Convolutional neural network-based magnetic resonance image differentiation of filum terminale ependymomas from schwannomas.

PURPOSE: Preoperative diagnosis of filum terminale ependymomas (FTEs) versus schwannomas is difficult but essential for surgical planning and prognostic assessment. With the advancement of deep-learning approaches based on convolutional neural networks (CNNs), the aim of this study was to determine whether CNN-based interpretation of magnetic resonance (MR) images of these two tumours could be achieved. METHODS: Contrast-enhanced MRI data from 50 patients with primary FTE and 50 schwannomas in the lumbosacral spinal canal were retrospectively collected and used as training and internal validation datasets. The diagnostic accuracy of MRI was determined by consistency with postoperative histopathological examination. T1-weighted (T1-WI), T2-weighted (T2-WI) and contrast-enhanced T1-weighted (CE-T1) MR images of the sagittal plane containing the tumour mass were selected for analysis. For each sequence, patient MRI data were randomly allocated to 5 groups that further underwent fivefold cross-validation to evaluate the diagnostic efficacy of the CNN models. An additional 34 pairs of cases were used as an external test dataset to validate the CNN classifiers. RESULTS: After comparing multiple backbone CNN models, we developed a diagnostic system using Inception-v3. In the external test dataset, the per-examination combined sensitivities were 0.78 (0.71-0.84, 95% CI) based on T1-weighted images, 0.79 (0.72-0.84, 95% CI) for T2-weighted images, 0.88 (0.83-0.92, 95% CI) for CE-T1 images, and 0.88 (0.83-0.92, 95% CI) for all weighted images. The combined specificities were 0.72 based on T1-WI (0.66-0.78, 95% CI), 0.84 (0.78-0.89, 95% CI) based on T2-WI, 0.74 (0.67-0.80, 95% CI) for CE-T1, and 0.81 (0.76-0.86, 95% CI) for all weighted images. After all three MRI modalities were merged, the receiver operating characteristic (ROC) curve was calculated, and the area under the curve (AUC) was 0.93, with an accuracy of 0.87. CONCLUSIONS: CNN based MRI analysis has the potential to accurately differentiate ependymomas from schwannomas in the lumbar segment.

Lightning strike­induced cauda equina syndrome: a case report.

Peripheral nerve injuries after being struck by lightning have been documented. Here, we report a case of cauda equina syndrome induced by lightning. A 27-year-old man presented with numbness, a burning sensation in the saddle region, and increased urinary urgency after being struck by lightning. He had absent Achilles reflexes and paresthesia in the saddle region upon neurological examination, and magnetic resonance imaging of the spine was normal. Electrophysiological studies indicated involvement of bilateral L5, S1, and S2 myotomes and revealed cauda equina lesions. 
Peripheral nerve injury induced by lightning is rare, and the evaluation of people with neurological complaints using electromyography will help determine the true incidence.

Cauda equina thickening: an approach to MRI findings.

There are many causes of cauda equina (CE) thickening on neuroimaging of the lumbar spine. The imaging features of CE thickening for the various conditions often overlap and are non-specific to clinch a definite diagnosis. Hence, the imaging findings have to be discerned in accordance with the patient's presenting history, clinical examination findings, and results from electrophysiology and laboratory studies. In this review, the authors aim to supplement the existing literature on imaging findings of CE thickening with a diagnostic framework for clinical workup. The authors also aim to familiarise readers with the interpretation of CE thickening on magnetic resonance imaging (MRI) and would like to illustrate the normal variants and pitfalls that could be mistaken for abnormal results.

Endoscopic spinal cord untethering using a 1 cm skin incision technique in pediatrics: a technical case report.

BACKGROUND: Spinal cord untethering by sectioning the filum terminale is commonly performed in tethered cord syndrome patients with minor abnormalities such as filar lipoma, thickened filum terminale, and low conus medullaris. Our endoscopic surgical technique, using the interlaminar approach, allows for sectioning the filum terminale through a very small skin incision. To our knowledge, this procedure has not been previously reported. This is the first case report involving a 1 cm skin incision. CASE PRESENTATION: A 9-month-old male patient was referred to our neurosurgical department due to a coccygeal dimple. MRI revealed a thickened fatty filum. After considering the treatment options for this patient, the parents agreed to spinal cord untethering. A midline 1 cm skin incision was made at the L4/5 vertebral level. Untethering by sectioning the filum terminale was performed by full endoscopic surgery using the interlaminar approach. The procedure was uneventful and there were no postoperative complications. CONCLUSIONS: In terms of visibility and minimizing invasiveness, our surgical technique of using the interlaminar approach with endoscopy allows for untethering by sectioning the filum terminale through a very small skin incision.

