- Email: [email protected]
Subarachnoid and epidural neurolysis
Subarachnoid and Epidural Neurolysis Ray H. d'Amours, MD and F. Michael Ferrante, MD
In many cases, treatment of severe cancer pain remains a great clinical challenge. Spinal (epidural and subarachnoid) neurolysis remains the treatment of choice for a minority of patients with cancer-related pain. Because of the risk of severe complications many practitioners are reluctant to employ these techniques. When used appropriately, in carefully selected patients, they can be an effective means of relieving suffering. The purpose of this article is to review the techniques of subarachnoid and epidural neurolysis for the treatment of cancer-related pain so that more clinicians may become familiar and comfortable with its use. An understanding of the material presented should help the practitioner maximize benefit for his patients and minimize the possibility of comp!ications or litigation. Copyright 9 1997 by W.B. Saunders Company
ince the first description of intrathecal injection of alcohol ~,_,11by Dogliotti in 1931,.12 the use of spinal (subarachnoid and epidural) neurolytic nerve blocks has played an important role in the management of cancer-related pain. Understandable concern about associated complications and a lack of properly trained personnel has limited the full implementation of spinal neurolysis as a pain management tool. The development of optimal strategies for prescription of oral analgesics and the frequent use of spinal opioids has somewhat diminished the importance of axial neurolytic techniques in managing intractable pain. Nonetheless, these methods remain the treatment of choice for a minority of patients. Spinal neurolysis is dangerous, but when used appropriatel); in carefully selected patients, it is effective, inexpensive, quickly accomplished, and associated with a low incidence of severe morbidit): The purpose of this report is to review the techniques of subarachnoid and epidural neurolysis for the treatment of cancer-related pain. It should be emphasized that, as with all neurolytic procedures, great care must be taken in patient selection and in the performance of these techniques. Doing so will help the practitioner maximize benefit for his patients and minimize the possibility of complications or litigation.3 Ethyl alcohol and phenol are the two agents commonly used for spinal neurolysis. Each has advantages but both can be effectively employed for either subarachnoid or epidural bloc -los. Both have been associated with delayed development of painful neuritis, though the incidence of peripheral neuritis is more
From the Department of Anesthesia, University of Pennsylvania Medical Center, Philadelphia, PA. Address reprint requests to Ray H. d'Amours, MD, Department of Anesthesia, 1101 Penn Tower, University of Pennsylvania Medical Center, Philadelphia, PA 19103. Copyright 9 1997 by W.B. Saunders Company 1084-208X/97/0110-$5.00/0
32
common with alcohol. 4 The baricity of these agents relative to cerebrospinal fluid determines how they will spread when injected directly into the subarachnoid space. For intrathecal use, the choice of agent is usually determined primarily by whether a hyperbaric or hypobaric solution is preferred. Absolute (100%) alcohol is available in commercially packaged ampules of 1 or 5 mL (Hope Pharmaceuticals, Santa Ana, CA). With a specific gravity of 0.8, it is hypobaric relative to cerebrospinal fluid and will rise quickly after intrathecal injection. Injection of absolute alcohol is typically associated with brief but intense pain. Ahhough ethanol is quickly absorbed from tissues, there is little risk of significant systemic effect with the small doses used for spinal neurolysis, s Alcohol effectsneurolysis by extraction of cholesterol, phospholipid, and cerebroside and ca,uses precipitation of lipoproteins and mucoproteins. 6 Alcohol is irritating to mucosa but does not effect intact skin. Phenol for injection is not available commercially but can be prepared by most hospital pharmacies. Prepared solutions should be kept refrigerated and shielded from light. Tile maximum concentration of phenol in saline that can be achieved at room temperature is 6.7%. 5 For intrathecal use phenol is usually mixed with glycerine to form a hyperbaric solution in a concentration o[4% to 10%. It can also be mixed with radiographic dye material to form a hyperbaric contrast solution at concentrations above those previously mentioned. Preparations of phenol in glycerine are very viscous and are not easily administered through spinal needles. Injections can be facilitated by using tuberculin syringes, and by warming the container of neurolytic solution in a hot water bath before drawing the drug into a syringe. Phenol in glycerine cannot be readily injected through epidural catheters. For this application 5% phenol in saline or water can be used. Phenol possesses local anesthetic activity so, unlike alcohol, pain upon injection is brief, if occurring at all. Frequently though, patients will report a brief, warm, tingling sensation. Clinically used concentrations of phenol can cause significant necrosis if left in prolonged contact with the skin. Phenol causes nonselective neurolysis by denaturing proteins from axons. 7.8 The extent of degeneration is concentration dependent.
Patient Selection In order to minimize complications with an)' type of neurolytic procedure, great care must be taken to select patients carefully. Many patients are referred by physicians who erroneously believe that neurolytic blocks are permanent and without significant risk. This simple notion of "permanent nerve blocks" is very seductive to both physicians and patients but often must be resisted. Described below are the most com-
Techniques in RegionalAnesthesia and Pain Management, Vol 1, No 1 (January), 1997: pp 32-37
monly accepted indications and contraindications for performance of axial neurolytic procedures.
