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Neurosurg 89:359-365, 1998

Microsurgical C-2 ganglionectomy for chronic intractable

occipital pain

ANDRES M. LOZANO,M.D., PH.D., GRAHAM VANDERLINDEN, M.D.,

ROBERTBACH00, M.D., PH.D., AND PETER ROTHBART, M.D.

Division ofNeurosurgery, The Toronto Hospital, and Department ofSurgery, University ofToronto,

Toronto, Ontario, Canada; Mississauga Hospital, Mississauga, Ontario, Canada; and The Rothbart

Pain Management Clinic, Toronto, Ontario, Canada

Object. The authors evaluated the effectiveness of microsurgical C-2 ganglionectomy in 39 patients with medically refractory chronic occipital pain. In this procedure the neurons transmitting sensory inputs from the occiputare removed and, unlike peripheral nerve ablation, axonal regeneration is not possible.

Methods. The patients in this series had symptoms for 1 to 43 years. In 22 patients the occipital pain was causedby trauma; in 17 patients the pain was spontaneous. Pain relieffailed in 17 patients who had undergone a previousoccipital neurectomy or C-2 rhizo1ysis. Twenty-three patients experienced pain that was described as shock1ike,electric, shooting, jabbing, stabbing, sharp, or exploding (Group I). Eight patients described their pain as dull ,pounding, aching, throbbing, or pressure1ike (Group II). The patients underwent unilateral or bilateral C-2 openmicrosurgical ganglionectomies.The postoperative follow-up period ranged from 19 to 48 months. Nineteen patients experienced an excellent result90% reduction in pain). Pain caused by trauma or that described using Group I terms responded best to gan

glionectomy (80% good or excellent response). In contrast, the majority of the patients with nontraumatic pain or thosedescribed using Group II descriptors did not achieve favorable results.

Conclusions. The authors conclude that: 1) patients who suffer from chronic occipital pain after having sustainedinjury obtain worthwhile benefit from microsurgical C-2 ganglionectomy; 2) patients suffering from migraine, tension, and vascular headaches involving the occipital area are most often not helped by this operation; and 3) termssuch as "shock," "electric," "shooting," 'Jabbing," and "sharp" used to describe occipital pain predict a favorablepain outcome following a C-2 ganglionectomy.

KE Y WORDS • occipital neuralgia •anesthetic block • rhizotomy

CHRONIC pain syndromes in the region of the occiputhave multiple origins and a long and complicatedhistory of surgical intervention. One disorder, oc

cipital neuralgia, consists of a paroxysmal occipital painextending from the suboccipital region to the vertex of thehead.2 ,25 The quality of pain is frequently described as"sharp," "shooting," "stabbing," and "electric," terms thatare usually associated with a neuropathic cause.v" canbe hypothesized that the pain is the consequence of abnormal somatosensory processing caused by injury or dys

function of sensory neurons at the level of the perikarya or axons. In contrast, in occipital pain associatedwith migraine or tension headache, or in pain with a possible cervicogenic cause, pain is frequently described as"diffuse," "aching," "throbbing," or "pressurelike." Thesedescriptors are consistent with a nociceptive origin" andsuggest that the pain may arise from a primary pathological disorder in soft tissues or vascular and bony structuresthat lie within the dermatome.Numerous causes of occipital pain have been proposed

including congenital malformations," neoplasms," degenerative disease of the spine,3,9,10,31 and disorders of the

Neurosurg. / Volume 89/ September, ]998

spinal nerve root • ganglionectomy • headache •

peripheral nervous system caused by metabolic.v" inflammatory.v-" and infectious'? conditions. Of particular interest, as a consequence of its anatomical peculiarities, the

sensory neurons and axons may be unusually vulnerable to mechanical injury and/or entrapment. 1,19,23 Theganglion and nerve root, which lie outside the spinal canalbetween the arch of C-I and the lamina of may bevulnerable to crush injury during traumatic hyperextension. The most common example of this type of injury is"whiplash," which is caused by a rear-end motor vehicle

accident. 12 Furthermore, the ganglia and posteriorrootare in direct contact with the lateral edge of the posterioratlantoaxial ligament (Fig. I), which, when hypertrophied,is thought to cause ganglion entrapment.F-"-" Engorgement of the extensive venous plexus that envelopsthe ganglia has also been implicated as a potentialsource of compression injury" as have ectatic arteries."Peripherally, potential sites of entrapment are the points atwhich the greater occipital nerve passes through thesemispinalis capitis or the aponeurotic attachment of thesternocleidomastoid muscle at the nuchal line.1Surgical intervention for chronic occipital pain has been

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A. M. Lozano, et al.