Fatty filum terminale and low-lying conus medullaris in Gollop-Wolfgang complex: a case report and review of literature.

BACKGROUND/IMPORTANCE: Gollop-Wolfgang complex is a rare skeletal dysplasia with only 200 cases reported in the literature. This disorder is usually associated with several extraosseous anomalies. This report describes the first case of a fatty filum terminale and a low-lying conus medullaris in a patient with this complex. A review of the current literature of the Gollop-Wolfgang complex accompanies this case, highlighting the documented extraosseous anomalies seen in this complex. CLINICAL PRESENTATION: We report a case of an 18-month-old patient with Gollop-Wolfgang complex who underwent cord untethering with release of the filum terminale after extensive workup showed the presence of a dyssynergic bladder and radiological evaluation revealed a fatty filum terminale and low-lying conus medullaris. CONCLUSION: Gollop-Wolfgang complex is a skeletal dysplasia usually associated with several extra skeletal anomalies. Our report describes the first case of a fatty filum terminale and low-lying conus medullaris in this complex, as well as provides an overview of the documented anomalies seen in this disorder. A multidisciplinary approach is recommended when treating these infants in order to ensure that occult manifestations of the complex are not missed.

Neurogenic intermittent claudication caused by vasculitis in the cauda equina: an autopsy case report.

PURPOSE: Intermittent claudication (IC) refers to leg pain that is induced by walking and relieved by rest. Neurogenic IC is usually associated with lumbar canal stenosis (LCS). We present rare findings from an autopsied patient who had neurogenic IC caused by vasculitis in the cauda equina. METHODS: We performed antemortem neurological and electrophysiological assessments, sural nerve biopsy, and post-mortem examination of the spinal cord and brain. RESULTS: A 61-year-old man noted sudden-onset leg pain that was not associated with any traumatic trigger. His leg pain consistently appeared when the patient walked and quickly faded on stopping. Spine surgery and cardiovascular departments both made a diagnosis of IC. However, magnetic resonance imaging (MRI) did not show LCS, and all ankle-brachial pressure indices were normal. He subsequently developed diffuse muscle weakness of the legs a month after disease onset. Myeloperoxidase antineutrophil cytoplasmic autoantibody was seropositive (140 IU/mL), and a sural nerve biopsy revealed axonal injury and angiitis. MRI showed multiple cerebral infarctions. He was diagnosed with microscopic polyangiitis (MPA) and underwent corticosteroid therapy. He died from complications two months after the onset. A post-mortem study revealed vasculitis in the subarachnoid space of the cauda equina, spinal cord, and brain parenchyma. The cauda equina showed a combined loss of small and large axonal fibres. The lumbar cord displayed central chromatolysis of the lower motor neurons. CONCLUSION: MPA is a rare cause of neurogenic IC when the symptom is acute and multimodal. Small-vessel vasculitis affecting the cauda equina may underlie MPA-associated IC.

Relationship between lumbar spinal stenosis and cauda equina movement during the Valsalva maneuver.

OBJECTIVE: To confirm the relationship between lumbar spinal stenosis (LSS) and cauda equina movement during the Valsalva maneuver. MATERIALS AND METHODS: Two radiologists at our institution independently evaluated cauda equina movement on pelvic cine MRI, which was performed for urethrorrhea after prostatectomy or pelvic prolapse in 105 patients (99 males; mean age: 69.0 [range: 50-78] years), who also underwent abdominopelvic CT within 2 years before or after the MRI. The qualitative assessment of the cine MRI involved subjective determination of the cauda equina movement type (non-movement, flutter, and inchworm-manner). The severity of LSS on abdominopelvic CT was quantified using our LSS scoring system and performed between L1/2 and L5/S1. We calculated the average LSS scores of two analysts and extracted the worst scores among all levels. RESULTS: Cauda equina movement was observed in 15 patients (14%), inchworm-manner in 10 patients, and flutter in five patients. Participants with cauda equina movement demonstrated significantly higher LSS scores than those without movement (P < 0.001, Wilcoxon's rank-sum test). A significant difference was observed in the worst LSS scores between participants without movement and those with inchworm-manner movement (P < 0.001, Bonferroni's corrected). There were no significant differences between participants without movement and those with flutter movement (P = 0.3156) and between participants with flutter movement and those with inchworm-manner movement (P = 0.4843). CONCLUSION: Cauda equina movement in cine MRI during the Valsalva maneuver is occasionally observed in patients with severe LSS, and may be associated with pathogenesis of redundant nerve roots.