Procedure Subarachnoid Neurolysis With Phenol
Indications 1. Intractable cancer-related pain. The use of subarachnoid or epidural neurolysis for chronic nomnalignant pain is usually not indicated. 2. Failure of antitumor therapy to control pain. 3. Failure of more conservative analgesic therapies, including appropriate use of potent opioids, adjnnctire agents, and neuraxial drug deliver): A recent set of guidelines for cancer pain management has suggested the general use of neuraxial drug deliver), prior to neuroablation except in specific instances. 9 4. Limited life expectanc): Although it is often difficult to accurately predict life expectanc); these procedures are usually reserved for cancer patients anticipated to live less than a year. Neurolytic blocks cannot be relied upon to provide indefinite analgesia, and the consequences of~delayed complications are greater for those with long life expectancies. Deferring neuroablation until life-expectancy is short-term minimizes the risk of development of deafferentation pain. 5. Pain that is primarily somatic in origin. Visceral or neuropathic pain is less reliably treated with spinal neurolytic procedures. Is Other neurolytic procedures, such as celiac plexus block, may be more appropriate. Deafferentation type pain may be worsened by neurolyric blockade. 6. Localized pain. Subarachnoid neurolysis is usually reserved for pain that is restricted to two or three dermatomes, except in certain cases where bowel, bladder, and motor control have already been lost. Epidural neurolysis may be useful for pain that covers a somewhat broader area. Cordotomy may be indicated when life-expectancy is longer. 8 7. Pain that is shown to respond to a trial of local anesthetic blockade. Neural blockade with local anesthetic should be used prognostically to determine the possible efficacy of neuroablation. However, success with local anesthetics does not ensure successful neuroablation.X~
First, the nerve roots that innervate the painful area must be identified from standard dermatomal diagrams. Sclerotomal charts II call be used to identify the innervation of an area of bone. The interspace chosen for needle insertion is the level at which these roots emerge from the spinal cord. This level will be somewhat cephalad to the corresponding bony level (Fig 1). An adjustable operating room table should be used to simplify positioning of the patient. Flouroscopy can be used to facilitate needle placement and to show the flow and distribu-
Contraindications 1. Patient is unable to tolerate positioning for the procedure. This may be overcome with proper choice of neurolytic agent (see below) or appropriate use of anesthesia. 2. Patient (or family) is unwilling to tolerate the risk of associated side effects. 3. Pain that does not respond to nerve blocks performed with local anesthetic. Ahhough neural blockade with local anesthetic may not always accurately predict the outcome with neurolytic blocks, one should not proceed when they are ineffective. 4. Pain that is primarily sympathetically maintained or resuhing from deafferentation. 5. Diffnse, poorly localized pain. 6. Coagulopath):
SUBARACHNOID AND EPIDURAL NEUROLYSIS
Z
1 5 coc.I
Fig 1.-Diagram of the adult spinal cord and vertebral column showing the relationship between the origin of the nerve roots in the spinal cord and their emergence from the neural foramina of the spine. When performing subarachnoid neurolysis, the needle is inserted through the bony interspace which corresponds to the level of origin of the nerve root in the spinal cord. For instance, to block the nerve roots of L1 the needle should be inserted through the Tl1-12 interspace. (Reprinted with permission from Haymaker W, Woodhall B" Peripheral nerve injuries. Philadelphia, PA, Saunders, 1945.)
33
tion of injected contrast material. Sufficient sedation is given so that the patient is relaxed but cooperative and communicative. If absolutely necessar); general anesthesia can be provided; this will eliminate valuable communication with the patient about the effect of injected drug and increase the likelihood of complications. The patient is positioned in the normal lateral decubitus position for spinal puncture, with the painful side down (a relative disadvantage of using phenol). After antiseptic cleansing of the needle insertion site, local anesthetic is used to form a skin wheal and to anesthetize the appropriate interspace. A 22-gauge or larger spinal needle should be used as it is almost impossible to inject glycerine solutions through anything smaller. The needle is directed into the appropriate interspace with the bevel pointed downward until free flow of cerebrospinal fluid is observed. An effort should be made to direct the needle toward the dependent side of the dura; doing so will allow injected solution to directly onto ipsilateral nerve roots and not directly onto the spinal cord or cauda equina. When performing thoracic dural puncture, particularly at midthoracic levels, it may be easier to use a paramedian approach becaus~ of the steep angle formed by the spinous processes. When'performing dural puncture above the spinous level L2, care should be taken to avoid trauma to the spinal cord. The needle should be advanced slowly and no further than necessary to achieve free flow of cerebrospinal fluid (CSF). Once free flow of cerebrospinal fluid has been obtained, the needle stylet is replaced to stem the flow of CSF and the patient is carefully and slowly rotated posteriorly so that his or her back is at a 45 ~ angle relative to the floor (Fig 2). The table is flexed directly beneath the point of needle insertion (Fig 3). In this position the posterior (sensory) nerve roots of the painful side will be most dependent (Fig 4). Pillows and straps should be used to stabilize the patient comfortably in this position. After the patient is correctly positioned the stylet is removed and once again free flow of CSF is confirmed. A one cc tuberculin syringe containing the phenol solution is firmly attached to the needle hub. An initial dose of 0.2 mL is injected, and the patient is asked to describe the resulting
/
/
/
/
/
/
Fig 2. When performing subarachnoid neurolysis with hyperbaric solutions of phenol the patient should be rotated posteriorly 45 ~ to bring the posterior nerve roots into the most dependent position.
34
sensation. Often the patient will experience a brief feeling of tingling and warmth along a particular dermatome. This sensation can be used to assess the correct location of the needle. If the sensation is experienced above or below the desired dermatome, the needle should be withdrawn and reinserted at the appropriate level. Alternativel); and in the case of patients receiving general anesthetics, the distribution of administered drug can be checked by first injecting a small dose (0.1 to 0.3 mL) of hyperbaric nonionic contrast material. After the initial 0.2 mL of drug is given and correct needle position is determined, subsequent serial doses of 0.1 mL are injected. Several minutes should be allowed between these serial doses to permit repeated neurological evaluation, with concentration on motor and sensory function of adjacent dermatomes. The total dose of phenol given is limited by the risk of injury to collateral structures. Larger volumes are more likely to contact anterior or adjacent nerve roots. The greatest risk exists for nerve blocks perforlned near the origin of innervation to the upper and lower extremities--the cervical and lumbar segments. 12 The cauda equina may be particularly vulnerable to unintentional neurolysis so injections below L1 should be approached with great caution. It has been suggested that subarachnoid neurolysis below L1-L2 should not be a'ttempted unless bowel or bladder disturbances are already present. 15 Prudent maximum doses administered in a single treatment are 1.0 to 2.0,mL for injections made in the thoracic levels, and 0.5 mL in the lumbar or cervical areas. 8A3-15If serial examination between doses reveals sensory or motor blockade of adjacent levels, or if the patient reports subjective sensations in these areas, no further injections are made. When attempting to block several adjacent nerve roots, it is better to use separate needle insertions at each level than to try to cover all levels by injecting a larger volume of drug. Once injection is complete, 0.2 mL of saline is used to clear the needle of phenol before it is withdrawn. This will prevent sinus tract formation resulting from deposited neurolytic solution. The patient should be maintained in position for 20 to 30 minutes after injection. Bolsters, padding and, if needed, additional personnel should be used to prevent unintentional movement.
