14 The Surgi cal Technologist OCTOBER 2005 Cauda Equina Lipoma Resection with Spinal Cord Untethering in an Adult JEFFR EY J CORTESE, CST, BHSA

ormally the spinal cord is a freely Spi nal cord anatomy moving structure within the spi- The spinal cord is a cylindrical bundle of nerve nal canal. The term “tethered spi- pathways that is 42 to 45 cm long and 2.5 cm Nnal cord” describes a condition in wide in the normal adult. Its rostral (cranial) end which the spinal cord is abnormally fastened is continuous with the brain stem, whereas the to an immovable structure, such as a lipoma, distal end forms a conical tapering, the conus vertebra, dura or skin. Although often initially medullaris. This is usually located at the border asymptomatic, any lesion that tethers the spi- of the first lumbar vertebrae. On occasion, it may nal cord puts the individual at risk of eventual reach only to the body of T12 or extend to the L2 neurological dysfunction. This dysfunction may level in the adult. From the conus medullaris, the occur during periods of axial growth in children lumbar and sacral nerve roots descend in a bun- or during periods of adipose deposition, which dle known as the cauda equina. The most termi- in the case of tethering may cause lipomatous nal portion of the spinal cord is the filum ter- structures to enlarge. Although the signs and minale. This connective tissue filament extends symptoms may include pain, most often they from the tip of the conus medullaris and attaches include loss of control of bowel or bladder, loss to the first segment of the coccyx (Figure 1). At of sensation in the feet, or motor dysfunction in birth, the conus medullaris is located near the L3 the sacral and lower lumbar segments. Surgical vertebrae; in the adult, it sits between the L1 and intervention of any of the lesions is directed at L2 vertebrae and occupies only the upper two- release of the tethering. One such case is pre- thirds of the vertebral canal. sented in this article.

OCTOBER 2005 The Surgical Technol og i st 15 262 OCTOBER 2005 1 CE CREDIT

Thickened filum terminale The most elementary form of tethering of the spinal cord occurs when the filum terminale is excessively thickened.2 In these cases, the filum terminale is often infiltrated with fatty tis- Conus medull ar is sue. Normally the filum is a fibrous structure that is a continuation of the arachnoid, which becomes the conus medullaris. A diameter greater than 2 mm, excluding fatty elements, is considered abnormal.5

Cauda equi na Lipoma Even though lumbosacral lipomas account for 29% of occult spinal dysraphisms, the embryo- logical development of spinal cord lipoma is not well understood.4 As in other forms of spinal dysraphism, normal elements are present, but are found in abnormal locations. One hypothe- sis is that disruption occurs during embryologi- cal development after the neural tube is formed, l i and subcutaneous fat is allowed to herniate into

Thomson-De marLearn ng.©2004 the region of the neural tube. The lipomatous tis- sue fuses with the neural tissue, and the result- ing lipoma tethers the spinal cord. Tethering may result in neurological dysfunction. The frequency of fat infiltrate within the filum terminale has been identified by several authors Filum term i na le Coccyx as described by Marchiori and Firth. Emery and

i l l f i l l i : iti Lendon found fat infiltrate in 4% to 6% of nor- Surg ca Techno ogy theSurg or ca Techno og stPos A Approach.Care ve mal adult subjects at postmortem. Modic et al i f

Repr nted rom reported that 5% of the population exhibits this condition, and Guiffre identified the condition FIGURE 1: The 31 pairs of spinal nerves associated with in less than 2%.5 localized regions of the spinal cord produce Spinal cord external segmentation. On this basis, the spi- Symptoms anatomy. nal cord is considered to consist of 31 segments, The symptoms of adult tethered cord syndrome each of which is traversed by paired dorsal and (TCS) have been described previously by Chap- ventral root filaments (Figure 2). man.1 The predominant symptom of adult TCS is pain in the lower back and legs that is exacerbated Physiology by physical activity, particularly flexion and exten- Neurons, glia, and pia mater have their own elas- sion of the lumbar spine. In practically all-adult ticities and viscosities. The interlacing fibers of patients with TCS, lower back and leg pain is char- these tissues resist traction in the longitudinal acterized by the “three B signs.”These are: inability direction. If the traction is sufficient to stretch the to sit with their legs crossed (like Buddha);difficul- spinal cord, the viscoelasticity of each structure ty bending slightly over the sink for dishwashing, can provide some protection to neurons, and glia or the podium while preaching or teaching classes; cells and can help maintain neuronal function.