Microsurgical approach for resection of the filum terminale internum in tethered cord syndrome-a case demonstration of technical nuances and vignettes.

BACKGROUND: In tethered cord syndrome due to filum terminale pathology, the surgical approach to achieve detethering of the spinal cord may vary. Traditionally, sectioning the filum through a laminectomy at the lumbosacral level is performed. METHOD: A microsurgical technique at a higher level to approach the filum below the conus tip is performed. This allows for removal of the entire distal portion of the filum through a limited interlaminar approach and dural opening. CONCLUSION: We propose a technique to transect the filum terminale below the conus tip and extract the distal filum by releasing it from its intradural attachments to minimize any remnants of the filum terminale.

Primary Malignant Lymphoma of the Cauda Equina Diagnosed after Decompression for Lumbar Spinal Stenosis: A Case Report.

Primary malignant lymphoma confinement to the cauda equina is rare. Only 14 cases of primary malignant lymphoma in the cauda equina have been reported. In these cases, the clinical features were similar to those of lumbar spinal canal stenosis (LSCS). This report describes a case of diffuse large B-cell lymphoma of the cauda equina that was diagnosed after decompression surgery for LSCS. An 80-year-old man presented with gait disturbance due to progressive muscle weakness in the lower extremities over the previous two months. He was diagnosed with LSCS, and decompression surgery was performed. However, the muscle weakness worsened after surgery; therefore, he was referred to our department. Plain magnetic resonance imaging (MRI) revealed swelling of the cauda equina. It demonstrated marked homogenous enhancement by gadolinium-diethylenetriamine pentaacetic acid. 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) revealed diffuse accumulation of 18F-FDG in the cauda equina. These imaging findings were consistent with those of cauda equina lymphomas. To confirm the diagnosis, we performed an open biopsy of the cauda equina. Histological examination indicated diffuse large B-cell lymphoma. Considering the patient's age and activities of daily living, further treatment was not performed. The patient died four months after the first surgery. Rapid progression of muscle weakness, which cannot be prevented by decompression surgery, and swollen cauda equina on MRI may be signs of this disorder. Gadolinium-enhanced MRI, 18F-FDG PET, and histological investigation of the cauda equina should be performed for diagnosing primary malignant lymphoma of the cauda equina.

Filum terminale arteriovenous shunt with nidus structure: a report of rare condition and treatment consideration.

BACKGROUND:  In the literature, filum terminale arteriovenous shunts (FTAVSs) always feature a single shunt point. Nidus-type FTAVSs have rarely been reported, and the best treatment strategy is unclear. This is a report of one exceptional case of a nidus-type FTAVS and surgical treatment of the lesion. CASE DESCRIPTION: The patient suffered from cauda equina syndrome for 9 months. Magnetic resonance imaging and spinal angiography revealed a nidus-type FTAVF at the L2 level. Surgical resection was performed in the hybrid operating room, and the nidus was completely resected with the assistance of intraoperative methylene blue angiography and neurophysiological monitoring. The postoperative neurological function was stable. CONCLUSIONS: A nidus-type arteriovenous shunt could originate from the FT, and in such cases, complete surgical resection with intraoperative neurophysiological monitoring in a hybrid operating room should be suggested.

Cauda equina syndrome from intradural metastasis of a non-neural tumor: case report and review of literature.