Subarachnoid Ethanol Injection The technique for subarachnoid block using alcohol is similar to that described for phenol, but because ethanol is hypobaric relative to CSF, the patient must be positioned differentl}: One advantage of alcohol used for neurolysis is that the patient can be positioned with the painful side up. From the lateral decubitus position the patient is rolled anteriorly forty five degrees (Fig 5). The table is flexed or a pillow is placed under the patient directly below the point of injection in order to curve the spine and move the sensor)' nerve roots to an uppermost position (Fig 6). The patient is then supported in this position with pillows and straps. Dural puncture at the appropri.ate level is performed, with the needle guided toward the upper half (painful side) of the dura. The needle bevel should be pointing upward. Once free flow of CSF is achieved, alcohol is injected in increments of 0.1 mL. Injection of alcohol evokes burning pain that is brief but intense. Reports from the patient about the exact location of this pain can be used to precisely guide needle placement. If the patient reports pain that corresponds to a sensor), level
o'AMOURS AND FERRANTE
Fig 3. Flexing the table directly beneath the point of needle insertion will make the targeted nerve roots more dependent. Hyperbaric solutionswill thereby flow toward the desired level.
above or below the one desired, tile needle can be withdrawn and repositioned. The patient must be warned to expect the pain of injection. The importance of quickly and accurately reporting the location of the pain should be emphasized. Assurance can be given that the pain will be brief and that it will likely diminish with subsequent injections. Prior injection of local anesthetic will diminish or eliminate the pain of injection but also ablate the ability to quickly identify misplaced drug. Once proper needle position has been confirmed, sequential injections of 0.1 mL are made. A total of 0.2 to 1.0 mL is injected to block one segment, lz,15 If desired, adjacent nerve roots can then be blocked by reinserting the needle at the appropriate interspace and repeating the procedure. One should not attempt to block more than three nerves at any one time. As with phenol, the patient is maintained in position for 20 to 30 minutes before moving.
/
/
/
/
/
/
Fig 4. A cross-sectional diagram showing a hyperbaric solution of phenol descending toward the posterior nerve root. The needle is inserted so that it pierces the dura toward the dependent side of the midline.
SUBARACHNOID AND EPIDURALNEUROLYSIS
Epidural Neurolysis AlthoughI less commonly used, epidural neurolysis does offer some.potential advantages over the subarachnoid route. The risk of dural puncture headache is minimized, and pain over a broader area can be treated,a6 with less risk of severe complications such as bowel and bladder dysfunction. Incremental treatment by repeated injection over several days through indwelling catheters allows a more gradual and controlled neurolysis. Treatment of bilateral pain is simplified. For some patients these advantages may be important but must be weighed against the specific disadvantages, as well as the extra time and expense associated with this techniqne. Serial injections administered over several days generally requires overnight stays in the hospital. Using patient position to control the flow and distribution of drugs injected into the epidural space is of limited value; unilateral blocks cannot be achieved reliably. Tile most common indication for this technique is for treatment of tumors causing widespread or bilateral pain in the chest or abdomen. Both phenol and alcohol can be used for epidural neurolysis. Alcohol is typically used in concentrations of 75 to 100%. Phenol is most commonly mixed with saline to form solutions of 5 to 6% although some practicioners will use concentrations as high as 15%. These higher concentrations require the addition of glycerine to the neurolytic solution. Typical doses are from 2 to 5 mL per injection, with injections repeated daily for 1 to 3 days as needed. 17,18 Epidural neurolysis is performed with the patient in the lateral decubitus position With the bed elevated 30 ~ head up. When phenol solutions are used, tile patient should be placed with the painful side dependent. For alcohol, it has been recommended, that the painful side be placed upward. In neithe'-Fcase should one expect the achievement of a unilateral block. Patients with bilateral pain can be placed supine, with 30 ~ head elevation after catheter insertion. The interspace is chosen based on the dermatomal distribution of the patient's pain. A standard nylon catheter is placed into the epidural space and the proper position confirmed with fluoroscopy after injecting a small amount (0.5 to 3.0 mL) of nonionic contrast solution. When performing epidural neurolysis, great care
35
x
j
,,
o~." Fig 5. Diagram showing proper patient position for use of hypobaric solutions of alcohol. The cross-sectional diagram shows the alcohol ascending toward the posterior nerve root. The needle is inserted so that it pierces the dura above the midline.
must be taken to ensure that the neurolytic solution is only injected into the epidural space and not into the subdural Or subarachnoid areas. The standard "loss of resistance" is not sufficient to confirm proper placement, 19 nor does aspiration through the catheter guarantee avoidance of subarachnoid or intravenous injection. If accidental injection into these areas occurs, the large volume of solution used can be expected to
cause significant complications. Therefore, use of fluoroscopy with contrast or some other method of visualization is essential to ensure correct needle position. Once proper position of the catheter has been confirmed, the neurolytic solution is slowly injected in increments of 0.2 to 0.5 mL, with pauses of several minutes between injections. Injection continues until the pain is relieved or the total
i, #
.sJ
Y f
W f ~
J
m
Fig 6. Pillows can be placed directly beneath the point of needle insertion to elevate the targeted solutions will then flow toward those roots,
36
nerve
roots. Hypobaric
D'AMOURS AND FERRANTE
amount of drug (2.0 to 5.0 mL) is injected. The catheter is securely fastened to the patient's back and the patient is maintained in position for 30 minutes. The procedure can be repeated daily until analgesia for 24 hours is achieved. Proper position of the catheter must be confirmed ever}, time before it is used for injection of neurolytic solutions. Using this technique, analgesia of a few weeks to a few months duration is usually achieved; the procedure can be repeated if pain returns.