Greater Occipital

FIG. Photograph displaying the surgical anatomy of the C-2 ganglion. Abbreviations: A = artery; Br. = branch;Inf. = inferior; Lat.= lateralis; M. = muscle; N. = nerve; Post. = posterior; Sup.= superior; Trans. = transverse. OriginallyFig. 2J reprinted from Wen HT, Rhoton AL Jr, Katsuta T, et al: Microsurgical anatomy of the transcondylar, supracondylar, and paracondylar extensionsof the far-lateral approach. Neurosurg87:562,1997.

undertaken when a headache is resistant to medical therapy and is no longer alleviated by nerve block(s) createdby local anesthetic and/or steroid medications. Surgicalapproaches include greater occipital nerve neurectomy, 15

percutaneous C-2 rhizolysis," C2-3 facet rhizolysis,"dorsal root rhizotomy,' CI-2 decompression," and C-2ganglionectomy.v-" The success of these procedures hasbeen variable. Occipital neurectomy is a simple procedure

and has the advantage of being easily performedwhile thepatient receives local anesthesia. Neurectomy, however,can be followed by axonal regeneration with the potentialfor pain recurrence and, thus, the results of occipital neurectomy can be disappointing. Early postoperative recurrence of pain is frequent- and the development of dysesthesia, hyperpathia, and allodynia, presumably due tosensory terminal regeneration and/or neuroma formation,has been reported." In addition, occipital neurectomyleaves the proximal C-2 elements, which can be the site ofthe pathological disorder, intact and free to generate ongoing dysfunction.

The C-2 ganglionectomy may offer certain advantagesover competing neurosurgical pain procedures. Dorsalroot ganglionectomy removes the primary sensory neu

ronal cell bodies. There is no possibility of axonal regeneration and no sparing of aberrant central axonal processes such as those entering the spinal cord through theanterior root,'> which could occur with posterior rhizotomy. The C-2 ganglion can be easily exposed microsurgically involving minimal bone resection. Indications forcervical ganglionectomy, however, are not well established and previous anecdotal reports involving few patients show variable results." To evaluate the safety andefficacy of C-2 ganglionectomy for the treatment of medically refractory chronic occipital pain, we have retrospectively analyzed outcome in 39 patients with neuralgic

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or nonneuralgic occipital pain who underwent this procedure. A preliminary report of this study was presented inabstract form.23

Clinical Material and Methods

Patient Population

Patients were referred for the treatmentof

their medically refractory occipital pain. Medical history was gathered and physical examination was conducted. Patientswere examined by means of cervical spine radiographsand magnetic resonance imaging of the craniovertebralarea at the discretion of the neurosurgeon.

Pain was evaluated preoperatively by using a visualanalog pain scale that rated each patient 's pain from 0 to10. Patients were asked to describe their pain. These descriptors were assigned to one of two groups on thepremise that the terms "shocklike," "electric," "shooting,""jabbing," "stabbing," "sharp," or "exploding" indicateda neuropathic origin (Group I) and that the terms "dull ,""pounding," "aching," "throbbing," or "pressurelike"(Group II) indicated a nonneuropathic cause. Most pa

tients had undergone a diagnostic local anesthetic blockprior to their referral to neurosurgery. This block was performed under fluoroscopic control by a radiologist whoused 1 ml of 0.25% marcaine deposited at the C-2 ganglion. The results of the block were not used in preoperative decision making.

Unilateral or bilateral C-2 ganglionectomy was performed in 39 patients with intractable occipital pain between 1990 and 1992. In all patients medical therapy hadfailed and in more than one-halfof the patients a previoussurgical intervention to alleviate the pain had failed. Theexclusion criteria for surgery were: 1) inadequate medica-

Neurosurg. / Volume 89/ September, 1998



Ganglionectomy at C-2 for occipital pain

tion trial; 2) psychiatric illness clouding the assessment ofpain; and 3) obvious structural or treatable cause of theoccipital pain. No patient in this series had a structurallesion demonstrated by imaging that was thought to beresponsible for the pain.

