurogenic pain.
Introduction Surgical indications do not predict therapeutic outcome as well as they should, and pain-relieving surgical procedures tend to be used when all other treatment modalities have failed. Therefore, to give well-founded guidelines for the use of neurosurgical techniques in pain control is no easy task. We can only go by available data, but which data? The data I have used for this papper are those we have collected with Sweet after an extensive search of the literature for a recent monograph on the neurosurgical treatment of persistent pain 6. In spite of this extensive search of the literature there remain difficulties in giving clear answers as to which patient should be considered for surgery because the * Invited Lecture, presented at the European Congress of Neurosurgery, Moscow, June 23-29, 1991.
results in the literature may refer to outdated interventions. In recent years there has indeed been a clear shift away from placing irreversible lesions in the nociceptive pathways towards reversible electrical stimulation in pain modulatory pathways and the intraspinal and intraventricular infusion of opioids. Lord Kelvin stated at the end of this century: "When you can measure what you are speaking about and express it in numbers, you know something about it: when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the stage of science". In the clinical data Sweet and myself collected, we have, to paraphrase Kelvin, not advanced to the stage of science but to the beginning of knowledge. Clinicians should not be ashamed of this state of affairs, but what we have to do in the future is to produce better data. I want to emphasize that the guidelines for surgical intervention which I will formulate here, do not have the force of law, and may vary according to circumstances, of which surgical expertise for a given procedure, "craftmanship", is of major importance.
Neurosurgical Indications in Cancer Pain Surgical indications are not always specific for a given pain syndrome, but is is traditional and it makes sense to make a distinction between pain in cancer and neurogenic pain. In cancer pain the survival time and the location of the pain are important guidelines. It seems fair to propose then when estimated survival is limited to 1-2 months, no ablative or stimulation procedures are indicated, but the administration of opioids via the cere-
172
J . M . Gybels: Indications for Neurosurgical Treatment of Chronic Pain
Table 1. Intraspinal and Intraventricular Administration of Opioids
(N) Mean
Success Toler. foll.up (month) % %
Intraspinal bolus* morphine 818 Continuous intraspinal morphine 129 Intraventricular morphine 281
1.5 2.5 9
71 81 90
Resp. Side dept. effect % %
occurs 0 11 0 5 4
rare 0 10
* 83% epidural and 17% intrathecal. From Gybels 5. With permission of the publisher.
bro-spinal fluid route and percutaneous neurolytic procedures. Table I summarizes the results of intraspina115 and intraventricular 9 administration of opioids. As can be seen, success rate is important and there are few complications. The method is reversible and relatively comfortable for the patient and his relatives. Most authors are of the opinion that the intraspinal administration of morphine is indicated for intractable cancer pain limited to the lower part of the body, but that after failure of intraspinal analgesia and also for either diffuse pains or those above the diaphragm, the intraventricular route is indicated. Tentatively we can say the treatment seems ecouraging enough so that one should promptly resort to a trial of it for cancer pain. The relative values of continuous infusion pumps versus intermittent, often patient-controlled devices are still under assessment. When survival time is estimated to be 2-5 months, there seems to be room for percutaneous neurolytic procedures and intraspinal and intraventricular infusion of opioids is currently very popular. In case of failure of these strategies, ablative procedures should be considered. We have ablative procedures available which are tailored to the location of the pain syndrome. In Table 2 we have summarized the results of the different interventions, indicating the initiator of the procedure, the number of cases taken into consideration for analysis and the percent of sucess at latest followup. The choice of clinical data always contains an element of subjectivity which is difficult to avoid; in our choice of the data 6 we have been guided by the degree of critical assessment of the authors, the availability of thoughtful reviews, the reputation of the authors and our own long-term experience. In case of unilateral pain in the extremities and the trunk anterolateral cordotomy is available. The data of open anterolateral cordotomy given in Table 2 have been derived from a few representive examples of big
Table 2. Ablative Procedures and Results Intervention
Open anterolateral cordotomy Spiller and Martin, 1912 Percutan. anterolateral cordotomy MuUan, 1963 Selective posterior rhizotomy Sindou, 1972 Stereotactic mesencephalotomy Wycis and Spiegel, 1962 Commissural myelotomy Armour, 1927 Stereotactic C1 central myelotomy Hitchcock, 1970 DREZ Nashold and Ostdahl, 1979
N
% Success at latest folk-up
542
69
3357
85
80
69
270
86
235
63
114
71
357
53
series which allow one to trace a general trend. Although cordotomy is now carried out less often than formerly, its capability of producing a completely painfree state in the appropriately selected and fortunate case should not be f o r g o t t e n - t h e more unilateral the pain the more likely is a gratifying result. Percutaneous anterolateral cordotomy is not an easy procedure and requires continuing practise in order to maintain consistently good results but for the neurosurgeon experienced in its use it is a significant improvement over the open operation. Pancoast syndrome pain is a good canditate for selective posterior rhizotomy. Preservation of the lemniscal fibers in this intervention allows more extensive rhizotomies which significantly less impairment of functional capacity of the limb then is the case with posterior rhizotomies and moreover the substrate for a subsequent electrostimulation procedure remains intact.
