Spinal congenital dermal sinus with dual ostia

J Neurosurg Pediatrics 3:000 000, 3:407 411, 2009 Spinal congenital dermal sinus with dual ostia Clinical article Ch a n g Su b Le e, M.D., 1 Ji Ho o n Ph i, M.D., 2 Se u n g -Ki Kim, M.D., Ph.D., 2 By u n g-ky u Ch o, M.D., Ph.D., 2 a n d Ky u-ch a n g Wa n g, M.D., Ph.D. 2 1 Department of Neurosurgery, School of Medicine, Jeju National University, Jeju; and 2 Division of Pediatric Neurosurgery, Seoul National University Children s Hospital, Seoul, Republic of Korea Object. Congenital dermal sinus (CDS) usually develops in the midline of the body as a single tract. To date, only a few patients with multiple CDS tracts and ostia have been reported. The authors analyzed the clinical features of patients with spinal CDS and multiple ostia and proposed a novel hypothesis for the pathogenesis of the atypical CDS. Methods. Five patients with spinal CDS and multiple ostia were included. The clinical, radiological, and operative features of these patients were reviewed retrospectively. Results. Three patients demonstrated bilateral paramedian ostia at the same or a very similar spinal level. One patient showed a paramedian and a midline ostium. One patient had 2 unilateral paramedian ostia at different spinal levels. The layers of the internal ending of CDS tracts were diverse. Complete removal of the tracts was possible in all patients. Two patients had dermoid tumors. All patients had an associated anomaly, such as a lumbosacral or the Currarino triad. The authors propose a zipping error hypothesis for the formation of dual ostia located at the spinal level of primary neurulation. An associated anomaly such as a lumbosacral may contribute to the formation of dual ostia. Conclusions. Unilateral or bilateral dual ostia may be present in patients with CDS, especially when an associated anomaly is present. The atypical CDS may develop from aberrant neural tube closure. (DOI: 10.3171/2009.1.PEDS08153) Ke y Wo r d s spinal congenital dermal sinus pathogenesis dual ostia Sp i n a l CDS is a rare type of spinal dysraphism that results from disturbed separation of the cutaneous ectoderm and neuroectoderm during embryonic development. 1 Although spinal CDS is a very uncommon disease, its clinical manifestation is often dramatic, with outbreaks of meningitis or spinal cord abscesses accompanied by severe neurological deficits. 1,2,14 However, through increased alertness for the disease in patients in primary care facilities, the majority of patients with spinal CDS now seek early medical attention for the presence of a skin ostium and other skin stigmata over the neuraxis. 1 The skin ostium of spinal CDS is typically located in the midline of the back, above the gluteal crease. 6 Prompt investigation is warranted for the observation of this single midline skin ostium or dimple in clinical practice. 14 Multiple ostia of spinal CDS have been rarely reported Abbreviation used in this paper: CDS = congenital dermal sinus. in the literature, but have received little attention. 1,5 Furthermore, there have been no reports regarding the bilateral paramedian location of spinal CDS ostia. In this study, we present 5 unusual cases of spinal CDS with double ostia. At least 1 ostium for each patient was located in the paramedian plane. Because the pathogenesis of spinal CDS has been well established and has been believed to be closely related to neural tube closure in the midline of the body, paramedian or multiple CDS ostia cannot be simply explained in this scheme. We propose a novel pathogenesis for these multiple ostia of spinal CDS. Methods We searched the database of operations of the Di- This article contains some figures that are displayed in color on line but in black and white in the print edition. 407

C. S. Lee et al. vision of Pediatric Neurosurgery at the Seoul National University Children s Hospital for the diagnosis of spinal CDS from October 1986 to March 2007. Of the 20 patients included in the database, 5 had dual ostia. Two patients were male and 3 were female. Age at the time of operation ranged from 3 months to 15 years (median 33 months). The following clinical and radiological data were reviewed retrospectively: 1) clinical presentation at diagnosis; 2) plain radiograph and MR imaging findings; and 3) operative and pathological findings including the internal endings and associated anomalies. Based on the clinical characteristics of CDS with multiple ostia, we have speculated on the pathogenesis of this atypical anomaly. Results Clinical Features All patients had dual skin ostia in the lower back, near the lumbosacral junction (Fig. 1). Three patients had bilateral paramedian ostia. The bilateral ostia were symmetrically