Cord Lipoma Research Articles

Intraoperative neuromonitoring and mapping during spinal cord untethering surgery; a single-centre paediatric neurosurgery unit experience.

A review of intraoperative neuromonitoring (IONM) and mapping (IONMa) utility during paediatric tethered cord surgery with particular attention to feasibility, measures to prevent injury, and postoperative outcome. A retrospective analysis of spinal cord untethering surgery between 2015 and 2022 was carried out. Cohort demographics, IONM and IONMa data, and procedural details were summarised and associations between variables explored. Clinical outcome was assessed 3-months post procedure via review of medical records. One hundred and twenty-two patients (median age: 3years old: IQR: 2-9, 61% female) underwent surgery. The most common diagnosis was thickened filum (n = 59, 48%). Urological dysfunction was the most common presenting complaint (62%). Electromyography (EMG), motor evoked potentials (MEP), somatosensory evoked potentials (SSEP), and bulbocavernosus reflexes (BCR) were successfully recorded in 100%, 99%, 90%, and 73% patients. Unsuccessful BCR monitoring only occurred in females (p < 0.001). The Triggered-EMG protocol identified nerve rootlets adhered to the filum or tethering structure in 16% of the cohort. Alert criteria breaches (> 30-50% reduction in SSEP, > 80% reduction in MEP amplitude, absent BCR) occurred in 13 patients (11%). These alert criteria breaches were reversed in 11 (85%) with no permanent neurological deficits. In 2 (15%), alerts were irreversible, and one developed a permanent neurological deficit. Signs and symptoms of tethered cord had either stabilised (≥ 64%), improved (≥ 20%), or worsened (≤ 4%) at 3-month postoperative review. IONM and IONMa are useful and effective tools in monitoring and identifying neural tissue, which can guide safe cord untethering and lipoma resection. Our results validate IONM and IONMa in surgery for cord untethering.

Case of large spermatic cord lipoma misdiagnosed as inguinal hernia

Clinically, a pure spermatic cord lipoma has not been recognized as a disease entity but regarded as an incidental finding at the time of hernia repair because it presents as groin symptoms and clinical findings are indistinguishable from those of inguinal hernia. We report the successful treatment of case of huge pure spermatic cord lipoma originally misdiagnosed as inguinal hernia. A 65year male patient presented with progressive swelling, on and off pain in left groin in the last 2 years. On examination it was partially reducible and ultrasonographic scan was showing as inguinal hernia. We proceeded for an open hernia repair, unexpectedly it revealed a large fatty mass attached to spermatic cord and there is no connection to peritoneal cavity near deep ring. Then it is excised and Lichtenstein tension free hernioplasty was done to prevent future development of hernia. Histopathological examination of excised specimen confirmed it is a lipoma of cord.

Bridging the spinal dysraphism spectrum between terminal myelocystocele and spinal cord lipoma: a report of two cases of true terminal lipomyelocystocele with holo-cord syrinx.

Terminal myelocystocele (TMC) is a rare form of spinal dysraphism which arises due to aberration in the secondary neurulation process involving the caudal cell mass. Terminal myelocystocele has been defined by Pang et al. based on essential and non-essential features. One of the non-essential features includes non dysraphic lipomas which do not tether to the neural placode. We are presenting two cases which meets all the essential criteria outlined by Pang et al. for TMC but also show the presence of a lipomatous component tethering to the neural placode, similar to a dysraphic lipoma. Through this article, we want to showcase a subset which represents "true" terminal lipomyelocystocele (TLMC), bridging the spectrum of spinal dysraphism between TMC and lipomyelomeningocele (LMM).