173
J. M. Gybels: Indications for Neurosurgical Treatment of Chronic Pain
In unilateral cephalofacial cancer pain stereotactic mesencephalotomy may be a possibility. Percutaneous rhizotomy of the fifth and when necessary ninth and tenth cranial nerves is probably the initial step for management of pain of these difficult neoplasms while extensive open rhizotomies of cranical nerves and cervical roots are now very rarely done. In bilateral pain of the lower part of the body commissural myelotomy and stereotactic C 1 central myelotomy probably find their sole and since the introduction of intrathecal opioids, indeed exceptional indication. The C 1 central myelotomy differs from comrnissural myelotomy in three important respects: 1) the larger spatial and especially lateral extension of the lesion; 2) its location is limited to a single level in the spinal cord not determined by the metameric distribution of the pain and 3) by the minimal injury to the dorsal columns. Finally, in diffuse pain, such as in case of multiple metastasis, pituitary destruction4 has its indication. The pain relief obtained in reputable centers by intrasellar alcohol injection, the relatively low stress of the procedure and the low complication rate suggest that this procedure is underutilized in the treatment of severe, diffuse cancer pain. The procedure is also an example of the complexities of the pain suppressive mechanisms of which we have become aware only following critical observations in man. When survival time is estimated to be more than 5 months ablative procedures have thier greatest utility; alternative procedures in this situation are administration of opioids via the cerebrospinal fluid route and stimulation of the periaqueductal periventricular gray 12 matter. The target for stimulation in nociceptive cancer pain is the PV-PAG area of the thalamus. The crucial point in the technique is to reach the correct target; for there are many indications, and the region in the mediodiencephalic mesencephalic junction zone, from which stimulation-produced relief can be obtained, is small indeed. The possibility of activating more or less selectively pain inhibitory pathways without destruction of nervous tissue has tremendous appeal: indeed, unwanted side effects which are a burden with destructive procedures, can be avoided, the effects of electrical stimulation are reversible and, before implanting a stimulating device usually a temporary test-stimulation can be performed. Neurostimulation techniques are not used much in
cancer pain, but as we will see, they are first choice procedures in neurogenic pain. Out of a total of 1534 patients with thalamic stimulation from 27 studies 101 cases were cancer pain patients.
Neurosurgical Indications in Neurogenie Pain Neurostimulation procedures are the first choice for neurogenic pain. We will discuss them first and then turn our attention to causalgia and reflex sympathetic dystrophy, tic douloureux, plexus avulsion and spasms of neural origin. Table 3 summarizes according to pathology the data of dorsal column stimulation (D.C.S.) and PVL-PVM stimulation. The percentages of success contain data from many different authors, short-term and long-term results are lumped together. Spinal cord stimulation for pain is frequently not a single and simple but a time-consuming and rather expensive technique. It is as yet not possible to correlate a particular pain condition with an expected success rate, but spinal cord stimulation is more effective for pain of neurogenic than somatic origin and particularly effective in those cases in which a vascular disorder is present. It has probably been over-used but its reversible character has largely avoided unwanted side effects. There are many clinical indications that deep brain stimulation can be very valuable for treating persistent neurogenic pain even in those conditions in which alternative treatments have failed. As in so many other methods of treatment for chronic pain, it remains difficult to evaluate the percentage of truly successful cases. Deep brain stimulation is not an established rou-
Table 3. Results of Dorsal Column (D.C.S.) and VPL-VPM (D.B.S.) Stimulation in Neurogenic, Low Back and Limb Ischaemia Pain (N)
Amputation/phantom limb 103 Brachial plexus avulsion 20 Thalamic pain Anaesthesis dolorosa Paraplegic pain 21 Post-cordotomy pain 19 Spinal cord/periph, nerve 21 Post-herpetic neuralgia 8 Causalgia Low back pain 487 Severe limb ischaemia 2l
D.C.S. (N) % Success
D.B.S. % Success
33 20
67 55 27 42 34 85 72 57 69 79
33 58 38 25 58 71
87 65 70 106 32 20 69 47 26 254
From Gybels 5. With permission of the publisher.