Success and Complication Rates Determining which drugs and techniques have the highest rates of success or complication is made difficult by a lack of controlled studies comparing methods, a n d b y var},ing definitions of success. Good results may reasonably be expected for greater than 50~ of patients undergoing subarachnoid neurolysis. lz Gerbershagan's review of the literature 15showed that 40~ of patients receiving subarachnoid block with alcohol required more than one injection. In 2,125 subarachnoid blocks performed with alcohol, 12% bad tentporar}' complications and 2~ had permanent Ideficits. Most temporary deficits (51%) lasted less than 1 x~eek and 18% endured for more than 4 months. Bladder dysfunction or paresis/paralysis of an extremity were the most common contplaints. The risk of bowel and bladder dysfunction increases with injection into lumbar Or. sacral segments. In 1986 Racz reported performing 467 epidural injections of phenol without any significant complication. 2~ Korevaar performed epidural injection of alcohol in 36 patients and reported success (greater than 70~ pain relief) in 89~ with a mean duration of analgesia of 3.3 ntonths. 17 No serious long-term complications were observed. A wide range of complications can be seen after axial neurolysis. Minor complications include postdural ptmcture headache, pain at the needle or catheter insertion site and minor skin infections. In addition to the serious complications mentioned above, there is risk of meningitis and neuritis. Both anterior and posterior spinal artery thrombosis have been described as a result of neurolytic blockade. 21.22 As stated earlier, the risk of complication can be reduced by careful patient selection and strict adherence to recommended techniques. The ntinimum effective dose of neurolytic should always be used. Clear and detailed explanation of possible adverse outcome should be offered to the patient and their famil):
SUBARACHNOID AND EPIDURAL NEUROLYSIS
References 1. Dogliotti AM: A new method of block anesthesia: Segmental peridural spinal anesthesia. Am J Surg 20:107-109, 1993 2. Swerdlow M: Medicolegal aspects of complications following pain relieving blocks. Pain 13:321-31, 1982 3. Jain S, Gupta R: Neurolytic agents in clinical practice, in Waldman SD, Winnie AP (eds): Interventional Pain Management. Philadelphia, PA, Saunders, 1996, pp 167-171 4. Lipton S: Neurolysis: Pharmacology and drug selection, in Patt RB (ed): Cancer Pain. Philadelphia, PA, Lippincott, 1993, pp 427-442 5. Rumsby MG, Finean JB: The action of organic solvents on the myelin sheath of peripheral nerve tissue-ll (short-chain aliphatic alcohols). J Neurochem 13:1509-1511, 1996 6. Smith MC: Historical findings following intrathecal injection of phenol solutions for the relief of pain. Br J Anaesth 36:387-406, 1964 7. Swerlow M: Neurolytic blocks of the Neuroaxis, in Part RB (ed): Cancer Pain. Philadelphia, PA, Lippincott, 1993, pp 343-358 8. Berry K, OIszewski J: Pathology of intrathecal phenol in man. Neurology 13:152-154, 1963 9. Ferrante FM, Bedder M, Chaney HM, et al: Practice guidelines for cancer pain management. A report by the American Society of Anesthesiologists Task Force on Pain Management, Cancer Section. Anesth 84:1243-1257, 1996 10. Haymaker W, Woodhall B: Peripheral nerve injuries. Philadelphia, PA, Saunders, 1945 11. Winnie AP: Subarachnoid neurolytic blocks, in Waldman SD, Winnie AP (eds): Interventional Pain Management. Philadelphia, PA, 1996, pp 401-405 12. Stovner J, Endressen R: Intrathecal phenol for cancer pain. Acta Anaestehsiol Scand 16:17-21, 1972 13. Ischia S, Luzzani A, Ischia A, et al: Subarachnoid neurolytic block (L5-$1) and unilateral percutaneous cervical cordotomy in the treatment of pain secondary to pelvic malignant disease. Pain 20:139-149, 1984 14. Gerbershagen HU: Neurolysis: subarachnoid neurolytic blockade. ActaAnaesthesiol Belg 1:45-57, 1981 15. Ferrer-Brechner T: Epidural and intrathecal phenol neurolysis for cancer pain: Review of rationale and techniques. Anesthesiol Rev 8:14-20, 1981 16. Korevaar WC: Transcatheter thoracic epidural neurolysis using ethyl alcohol. Anaesthesia 69:989-993, 1988 17. Coombs DW; Potential hazards of transcatheter serial epidural phenol neurolysis. Anesth Analg 64:1205-1207, 1985 18. Mehta M, Salmon N: Extradural block. Confirmation of the injection site by x-ray monitoring. Anaesthesia 40:1009-1012, 1985 19. Racz GB, Jeavner J E: Letter Anesth Analg 65:822-823, 1986 20. Hughes JT: Thrombosis of the posterior spinal arteries. Neurology 20:659-664, 1970 21. Totki T, Kato "1",Nomoto Y, et al: Anterior spinal artery syndrome: A complication of cervical intrathecal phenol injection. Pain 6:99-104, 1979
37
In many cases, treatment of severe cancer pain remains a great clinical challenge. Spinal (epidural and subarachnoid) neurolysis remains the treatment of choice for a minority of patients with cancer-related pain. Because of the risk of severe complications many practitioners are reluctant to employ these techniques. When used appropriately, in carefully selected patients, they can be an effective means of relieving suffering. The purpose of this article is to review the techniques of subarachnoid and epidural neurolysis for the treatment of cancer-related pain so that more clinicians may become familiar and comfortable with its use. An understanding of the material presented should help the practitioner maximize benefit for his patients and minimize the possibility of comp!ications or litigation. Copyright 9 1997 by W.B. Saunders Company
