Received: 14 July 2002Revised: 10 August 2002Published online: 14 December 2002© Springer-Verlag 2002

Abstract Object: The authors triedto reveal some unique features of li-pomeningomyelocele (LMMC), in-cluding clinical presentation, factorsprecipitating onset of symptoms,pathologic entities of LMMC associ-ated with tethered cord syndrome,and surgical outcome in LMMC pa-tients. Methods and results: Seventy-five patients with LMMC were en-rolled in this study. Neuro-imagingand intraoperative findings allowedclassification of LMMC into threetypes: type I, type II, and type III.The patients were divided into twogroups by age: A (51 patients), frombirth to 3 years, and B (24 patients),from 3 to 24 years. For prevention ofretethering of the cord, a mega-duralsac rebuilding procedure was per-formed in 15 patients. During amean postoperative follow-up periodof 4 years, the surgical outcome wassatisfactory in terms of improvedpain and motor weakness, but disap-pointing with reference to the resolu-tion of bowel and bladder dysfunc-tion. Among these 75 patients withLMMC, preoperative deficits wereimproved after surgery in 29 (39%),

remained stable in 28 (37%),changed slightly in 13(17%), andworsened in 5 (7%). Patients ingroup A achieved better outcomesthan those in group B. Depending onthe type of lesion, patients with typesI and II LMMC have better out-comes than those with type IIILMMC. Finally, retethering of thecord with neurological deteriorationoccurred in 4 (5.3%) of the 75 pa-tients, but no retethering was foundin the 15 patients who were recentlytreated with a mega-dural sac re-building procedure. Conclusion: Ourdata continue to support the opinionthat early diagnosis and optimal sur-gery are still essential for the treat-ment of patients with LMMC, sincethere is a high likelihood of residualneurological functions that can bepreserved. Based on our surgical ex-perience of untethering and decom-pression of lipomas, a mega-duralsac repair is useful to prevent reteth-ering of the cord.

Keywords Lipomeningomyelocele ·Tethered cord · Urodynamic function ·Retethering

Childs Nerv Syst (2003) 19:23–29DOI 10.1007/s00381-002-0674-0 O R I G I N A L PA P E R

Joon-Ki KangKwan-Sung LeeSin-Soo JeunIl-Woo LeeMoon-Chan Kim

Role of surgery for maintaining urologicalfunction and prevention of retetheringin the treatment of lipomeningomyelocele: experience recorded in 75 lipomeningomyelocele patients

Introduction

Lipomeningomyelocele (LMMC) is one of the maincauses of the tethered cord syndrome (TCS) [5, 9, 10, 15,18, 19, 23]. Symptoms of LMMC are mainly related totraction on the lower spinal cord and include motor defi-cits, spasticity, sensory disturbance, urodynamic and uro-

rectal dysfunctions, and secondary orthopedic deformi-ties. The natural course of the disease is usually poor:lower spinal cord function gradually deteriorates withoutappropriate treatment of tethered cord [9]. Release of atethered cord with anatomical reconstruction of the vari-ous tissue layers during infancy or early childhood, onthe other hand, has been shown to prevent this symptom-

J.-K. Kang (✉) · K.-S. Lee · S.-S. JeunI.-W. Lee · M.-C. KimDepartment of Neurosurgery, Kangnam St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, 505 Banpo-dong Seocho-gu, Seoul 137–040, Koreae-mail: jkkmd@cmc.cuk.ac.krTel.: +82-2-5901342Fax: +82-2-5944248

atic progression [9, 14]. However, even after an initiallysuccessful untethering procedure, many patients exhibitradiological evidence of adhesion of the residual lipomato the dural sac [3, 6, 21]. Also, it is well known that notall patients experience functional improvement follow-ing surgery for LMMC with TCS. These unfavorable re-sults may be due to damage to the spinal cord during theoperation or to retethering of the spinal cord by the sur-rounding scar tissue. Various methods have been devel-oped by many pediatric neurosurgeons to prevent post-operative retethering. We have used a mega-dural sac re-pair procedure after untethering and have obtained favor-able results with this. In the present study, we tried tofind unique features of LMMC in terms of clinical pre-sentation, precipitating factors for onset of symptoms,various pathologic entities, and surgical outcome from along-term follow-up review of 75 LMMC patients. Wealso tried to find the factors involved in postoperative re-tethering.

Materials and methods

From 1980 to 2001, 115 patients with TCS were treated at theKangnam St. Mary’s Hospital. They included 75 patients whowere operated on for a condition diagnosed as LMMC, and thesewere enrolled in this study. Clinical characteristics, radiologicalfeatures, pathological classifications and surgical outcome weresummarized by retrospective analysis. In cases of lumbosacralLMMC we classified the patients into three types according to theradiological features and operative findings: type I, “caudal type”;type II, “dorsal type”; and type III, “transitional or mixed type”(Fig. 1).