16 The Surgical Technologist OCTOBER 2005 and difficulty holding a baby or light object (5 lb or rofibromatosis, meningiomas, dermoid or less) at waist level while standing.1 epidermoid tumors Neurologic signs are motor and sensory defi- ● polyneuropathy or isolated peripheral neu- cits in the lower extremities, hyporeflexia of one ropathy or more tendons, increased urinary retention, ● incomplete forms of viral infection of the and musculoskeletal deformities. These include peripheral nerve scoliosis, hyperlordosis, and deformities of the ● Guillain-Barre lower extremities, such as atrophy, hammertoes, ● early stages of degenerating diseases and and high-arched feet.1 familial spastic paraplegia ● any disorder that causes incontinence Differential Diagnosis ● scoliosis of other etiology, such as tuberculo- Chapman described a vast array of differential sis of vertebrae and epidural space diagnoses and other possible causes of symp- ● congenital or acquired deformities due to toms that must be ruled out. These include:1 musculoligamentous or bony abnormalities, ● intrinsic spinal cord tumors (ependymomas, particularly those of the lumbar vertebrae astrocytomas) ● articular facets that cause referred pain in the ● multiple sclerosis groin, buttock, or greater trochanteric area ● lumbosacral syringomyelia ● skeletal system disorders, such as herniated ● arteriovenous malformations disc (Table 1), spondylosis, spondylolisthesis, ● poliomyelitis osteoarthritic spondylosis, and lumbar canal ● an epidural or intradural mass compressing stenosis the spinal cord, such as schwannomas, neu-

FIGURE 2: Anterior view of the spinal Gray matter Filaments of dorsa l root cord. Whi te matter Anteri or med i an f i ssure

l i Filaments o f ventra l root

Thomson-De marLearn ng.©2004 Ventral root

Spi na l gang li on Spi na l nerve i l l f i l l i : iti Surg ca Techno ogy theSurg or ca Techno og stPos A Approach.Care ve i f Repr nted rom

OCTOBER 2005 The Surgical Technologist 17 Imaging studies tion, the dura is found to be significantly thinner Imaging studies are useful for making the than in normal individuals. diagnosis of TCS: plain film studies, MRI, and myelography combined with CT and ultraso- Surgicaltechnique nography. Magnetic resonance imaging is cur- The surgical release of the tethered cord presents rently the most useful imaging study for patients a challenge to even the most experienced neuro- with TCS. There are several imaging clues used surgeon. Complete understanding of the anato- to help in the diagnosis: my involved and meticulous microsurgical tech- ● a thick filum terminale (>2 mm in diameter), niques are called upon. ● the presence of structures that suggest lack The goal of surgery is to release the tethered of viscoelasticity, such as fibroadipose tis- neural elements and reduce the bulk of the associ- sue in the filum terminale, and obliteration ated lipoma.1 This is more easily achieved in dor- of the subarachnoid space, which suggests sal or caudal lesions than with traditional ones. adhesion around the caudal spinal cord or With the latter, the presence of important neural nerve roots elements within the lipoma may make it impos- ● an elongated spinal cord sible to safely achieve complete untethering. ● a posteriorly displaced conus medullaris or The risk of neural injury is also affected by filum, directly attached to the posterior the- the confusing relationships between neural ele- cal lining at or near the L5 lamina ments, lipoma, and the extent of the dural defect in cases of extensive lateral asymmetry of the A capacious sacral subarachnoid space is found lesion with distortion of the conus. In such cases, in 50% of patients and is associated with posteri- there is little normal anatomy to provide the sur- or displacement of the filum.4 During the opera- geon with adequate intraoperative orientation. The surgeon must rely on neurophysiological FIGURE 3: monitoring techniques to avoid neural injury. Bipolar The patient is administered general anesthe- sia via endotracheal intubation, and a Foley cath- coagulation eter is placed. He or she is rotated into the prone of epidural position onto a well-padded operating table fitted with a Wilson frame or a similar type of device. vessels. Extreme attention is paid to the protection of all pressure points, as the surgery can last sev- eral hours. If needed, the head can be suspend- ed in a Mayfield or Sugita head-holding device to reduce the risk of direct intraocular pressure. The patient should receive 1 gram of Cefazolin, FIGURE 4: 2 grams of Solumedrol, 250 cc of 20% Mannitol, Durotomy and 40 mg of Lasix prior to the incision. Contin- uous monitoring of the somatosensory evoked started at potential (SSEP), as well as the motor evoked upper level potentials (MEP) should be employed during the resection of the lipoma due to dissection around of lipoma. vital nervous structures. The patient is prepped and draped in the usual sterile fashion. A preliminary radiograph may be obtained to reduce the length of the inci- sion. A midline incision is made with a #20 blade