BACKGROUND: Cauda equina syndrome (CES) is a challenging condition and it can be caused by variable entities. Leptomeningeal carcinomatosis (LC) is a multifocal seeding of the leptomeninges by malignant cells and it is observed in 1-8% of patients with solid tumors. Diagnosis of intradural metastases of the cauda equina is often delayed due to the non-specific characteristics of this condition but also to the delay of presentation of many patients. Cauda equina metastases usually occur in advanced cancers, but rarely can be the first presentation of disease. CASE DESCRIPTION: A 63-year-old man presented with 6 months history of low back pain and 20 d history of bilateral sciatica, hypoesthesia of the legs and the saddle, flaccid paraparesis and bowel incontinence determine by multiple nodular small lesions on the entire cauda equina with contrast-enhancement. Total-body CT showed a millimetric lesion at the lung. The patient underwent L2-L5 laminectomy and subtotal removal and histological examination showed a small cell lung carcinoma metastasis. CONCLUSIONS: In the literature, 54 cases of CES from non-CNS tumor metastasis are described. The diagnosis is challenging, back pain, with or without irradiation to the lower limbs, is the most frequently reported disturbance. In about 30% of patients there is no known malignancy and CES is the first clinical presentation. Treatment of choice is surgery, followed by radiotherapy and less frequently adjuvant chemotherapy. The surgical removal is almost always incomplete and functional outcome is often not satisfactory. Prognosis is poor.

Mobile cauda equina ependymoma, case report and literature review.

The aim of this study was to describe a very rare presentation of ependymoma that can derive from intraoperative complications for surgeons and increased morbidity for the patients. Multiple cases of mobile cauda equina tumors leading to inadequate approach have been reported in the literature, however, the reports of ependymoma histology are very rare. This report describes the third adult case in recent years and a retrospective review of cases reported in the literature until today. We show the clinical and radiographic presentation of a 79 years old patient that presented a mobile cauda equina tumor in the preoperative image, who went to surgery for resection and arthrodesis, obtaining in post-operative histology the diagnostic of ependymoma. The preoperative image shows the migration of the tumor avoiding the wrong approach. The patient went to surgery for laminectomy, pedicular screw arthrodesis L1-S1, and tumor removal, obtaining a complete resection and confirmed histology diagnostic of ependymoma, unfortunately, the patient died five days after by a cardiac arrest. The recent literature reports only four cases of mobile ependymoma, two of them in pediatrics patients and just only two adult cases, which means this is the third adult case of an ependymoma. Mobile cauda equina ependymoma is a very rare neoplasm presentation but is an entity that can lead to mistakes in the approach and may be useful for the neurosurgeons who day per day treat this pathology beware of this possibility.

Targeted embolisation for coexisting conus medullaris arteriovenous malformation and cauda equina arteriovenous fistulas with a varix on a shared drainer†.

BACKGROUND: The coexistence of vascular malformations in the conus medullaris and cauda equina has been rarely reported, and the complex angioarchitecture in multiple arteriovenous lesions remains poorly understood. CASE DESCRIPTION: A 17-year-old woman presented with a sudden-onset, stepwise worsening of weakness and pain in the bilateral legs. Angiography revealed conus medullaris arteriovenous malformation and cauda equina arteriovenous fistulas. One of the drainers was shared between the coexisting lesions and harboured a varix. Targeted embolisation of a fistulous point in the conus lesion was performed with precaution to prevent occluding the common drainage route, which led to symptom improvement with angiographical diminishment of the varix. CONCLUSIONS: Recognising that communications between drainers can be observed in multiple spinal arteriovenous lesions is important in facilitating a safe embolisation. Cautious assessment of angiogram with fusion images of cone-beam computed tomography and volumetric T2 magnetic resonance imaging can help in establishing the diagnosis and treatment strategy.

Cauda Equina Atrophy in Amyotrophic Lateral Sclerosis on Routine Lumbar Magnetic Resonance Imaging.

OBJECTIVE: The aim of the study was to evaluate the cross-sectional area of the cauda equina in amyotrophic lateral sclerosis (ALS) on routine lumbar magnetic resonance imaging and investigate the diagnostic accuracy in comparison with age- and sex-matched non-ALS controls. METHODS: This retrospective study included 15 ALS patients and 15 age- and sex-matched non-ALS controls. Two independent neuroradiologists measured and compared the total cross-sectional area of the cauda equina of ALS patients and the non-ALS controls at the level of the L3 and L4 using axial T2-weighted images. The cutoff value, sensitivity, specificity, and area under the curve were measured. The interobserver reproducibility of the 2 independently obtained measurements was evaluated. RESULTS: The total cross-sectional area of the cauda equina in the ALS group was significantly smaller than that in the non-ALS group (L3: median, 66.73 vs 90.19 mm 2 , P < 0.001; L4: median, 52.9 vs 67.63 mm 2 , P < 0.001). The cutoff values at L3 and L4 were 76.95 and 61.04 mm 2 with a sensitivity and specificity of 1 and 0.87 and 0.8 and 0.87, respectively. The area under the curve at L3 and L4 were high at 0.96 and 0.94, respectively. The interobserver reproducibility was 0.88 at L3 and 0.89 at L4. CONCLUSIONS: The ALS patients showed significant atrophy of the cauda equina compared with non-ALS patients.