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Fig. 1 Classification of lipomeningomyelocele. Type I caudaltype, with lipoma terminating the caudal portion of the cordthrough the dural defect; type II dorsal type, with lipoma attachedto the placode and neural elements suspended from the undersur-face of the placode; type III transitional or mixed type, where lipo-ma is mixed with neural elements and placode through the duraldefect

Fig. 2a, b Schematic drawings of the operation. a After debulkingof lipomas, reconstruction of dura with Gore-Tex (G) was per-formed. b A mega-dural sac was constructed to maintain the CSFcirculation (arrows) and prevent retethering of the cord

Fig. 3a, b MRI of a 2-month-old girl with LMMC. a Preoperativesagittal TI-weighted MRI scan demonstrating intraspinal lipomawith tethered spinal cord. b Postoperative sagittal T1-weightedMRI scan demonstrating untethered spinal cord within a capaciousdural sac

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All these patients were treated initially in our department, andthe operative procedures were mostly consistent in these series asfollows. An effort was made to delineate the lipoma extradurallyand trace it back until the point of insertion into the spinal cordwas exposed. The lipoma was debulked microsurgically to permitthe conus to move more freely within the spinal canal, and anytethering bands were identified and divided. The pia was approxi-mated by suturing with 8-0 prolene over the residual lipoma on thesite of placode. Finally, a mega-dural sac was constructed withlyophilized dura or Gore-Tex, with the purpose of maintaining theCSF circulation and preventing retethering of the cord(this proce-dure was performed in 15 of the patients referred most recently)(Fig. 2). As a result, this procedure allowed the spinal canal to ex-pand in the posterior direction, creating a circumferentially widespace capable of accommodating the neural element within the du-ral sac (Fig. 3).

We also divided the patients into two groups by age: group A,less than 3 years old; group B, 3–24 years. For the assessment ofsurgical outcomes, patients were graded as clinically improved,stable, mildly changed (only mild voiding difficulty postoperative-ly), and worsened. We conducted pre- and postoperative urody-namic studies in 17 patients to evaluate the functional outcome(Fig. 4).

Results

This patient population was made up of 40 male and 35female patients. There were 51 patients under 3 years old(group A) and 24 over 3 years old (group B). The medi-an follow-up period was 4 years (range 6 months to18 years). Age distribution and types of the lesions aresummarized in Table 1.

Initial clinical symptoms and signs were as follows:diffuse and nondermatomal leg pain referred to the ano-rectal region was the most common presenting symptom,and sensorimotor deficits in the lower extremities andbladder and bowel dysfunction were also common find-

ings (Table 2). Patients with type III LMMC had moreneurological deficit than the patients with type I LMMC.

Preoperative urodynamic studies (UDS) were per-formed in 17 patients (8 in group A, 9 in group B), 11 ofwhom (3 in group A, 8 in group B) had urodynamic dys-function and 6 (5 in group A, 1 in group B) had normalurodynamic function.

Among these 75 patients with LMMC, preoperativeneurological deficits improved after surgery in 29 pa-tients (39%), remained stable in 28 (37%), changedslightly in 13 (17%), and worsened in 5 (7%) (Table 3).Patients in group A obtained better outcomes than thosein group B (Table 4). According to the type of lesions,patients with types I and II LMMC obtained better out-

Table 1 Age distribution and types of lesion in 75 lipomeningo-myelocele (LMMC) patients

Age distribution All patients By type of lesion

N=75 I: N=25 II: N=32 III: N=25n n n n

Birth to 1 month 8 1 6 12–6 months 20 7 9 47–12 months 11 3 6 213 months 12 6 4 2

to 3 years4–6 years 4 1 2 17–10 years 7 5 1 111–16 years 8 2 2 417–25 years 5 2 3

Table 2 Clinical symptoms and signs in 75 patients with LMMC

Symptoms and signs No. of patients Type of lesion

I II III

Sensory deficits 30 5 12 13Motor weakness 34 9 11 14Pain in back, legs 44 9 18 17Incontinence 38 8 13 17Increased reflex 20 5 7 8Diminished reflex 37 7 14 16Deformity of foot 28 7 8 13

Table 3 Surgical outcomes in 75 patients with LMMC by clinicalgrade

Type Improved Stable Mild change Worse (n) (n) (n) (n)

I (N=25) 17 7 1II (N=32) 11 12 8 1III (N=18) 1 9 4 4Total 75 29 (39%) 28 (37%) 13 (17%) 5 (7%)

comes than those with type III LMMC. Improvement orstable disease was observed in 24 out of 25 patients withtype I and 23 out of 32 patients with type II LMMC, butonly 10 out of 18 patients with type III showed improvedor stable disease, and the symptoms worsened in 4 pa-tients.