174
J.M. Gybels: Indications for NeurosurgicalTreatment of Chronic Pain
Table4. Results of Three Currently Used Procedures in Trigeminal Neuralgia
Trigem. thermal rhizotomy Trigem. glycerolrhizotomy Microvasc. decompressionin posterior fossa
(N)
Follow-up % Success
:t: 8000 2019 1232
6m.-16y. 84 2 m.- 8 y. 82 av. 46m. 77.5
m : months, y : years. From Gybelss. With permission of the publisher. tine method and is mostly performed by those neurosurgeons who have a major interest in pain and its physiopathology; in their hands it is a very safe method. It is obvious that knowledge of how electrical stimulation of the brain has a suppressive effect on chronic pain remains fragmentary and that in explaining it one is on less firm ground than was initially thought. In those conditions in which pain is due to an injury of a peripheral nerve rather favourable results are reported with peripheral nerve stimulation. In a total of 335 cases success was obtained in 51%. Long-term results are best in peripheral neurogenic pain of the upper extremities. It is not rare that as time passes, one has to stimulate less and less to obtain the same painsuppressive effect. In causalgia and reflex sympathetic dystrophy, sympathetic blockade, followed eventually by sympathectomy is the rule. It should however be remembered that many patients with nerve injury are not relieved of their pain with sympathetic blockade and that surgery of the peripheral nerve occasionaly may provide excellent pain relief3. However, I do not know of any guidelines predicting which patient will be helped by peripheral nerve surgery and who will not. It seems that the longer those pains have been left untreated by sympathetic blockade the less likely they are to respond to it. The increasing knowledge of sympathetic blocking pharmaceuticals and new methods of applying them either by mouth or intravenous regional injections in the limbs have decreased in an important manner the need for operative sympathectomy. One also has the impression that the ease of excecution of percutaneous approaches to the sympathetic system has led to a somewhat cavalier assessment of the completeness of sympathetic denervation they achieve. Tic douloureux, not well managed by drugs, is a straightforward surgical indications but there is no unanimity as to the type of intervention. As can be seen in Table 4 a great number of data are available. Our intensive search 6 confirms numerous lines of evidence
that the mechanism responsible for essential trigeminal neuralgia is often mysteriously labile. The peculiar propensity for the pain in this nonlethal disorder to stop on minimal and even presumably unrelated manoeuvers demands an unusually conservative surgical approach in the first instance because of the amazing likelihood of its succees. It is crucial to recognize that the debate as to the cause or causes of the disorder need not be resolved in order logically to lead to this decision. It is immaterial whether the cause is abnormal myelination of sensory trigeminal fibers or extensive pressure against them, or both or neither. We conclude from an analysis of the available results that performance of a conservatice percutaneous lesion represents the best tactic as the first invasive procedure. Specifically, we mean R F lesion 14, glycerol in small amounts 7, or balloon inflation 1~ in Meckel's cave for less than a minute. These procedures correctly performed are likely to be virtually free of dysaesthesias or corneal anaesthesia as well as the many minor and major complications which may follow open operation in the posterior fossa 8. Not everybody will agree with this conclusion as has been clearly demonstrated in the many letters to the editor which followed Adams' scholarly article 1 regarding the role of microvascular compression in tic douloureux. It seems then that the present technique of Nashold and colleagues ~ is of proven efficacy with a low rate of complications for pain related to avulsion of sensory rootlets from the cord. For treatment of the neurogenic pains of traumatic paraplegia the rostral "boundary or end zone" pains are more likely to be relieved than the more diffuse, more caudal pains. However, the low rate of neural complications makes such cases suitable for critical evaluation of the operation. For other types of pain the use of the operation is in the exploratory phase with the exception of the pains related to lumbar arachnoiditis and other causes of failure of lumbosacral surgery for pain. In this group the procedure appears proven to be of no value. It is worthwhile here to draw attention to one of the postmortem studies of D R E Z lesions published to-day. This is the case of Richter and Schachenmayr 13. The histological sections following death on the 5 th postoperative day revealed that almost the entire posterior horn was replaced by a pseudocyst which was described by the pathologist as due to the original root avulsion. There was a complete absence of any tissue for virtually the entire extent of the posterior horn. Clearly in this patient no irritative focus in the posterior horn was causing the pain. This
J. M. Gybels: Indications for Neurosurgical Treatment of Chronic Pain important case is a lesson in humility and also strongly suggests that we should be looking elsewhere as well in the CNS for the pathophysiological process in plexus avulsion pain. The intraspinaI administration of morphine in neurogenic pain is not well explored and remains controversial, but a few of us are finding long sustained pain relief in some patients whose lasting intense pain is unrelated to cancer. I myself have seen some excellent long-term pain relief with continuous intrathecal Baclofen administration in some patients with p a i n f u l spasms due to spinal cord lesions.