18 The Surgical Technologist OCTOBER 2005 centered over the operative site. Monopolar elec- FIGURE 5: trosurgery is used to obtain hemostasis and is used to carry the dissection to the fascia. Two Surge of CSF curved Weitlaner retractors are placed into the seen as wound. The fascia is opened in the midline with the electrosurgical pencil. Subperiosteal dis- arachnoid section is further carried out from the spinous membrane is processes to the facets of each vertebra bilater- ally utilizing monopolar electrosurgery and punctured with periosteal elevators. Once sufficient soft tissue bipolar forceps. exposure has been achieved, the Weitlaner retrac- tors are replaced with a bilateral self-retaining Meyerding retractor. FIGURE: 6 A bilateral laminectomy is performed first by removing the spinous processes with a Leksell or Overall image Stille-Horsley rongeur. The extent is determined of lipoma and by the amount of removal that will adequately expose the conus medullaris and filum termi- tethered cord. nale. Any bone bleeding can be controlled with the application of bone wax. Finer removal of the lamina is achieved by using a Kerrison ron- geur and a high-speed drill where necessary. The laminectomy is carried laterally as far as the facet joints. If needed, a minimal facetectomy may be performed to gain adequate exposure of the dura. microscissors. Any small bleeding points on the Attention must be paid not to remove too much edges of the dura are coagulated with the bipolar facet, as that level will become unstable and will unit. Tacking sutures of 4-0 braided nylon on a require a fusion arthrodesis. After fine hemostasis taper needle are used to hold open the dura at the is achieved with bipolar electrosurgery, the intra- edges. These are tagged with mosquito hemo- dural portion of the operation will begin. stats and secured to the surgical drapes. Once sufficient exposure of the lipoma has Intradural phase been created, attention is directed to the identi- A well-balanced surgical microscope is brought fication of normal anatomy within the thecal sac. into the field. Any small epidural vessels are The microscope is used to identify the lowest coc- coagulated and divided using bipolar electrosur- cygeal nerve root exit and to confirm the junc- gery and microscissors (Figure 3). A durotomy tion of the spinal cord and filum (Figure 6). The is performed using a micro #11 blade (Figure 4). nerve roots are usually grossly displaced by the An arachnoid plane is created between the dura lipoma, making identification tedious and diffi- and arachnoid using a blunt Rhoton micro-nerve cult. Bipolar stimulation of suspected nerve roots hook. Care must be taken when dissecting, as the confirmed by spinal cord monitoring would help lipoma will sometimes be situated at the location distinguish the normal anatomy from the lipoma of the durotomy. Once the arachnoid has been or thickened arachnoid (Figure 7). opened, a surge of cerebral spinal f luid (CSF) Once the nerve roots have been successful- will escape from the durotomy, and the spinal ly identified, resection of the lipoma is carried cord will relax (Figure 5). Further opening of the out using a 36 kHz ultrasonic aspirator with a dura is carried out superior and inferior to the 1.5-2 mm tip, such as the CUSA EXel™. Since the lipoma with the aid of the arachnoid knife and lipoma is mostly water, the tumor will appear