ince the first description of intrathecal injection of alcohol ~,_,11by Dogliotti in 1931,.12 the use of spinal (subarachnoid and epidural) neurolytic nerve blocks has played an important role in the management of cancer-related pain. Understandable concern about associated complications and a lack of properly trained personnel has limited the full implementation of spinal neurolysis as a pain management tool. The development of optimal strategies for prescription of oral analgesics and the frequent use of spinal opioids has somewhat diminished the importance of axial neurolytic techniques in managing intractable pain. Nonetheless, these methods remain the treatment of choice for a minority of patients. Spinal neurolysis is dangerous, but when used appropriatel); in carefully selected patients, it is effective, inexpensive, quickly accomplished, and associated with a low incidence of severe morbidit): The purpose of this report is to review the techniques of subarachnoid and epidural neurolysis for the treatment of cancer-related pain. It should be emphasized that, as with all neurolytic procedures, great care must be taken in patient selection and in the performance of these techniques. Doing so will help the practitioner maximize benefit for his patients and minimize the possibility of complications or litigation.3 Ethyl alcohol and phenol are the two agents commonly used for spinal neurolysis. Each has advantages but both can be effectively employed for either subarachnoid or epidural bloc -los. Both have been associated with delayed development of painful neuritis, though the incidence of peripheral neuritis is more
From the Department of Anesthesia, University of Pennsylvania Medical Center, Philadelphia, PA. Address reprint requests to Ray H. d'Amours, MD, Department of Anesthesia, 1101 Penn Tower, University of Pennsylvania Medical Center, Philadelphia, PA 19103. Copyright 9 1997 by W.B. Saunders Company 1084-208X/97/0110-$5.00/0
32
common with alcohol. 4 The baricity of these agents relative to cerebrospinal fluid determines how they will spread when injected directly into the subarachnoid space. For intrathecal use, the choice of agent is usually determined primarily by whether a hyperbaric or hypobaric solution is preferred. Absolute (100%) alcohol is available in commercially packaged ampules of 1 or 5 mL (Hope Pharmaceuticals, Santa Ana, CA). With a specific gravity of 0.8, it is hypobaric relative to cerebrospinal fluid and will rise quickly after intrathecal injection. Injection of absolute alcohol is typically associated with brief but intense pain. Ahhough ethanol is quickly absorbed from tissues, there is little risk of significant systemic effect with the small doses used for spinal neurolysis, s Alcohol effectsneurolysis by extraction of cholesterol, phospholipid, and cerebroside and ca,uses precipitation of lipoproteins and mucoproteins. 6 Alcohol is irritating to mucosa but does not effect intact skin. Phenol for injection is not available commercially but can be prepared by most hospital pharmacies. Prepared solutions should be kept refrigerated and shielded from light. Tile maximum concentration of phenol in saline that can be achieved at room temperature is 6.7%. 5 For intrathecal use phenol is usually mixed with glycerine to form a hyperbaric solution in a concentration o[4% to 10%. It can also be mixed with radiographic dye material to form a hyperbaric contrast solution at concentrations above those previously mentioned. Preparations of phenol in glycerine are very viscous and are not easily administered through spinal needles. Injections can be facilitated by using tuberculin syringes, and by warming the container of neurolytic solution in a hot water bath before drawing the drug into a syringe. Phenol in glycerine cannot be readily injected through epidural catheters. For this application 5% phenol in saline or water can be used. Phenol possesses local anesthetic activity so, unlike alcohol, pain upon injection is brief, if occurring at all. Frequently though, patients will report a brief, warm, tingling sensation. Clinically used concentrations of phenol can cause significant necrosis if left in prolonged contact with the skin. Phenol causes nonselective neurolysis by denaturing proteins from axons. 7.8 The extent of degeneration is concentration dependent.
Patient Selection In order to minimize complications with an)' type of neurolytic procedure, great care must be taken to select patients carefully. Many patients are referred by physicians who erroneously believe that neurolytic blocks are permanent and without significant risk. This simple notion of "permanent nerve blocks" is very seductive to both physicians and patients but often must be resisted. Described below are the most com-
Techniques in RegionalAnesthesia and Pain Management, Vol 1, No 1 (January), 1997: pp 32-37
monly accepted indications and contraindications for performance of axial neurolytic procedures.