Postoperative UDS were performed in 13 patients,and the mean follow-up period was 2.5 years. Postopera-tively, 3 patients showed an improvement in bladderfunctions (2 in group A, 1 in group B), 9 patients showedno change in bladder dysfunction (4 in group A, 5 ingroup B), and 1 patient in group B had aggravated blad-

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Fig. 4a, b Urodynamic studies(UDS) of a 2-year-old girl withLMMC. a Preoperative UDSshows decreased complianceand abnormal reflex. b UDSperformed 2 months postopera-tively shows improvement ofcompliance and disappearanceof abnormal reflex. Pdet detru-sor, Pabd abdominal pressure,Pves bladder pressure, Vinf vol-ume infused

Table 4 Comparison of surgical outcomes in groups A and B

Outcome Group A (N=51) Group B (N=24)n (%) n (%)

Improved 25 (49%) 4 (16%)Stable 21 (41%) 7 (29%)Mildly changed 4 (7.8%) 9 (37.5%)Worse 1 (1.9%) 4 (16%)

der dysfunction after surgery. Complications related tooperations were postoperative CSF leakage (5 cases,6.7%) and newly developed neurological deficits (6cases, 8%). Four patients (5.3%) required reoperation be-cause of subsequent symptomatic retethering. Neither re-tethering nor new neurological deficits occurred in the15 patients who underwent mega-dural sac grafting pro-cedures. The surgical outcome was satisfactory in termsof improvements in pain and motor weakness, but disap-pointing with reference to resolution of bowel and blad-der dysfunction.

Discussion

Hoffman et al. [9] have stressed the importance of earlytreatment of LMMC patients, because the likelihood ofavoiding or reversing a neurological deficit by surgicaltreatment is greatest early on and decreases with age,presumably indicating that with delayed treatment,chronic traction on the spinal cord ultimately leads to ir-reversible deficits. McLone et al. [15], Lamarca et al.[14], and Herman et al. [8] have also recommended earlysurgical intervention for LMMC. In agreement withthese authors, we advocate repair of these lesions within1–6 months of birth or as soon as they are detected in pa-tients referred after this age.

Chapman [5] classified intraspinal lipomas into threetypes: caudal, dorsal and transitional, which were relatedto the attachment pattern of the lipoma on the caudalportion of the cord. Many authors use LMMC as a gen-eral term indicating all variations of intraspinal or lum-bosacral lipomas [9, 10, 22, 26]. Arai et al. [1] defined aclassification scheme with five types of lumbosacral li-pomas:

1. Dorsal type2. Caudal type3. Combined type4. Filar type5. Lipomeningomyelocele

These authors define LMMC as one of the subtypes oflumbosacral lipoma, and classify it as follows: type I(caudal), lipoma terminating the caudal portion of thecord through the dural defect; type II (dorsal), lipoma at-tached to the placode and neural elements suspended be-low the placode; and type III (transitional or mixed), li-poma mixed with neural elements and placode throughthe dural defect.

The aims of surgery are to remove the fibroadiposemass, to relieve the tethering effect on the spinal cord, topreserve neural tissues, and to prevent retethering of thespinal cord. Basic surgical procedures are the same foreach type of lipoma, but the degree of difficulty of thesurgery is different for each type. Arai et al. [1] reviewed

their large series of patients with lumbosacral lipoma andreported that caudal and filar lipomas had simple attach-ments and tethered the caudal end of the cord, so that un-tethering of the spinal cord could easily be achieved.However, complete untethering was often not achievedbecause of injury to the functional neural elements, espe-cially when an LMMC of the combined type was con-cerned, in which case surgery is accompanied by somerisks. According to Pierre-Kahn et al. [20], lipomas ofthe conus are compatible with dorsal and combined typesof lipomas: lipoma of the filum, in which surgery isharmless and beneficial, and lipoma of the conus, forwhich surgery involves considerable risk. We have foundthat surgery is relatively simple and its results ratherbeneficial in types I (dorsal) and II (caudal) LMMC,while it involves considerable risk in type III (transition-al or mixed) LMMC, especially when its aim is exten-sive separation of the lipoma from the attached spinalcord.