Surgical Procedure

The relevant surgical anatomy is depicted in the photograph shown in Fig. 1.Anesthesia was induced in the patients and they were orotracheally intubated and positioned prone with the head flexed in a Mayfield headrest.A midline incision extending from the base of the occiputto C-3 was made through the skin and subcutaneous tissues. The muscle attachments to the spinous processes andlaminae of C-l and were incised and retracted laterally. The vertebral artery was carefully avoided throughoutthe dissection. With the aid of the operative microscope,the robust epidural venous plexus enfolding the ganglion was incised and coagulated. was necessary toremove the inferior border of the C-l lamina to expose the

ganglion in approximately one-half of the cases. The

ganglion was identified as an area offocal increase ingirth proximal to the primary rami. The variable fuseddurallepineurial sleeve containing the dorsal rootlets of

the ganglion and the anterior rootlets was dissected proximally. Distally, the dorsal and ventral primaryrami of the root were followed laterally by dissectingthe venous plexus by using a right-angled hook, bipolarcautery, and sharp dissection. The neural elements immediately proximal and distal to the ganglion were cauterized and cut with a No. 15 blade and the ganglia wereexcised. In no case was there an apparent opening into thesubarachnoid space or a release of cerebrospinal fluid.Hemostasis was maintained using cautery and, in somecases, gelfoam. The fascia and skin were closed in a standard fashion. Bilateral ganglionectomies were performedin a similar manner. Patients were extubated in the operating room and taken to the recovery room.Following surgery, patients remained in the hospital for

approximately 2 days (range 1-10 days). They were seenat a follow-up visit 4 weeks after surgery and their caseswere followed for a median of 28 months (range 19-72months).

Evaluation ofSurgical Outcome

The response to ganglionectomy was divided into threecategories based on criteria set out preoperatively and byusing a pain visual analog scale and a questionnaire.Excellent pain rel ief was defined as greater than 90%;good pain reliefas 50to 90%; and failed pain reliefas lessthan 50%. We defined a satisfactory result as pain reliefgreater than 50%. Ganglia were submitted for histological examination. The outcome following ganglionectomy was evaluated using chi-square analysis. Statisticalsignificance was achieved at a probability value of lessthan 0.05.

Results

Characteristics of the Study Population

Thirty-nine patients with occipital pain underwent


ganglionectomy. There were 13 women (33%) with amedian age of 42 years (range 25-61 years) and 26 men(67%) with a median age of 43 years (range 35-60 years).The origin of the occipital pain was traumatic in 22patients (56%) and nontraumatic or spontaneous in 17 patients (44%). In the group that suffered trauma, 15patients(68%) were involved in motor vehicle accidents, the

mechanism of injury being rear-end vehicular collisionwith presumed flexion-hyperextension of the neck in 13patients. One patient who developed occipital shootingpain had been involved a motor vehicle accident that precipitated the need for a ventriculoperitoneal shunt procedure. The occipital pain was reported within days of theshunt introduction.The duration of symptoms prior to ganglionectomy in

the 22 patients with pain caused by trauma ranged from 1to 30 years (median 5 years). In the seven patients (32%)who did not suffer from an automobile accident-relatedinjury, the onset of the pain was related to falls in fourpatients. One patient reported a hair avulsion injury occurring in a bicycle factory, one patient was involved in a

motorcycle accident, and one had an upper body twistinginjury. Ganglionectomy was performed a mean of 6 years(range 1-30 years) after onset of symptoms in this groupof patients whose traumatic pain was not caused by anautomobile accident.The most common diagnosis in the 17 patients with

spontaneous occipital pain was migraine headache in nine(53%), with symptoms present for 5 to 30 years. Themedian time to ganglionectomy in this group was 15years. The remaining eight patients (47%) with nontraumatic occipital pain reported a relationship between theonset of pain and the following precipitating factors: allergic reaction, Meniere's disease, diagnostic lumbar spinalmyelogram, vaginal delivery of a full-term infant, cervicalanterior discectomy and fusion, and ankylosing spondylitis, each in one patient; and no identifiable precipitatingevent in two patients. These patients had symptoms ranging in duration from 13 to 43 years with a median time toganglionectomy of 18 years.In the 39 patients, the medical history was significant