Nondysraphic Intramedullary Spinal Cord Lipomas in the Adult Population

ObjectiveIntramedullary spinal cord lipomas without spinal dysraphism are rare. Although they are benign tumors, they can cause significant neurological deficits. Their tight adherence to the spinal cord presents a challenge for resection. Therefore, we review our institutional experience treating adult patients with intramedullary lipomas in the absence of dysraphism and report long-term outcomes after resection. MethodsAll adult patients undergoing resection of intramedullary spinal cord lipomas at a comprehensive cancer center between June 2011 and June 2023 were retrospectively identified. Patients with spinal dysraphism or extramedullary lipomas were excluded. Patients were included if they had microscopic surgical debulking with tissue sampling confirming the diagnosis. ResultsSix patients were identified with a mean age of 35.0±11.5 years and 67% were female. Four cases localized to the thoracic spine. Symptoms included pain, numbness, and lower extremity motor weakness; only one patient reported bowel and bladder dysfunction. All patients experienced transient neurological decline in the immediate post-operative period. Five recovered to independent ambulation at long-term follow-up, including one recovering to full strength. One patient required a repeat resection after four years due to tumor progression and functional decline. Tumor progression was not recorded in the other patients. ConclusionsSubtotal resection is a safe and effective treatment. Detethering of the spinal cord, resection of exophytic components, and tumor debulking can improve symptoms and prevent further deterioration in most cases. The resection can be assisted using a laser to vaporize the fatty tissue of the lipoma without physical manipulation of the spinal cord.

Cord lipoma in minimally invasive surgical repairs of inguinal hernias: a prospective study.

Cord lipomas are frequent findings in laparoscopic inguinal hernia surgeries in male patients. The symptoms of lipoma and the potential benefits of removing them are often overlooked because the focus is on the primary pathology of the hernia itself. Current recommendations are to reduce this fatty content, when present. When inguinal cord lipomas are left untreated in inguinal hernia surgery they can potentially cause symptoms and be detected in follow-up imaging exams. The objective of this study was to study incidence of cord lipomas in a cohort operated on by a single group specializing in abdominal wall surgery, as well as to analyze the possible relationship of this finding with the patient's symptoms, the characteristics of the operated hernia and postoperative outcome. This is a prospective study of male patients operated on for inguinal hernia laparoscopically or robotically in a single reference center. Of the total of 141 hernias, the distribution according to European Hernia Society classification showed that 45.4% were lateral, 19.1% medial and 35.5% mixed, highlighting a variety in the presentation of hernias. Analysis of the size of the hernias revealed that the majority (35.5%) were ≤ 1.5cm. Inguinal cord lipoma was present in 64.5% of the samples, with no statistically significant association between the presence of the lipoma and an indirect hernia sac or obesity. The incidence of surgical site occurrences (SSO) was 9,2%, with seroma and hematoma. No recurrences were observed during follow-up, indicating a successful approach. There were no statistically significant relationships between SSO, the presence of lipoma and indirect hernial sac.

Adult genitourinary sarcomas: A single-centre experience over 25 years.

e23532 Background: Genitourinary sarcomas are a rare entity. This study is a retrospective review of the patient characteristics, types of adult GU sarcomas, treatments and outcomes in a single institution over the past 25 years. Methods: Survival probabilities were estimated and plotted using the Kaplan-Meier method. Estimates along with 95% pointwise confidence intervals were reported. Recurrence-free survival (RFS) is defined as time from when the patient was disease-free to recurrence. Otherwise, patients were censored at last disease evaluation. OS was defined as time from when the patient was disease-free to death due to any cause. Patients still alive were censored at last known alive. Results: 29 patients presented with various types of GU sarcomas, with the majority being paratesticular tumors (n = 22, 75.9%). Others included bladder leiomyosarcomas (n = 5), prostatic leiomyosarcoma (n = 1), renal leiomyosarcoma (n = 1). Median age for diagnosis was 51 years (range: 21-79) for leiomyosarcoma vs 61 (range: 36-89) for liposarcoma. Among the paratesticular tumors majority were (n = 16) were liposarcoma, remaining 5 being leiomyosarcoma and 1 being rhabdomyosarcoma. Majority tumors were stage III and above (n = 16, 55.17%), high and intermediate grade (65.51%). All tumors were resected ± adjuvant therapy (n = 4). Leiomyosarcomas had a higher stage (66%) and grade (83%) at diagnosis, recurrence rate was also higher at 37.5% (vs 6.6% for liposarcoma) along with a higher mortality (41.6%). Commonest site of recurrence for leiomyosarcoma was the lungs (n = 3, 100%). Treatment for recurrence commonly involved radiotherapy, pembrolizumab etc. Paratesticular liposarcomas were found to be associated with a lipomatosis syndrome with n = 5 (31.25%) having lipomas elsewhere in the body and n = 2 (12.5%) patients having had previously resected spermatic cord lipoma. Paratesticular sarcomas often required (n = 15, 68%) revision surgery due to being initially diagnosed as a hernia, cord lipoma or hydrocele and requiring high ligation of the cord with hemiscrotectomy and radical orchiectomy ± LND on revision surgery, which often demonstrated a focus of residual tumor in liposarcomas (n = 5, 31%). N = 4 patients (25%) had positive margins in spite of revision surgery. Majority of these were MDM2+ positive on FISH (n = 9, 56%). Overall, GU sarcomas had an RFS of 63% (53-94%) and OS of 82% (53-94%) at 36 months since NED was achieved. The median length of follow-up was 19.9 months for leiomyosarcoma, 33.8 months for liposarcoma. Conclusions: Leiomyosarcomas in adults have worse outcomes compared to other GU sarcomas especially if it originates in the bladder. [Table: see text]

