Spinal lipomas of the conus medullaris and filum terminale are the most common forms of occult spinal dysraphism. Clinical presentations vary based on anatomic location and size. Filum terminale lipomas occur in up to 5% of the general population based on cadaveric and magnetic resonance imaging studies. Most filum terminale lipomas are asymptomatic and rarely require treatment. This is the first known reported case of a 64-year-old woman presenting with lumbar radiculopathy with cascading spondylolisthesis at L3 to L4 and L4 to L5, synovial facet cyst at L4 to L5, and concurrent large filum terminale lipoma. After nonoperative management strategies failed, an extensive discussion about the source of her symptoms was completed. It was believed that the primary driver of her radicular pain was the synovial cyst and spondylolisthesis at L4 to L5, despite the large size of the lipoma. Surgical treatment entailed an L4 to L5 anterior lumbar interbody fusion, posterior spinal instrumentation and fusion using robotic-assisted navigation, and decompression of the synovial cyst through a transfacet approach. Postoperatively, the patient's buttock and leg pain was resolved. She returned to work with no restrictions and reported no pain or neurological symptoms at her final follow-up. Incidental filum terminale lipomas may be safely observed when surgically managing a patient with a concurrent, adjacent, and symptomatic degenerative lumbar spondylolisthesis and synovial facet cyst. In patients undergoing surgery for symptomatic degenerative lumbar spondylolisthesis with an associated synovial facet cyst, an incidentally identified, adjacent intradural filum terminale lipoma without tethered cord symptoms can generally be managed nonoperatively, avoiding unnecessary intradural exploration and its associated risks.

Intradural spinal lipomas are a form of closed dysraphism and a frequent cause of tethered cord. Although usually adipocyte predominant, rare lesions may contain additional histological elements that can yield unexpected intraoperative behavior. A 13-year-old boy presented with progressive right foot deformity, distal weakness, gait limitation, and a low conus at S1-2 with a large terminal lipoma on spine MRI. He underwent detethering with debulking and L5 osteoplastic laminoplasty under intraoperative neuromonitoring (IONM). During microsurgical dissection, a pink band along the right aspect of the lipoma appeared unlike a nerve root. Targeted stimulation produced contraction within the thecal sac. The segment was isolated and divided under IONM guidance. Histopathological analysis confirmed skeletal muscle fibers intertwined with lobulated adipose tissue and fibrovascular elements of the filum terminale, consistent with a myolipoma. The patient had no postoperative sensory changes and progressed satisfactorily. Electrically evoked lipoma contraction is a physiological signature suggestive of myolipoma and can refine the extent of safe untethering. Although IONM adds value beyond evoked potential mapping by eliciting myogenic contraction and helping discriminate resectable elements from neural structures, the resulting EMG tracing becomes difficult to interpret in the presence of muscle and detethering proceeds based on visual assessment. https://thejns.org/doi/10.3171/CASE25811.

To describe prenatal imaging findings and postnatal outcomes in fetuses diagnosed with saccular forms of closed spinal dysraphism (CSD). This retrospective single-centre study included fetuses diagnosed with non-genetic, non-syndromic CSD between January 2018 and June 2023. Prenatal ultrasound and MRI findings were reviewed, with postnatal outcomes assessed in those managed expectantly, focusing on neurosurgical interventions, motor function, and urologic and bowel outcomes. Eighteen cases were identified; twelve opted for expectant management and had postnatal follow-up. The most common lesion was dysraphic spinal cord lipoma (10/18, 55.6%), followed by limited dorsal myeloschisis (3/18, 16.7%), myelocystocele (3/18, 16.7%) and meningocele (2/18, 11.0%). Chiari malformation and related brain abnormalities were absent at the time of diagnosis in all cases. Most fetuses (88.9%, 16/18) had a low-lying conus medullaris, and 70.6% (12/17) had a sac wall thickness ≥ 2 mm. Postnatally, 75% (9/12) underwent surgical detethering. At ≥ 30 months, all children could walk independently with or without orthoses. However, urologic complications were common in children age ≥ 48 months: 80% (4/5) required clean intermittent catheterization (CIC), 60% (3/5) had urinary incontinence, and 40% (2/5) experienced bowel incontinence. Prenatal imaging features at the lesion level are key for diagnosing CSD. While motor outcomes are favorable, urologic and bowel dysfunctions are frequent in postnatal life.