for hypertension controlled by medication in two patients,peptic ulcer disease in four patients, and breast cancertreated by mastectomy in one patient. Three patients hadundergone spinal surgery before the onset of their painsyndrome: two had lumbar spinal fusion after trauma andone had anterior cervical surgery for a C-6 radiculopathy.Of the 39 patients in this series, three patients had undergone previous cranial procedures. In one of these cases,which involved ventriculoperitoneal shunt placement, the

occipital pain was likely related to the surgery and in theother two it was considered unrelated and classified asspontaneous.The occipital pain was located at the level of the upper

cervical spine and radiated over the occiput to the vertexin all patients. In 27 patients (69%) pain also radiated tothe supraorbital, retroorbital, or frontotemporal region. Of

these, 16 patients (59%) had a traumatic cause of theirpain syndrome. The pain was unilateral in 24 (62%) ofthe39 patients. Patients suffering from trauma were morelikely to have unilateral pain (16 [73%] of22). In contrastto patients with pain arising from trauma, patients with

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TABLE 1

Prior surgical management ofoccipital pain in 24 patients whounderwent microsurgical C-2 ganglionectomy

Procedure Outcome

C-2 rhizolysis

transient relief

no reliefincreased pain

facet rhizolysis

transient relief

no relief

occipital neurectomy

transient relief

no relief

transcutaneous stimulation

No. of Patients (%)

13 (33)

7 (54)

4 (31)2 (15)

16 (41)

8 (50)

8 (50)

4 (10)

3 (75)

1 (25)2 (5)

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pain due to spontaneous causes were more likely to havebilateral pain (nine [53%] of 17).

Descriptors ofPain Syndromes

In23 patients (59%), the occipital pain was described assharp, shooting, stabbing, jabbing, electric, or exploding(Group I descriptors). The causes of injury in this groupwere traumatic in 17 patients (74%) and spontaneous insix (26%). In eight patients (21%) the occipital pain wasdescribed as dull, aching, throbbing, or pressurelike(Group II descriptors). In these patients, the cause wasspontaneous in seven patients (88%) (six of seven patientsin the migraine subgroup) and traumatic in one (nonmotorvehicle accident [13%]). Of note, no patient whose occipital pain was precipitated by a motor vehicle accident wascategorized by Group II descriptors exclusively. A mixture ofthe descriptors was reported for eight patients (four[50%] who suffered from traumatic injury and four [50%]

whose pain was spontaneous).

Diagnostic Studies andPrevious Treatment

Radiological studies were available for 25 patients, 13of whom exhibited abnormalities on cervical spine x-rayfilms. The most common findings were mild-to-moderateosteoarthritic changes in the facet joints and degenerativedisc disease. One patient had undergone a cervical fusionprior to the injury that precipitated the occipital pain.Almost all patients responded to local anesthetic thera

py prior to ganglionectomy, although the duration of

effect was highly variable. A diagnostic ganglionicblock consisting of 1ml of 0.25% marcaine injected underfluoroscopic guidance had a positive effect 50% pain

relief) in 38 patients (97%).Sixty-two percent of the patients (24 of39) had under

gone at least one surgical procedure as treatment foroccipital pain before they underwent ganglionectomy(Table 1). Percutaneous rhizolysis had been performed in 13 patients (33%), in equal frequency for thetraumatic and spontaneous pain groups. The outcome of

rhizolysis was variable. Seven patients (54%) reported transient reduction or relief of pain lasting between 3weeks and 6 months. Four patients (31%) had no relief oftheir pain and two patients (15%) reported an increase inpain after rhizolysis. Percutaneous facet joint rhizoly-

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FIG. 2. Bar graph depicting responses to C-2 ganglionectomy.The trauma pain group included 22 patients and the spontaneouspain group 17 patients. Results are expressed as percentages oftotal patients in each group who achieved the following responses:excellent 90% pain relief); good (50-90% pain relief); orfail(ed) treatment 50% pain relief).

sis had been performed in 16 patients (41%), an equalnumber of trauma and spontaneous pain patients. Eightpatients (50%) reported no relief from pain and an equalnumber reported at least a transient decrease in pain.