located at the same or at a slightly different spinal level in these patients. One patient had a paramedian ostium and a midline ostium, both of which were located at the same spinal level. One patient had 2 unilateral paramedian ostia on the left side. The unilateral ostia were located at different spinal levels in this patient. Three patients had skin manifestations other than the ostia. One patient had a skin hemangioma around an ostium, and 2 patients had a low-back mass that indicated the presence of an underlying. Discharge from the skin ostium was the most common symptom observed in all patients. The discharge was purulent in 4 patients and resulted from superficial infection of the sinus tract, but no patient developed meningitis or a deep-seated abscess. Recurrent nonpurulent discharge (keratin debris) was found in the remaining patient. Three patients demonstrated neurological problems. One patient showed toe deformity and a hyperreflexic bladder on urodynamic study. One patient had neurogenic claudication of both legs and a hyperreflexic bladder on urodynamic study. One patient had bilateral L-5 and S-1 radiculopathy. Plain radiographs revealed scoliosis and hemivertebrae in 2 patients. One patient had an L-1 hemivertebra (remote from the bilateral CDS tracts at the L-5 level) with scoliosis. The other patient had an L-4 accessory hemivertebra (the same level as the bilateral CDS) with L-5 spina bifida and scoliosis. Block vertebrae and partial agenesis of the sacrum was found in 1 patient with the Currarino triad. On spinal MR imaging, spinal cord tethering with a low-lying conus was found in all patients. Two patients showed a syrinx in the spinal cord. In all patients, an associated anomaly was detected on preoperative spinal MR imaging: a fatty filum in 1 patient, the Currarino triad in 1 patient, and a lumbosacral in 3 patients. Operative Findings and Follow-up The purposes of surgery were to remove the CDS tracts (and, if present, dermoid tumors), to release the low-lying spinal cord, and to correct the associated anomaly such as a lumbosacral. The CDS tracts were traced from the external ostium up to where the squamous epithelium was invisible on frozen biopsy specimens. The anatomical locations of internal ending were diverse: paraspinal muscles, dura, a in the subarachnoid space, and neural structures (a spinal rootlet). The internal endings of 2 tracts were at the same layer in 3 patients, but were at different layers in 2 patients. Dermoid tumors were found in 2 patients. In the patient with the Currarino triad, the presacral mass consisted of 2 dermoid tumors connected by a CDS tract. The CDS tracts and dermoid tumors were totally removed, and complete spinal cord untethering was achieved in all patients. The presence of squamous epithelium lining the sinus tracts was confirmed in all patients by pathological examination. 12 Postoperatively, no permanent neurological deficit was observed in any patient. The patients were followed up for a median period of 84 months (range 10 145 months). No patients developed retethering or recurrent infection during the followup periods. Clinical and operative findings are summarized in Table 1. Illustrative Case This 8-month-old boy (Case 1) was presented at the outpatient clinic of the Department of Orthopedic Surgery for a deformity in his left second toe. The patient was referred to the Division of Pediatric Neurosurgery for the evaluation of skin ostia on his back. On physical examination, a prominent skin dimple was found on his back near the lumbosacral junction. The dimple had a small ostium and was located in the left paramedian plane. Another tiny ostium was found on the right side. A small amount of purulent discharge emerged from the left ostium. Plain Fig. 1. Images showing bilaterally located cutaneous ostia in Case 2 (A) and Case 3 (B and C). The bilateral dermal sinus tracts are marked with arrows in the preoperative photograph (A), axial MR image (B), and intraoperative photograph (C). 408