175 rosurgical pain research has been the rarity of wellcontrolled research to evaluate ist operative procedures, although there is good evidence that surgery can act as a powerful placebo 2. The more subjective the outcome may be, the greater is the rationale of a double-blind trial. The question is: can it be done? Certainly a first and easy to realize step could be that patients, in whom surgery is performed, are assessed by independent observers.
Acknowledgements The author thanks Mrs. M. Feytons-Heerenand Mr. P. De Sutter for expert technical assistance. Part of the work was supported by the F.G.W.O. of Belgium (grant 3.0031.87).
Suggestions for the Improvement of Guidelines It must be clear by now that there are indeed specific indications for neurosurgical techniques in pain control. The most basic rule is that there should be an identified organic cause for the pain syndrome, either nociceptive or neurogenic or both; moreover when for a given pain syndrome several procedures are a possibility, preference should be given to the least invasive, least expensive, with the lowest morbidity and the highest comfort for the patient. On purpose I have not compared neurosurgical treatment with other treatment modalities such as the administration of drugs and cognitive-behavioural multidisciplinary treatment programs. And we have to admit that it is striking that patients I will subject to a surgical procedure in the clinic next door will be managed by pharmacological, psychological and anaesthesiological techniques. The key question is whether long-term results are superior with any one of these management strategies. To improve guidelines for surgical intervention many steps can be taken but I would like to make two suggestions which can be rather easily realized. First, the criteria for "success" are often inadequately specified. However in the last decade a number of reliable measures for assessing chronic pain have been proposed. They have been reviewed recently by Williams 16 and we should be able to give a meaningful number to a given individual result. Current differences of opinion as to the usefulness of a given treatment will be more likely to be resolved when we have firmer facts. Second, in nonsurgical fields, in the evaluation of a given treatment such as drug administration, the crucial role of the controlled prospective randomized trial has received general acceptance, and there are now many textbooks on clinical trials, but there are, however, few references to surgical trials and complex factors that are unique to surgery. One of the deficiencies in neu-
References 1. Adams CBT (1989) Microvascular compression: an alternative view and hypothesis. J Neurosurg 70:1-12 2. Beecher HK (1961) Surgery as placebo. J Am Med Ass 176:
1102-1107 3. Campbell JN, Raja SN, Meyer RA (1988) Painful sequelae of nerve inury. In: Dubner R et al. (eds) Pain research and clinical management, Vol 3. Elsevier, Amsterdam, pp 135-143 4. Greco T, Sbaragli F, Cammilli L (1957) L'alcolizzazionedella ipofisi per via transfenoidale nelle terapia di particoloari tumori maligni. Settim Med 45:355-356 5. GybelsJM (1991) Indications for the use of neurosurgical techniques on pain control. In: Bond MR etal. (eds) Proceedings of the VIth World Congress on pain. Elsevier, Amsterdam, pp 475-482 6. Gybels JM, Sweet WH (1989) Neurosurgical treatment of persistent pain. Karger, Basel 7. H/ikansonS (1981) Trigeminal neuralgia treated by the injection of glycerolinto the trigeminal cistern. Neurosurgery9:638-646 8. Jannetta PJ (1976) Microsurgical approach to the trigeminal nerve for tic douloureux. Prog Neurol Surg 7:180200 9. LeavensME, Hill CS, Cech DA, WeylandJB, Weston JS (1982) Intrathecal and intraventricular morphine for pain in cancer patients: initial study. J Neurosurg 56:241-245 10. Mullan S, Lichtor T (1983) Percutaneous microcompressionof the trigeminal ganglion for trigeminal neuralgia. J Neurosurg 59:1007-1012 11. Nashold BS, Ostdahl RH (1979) Dorsal root entry zone lesions for pain relief. J Neurosurg 51:59-69 12. Richardson DE, Akil H (1977) Long-term results of periventricular gray self-stimulation. Neurosurgery 1:199-202 13. Richter H-P, SchachenmayrW (1984) Is the substantia gelatinosa the target in dorsal root entry zone lesions? An autopsy report. Neurosurgery 15:913-916 14. Sweet WH (1968) Trigeminal neuralgias. In: Alling CC (ed) Facial pain. Lea and Febiger, Philadelphia, pp 89-106 15. Wang JK, Nauss LA, Thomas JE (1979) Pain reliefby intrathecally applied morphine in man. Anesthesiology50:14%151 16. Williams RC (1988) Toward a set of reliable and valid measures for chronicpain assessmentand outcomeresearch. Pain 35: 239251 Correspondence and Reprints: Prof. J. M. Gybels, Department of Neurology and Neurosurgery, UZ Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