Ganglionectomy Procedures andResults

Twenty-four patients (62%) underwent unilateral (12right-sided and 12 left-sided ganglionectomy) and 15(38%) bilateral ganglionectomy. Patients with spontaneous occipital pain were more likely to have bilateralsurgery (nine [53%] of 17), whereas 62% of the patientswhose pain was caused by trauma had unilateral symp

toms and unilateral surgery. There were no instances ofintraoperative or postoperative cerebrospinal fluid leaksand the brisk bleeding that was often encountered from theepidural venous plexus enfolding the ganglion wasreadily controlled by a combination ofbipolar coagulationand application of gelatin sponges and gentle pressure.There were no operative complications in any patient.Histological analysis of the surgical specimens revealednormal ganglia and nerves in 36 patients. In two patients,mild neuronal loss and mild fibrosis were noted.The results of ganglionectomy are shown in Fig. 2.

Overall 19 patients experienced an excellent result90% reduction in pain), seven patients had a good result(50-90% reduction in pain), and 13 patients experiencedtreatment failure 50% reduction). Greater than 90%

reduction in occipital pain was achieved in 64% oftraumapatients compared with 29% of patients in whom thecause was nontraumatic or spontaneous (p 0.05). Theprocedure was clinically successful 50% reduction inpain) in 82% ofpatients with occipital pain resulting fromtrauma, which was significantly higher (p 0.05) than thepercentage of patients with spontaneous origin (47%).Seventy-three percent of patients involved in a motorvehicle accident reported greater than 90% pain rel iefcompared with 43% ofpatients who suffered trauma fromanother cause (p 0.05; Fig. 3 upper). An excellent resultwas achieved in only 11% of patients who suffered from





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FIG. 3. Bar graphs showing responses to C-2 ganglionectomywith respect to the role ofpain origin. Upper: Traumapain group:15 patients in the motor vehicle accident (MYA) subgroup andseven patients in the nonmotor vehicle accident (other) group.Lower: Spontaneous pain group: nine patients suffering frommigraine and eight patients with pain from another nontraumaticcause. Results are expressed as percentages oftotal patients in each

group who achieved the responses excellent, good, or fail(ed)treatment defmed in the legend to Fig. 2.

migraines compared with 50% ofpatients with pain due toa spontaneous cause other than migraine (p 0.05; Fig. 3lower). The highest failure rate was found in patients withmigraines (67%), double the rate in patients with nonmigraine spontaneous syndromes and more than triple that inpatients whose pain was due to trauma.Response to ganglionectomy analyzed by patient

grouping according to the use of pain descriptors is presented in Fig. 4. Patients who described their pain asshooting, stabbing, burning, or exploding (Group I descriptors) had a 78% success rate, with 70% reporting an

excellent result. In contrast, patients whose pain was characterized as dull, aching, or throbbing (Group II descriptors) had a 63% failure rate and none of these patientsachieved an excellent result with ganglionectomy. Use of

both descriptor groupings predicted a 63% success rate (250% pain relief).Although the anesthetic block had a positive effect

in 97% of the patients in this series, ganglionectomy wasalso undertaken in the one patient who did not respond tothe block because the occipital pain was temporally related to a rear-end motor vehicle accident. Interestingly, ganglionectomy had no effect on her pain syndrome.


FIG. 4. Bar graph showing responses to C-2 ganglionectomywith respect to the role of descriptors. There were 23 patients inGroup (pain described as sharp, stabbing,jabbing, electric, and soforth) and eight patients in Group II (paindescribed as dull,pounding, aching, throbbing, pressurelike). Results are expressed as percentages of total patients in each group who achieved the responses excellent, good, or fail(ed) treatment defined in the legend to

Fig. 2.

A potential complication ofthe surgical management ofoccipital pain is the production of a deafferentation syndrome, characterized by hyperpathia and allodynia in the

or dermatome. In the current series, seven patients presented with sensory loss and a component of

burning pain suggestive of a deafferentation syndromeprior to ganglionectomy. Four of 13 patients developed deafferentation pain after percutaneous rhizolysis (incidence of 31%), one after occipital neurectomy,and one after alcohol injection into the occipital nerve; inone patient deafferentation pain was an initial feature of

the pain syndrome. Among these cases, six were relievedby ganglionectomy. At last follow-up evaluation, only onecase of deafferentation occurred as a result of ganglionectomy (2.6% incidence).