OCTOBER 2005 The Surgical Technologist 19 FIGURE 7: ity of the filum is confirmed, the filum is careful- ly transected using bipolar electrosurgery and Filum terminale the micro scissors (Figure 9). If the anterior spi- (white arrow) nal artery and vein encountered are larger than 500 m, they are left intact. Resection of a 0.5 and cauda u cm long filum will prevent scar formation from equina with bridging the two sectioned ends, later resulting sacral nerve in cord retethering. The wound is copiously irrigated with saline roots (green containing a Bacitracin antibiotic. The arach- arrow). noid and dural layers are closed with a water- tight, continuous, locking suture of 4-0 braided :FIGURE 8 nylon on a taper needle. Fibrin glue or a dural matrix (DuraGen®) may be placed on the suture Bipolar coagula- line to further inhibit CSF leakage. The retrac- tion of lipoma tors are removed, and fine hemostasis is achieved with mono- and bipolar electrosurgery. to reduce the Each layer is irrigated with the Bacitracin overall bulk of antibiotic solution on the way out. The fascia is approximated with 0 polyglactin 910 on a taper the tumor. needle in an interrupted fashion. The subcuta- neous and subcuticular layers are closed by an interrupted suture of 3-0 polyglactin 910 suture on a cutting needle. Any skin irregularities are FIGURE: 9 corrected with 5-0 plain gut. A sterile dressing is applied, and the patient is rotated back onto Bipolar the gurney. coagulation of Surgicalcomplications filum terminale Skandar et al reported in 2001 on the release of prior to tran- TCS in 34 adults. The authors studied the hos- pital records of 34 consecutive patients who section with presented in adulthood with tethered cord syn- microscissors. drome and conducted follow-up phone inter- views with 28 of them. Long-term surgical results and patient out- to vaporize with the application of the CUSA. come ratings were encouraging in these patients.

Alternatively, a CO2 laser with an energy level of After a mean clinical follow-up period of four 6 to 15 W can be utilized to debulk the tumor. years, significant improvement occurred in 22 Yet, another method of debulking is the use of of 27 patients presenting with pain, 13 of 27 bipolar forceps and microscissors to dissect the patients with motor or sensory dysfunction, and lipoma away from the spinal cord (Figure 8). 11 of 18 patients with bowel and bladder distur- Any blood vessels encountered in the resec- bance. In addition, telephone interviews were tion can be coagulated with the 0.5 mm tip bipo- obtained after a period of 8.6 years. lar forceps and transected with microscissors. Twenty-two (79%) of 28 patients called the Resection is carried out as close to the spinal operation a long-term success; 21 (75%) of 28 cord and nerve roots as possible. Once inelastic- patients believed that they had significant post-

20 The Surgical Technologist OCTOBER 2005 operative improvement, not just stabilization, in that cause traction on the spinal cord. These may pain and/or neurological function. include bending movements, the lithotomy posi- Surgical complications were generally minor. tion during childbirth, movement occurring Among these complications included one cere- during motor vehicle accidents, and others. brospinal f luid leak and five pseudomeningo- In adult patients, intradural structures are celes. Two patients complained of worsening frequently scarred and surrounded by signifi- motor or sensory dysfunction and one of wors- cant arachnoidal adhesions that are very likely to ening bladder dysfunction, whereas four patients contribute to the patient’s symptoms; this scar- experienced persistent pain and one complained ring is often severe enough to make it more dif- of worsening pain postoperatively. According to ficult to dissect the edge of the spinal cord from the patients, the vast majority of these complica- the surrounding dura. In addition, the anatomy tions were minor. may be very unusual and confusing. Therefore, caution should be exercised during the dissec- Conclusion tion, and preoperative computerized tomogra- It is commonly believed that children who have phy and magnetic resonance images must be a congenital tethered spinal cord benefit from studied very carefully before surgery. surgical untethering because it prevents neuro- The risks of surgery must be weighed against logical deterioration. However, controversy has the potential benefit to the patient. In cases in surrounded the issue of surgery in newly diag- which there is documented clinical deteriora- nosed adult patients. The incidence of occult spi- tion, there is little question about the advisabil- nal dysraphism is unknown and, although it is ity of operative treatment. In cases of patients likely that some patients remain asymptomatic, who are asymptomatic or have long standing a diagnosis is never made. A subset of patients stable neurological deficits, there is greater con- with the congenital syndrome develops pro- troversy regarding the usefulness of prophylac- gressive symptoms and signs in adulthood. Such tic surgery. deterioration may occur after sudden movements