Without therapy or with inappropriate therapy, theneurological function of patients deteriorates with in-creasing age and the patients finally become incapacitat-ed. Fixation and/or tethering of the spinal cord and rootsare undoubtedly the major causes of worsening. Thesefactors probably explain the late or slowly progressivedeterioration noted in these patients. Koyanagi et al. [13]reviewed a lumbosacral lipoma series, finding that in atleast 38% of the patients with urinary symptoms the on-set of these had been quite late, after the establishment ofbladder control, and that 89% of the patients with motordeficits had first been seen to have motor problems a rel-atively long time after birth. Previous clinical studies [9,10, 19] also demonstrated progressive neurological defi-cits with age in this disorder. Bulsara et al. [4] reviewedtheir series of lipomeningomyelocele, intraspinal lipomaand filum terminale lipoma patients; they found that allgroups had the most significant improvement in motorfunction after surgery. Greater improvements in pain,bladder function, and sensation were observed followingsurgery for lipomas of the filum terminale. The leastmarked improvement in these groups was seen in theLMMC group [4].

It is important to emphasize that the goal of the opera-tions in this study was to untether the cord and resect asmuch of the lipoma as possible without injury to the cordand nerve roots. In addition, it is important to restore thedural sac to prevent postoperative retethering and tomaintain a normal CSF circulation space. Bulsara et al.[4] report that early operative intervention leads to agood outcome and that younger patients tend to improvemore than older patients. In our series, group A patientsshowed less pronounced neurological deterioration aftersurgery than did group B patients.

The exact mechanisms of progressive neurological de-terioration in patients with lumbosacral lipoma have notbeen fully clarified. Tethering of the spinal cord and com-

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pression by the lipoma are thought to be responsible forneurological deterioration [16]. It is well documented thatthe spinal cord and canal are similar in length in early fe-tal life but the conus medullaris ascends rapidly in the la-ter stage of intrauterine development. Further ascent to alevel adjacent to L-1 and L-2 is noted by the 2nd postna-tal month in the normal child [10]. An arrest of the nor-mal ascent could produce tension with local ischemia ofthe lower spinal cord and nerve roots [2, 11, 25]. Lipomaprevents the normal ascent of the spinal cord by tetheringand causes neuronal dysfunction. Acute deteriorationmay occur following extreme flexion of the spinal col-umn, as reported by Pang and Wilberger [17].

Our results indicate that the type of lesion of the lipo-ma is related to the preoperative neurological status.Chapman et al. [5] reported that 36% (5/14) of patientswere improved, 43% (6/14) unchanged, and 21% (3/14)worse after surgery for intraspinal lipoma patients. In theseries of Pang et al. [17] 29% (6/21) were improved,67% (14/21) were unchanged and 4% (1/21) were worse.However, in Harrison et al.’s [7] series of lumbosacral li-poma patients the authors reported a good outcome: 65%(13/20) improved and 35% (7/20) were unchanged,while Koyanagi et al. [12] obtained improvement in34.6% (9/26) of symptomatic patients. In our own seriesof 75 patients with LMMC, 39% (29/75) were improved,in 37% (28/75) disease remained stable, there was mildchange in 17% (13/75), and 7% (5/75) were worse aftersurgery.

The prevalence of urological dysfunction in TCS isextremely high. Vernet et al. [24] investigated the urody-namic studies in the management of children with teth-ered spinal cord. They evaluated the results of pre- andpostoperative urodynamic studies in their 25 patients.Ten of 15 patients who had preoperative urological dete-rioration had experienced improvement or stabilization.With respect to urodynamic studies, there were signifi-cant increases in total and pressure-specific bladder ca-pacities following untethering. In our series, among 13

patients in whom postoperative urodynamic studies wereperformed, 2 patients in group A (2/6) and 1 patient ingroup B (1/7) obtained improvement of bladder dysfunc-tion. In 1 patient with worsened bladder function this isthought to have resulted from mechanical and vascularinsults to the cord during the operation.

Retethering usually resulted from postoperative duraladhesion, which is undoubtedly common after LMMCrepair [21, 23]. We devoted some thought to wonderingwhat we could do during the primary repair to preventrecurrence of tethering. Closure of the meningeal com-ponents, pia mater, pia arachnoid and dura mater is es-sential for prevention of retethering. Attempted mega-dural sac grafting on the dural defect area to maintain theCSF flow suspended the neural elements. Posterior ex-pansion of the spinal canal can create a wide space to ac-commodate the neural elements within the subarachnoidspace. In our series, 4 patients (5.3%) who underwentconventional dural repair experienced retethering of thecord. However, there was no retethering in 15 patients inwhom mega-dural sac repair was performed.

Conclusions

Our data continue to support the opinion that early diag-nosis and adequate release of the tethered cord are of keyimportance to successful management of patients withLMMC. The improvements in pain and motor weaknessafter surgery were satisfactory, but the resolution ofbladder dysfunction was disappointing in older patients.With reference to the type of lesion, a better outcomewas noted in patients with types I and II LMMC than inthose with type III LMMC. For the prevention of reteth-ering of the cord and promotion of functional recoveryfrom neurological deterioration, we would like to em-phasize the importance of a well-planned mega-duralgraft procedure in the dural defect area in every primarysurgical intervention.

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