Procedure Subarachnoid Neurolysis With Phenol
Indications 1. Intractable cancer-related pain. The use of subarachnoid or epidural neurolysis for chronic nomnalignant pain is usually not indicated. 2. Failure of antitumor therapy to control pain. 3. Failure of more conservative analgesic therapies, including appropriate use of potent opioids, adjnnctire agents, and neuraxial drug deliver): A recent set of guidelines for cancer pain management has suggested the general use of neuraxial drug deliver), prior to neuroablation except in specific instances. 9 4. Limited life expectanc): Although it is often difficult to accurately predict life expectanc); these procedures are usually reserved for cancer patients anticipated to live less than a year. Neurolytic blocks cannot be relied upon to provide indefinite analgesia, and the consequences of~delayed complications are greater for those with long life expectancies. Deferring neuroablation until life-expectancy is short-term minimizes the risk of development of deafferentation pain. 5. Pain that is primarily somatic in origin. Visceral or neuropathic pain is less reliably treated with spinal neurolytic procedures. Is Other neurolytic procedures, such as celiac plexus block, may be more appropriate. Deafferentation type pain may be worsened by neurolyric blockade. 6. Localized pain. Subarachnoid neurolysis is usually reserved for pain that is restricted to two or three dermatomes, except in certain cases where bowel, bladder, and motor control have already been lost. Epidural neurolysis may be useful for pain that covers a somewhat broader area. Cordotomy may be indicated when life-expectancy is longer. 8 7. Pain that is shown to respond to a trial of local anesthetic blockade. Neural blockade with local anesthetic should be used prognostically to determine the possible efficacy of neuroablation. However, success with local anesthetics does not ensure successful neuroablation.X~
First, the nerve roots that innervate the painful area must be identified from standard dermatomal diagrams. Sclerotomal charts II call be used to identify the innervation of an area of bone. The interspace chosen for needle insertion is the level at which these roots emerge from the spinal cord. This level will be somewhat cephalad to the corresponding bony level (Fig 1). An adjustable operating room table should be used to simplify positioning of the patient. Flouroscopy can be used to facilitate needle placement and to show the flow and distribu-
Contraindications 1. Patient is unable to tolerate positioning for the procedure. This may be overcome with proper choice of neurolytic agent (see below) or appropriate use of anesthesia. 2. Patient (or family) is unwilling to tolerate the risk of associated side effects. 3. Pain that does not respond to nerve blocks performed with local anesthetic. Ahhough neural blockade with local anesthetic may not always accurately predict the outcome with neurolytic blocks, one should not proceed when they are ineffective. 4. Pain that is primarily sympathetically maintained or resuhing from deafferentation. 5. Diffnse, poorly localized pain. 6. Coagulopath):
SUBARACHNOID AND EPIDURAL NEUROLYSIS
Z
1 5 coc.I
Fig 1.-Diagram of the adult spinal cord and vertebral column showing the relationship between the origin of the nerve roots in the spinal cord and their emergence from the neural foramina of the spine. When performing subarachnoid neurolysis, the needle is inserted through the bony interspace which corresponds to the level of origin of the nerve root in the spinal cord. For instance, to block the nerve roots of L1 the needle should be inserted through the Tl1-12 interspace. (Reprinted with permission from Haymaker W, Woodhall B" Peripheral nerve injuries. Philadelphia, PA, Saunders, 1945.)
33
tion of injected contrast material. Sufficient sedation is given so that the patient is relaxed but cooperative and communicative. If absolutely necessar); general anesthesia can be provided; this will eliminate valuable communication with the patient about the effect of injected drug and increase the likelihood of complications. The patient is positioned in the normal lateral decubitus position for spinal puncture, with the painful side down (a relative disadvantage of using phenol). After antiseptic cleansing of the needle insertion site, local anesthetic is used to form a skin wheal and to anesthetize the appropriate interspace. A 22-gauge or larger spinal needle should be used as it is almost impossible to inject glycerine solutions through anything smaller. The needle is directed into the appropriate interspace with the bevel pointed downward until free flow of cerebrospinal fluid is observed. An effort should be made to direct the needle toward the dependent side of the dura; doing so will allow injected solution to directly onto ipsilateral nerve roots and not directly onto the spinal cord or cauda equina. When performing thoracic dural puncture, particularly at midthoracic levels, it may be easier to use a paramedian approach becaus~ of the steep angle formed by the spinous processes. When'performing dural puncture above the spinous level L2, care should be taken to avoid trauma to the spinal cord. The needle should be advanced slowly and no further than necessary to achieve free flow of cerebrospinal fluid (CSF). Once free flow of cerebrospinal fluid has been obtained, the needle stylet is replaced to stem the flow of CSF and the patient is carefully and slowly rotated posteriorly so that his or her back is at a 45 ~ angle relative to the floor (Fig 2). The table is flexed directly beneath the point of needle insertion (Fig 3). In this position the posterior (sensory) nerve roots of the painful side will be most dependent (Fig 4). Pillows and straps should be used to stabilize the patient comfortably in this position. After the patient is correctly positioned the stylet is removed and once again free flow of CSF is confirmed. A one cc tuberculin syringe containing the phenol solution is firmly attached to the needle hub. An initial dose of 0.2 mL is injected, and the patient is asked to describe the resulting
/
/
/
/
/
/
Fig 2. When performing subarachnoid neurolysis with hyperbaric solutions of phenol the patient should be rotated posteriorly 45 ~ to bring the posterior nerve roots into the most dependent position.
34
sensation. Often the patient will experience a brief feeling of tingling and warmth along a particular dermatome. This sensation can be used to assess the correct location of the needle. If the sensation is experienced above or below the desired dermatome, the needle should be withdrawn and reinserted at the appropriate level. Alternativel); and in the case of patients receiving general anesthetics, the distribution of administered drug can be checked by first injecting a small dose (0.1 to 0.3 mL) of hyperbaric nonionic contrast material. After the initial 0.2 mL of drug is given and correct needle position is determined, subsequent serial doses of 0.1 mL are injected. Several minutes should be allowed between these serial doses to permit repeated neurological evaluation, with concentration on motor and sensory function of adjacent dermatomes. The total dose of phenol given is limited by the risk of injury to collateral structures. Larger volumes are more likely to contact anterior or adjacent nerve roots. The greatest risk exists for nerve blocks perforlned near the origin of innervation to the upper and lower extremities--the cervical and lumbar segments. 12 The cauda equina may be particularly vulnerable to unintentional neurolysis so injections below L1 should be approached with great caution. It has been suggested that subarachnoid neurolysis below L1-L2 should not be a'ttempted unless bowel or bladder disturbances are already present. 15 Prudent maximum doses administered in a single treatment are 1.0 to 2.0,mL for injections made in the thoracic levels, and 0.5 mL in the lumbar or cervical areas. 8A3-15If serial examination between doses reveals sensory or motor blockade of adjacent levels, or if the patient reports subjective sensations in these areas, no further injections are made. When attempting to block several adjacent nerve roots, it is better to use separate needle insertions at each level than to try to cover all levels by injecting a larger volume of drug. Once injection is complete, 0.2 mL of saline is used to clear the needle of phenol before it is withdrawn. This will prevent sinus tract formation resulting from deposited neurolytic solution. The patient should be maintained in position for 20 to 30 minutes after injection. Bolsters, padding and, if needed, additional personnel should be used to prevent unintentional movement.