Discussion

The present study shows that ganglionectomy provides good-to-excellent reduction in chronic occipital painin selected patients. The character of the pain and thewords used to describe the pain are important predictorsof the response to ganglionectomy. Patients whodescribed their pain by using neuropathic terms, such asshocklike, electric, shooting, jabbing, stabbing, sharp, orexploding, had better results than those who described

their pain in terms that suggest nociceptive activation,such as aching, pounding, throbbing, or pressurelike.More than 80% of patients with trauma as a precipitant

achieved good or excellent results. In contrast, in patientswith nontraumatic occipital pain the results were poorer.More than 50% ofthese patients did not experience worthwhile improvement (> 50% reduction in pain) with theirsurgery. This was particularly the case in patients with ahistory ofmigraine headaches in whom surgery produceda satisfactory result in only 30%.The majority of patients in this series had undergone a

previous surgical attempt at treating their pain. Previous

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failure to respond to surgical treatment of occipital painrhizolysis, occipital neurectomy, or facet denerva

tion) was not a predictor of the response to ganglionectomy.In those cases in which ganglionectomy produced

pain relief, it was immediate and generally sustained forthe follow-up period. Similarly, those patients who did not

respond experienced immediate treatment failures ratherthan an initial response that was subsequently lost. Thereasons for failures of ganglionectomy are not clear.The most likely explanation is the persistence ofpain generators outside the dermatome. The immediate timecourse of the surgical failures argues against pain recurrence secondary to neural sprouting from adjacent nonlesioned neural elements.

is clear that the response to a nerve root local anesthetic block cannot be used to predict the outcome ofganglionectomy and we cannot recommend its use, aspracticed in this study, in surgical decision making. Howcan one reconcile the apparently contradictory results inthe present series: 38 of 39 patients reported significantrelief of occipital pain with a nerve root block; how

ever, only 26 of the 38 patients reported satisfactory painrelie f after ganglionectomy? One possibility is thatthe local anesthetic block may extend beyond the intended sites. Spread to adjacent nerves, particularly the firstand third cervical nerves and fibers of the semicapitalismuscle, is possible. Alternatively, it is possible that theeffect of the local anesthetic medication is exerted in partat the level of the spinal cord and not just the peripheralnerve. The clinical effectiveness of systemic marcaine- orxylocaine-mediated analgesia at doses below those necessary to produce conduction block in A-a or C fibers iswelldocumented." In addition, the effects ofoccipital anesthetic blocks can, in some cases, far outlast the expected biological life of the anesthetic agent.13 The mechanism by

which these analgesic effects are produced is poorlyunderstood. has recently been reported that in certainpatients with pain, close to 60% ofthe efficacy ofthe localanesthetic nerve block in patients may be due to a placeboeffect."

Conclusions

The results of the present study demonstrate that thesyndrome of chronic occipital pain must be subdivided byorigin to predict more accurately the response to ganglionectomy in patients who have experienced failed medical and/or prior surgical therapy. From our data, it can bepredicted that ganglionectomy will be successful (250% reduction in pain) in 80% of patients with chronic

occipital pain with an antecedent history of trauma. Patients who suffer whiplash injury from a rear-end motorvehicle accident can expect a 70% chance of reducingtheir pain by greater than 90%. This is in contrast to an11% chance of the same degree of pain reduction inpatients with migraine headaches. This disparity in outcome may, in part, be reflected in the underlying pathophysiological mechanisms ofthe pain. Patients with whiplash injury use neuropathic descriptors to characterizetheir pain, whereas patients with migraines use the classicnociceptive descriptors. As shown here, successful outcome after ganglionectomy approaches 80% when

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neuropathic descriptors are used, but is less than 40% forpatients describing nociceptive pain. Patients with occipital pain of traumatic origin, in particular those withwhiplash injury who describe neuropathic pain, are mostlikely to benefit from ganglionectomy.

Acknowledgment

We thank Dr. R. R. Tasker for his critical review of the manuscript.

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Manuscript receivedNovember 19, 1997.Accepted in final form May 19, 1998.Dr. Lozano is a Medical Research Council of Canada Clinician

Scientist.Address reprint requests to: Andres M. Lozano, M.D., Ph.D., Di

vision of Neurosurgery, Toronto Western Hospital, 399 BathurstStreet, Toronto, Ontario, M5T 2S8 Canada. email: [email protected].

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Dolor Cervical