Unveiling the Uncommon: Intradural Extramedullary Cord Lipoma Inducing Chest Wall Pain in a Middle-Aged Female Patient-A Case Report

BACKGROUND: Intradural extramedullary lipomas are rare spinal cord tumors that remain asymptomatic until compression of the spinal cord results in neurological symptoms. Anterior chest wall pain as the initial presentation is uncommon and can contribute to the delayed diagnosis, as it prompts clinicians to rule out other pathologies. CASE REPORT: The patient is a 44-year-old woman who presented with chronic anterior chest wall pain, instability, imbalance, and upper motor neuron signs. Imaging was obtained, and magnetic resonance revealed an intradural extramedullary mass composed of adipose tissue from T2 to T5, indicative of a spinal lipoma. Subsequently, the patient underwent complete excision and laminoplasty successfully, immediately improving all symptoms. CONCLUSIONS: Diagnosing intradural extramedullary lipomas is intricate and often incidental, with varied presentations depending on tumor localization and size. While uncommon, it is crucial to maintain a heightened level of suspicion when evaluating persistent, unexplained pain resistant to conservative treatments and accompanied by neurological symptoms. KEY WORDS: Chest wall pain, spinal cord lipomas, case report

Non-dysraphic intramedullary spinal cord lipoma: A case report

Introduction: Intramedullary nondysraphic spinal lipomas are extremely rare among primary spinal cord tumors. These patients present with nonspecific sensory symptoms followed by deterioration of motor symptoms. As the safety margins for neurological preservation are thin, meticulously locating the extent of the tumor and choosing the resection modalities is essential. Case Report: We report a rare case of a 35-year-old male who presented with progressive difficulty in walking for six months associated with numbness and tingling sensation in the bilateral upper and lower limbs. He was diagnosed with nondysraphic intramedullary cervicothoracic lipoma and underwent subtotal resection of the tumor. Conclusion: Nondysraphic intramedullary spinal cord lipomas are rare and may present as nonspecific neurological symptoms. Hence, they should be considered differentials of intramedullary spinal cord tumors. Surgery appears to be the mainstay of treatment.

Results of Surgical Treatment of Occult Spinal Dysraphisms-A Single Centre Experience.

Occult spinal dysraphisms (OSDs) are caused by various defects in the embryogenesis of the spinal cord and represent an obstacle to the ascent of the conus, which allows the conus to pass from the lower levels of the spinal canal to the final position between L1 and L2 during normal foetal life. When an OSD tethers the spinal cord at the lower levels, it can lead to neurological symptoms, better known as tethered cord syndrome. Surgical treatment of OSD is primarily aimed at untethering the spinal cord. In asymptomatic patients, this can protect against the long-term development of neurological deficits. In symptomatic patients, this can halt or limit the progression of existing symptoms. The aim of this study is to examine all paediatric and adult patients diagnosed with OSD and treated in the Department of Neurosurgery at the University Medical Centre Ljubljana during the 5-year period of 2016-2021. All patients diagnosed with OSD during this period were included in the study. Patient characteristics, treatment modalities and outcomes were studied with the aim of describing the differences between the paediatric and adult population and defining the rationality of treating these pathological conditions. We included in the study 52 patients with 64 occult dysraphic lesions. Adults (>18 years old) represented 15/52 (28.8%) of all patients, while 37/52 (71.8%) were children. The most common OSDs were conus lipomas, followed by dermal sinus tracts, filum terminale lipomas and split cord malformations. Surgical treatment was performed in 35/52 (67.3%) cases, while conservative management was chosen in 17/52 (32.6%) cases. The preoperative presence of symptoms was statistically higher in adults than in children (p = 0.0098). Surgery on complex spinal cord lipomas was statistically related to a higher rate of postoperative neurological complications (p = 0.0002). The treatment of OSD is complex and must be based on knowledge of the developmental anomalies of the spine and spinal cord. Successful surgical treatment relies on microsurgical techniques and the use of neuromonitoring. Successful treatment can prevent or limit the occurrence of neurological problems.