Subarachnoid Ethanol Injection The technique for subarachnoid block using alcohol is similar to that described for phenol, but because ethanol is hypobaric relative to CSF, the patient must be positioned differentl}: One advantage of alcohol used for neurolysis is that the patient can be positioned with the painful side up. From the lateral decubitus position the patient is rolled anteriorly forty five degrees (Fig 5). The table is flexed or a pillow is placed under the patient directly below the point of injection in order to curve the spine and move the sensor)' nerve roots to an uppermost position (Fig 6). The patient is then supported in this position with pillows and straps. Dural puncture at the appropri.ate level is performed, with the needle guided toward the upper half (painful side) of the dura. The needle bevel should be pointing upward. Once free flow of CSF is achieved, alcohol is injected in increments of 0.1 mL. Injection of alcohol evokes burning pain that is brief but intense. Reports from the patient about the exact location of this pain can be used to precisely guide needle placement. If the patient reports pain that corresponds to a sensor), level
o'AMOURS AND FERRANTE
Fig 3. Flexing the table directly beneath the point of needle insertion will make the targeted nerve roots more dependent. Hyperbaric solutionswill thereby flow toward the desired level.
above or below the one desired, tile needle can be withdrawn and repositioned. The patient must be warned to expect the pain of injection. The importance of quickly and accurately reporting the location of the pain should be emphasized. Assurance can be given that the pain will be brief and that it will likely diminish with subsequent injections. Prior injection of local anesthetic will diminish or eliminate the pain of injection but also ablate the ability to quickly identify misplaced drug. Once proper needle position has been confirmed, sequential injections of 0.1 mL are made. A total of 0.2 to 1.0 mL is injected to block one segment, lz,15 If desired, adjacent nerve roots can then be blocked by reinserting the needle at the appropriate interspace and repeating the procedure. One should not attempt to block more than three nerves at any one time. As with phenol, the patient is maintained in position for 20 to 30 minutes before moving.
/
/
/
/
/
/
Fig 4. A cross-sectional diagram showing a hyperbaric solution of phenol descending toward the posterior nerve root. The needle is inserted so that it pierces the dura toward the dependent side of the midline.
SUBARACHNOID AND EPIDURALNEUROLYSIS
Epidural Neurolysis AlthoughI less commonly used, epidural neurolysis does offer some.potential advantages over the subarachnoid route. The risk of dural puncture headache is minimized, and pain over a broader area can be treated,a6 with less risk of severe complications such as bowel and bladder dysfunction. Incremental treatment by repeated injection over several days through indwelling catheters allows a more gradual and controlled neurolysis. Treatment of bilateral pain is simplified. For some patients these advantages may be important but must be weighed against the specific disadvantages, as well as the extra time and expense associated with this techniqne. Serial injections administered over several days generally requires overnight stays in the hospital. Using patient position to control the flow and distribution of drugs injected into the epidural space is of limited value; unilateral blocks cannot be achieved reliably. Tile most common indication for this technique is for treatment of tumors causing widespread or bilateral pain in the chest or abdomen. Both phenol and alcohol can be used for epidural neurolysis. Alcohol is typically used in concentrations of 75 to 100%. Phenol is most commonly mixed with saline to form solutions of 5 to 6% although some practicioners will use concentrations as high as 15%. These higher concentrations require the addition of glycerine to the neurolytic solution. Typical doses are from 2 to 5 mL per injection, with injections repeated daily for 1 to 3 days as needed. 17,18 Epidural neurolysis is performed with the patient in the lateral decubitus position With the bed elevated 30 ~ head up. When phenol solutions are used, tile patient should be placed with the painful side dependent. For alcohol, it has been recommended, that the painful side be placed upward. In neithe'-Fcase should one expect the achievement of a unilateral block. Patients with bilateral pain can be placed supine, with 30 ~ head elevation after catheter insertion. The interspace is chosen based on the dermatomal distribution of the patient's pain. A standard nylon catheter is placed into the epidural space and the proper position confirmed with fluoroscopy after injecting a small amount (0.5 to 3.0 mL) of nonionic contrast solution. When performing epidural neurolysis, great care
35
x
j
,,
o~." Fig 5. Diagram showing proper patient position for use of hypobaric solutions of alcohol. The cross-sectional diagram shows the alcohol ascending toward the posterior nerve root. The needle is inserted so that it pierces the dura above the midline.
must be taken to ensure that the neurolytic solution is only injected into the epidural space and not into the subdural Or subarachnoid areas. The standard "loss of resistance" is not sufficient to confirm proper placement, 19 nor does aspiration through the catheter guarantee avoidance of subarachnoid or intravenous injection. If accidental injection into these areas occurs, the large volume of solution used can be expected to
cause significant complications. Therefore, use of fluoroscopy with contrast or some other method of visualization is essential to ensure correct needle position. Once proper position of the catheter has been confirmed, the neurolytic solution is slowly injected in increments of 0.2 to 0.5 mL, with pauses of several minutes between injections. Injection continues until the pain is relieved or the total
i, #
.sJ
Y f
W f ~
J
m
Fig 6. Pillows can be placed directly beneath the point of needle insertion to elevate the targeted solutions will then flow toward those roots,
36
nerve
roots. Hypobaric
D'AMOURS AND FERRANTE
amount of drug (2.0 to 5.0 mL) is injected. The catheter is securely fastened to the patient's back and the patient is maintained in position for 30 minutes. The procedure can be repeated daily until analgesia for 24 hours is achieved. Proper position of the catheter must be confirmed ever}, time before it is used for injection of neurolytic solutions. Using this technique, analgesia of a few weeks to a few months duration is usually achieved; the procedure can be repeated if pain returns.