Spinal congenital dermal sinus with dual ostia TABLE 1: Clinical features of 5 patients with multiple CDS ostia* Case No. Age, Sex Discharge From Ostia Other Skin Stigmata Neurological Problems 1 8 mos, M purulent hemangioma toe deformity, hyperreflexic bladder 2 15 yrs, F purulent claudication, hyperreflexic bladder Plain Radiograph Abnormality CDS Ostia Internal Endings L-1 hemivertebra, scoliosis block vertebra S1 2, partial sacral agenesis 3 9 yrs, F purulent L-4 accessory hemivertebra, L-5 spina bifida, scoliosis 4 3 mos, F purulent subcut mass bilat L-5 & S-1 radiculopathy 5 2 yrs, M nonpurulent (keratin debris) (lt L-5, rt L-5) (lt L5 S1, rt L-5) (lt L-4, rt L-4) paramedian (upper S1 2) & midline (lower S-2) subcut mass unilat paramedian (upper L4 5, lower S1 2) spinal rootlet (lt); dura (rt) paraspinal muscle (lt & rt) Dermoid Tumor ruptured dermoid Associated Anomaly fatty filum 2 dermoid Currarino triad dura (lt & rt) lumbosacral intradural (upper); dura (lower) intradural (upper & lower) lumbosacral lumbosacral * In all patients, CDS tracts and dermoid tumors were totally removed and complete untethering was achieved. Abbreviation: subcut = subcutaneous. radiographs showed scoliosis and a hemivertebra in the lumbar spine, and spinal ultrasonography revealed spinal cord tethering. Spinal MR imaging demonstrated a lowlying conus at the L4 5 level, a syrinx from the T-8 level to the conus, and the presence of bilateral paramedian dermal sinus tracts originating from the skin at the L-5 level. It was unclear whether the tracts were connected with neural tissue. Intraoperative examination revealed that the right CDS tract terminated at the dura mater and that the left tract adhered to the spinal rootlets. Cream-like material was removed from the intradural space, which suggested a ruptured dermoid tumor. A thickened filum with fatty infiltration was observed. The CDS tracts were removed thoroughly, and complete untethering was performed. Pathological examination revealed squamous epithelium lining the sinus tracts (Fig. 2). Discussion Congenital dermal sinus with multiple ostia is an uncommon finding. In the literature, only a few patients with CDS and dual ostia have been reported. Kajiwara et al. 5 reported on 2 patients with dual dimples in the sacrococcygeal area. The dimples were all located in the midline. Because the dimples were located at a lower level than the usual ostium of CDS, they were considered atypical manifestations, but the presence of dual ostia received little attention. 13 In a review of 28 patients with spinal CDS, Ackerman and Menezes 1 reported that 1 patient had 2 ostia overlying a single CDS tract. The exact location of these dual ostia was not detailed in the article. Finally, there is a curious report of a patient who had bilaterally located retroauricular dermal sinus tracts. 9 However, the pathogenesis of retroauricular CDS is not related to the neural tube closure, but to the embryogenesis of the ears. Therefore, to the best of our knowledge, paramedian dual ostia of spinal CDS have not been reported. Congenital dermal sinus is known to originate from the incomplete disjunction between cutaneous ectoderm and neuroectoderm during primary neurulation (the nondisjunction theory). 6 It is also possible that CDS is the consequence of a patent accessory neurenteric canal (the patent neurenteric canal theory). 7,10 However, neither of these theories suitably explains the pathogenesis of bilateral, paramedian, and multiple ostia. In our patient series, bilateral paramedian CDS tracts were symmetrically located at the same or very similar spinal levels. In contrast, unilateral paramedian CDS tracts were located at overtly different levels. Therefore, the pathogeneses of these 2 kinds of anomalies may not be the same. We initially speculated that the bilateral paramedian CDS could be explained by the split notochord theory, that is, if a split notochord results in the formation of dual neural tubes, each neural tube could have a CDS at the same level and consequently bilaterally located CDS. According to Pang et al., 10 a split notochord can also be combined with a midline CDS. However, there were no other anomalies that could be caused by the split notochord syndrome in our patients, such as abnormalities in the spinal cord and the dura, although 1 patient had an accessory hemivertebra at the same level as the CDS tracts. 4 Moreover, the fact that bilateral ostia were located at the same or very similar spinal levels favors their uniform origin rather than an origin from independent nondisjunction processes. It is known that there are 3 5 initiation points along the neural tube and that neural tube defects are believed to occur mainly at junctions between the ascending and descending closures. 3,8 Therefore, a buckling of the gap 409