Glial fibrillary acidic protein immunopositive neuroglial tissues with or without ependyma-lined canal in spinal lipoma of filar type: Relationship with retained medullary cord.

Retained medullary cord (RMC) and filar lipomas are believed to originate from secondary neurulation failure; filar lipomas are reported to histopathologically contain a central canal-like ependyma-lined lumen with surrounding neuroglial tissue with ependyma-lined central canal (NGT w/E-LC) as a remnant of the medullary cord, which is a characteristic histopathology of RMC. With the addition of glial fibrillary acidic protein (GFAP) immunostaining, we reported the presence of GFAP-positive NGT without E-LCs (NGT w/o E-LCs) in RMC and filar lipomas, and we believe that both have the same embryopathological significance. We examined the frequency of GFAP-positive NGT, with or without E-LC, in 91 patients with filar lipoma. Eight patients (8.8%) had NGT w/E-LC, 25 patients (27.5%) had NGT w/o E-LC, and 18 patients (19.8%) had tiny NGT w/o E-LC that could only be identified by GFAP immunostaining. Combining these subgroups, 56% of the patients (n = 51) with filar lipoma had GFAP immunopositive NGT. The fact that more than half of filar lipomas have NGT provides further evidence that filar lipoma and RMC can be considered consequences of a continuum of regression failure that occurs during late secondary neurulation.

Spinal cord lipomas: lessons learned in the era of total resection.

Recent years have seen a paradigm shift towards total/near-total resection in spinal cord lipoma surgery. As this procedure is technically challenging, surgical candidates need to be selected appropriately through accurate image assessment and classification. The purpose of this paper is to describe a surgical series of paediatric spinal cord lipomas, their diagnosis, results and complications. We undertook a retrospective review of paediatric patients with spinal cord lipomas who underwent surgery between 2008 and 2022. The variables studied were age, gender, preoperative symptoms according to the Necker Functional Score (NFS), type of lipoma according to Morota's classification, functional and radiological surgical outcomes using the cord-sac ratio (CSR), need for re-operation, complications and follow-up. A total of 25 patients (average age 36months) underwent surgery. According to Morota's classification, MRI showed 13 type 1 lipomas, two type 2, two type 3 and eight type 4. The preoperative NFS was 16.06, with urological abnormalities being the most frequent manifestation. Total/near-total resection was attempted since 2015. Five patients with type 1 lipoma required re-operation due to clinical deterioration with suspected retethering, all of them with a CSR > 0.3. The series average CSR was 0.417. This paper highlights the importance of proper classification for a correct surgical approach to obtain favourable results and minimise possible complications. Based on our experience, given our results regarding the percentage of fistulae and retethering rates, we limited radical resection to symptomatic type 1 lipomas. Our future aim is to obtain better CSR rates and to decrease the retethering percentage.

Non-dysraphic intramedullary spinal cord lipoma of the child: Report of 3 cases

Background and purposeNon-dysraphic intramedullary spinal cord lipomas (NDSCL) represent 1% of spinal cord tumors. They are less frequent than dysraphic spinal cord lipomas and clinical presentation is unspecific. There are no guidelines on surgical management. Material and methodsWe report three observations of NDSCL in children, focusing on the clinical presentation, surgical management and postoperative outcome. ResultsThe patients, one female and two males, aged from 5 months to 10 years presented with neurological deterioration, pain, spinal rigidity and in two cases, a subcutaneous mass. Spinal MRI found intradural lipomas without spina bifida, located in the cervico-thoracic area in all cases. The lipoma extended to the medulla oblongata in two cases and was in the lumbar region in the third. These lipomas were massive, requiring decompression surgery. Surgery confirmed the lipoma to be subpial. We performed debulking of the lipoma without attempting total resection, and with or without dural plasty and laminoplasty, followed by minerva cast in two cases, and avoidance of standing in the youngest. Satisfactory recovery occurred in all three cases. After a follow-up between 4 months and 9 years, the outcome was favorable in all cases, and no patient presented with secondary spinal deformation or lipoma progression. ConclusionNDSCL is a rare entity, which often manifests with progressive pain and neurological deficits. In our experience, partial resection with or without dural plasty and laminoplasty has been associated with satisfactory postoperative outcomes and no recurrence of symptoms. We should be attentive to the risk of postoperative spinal deformity in these young patients.