Success and Complication Rates Determining which drugs and techniques have the highest rates of success or complication is made difficult by a lack of controlled studies comparing methods, a n d b y var},ing definitions of success. Good results may reasonably be expected for greater than 50~ of patients undergoing subarachnoid neurolysis. lz Gerbershagan's review of the literature 15showed that 40~ of patients receiving subarachnoid block with alcohol required more than one injection. In 2,125 subarachnoid blocks performed with alcohol, 12% bad tentporar}' complications and 2~ had permanent Ideficits. Most temporary deficits (51%) lasted less than 1 x~eek and 18% endured for more than 4 months. Bladder dysfunction or paresis/paralysis of an extremity were the most common contplaints. The risk of bowel and bladder dysfunction increases with injection into lumbar Or. sacral segments. In 1986 Racz reported performing 467 epidural injections of phenol without any significant complication. 2~ Korevaar performed epidural injection of alcohol in 36 patients and reported success (greater than 70~ pain relief) in 89~ with a mean duration of analgesia of 3.3 ntonths. 17 No serious long-term complications were observed. A wide range of complications can be seen after axial neurolysis. Minor complications include postdural ptmcture headache, pain at the needle or catheter insertion site and minor skin infections. In addition to the serious complications mentioned above, there is risk of meningitis and neuritis. Both anterior and posterior spinal artery thrombosis have been described as a result of neurolytic blockade. 21.22 As stated earlier, the risk of complication can be reduced by careful patient selection and strict adherence to recommended techniques. The ntinimum effective dose of neurolytic should always be used. Clear and detailed explanation of possible adverse outcome should be offered to the patient and their famil):
SUBARACHNOID AND EPIDURAL NEUROLYSIS
References 1. Dogliotti AM: A new method of block anesthesia: Segmental peridural spinal anesthesia. Am J Surg 20:107-109, 1993 2. Swerdlow M: Medicolegal aspects of complications following pain relieving blocks. Pain 13:321-31, 1982 3. Jain S, Gupta R: Neurolytic agents in clinical practice, in Waldman SD, Winnie AP (eds): Interventional Pain Management. Philadelphia, PA, Saunders, 1996, pp 167-171 4. Lipton S: Neurolysis: Pharmacology and drug selection, in Patt RB (ed): Cancer Pain. Philadelphia, PA, Lippincott, 1993, pp 427-442 5. Rumsby MG, Finean JB: The action of organic solvents on the myelin sheath of peripheral nerve tissue-ll (short-chain aliphatic alcohols). J Neurochem 13:1509-1511, 1996 6. Smith MC: Historical findings following intrathecal injection of phenol solutions for the relief of pain. Br J Anaesth 36:387-406, 1964 7. Swerlow M: Neurolytic blocks of the Neuroaxis, in Part RB (ed): Cancer Pain. Philadelphia, PA, Lippincott, 1993, pp 343-358 8. Berry K, OIszewski J: Pathology of intrathecal phenol in man. Neurology 13:152-154, 1963 9. Ferrante FM, Bedder M, Chaney HM, et al: Practice guidelines for cancer pain management. A report by the American Society of Anesthesiologists Task Force on Pain Management, Cancer Section. Anesth 84:1243-1257, 1996 10. Haymaker W, Woodhall B: Peripheral nerve injuries. Philadelphia, PA, Saunders, 1945 11. Winnie AP: Subarachnoid neurolytic blocks, in Waldman SD, Winnie AP (eds): Interventional Pain Management. Philadelphia, PA, 1996, pp 401-405 12. Stovner J, Endressen R: Intrathecal phenol for cancer pain. Acta Anaestehsiol Scand 16:17-21, 1972 13. Ischia S, Luzzani A, Ischia A, et al: Subarachnoid neurolytic block (L5-$1) and unilateral percutaneous cervical cordotomy in the treatment of pain secondary to pelvic malignant disease. Pain 20:139-149, 1984 14. Gerbershagen HU: Neurolysis: subarachnoid neurolytic blockade. ActaAnaesthesiol Belg 1:45-57, 1981 15. Ferrer-Brechner T: Epidural and intrathecal phenol neurolysis for cancer pain: Review of rationale and techniques. Anesthesiol Rev 8:14-20, 1981 16. Korevaar WC: Transcatheter thoracic epidural neurolysis using ethyl alcohol. Anaesthesia 69:989-993, 1988 17. Coombs DW; Potential hazards of transcatheter serial epidural phenol neurolysis. Anesth Analg 64:1205-1207, 1985 18. Mehta M, Salmon N: Extradural block. Confirmation of the injection site by x-ray monitoring. Anaesthesia 40:1009-1012, 1985 19. Racz GB, Jeavner J E: Letter Anesth Analg 65:822-823, 1986 20. Hughes JT: Thrombosis of the posterior spinal arteries. Neurology 20:659-664, 1970 21. Totki T, Kato "1",Nomoto Y, et al: Anterior spinal artery syndrome: A complication of cervical intrathecal phenol injection. Pain 6:99-104, 1979
37