Arteriovenous malformations of the filum terminale: clinical characteristics, angioarchitecture, and management of a rare spinal vascular pathology.

OBJECTIVE: The goal of this study was to describe clinical and neuroradiological features of arteriovenous malformations of the filum terminale (FT AVMs) and to present the authors' diagnostic and therapeutic management in this rare disease. METHODS: The presented cases were retrieved from a retrospectively collected database of all spinal vascular malformations treated between June 1992 and December 2021 at the Rheinisch-Westfälische Technische Hochschule (RWTH) University Hospital Aachen. Pretreatment and follow-up clinical and neuroradiological data were analyzed for this study. RESULTS: Data in 15 patients with FT AVM with a mean age of 60 years were included, with an overall incidence of FT AVM of 19% among all spinal AVMs in our cohort. Twelve of 15 (80%) patients were men. Nonspecific but typical clinical and MR findings of thoracolumbar congestive myelopathy were found in all patients. Spinal MR angiography, performed in 10 patients, identified in all cases the arterialized FT vein as well as a lumbar/lumbosacral location of an AV shunt. Digital subtraction angiography (DSA) showed an arterial supply solely via the FT artery in 12/15 (80%) patients and via an additional feeder from the lumbosacral region in the other 3/15 (20%) patients. All patients were treated surgically. During 1-year follow-up, 2 patients presented with recurrent FT AVM due to further arterial supply from the lumbosacral region, and were treated surgically. Neurological status was improved in all patients within the 1-year follow-up, with marginal further changes during long-term follow-up. CONCLUSIONS: Congestive myelopathy is the major pathological mechanism of symptoms in these patients, with no evidence for intradural bleeding. Missing the presence of possible multiple arterial supply of FT AVM during DSA may result in misdiagnosis and/or insufficient treatment. Due to the frequently prolonged course of FT artery, resection of the FT AVM may be a favorable treatment modality in comparison with endovascular treatment. Follow-up examinations are obligatory within the first 3 years after treatment, and further MR angiography and DSA examinations are indicated if congestive myelopathy persists.

Minimal invasive interlaminar approach for untethering of fatty filum terminale in pediatric patients - how I do it.

BACKGROUND: Fatty filum terminale is a form of spinal dysraphism and a third of all patients develop symptoms such as sensory, motor, and urinary impairment. Early surgery at 6 months has the advantage that the bone density is still soft, and the patients are not ambulatory yet, promoting faster healing. METHOD: We present our minimal invasive surgical technique for FFT untethering. CONCLUSION: Due to the low complication rate and the potentially high benefit of surgery, prophylactic untethering is recommended.

Filum terminale transection in pediatric tethered cord syndrome: a single center, population-based, cohort study of 95 cases.

PURPOSE: The purpose of this study was to evaluate outcome following surgical transection of filum terminale (FT) in symptomatic and asymptomatic pediatric patients with radiological findings consistent with tethered cord syndrome (TCS). METHODS: Patients < 17 years who underwent untethering surgery between 2007 and 2018 were screened for eligibility. Those who had undergone primary transection of the FT, and had preoperative radiological findings of fatty filum, thickened FT, or low-lying conus, below the pedicles of L2, were included. The cohort was divided into symptomatic and asymptomatic depending on clinical presentation. Surgical complications and functional outcome was recorded. RESULTS: In total, 95 patients were included, of whom 62 were symptomatic. In symptomatic patients, the main indications for radiological evaluation were scoliosis (29%) and motor symptoms (19%). In asymptomatic patients, skin stigmata (76%) were the most common finding. Fatty or thick FT was the most common radiographic finding, seen in 61% of symptomatic and 79% of asymptomatic cases. All patients underwent transection of the FT and were followed for a median of 1.8 years. A postoperative complication occurred in 12%, all Ibanez type Ib and managed without invasive treatment. For the symptomatic cohort, significant improvement was seen for both urodynamic assessment (48% improved, p = 0.002) and sensorimotor function (42% improved, p < 0.001). CONCLUSIONS: Neurological improvement or halted deterioration was seen in the majority of symptomatic cases. Asymptomatic patients did not experience any severe complications. Filum transection should be offered to symptomatic and asymptomatic patients upon diagnosis of fatty filum, thickened FT, or low-lying conus.