C. S. Lee et al. Fig. 2. Case 1. An illustrative case with multiple skin ostia. A: Skin ostia (arrows, the right-side ostium is not clearly visible on the surface) are not located at the midline. B and C: Axial MR images show sinus tracts that run through subcutaneous fat bilaterally. D: Plain radiograph reveals scoliosis and hemivertebrae. E and F: Intraoperative photographs demonstrate bilateral sinus tracts (arrows, E), one of which is connected with spinal nerve rootlets (arrow, F). between the areas of ascending and descending closure of the neural tube (like an error in a zipper closure) leads to bilateral neural fold redundancy, and after the completion of neural tube closure at the midline, redundant neural folds on each side may leave holes or tracts, and may result in bilateral CDS at the same or very similar spinal levels (the zipping error hypothesis; Fig. 3). Several patients with a lumbosacral and paramedian single CDS tract have been reported. 11 It is our speculation that if a tous mass occupies a portion of the unilateral neural fold, it may lead to the development of a redundant neural fold around the mass in the same side, which may result in CDS in or off the midline on the lesion side at different spinal levels. Consequently, multiple CDS tracts can develop in the side of the (Fig. 4). However, these conjectures cannot be applied to CDS with multiple ostia at low sacral areas where secondary neurulation occurs. In such cases, multiple skin ostia may be regarded as a part of aberrant secondary neurulation and a type of subsequent skin manifestation. Conclusions Preexisting theories of the pathogenesis of CDS do not suitably explain the development of multiple CDS ostia. In this report, we propose a zipping error hypothesis of aberrant neural tube closure to explain the development of multiple CDS lesions, but we concede that this hypothesis needs to be tested. Disclosure This article was supported in part by a grant (No. 04-2002-008-0) from the Seoul National University Hospital, Seoul, Republic of Korea. The authors report no conflict of interest concerning the Fig. 3. Images demonstrating the zipping error hypothesis of CDS with dual ostia. Buckling of the gap between the ascending and descending closure areas of the neural tube (A) results in bilateral redundancy (B, enlarged view of bilateral neural fold redundancy). After continuation of the tube closure process at midline, redundant regions of neural fold on each side may leave holes or tracts. The photograph (C) shows a simulation of the zipping error and the creation of bilateral dual ostia. 410

Spinal congenital dermal sinus with dual ostia Fig. 4. A speculative schematic drawing of multiple CDS ostia associated with lumbosacral. The lip of a unilateral neural fold may bulge during the process of formation. An enlarging mass on the neural fold pushes the adjacent neural folds (arrows) and creates redundancy. Redundant neural folds adjacent to the can create ostia off the midline at different spinal levels. materials or methods used in this study or the findings specified in this paper. References 1. Ackerman LL, Menezes AH: Spinal congenital dermal sinuses: a 30-year experience. Pediatrics 112:641 647, 2003 2. Benzil DL, Epstein MH, Knuckey NW: Intramedullary epidermoid associated with an intramedullary spinal abscess secondary to a dermal sinus. Neurosurgery 30:118 121, 1992 3. Copp AJ, Greene ND, Murdoch JN: The genetic basis of mammalian neurulation. Nat Rev Genet 4:784 793, 2003 4. Dias MS, Pang D: Split cord malformations. Neurosurg Clin N Am 6:339 358, 1995 5. Kajiwara H, Matsukado Y, Hiraki T, Yokota A: Intraspinal communication of sacrococcygeal dermal sinuses. Childs Nerv Syst 1:264 267, 1985 6. Kanev PM, Park TS: Dermoids and dermal sinus tracts of the spine. Neurosurg Clin N Am 6:359 366, 1995 7. Kulkarni V, Daniel RT, Haran RP: Extradural endodermal cyst of posterior fossa: case report, review of the literature, and embryogenesis. Neurosurgery 47:764 767, 2000 8. Moore KL, Persaud TVN: The Developing Human: Clinically Oriented Embryology, ed 7. Philadelphia: WB Saunders, 2003, p 428 9. Nejat F, Dias MS, Eftekhar B, Roodsari NN, Hamidi S: Bilateral retro-auricular dermal sinus tracts with intradural extension. Case report. J Neurosurg 99:163 166, 2003 10. Pang D, Dias MS, Ahab-Barmada M: Split cord malformation: Part I: a unified theory of embryogenesis for double spinal cord malformations. Neurosurgery 31:451 480, 1992 11. Pierre-Kahn A, Zerah M, Renier D, Cinalli G, Sainte-Rose C, Lellouch-Tubiana A, et al: Congenital lumbosacral s. Childs Nerv Syst 13:298 334, 1997 12. Rajpal S, Salamat MS, Tubbs RS, Kelly DR, Oakes WJ, Iskandar BJ: Tethering tracts in spina bifida occulta: revisiting an established nomenclature. J Neurosurg Spine 7:315 322, 2007 13. Steinbok P: Intraspinal communication of sacrococcygeal dermal sinuses. Childs Nerv Syst 2:279, 1986 14. Wang KC, Yang HJ, Oh CW, Kim HJ, Cho BK: Spinal congenital dermal sinus experience of 5 cases over a period of 10 years. J Korean Med Sci 8:341 347, 1993 Manuscript submitted June 24, 2008. Accepted January 19, 2009. Address correspondence to: Kyu-Chang Wang, M.D., Ph.D., Di - vision of Pediatric Neurosurgery, Seoul National University Children s Hospital, Seoul 110-744, Republic of Korea. email: kcwang@ snu.ac.kr. 411