The increasing utilization of magnetic resonance imaging has facilitated the detection of intraspinal abnormalities in congenital scoliosis (CS) caused by hemivertebra. However, the risk of intraspinal abnormalities across different hemivertebra patterns remains unclear. The aim of this study was to compare the prevalence of intraspinal abnormalities between single hemivertebra and multiple hemivertebra and identify key associated risk factors. A total of 1,048 patients with CS caused by hemivertebra who received surgical correction were included. The radiographic and clinical data for each patient were collected and analyzed. Intraspinal abnormalities were present in 16.5% of patients, including syringomyelia (9.2%), lipoma filum terminale (6.0%), low-lying conus medullaris (3.1%), tethered spinal cord (2.9%), diastematomyelia (2.4%), and Chiari malformation (1.9%). Patients with multiple hemivertebra demonstrated a significantly higher intraspinal abnormalities incidence than those with single hemivertebra (24.4% vs. 14.1%, p < 0.001). In single hemivertebra (HV), 51 of 114 patients (44.7%) have intraspinal abnormalities located outside the region of bony HV, while the figure is 26 of 59 (44.1%) in patients with multiple HVs. Multivariate logistic regression showed that female sex [odds ratio (OR) = 1.800, p = 0.001], semisegmented/nonsegmented morphology (OR = 1.499, p = 0.003), and multiple hemivertebra (OR = 1.957, p = 0.001) are the risk factors of intraspinal abnormalities in all cases. Although 12.1% of all patients with intraspinal abnormalities had positive neurological findings, this was not statistically significant compared with those without intraspinal abnormalities (9.0%). Patients with multiple hemivertebra have a 1.96-fold higher risk of intraspinal abnormalities compared with those with a single hemivertebra. Importantly, intraspinal abnormalities are associated with female sex, multiple hemivertebra, and nonsegmented morphology, but not neurological symptoms, and caution should be paid to the intraspinal abnormalities outside of the bony lesions.

Spinal dysraphism consists a group of congenital anomalies due to defective neural tube closure, among which diastematomyelia or split cord malformation is rare. Split cord malformation is classified into Type I and Type II, with Type II being less common and often asymptomatic. These anomalies may coexist with various spinal anomalies, as tethered cord, neural lipoma, hemimyelocele, and dorsal dermal sinus, forming a complex spectrum. Adult presentations are particularly uncommon and usually incidental. We herein report a 23-year-old male with chronic low back pain and a congenital midline lumbar swelling. Neurological examination and routine investigations were unremarkable. Magnetic resonance imaging revealed Type II diastematomyelia with two hemicords within a single dural sac from L4 to L5, low-lying conus medullaris, hemimyelocele with neural lipoma at L5-S1, tethered cord with filum terminale lipoma extending to S3-S4, and a dorsal dermal sinus tract. Despite the radiological complexity, the patient remained neurologically intact. Neurosurgical intervention was advised; however, the patient chose conservative management with close follow-up. This case highlights a rare adult presentation of complex spinal dysraphism with minimal symptoms. While diastematomyelia Type II is typically diagnosed in childhood, adult cases are infrequent and often delayed. Magnetic resonance imaging is crucial for diagnosis, particularly in asymptomatic individuals with cutaneous markers. Though surgery is generally recommended to prevent neurological decline, conservative management may be appropriate in selected stable cases. This case emphasizes the need to consider spinal anomalies in adults with chronic back pain and the importance of multidisciplinary evaluation.