V-049 THE IMPORTANCE OF PROCTORING- MISSING THE “TEN GOLDEN RULES” OF TAPP

Abstract Claus in 2020 published the “Ten golden Rules” for a minimally Invasive safe approach to the Myopectineal Orifice. During the first proctoring session of a TAPP procedure for the repair of a left side inguinal hernia we revised the application of the rules by the trainee. The proctor invited the trainee to study the paper before the session of surgery. The first and the last 3 rules were followed by the trainee but there was a lack of the 4-5-6-7 rules. The knowledge of the anatomy of the inguinal region allows the surgeon to create a preperitoneal box for a mesh at least 15×15cm covering all the possible origins for hernia. In particular we focused our attention to the rule 7. The trainee was missing to check the emptiness of the deep inguinal ring that was covered, in the iliopubic tract, by fat sliding to the scrotal region. After dissection a big cord lipoma was reduced in the abdomen. Missing this rule should be a problem because the patient could feel,after the inguinal hernia repair, a bulging and discomfort in the inguinal region. The imaging could not be helpful and the clinical visit could report a “false Positive” for the presence of bulging without a real hernia. In a similar case we reoperate a man after a TAPP procedures for a bulging in inguinal region, pain and discomfort miming a recurrence but we only found a large cord lipoma that we resected.

A case of Mullerian choristoma in lipomyelocele

Objective: Müllerian choristoma associated with spinal dysraphism is a rare diagnosis. Case: We present a case of heterotopic fallopian tube tissue found in a lipomyelocele. The patient, a 19-year-old woman, complained of swelling and pain in her lower back. Magnetic resonance imaging revealed spina bifida occulta at L3, tethered cord, and L3 lipoma. L3 - L4 laminectomy was performed, and the lipoma was removed. Histological examination revealed the presence of ectopic fallopian tube tissue within the lipoma.

Transition from partial to near-total/radical resection of spinal cord lipomas.

The objective of this retrospective study was to compare the outcomes and associated complication rates in the surgical management of spinal cord lipomas following a change of practice within our institution from partial resection (PR) to near-total/radical resection (NTR). Twenty-four children underwent surgical treatment for symptomatic spinal cord lipomas between 2009 and 2020. The near-total/radical resection group included 20patients with spinal cord lipomas and the comparison group included 6 patients with spinal cord lipomas who underwent partial resection. Filar lipomas were excluded. The mean age of the patients was 7years (range 1-14years). Post-operatively, a higher proportion of NTR patients (17/20, 85%) demonstrated improvement or stabilisation in Necker-Enfants Malades scores compared to PR patients (3/6, 50%) with a mean follow-up of 48 and 108months respectively. Two patients underwent re-do untethering surgery, both of which initially underwent partial resection surgery. Complication rates did not significantly differ between the two groups. Our data supports the view that near-total/radical resection should be considered the technique of choice over the conventional method of partial resection for spinal cord lipomas with no significant increase in complication rates.

Vestigial Tail Associated to Spinal Lipomas: Report of Seven Cases

Objective: Vestigial tail is a rare form of cutaneous stigmata often related to occult spinal dysraphism. We present 7 cases of vestigial tail associated to tethered cord and spinal lipomas in the Pediatric Neurosurgery Service of the Hospital Civil de Guadalajara. Methods: In this retrospective study from 2017-2022 we reviewed the spinal dysraphism data base of the Hospital de Guadalajara and included the cases of vestigial tails. Results: 7 patients, 5 female and 2 males with vestigial tails were included. Six different morphologies of tails are described so as their location and relationship to occult spinal dysraphism. All the patients received surgical treatment. Complete resection of the cutaneous stigmata and cord detethering were performed in four cases related to fatty filum terminale and the remaining three of the patients required radical resection of associated complex conus medullaris lipomas. All the surgical procedures were performed with microsurgical techniques and neurophysiological monitoring. Conclusions: The different classifications include two main forms of tails, true tail and false tail. Most true tails represent only a cosmetic issue, while the false ones are often in close relationship with spinal dysraphism. Considering the risk of underlying malformations associated with false human tails, the preoperative assessment should include a thorough neurological examination, and a spine magnetic resonance imaging. We present the association of several forms of spinal lipomas related to vestigial tails. Keywords: Vestigial tail, Tethered cord, Spinal lipoma, Pseudo tail, Occult spinal dysraphism.