TABLE 1. Differential Diagnosis: Herniated disc vs. tethered cord syndrome Herniated di sc Tethered cord syndrome Radi at i ng pa in i n a dermatoma l pattern Pai n extend i ng to var i ous l ocat i ons : med ial, l atera l, anteri or, and poster i or Pai n rare i n the gro i n or rectum Pain i n gro i n or rectum common Aggravati on by cough i ng, sneez i ng Coughi ng, sneez i ng have no effect Litt l e effects of three “B” postures Three “B” postures aggravate pain ( 100% of pat i ents ) Pai n re li ef by s l ouch i ng, worse by s i tt i ng stra i ght Prefer si tt i ng stra i ght to s l ouch i ng Pai n re li ef after lyi ng sup i ne on hard bed Aggravati on after s l eep i ng sup i ne Motor dysfuncti on i n 1 or 2 myotomes Wide d i str i but i on w i thout a s i mp l e myotoma l pattern Dermatomal def icit ( 1 or 2 ) Patchy dstri i but i on ; per i nea l hypera l ges ia Incont i nence rare, except wi th m idli ne hern ia Uri nary or recta l i ncont i nence common Aggravati on by stra i ght l eg-ra isi ng No ef fect of stra i ght l eg-ra isi ng test No specifi c deform i ty Exaggerated l ordos is; hi gh arched f eet ; di fference in size of l egs or feet

OCTOBER 2005 The Surgical Technologist 21 Acknowledgments References I wish to thank my fiancé, Jennifer N Prigg, DO, 1. Chapman P. Spinal Lipoma Controversy. for her support and companionship throughout Neurosurgery. January 1999;44: 186-193. the past two years. I wish, as always, to thank, 2. Flannery AM. Diagnosis and Surgical Treat- John L Zinkel, MD, PhD, FACS, for his support ment of Congenital Lesions of the Nervous and friendship throughout the past 11 years. System. In: MB Allen, Jr and RH Miller, eds. Essentialsf o Neurosurgery, A Guide to Clini- About the author cal Practice. New York: McGraw-Hill, Inc; Jeffrey J. Cortese, CST, BHSA, has been a cer- 1995:121-131. tified surgical technologist for since 1996. A 3. Intraoperative participation and discussion graduate of Baker College-Mt Clemens Cam- of presented surgical case with John L Zinkel, pus, Cortese is employed at Upper Cumber- MD, PhD, FACS land Physicians Surgery Center in Cookeville, 4. Koch SE, Koch TK, and Edwards MS. A sub- Tennessee, and Livingston Regional Hospital in tle sign of spinal cord lipoma. Clinical Pediat- Livingston, Tennessee. Jeff earned his bachelor’s rics. March 1995; 34(3):156-7. of health service administration degree from 5. Marchiori DM and Firth R. Tethered Cord Syn- Baker College in Clinton Township, Michigan, dromes. Journal of Manipulative & Physiologi- in May 2005. cal Therapeutics. May 1996; 19(4): 265-267. 6. Skandar JI, Fulmer BB, Hadley MN, & Oakes WJ. (2001). Congenital spinal cord syndrome in adults. Neurosurgery Focus. 10(1): Article 7.

22 The Surgical Technologist OCTOBER 2005