Detethering of MRI-Demonstrated Tethered Cord Syndrome.

INTRODUCTION: Recognition of tethered cord syndrome (TCS) in children is important because as the child grows, the spinal cord is stretched, leading to ischemia and subsequent neurological deficits, including bowel or bladder dysfunction, back and leg pain, or lower extremity weakness. Imaging findings raising concerns for tethering include presence of a fatty and/or thickened filum or a conus medullaris located caudal to L2. OBJECTIVES: The objective of this study was to describe the symptomatic presentation of TCS in our institution, detect demographic and diagnostic predictors of signs and symptoms, assess changes in symptoms over time, and examine whether demographic and diagnostic variables affect changes in symptoms over time. METHODS: Using a retrospective chart review from patients who underwent detethering at our institution between April 1, 2015 and March 31, 2019, we report on the signs and symptoms of patients undergoing detethering surgery at presentation and examine possible demographic and diagnostic predictors of those symptoms and changes in symptoms over time. Logistic regression analyses were used to determine whether symptoms at presentation were related to demographic and diagnostic predictors and to assess a change in symptoms over time. RESULTS: A total of 273 patients underwent detethering and were analyzed. Of these, 144 (53%) were <5 years of age, 151 (55%) were male, 233 (85%) had a fatty filum, 179 (66%) had a thickened filum, and 106 (39%) had a low-lying conus. Patients <5 years of age were less likely to have urological, gastrointestinal, and neurological or orthopedic symptoms; patients with thickened fila (i.e., greater than 2 mm in diameter regardless of fat-infiltration) were less likely to have urological symptoms; and patients with low-lying coni were less likely to have gastrointestinal symptoms. Patients exhibiting symptoms at presentation had reduced rates of symptoms at the follow-up, but a reduction in rates of symptoms over time was unrelated to demographic or diagnostic variables. Surprisingly, 123 (45%) patients presented with intractable constipation. CONCLUSION: In the population studied, several presenting symptoms, particularly constipation, were commonly reported. Children <5 years old were less likely to manifest clinically evident neurological/orthopedic, urological, and gastrointestinal symptoms than the older cohorts. Patients were less likely to report symptoms at both their first and second postoperative visit compared to presentation.

MRI characteristics of the fetal tethered spinal cord: a comparative study.

Purpose: To compare fetuses and children with confirmed tethered cord syndrome to age-matched controls to provide a reference for prenatally identifying tethered spinal cord and to identify salient points on MRI for diagnosis.Materials and Methods: This retrospective study enrolled 13 fetuses and 20 children with tethered cord syndrome, and age-matched counterparts were included as controls. The MRI features including concomitant malformations, position of the conus medullaris, and thickened filum terminale of the two patient groups were evaluated and compared. Levels of the conus medullaris were discriminated between patients and an equivalent number of controls.Results: Various concomitant malformations manifested on the MRI of all patients, and there were differences between the two patient groups. Significant differences of the level of the conus medullaris were found between the fetal and child patients (U, 26.50; Z, -3.87; p < 0.001) and between the normal fetus and child controls (U, 23.50; Z, -4.13; p < 0.001). The position of the conus medullaris was visibly lower in the patient groups than in the control groups. No significant difference in the diameters of the filum terminale was found between the fetal and child patients (p = 0.67).Conclusions: The current study's results indicate that tethered spinal cord syndrome can be diagnosed in utero with MRI combined with several characteristics, particularly the position of the conus medullaris. Special attention should be paid to the gestational age of the fetus because normal changes in spinal cord position occur with gestational development.

[Filum Lipoma].

Filum lipomas, a subtype of spinal lipomas, are ectopic fat tissue deposits of the filum terminale categorized as closed spinal dysraphism. They are occasionally and incidentally observed on MRI images, but generally require little surgical treatment. Early untethering surgery is recommended for symptomatic patients, whereas asymptomatic patients presenting normal level of the conus medullaris require no therapy and are regarded as having a normal variation. Prophylactic untethering surgery can be an option for asymptomatic patients with low set conus medullaris. Untethering surgery should be safely conducted using electrophysiological procedures. Herein, we summarize the clinical characteristics of the filum lipoma and describe our routine surgical procedures.