Spinal cord lipomas in children: surgical resection and outcome

Spinal cord lipomas in children: surgical resection and outcome

Teaching NeuroImage: Lower Limb Muscle Weakness Due to Intramedullary Spinal Cord Lipoma.

A 24-year-old man presented with a 6-month history of weakness of the right lower limb, without upper extremity weakness. Spinal cord CT/MRI showed an extensive intramedullary lesion from C7 to T4, with classical radiologic features of lipoma (Figure). There was no spinal dysraphism. Subtotal resection of the lesion was performed. The pathology confirmed the diagnosis of lipoma. Postoperatively, the patient's motor function temporarily deteriorated. The symptoms improved after 2-month rehabilitation. Nondysraphic spinal intramedullary lipomas are extremely rare, constituting approximately <1% of all intraspinal tumors.1,2 MRI is the most sensitive imaging protocol; typical radiologic appearances can confirm diagnosis and avoid biopsy.

Recurrent Tethering in Conus Lipomas: A Late Complication Not to Be Ignored

Recurrent symptomatic tethered cord (RTC) is a long-term complication of spinal cord lipomas, responsible for progressive motor deficits, urologic dysfunction, and aggravation of spinal deformities. We retrospectively analyzed all cases of recurrent tethering after spinal cord lipoma surgery, the clinical and radiologic features that led to the diagnosis, the surgical management, and the neuro-orthopedic outcome at the last follow-up. The study was carried out over 20 years on 209 pediatric patients from a single institution, initially treated for a conus lipoma. Nine patients (4.8%) were surgically treated for an RTC. The age at retethering ranged from 2 to 12 years (median, 7.4 years). The time until the first and the second surgical procedure ranged from 19 to 140 months (median, 92 months [7.5 years]). The follow-up period after the second surgery ranged from 3 months to 13 years (median, 50 months). Regarding symptoms, pain responded well to surgery. Gait disturbances improved in 50% of patients after surgery. One patient with bladder dysfunctions also improved. The remaining patients maintained their presurgical status. When RTC is confirmed, the child should be referred to surgery as soon as possible, because we show that the postoperative clinical outcome improved and surgery did not worsen patients' condition. Follow-up should be as long as possible for these patients.

Embryopathological relationship between retained medullary cord and caudal spinal lipoma

PurposeRetained medullary cord (RMC) is a condition in which the cord-like structure (C-LS) is continuous from the conus and extends to the dural cul-de-sac, causing spinal cord tethering, which is thought to originate from the secondary neurulation failure. Although diagnostic criteria for RMC have not yet been fully established, the following three items are generally considered important: (1) Typical morphological features on neuroimaging and intraoperative view. (2) The electrophysiological border between the conus and C-LS. (3) Ependyma-lined canal with surrounding neuroglial tissues (E-LC w/NGT) on histopathological examination of C-LS. To clarify the differences with caudal lipoma, which are also considered to be secondary neurulation disorders, in their embryological backgrounds, the clinicopathophysiological findings were compared. MethodsFive patients with RMC and 11 with caudal lipomas participated in this study. ResultsAll five patients with RMC naturally satisfied all three items. Four patients histopathologically showed a small amount of fibroadipose tissue. Regarding the first item in caudal lipoma, neuroimages demonstrated C-LS running parallel with or in the lipoma in all patients. In terms of the second item, the electrophysiological border was identified in 3 out of 4 patients in whom a sufficient operative field was obtained. Concerning the third item, E-LC w/NGT was noted in 6 of 7 patients in whom the lipoma was resected as a column. Areas of fibroadipose tissue histopathologically accounted for more than half of the total area. ConclusionThe caudal lipomas fulfilled most of the three items, and the only prominent difference between these two is the difference in the proportions of fibroadipose and fibrocollagenous tissues. These findings provide further evidence for the idea that RMC and caudal lipoma can be considered consequences of a continuum of regression failure during secondary neurulation, and it may not be possible to distinguish between the two clearly.