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.

Closed spinal dysraphism (CSD) encompasses a heterogeneous group of spinal cord deformities, which can be accompanied by several types of skin stigmata. These skin stigmata may include inconspicuous features, such as sacral dimples and deformed gluteal clefts, but the association between such mild skin stigmata and CSD is uncertain. This study aimed to reevaluate the indication for magnetic resonance imaging (MRI) in patients with skin stigmata while considering the indication for surgery. A retrospective analysis was conducted on magnetic resonance images of 1255 asymptomatic children with skin stigmata between 2003 and 2015. Skin stigmata classification was based on medical chart data. All subtypes of CSDs except for filum terminale lipomas (FTL), FTL thicker than 2 mm or with low conus medullaris, were considered to meet the surgical indication. CSD prevalence was estimated while considering the surgical indications and assessed after excluding all FTL cases. Skin stigmata were classified into seven types, dimple, deformed gluteal cleft, hair, subcutaneous mass, appendage, discoloration, and protruding bone, and included 1056 isolated and 199 complex ones. The prevalence of CSD was 19.5%, 6.8%, and 0.5% among patients with isolated dimples (n = 881) and 13.9%, 5.8%, and 0.7% among those with isolated deformed gluteal clefts (n = 136) for all cases, surgical indications, and patients without FTL, respectively. Dimples and deformed gluteal clefts had a low prevalence of CSD requiring surgical intervention, and cases without FTL were rare. Asymptomatic patients with mild skin stigmata may not require immediate MRI.

The purpose of this paper is to investigate occult spinal dysraphisms (OSD) using lumbar ultrasonography (LUS) in newborns presenting with specific skin markers or sacrococcygeal dimple. From 2012 to 2015, we performed LUS in newborns with cutaneous stigmata and/or sacroccygeal dimple. Magnetic resonance imaging (MRI) was performed in all patients with abnormal ultrasound or features of neurological involvement in order to detect spinal lesions. We prospectively evaluated 475 newborns who presented cutaneous stigmata performing LUS during their 4 weeks of life though 439 completed the study. All patients had a follow-up of almost 12 months. Of these, 39 presented abnormal ultrasonography and underwent MRI. In this group, spinal dysraphism was confirmed in 12 patients. When considering skin markers, dermal sinus correlated with higher risk of spinal cord lesions, on the other hand the presence of simple sacral dimple alone denoted a very low risk of occult spinal dysraphism. The simultaneous presence of more skin markers and/or the presence of lumbar ultrasonography abnormality regarding the level of the conus, pulsatility, and the position of the cord, thickness of the filum terminale, or the presence of an intratecal mass, lipoma, or dermal sinus tract indicated the necessity to perform MRI in order to detect spinal cord abnormalities because of higher risk of spinal lesions. LUS in newborns with specific skin markers is a valid method to select patients in which MRI can be performed to detect OSD. The presence of a simple sacral dimple alone is a negligible marker for occult neural pathology while the presence of isolated dermal sinus or more than one cutaneous marker could be considered indicative of higher risk of spinal dysraphism.

Lumbosacral lipoma is reported to occur in 4-8 of 100,000 patients. Sixty-six percent of lipomyelomeningocele in young patients have accompanied by hypertrophic filum terminale. It is rare to find two isolated spinal lipomas simultaneously. Embryological origin of dorsal and filar lipomas is different from each other and hence rarer to find them together. Radical resection is now being preferred for better long-term progression-free survival. We report an interesting case of spinal dysraphism in a 4-month-old female child with protruding, nontender, soft, subcutaneous 5 cm × 7 cm mass of the lumbosacral area that had been present since birth. Other anomalies included polydactyly of left hand. Magnetic resonance imaging demonstrated two isolated spinal lipomas, a transitional type and a terminal type filum lipoma with an interval of normal filum between the two. The findings were confirmed at surgery and detethering done along the white plane with neural placode reconstruction as described by Dachling Pang. The child had an uneventful postoperative recovery.

OBJECTIVE Cutaneous stigmata or congenital anomalies often prompt screening for occult spinal dysraphism (OSD) in asymptomatic infants. While a number of studies have examined the results of ultrasonography (US) screening, less is known about the findings when MRI is used as the primary imaging modality. The object of this study was to assess the results of MRI screening for OSD in infants. METHODS The authors undertook a retrospective review of all infants who had undergone MRI of the lumbar spine to screen for OSD over a 6-year period (September 2006-September 2012). All images had been obtained on modern MRI scanners using sequences optimized to detect OSD, which was defined as any fibrolipoma of the filum terminale (FFT), a conus medullaris ending at or below the L2-3 disc space, as well as more complex lesions such as lipomyelomeningocele (LMM). RESULTS Five hundred twenty-two patients with a mean age of 6.2 months at imaging were included in the study. Indications for imaging included isolated dimple in 235 patients (45%), asymmetrically deviated gluteal cleft in 43 (8%), symmetrically deviated (Y-shaped) gluteal cleft in 38 (7%), hemangioma in 28 (5%), other isolated cutaneous stigmata (subcutaneous lipoma, vestigial tail, hairy patch, and dysplastic skin) in 31 (6%), several of the above stigmata in 97 (18%), and congenital anomalies in 50 (10%). Twenty-three percent (122 patients) of the study population had OSD. Lesions in 19% of these 122 patients were complex OSD consisting of LMM, dermal sinus tract extending to the thecal sac, and lipomeningocele. The majority of OSD lesions (99 patients [81%]) were filar abnormalities, a group including FFT and low-lying conus. The rate of OSD ranged from 12% for patients with asymmetrically deviated gluteal crease to 55% for those with other isolated cutaneous stigmata. Isolated midline dimple was the most common indication for imaging. Among this group, 20% (46 of 235) had OSD. There was no difference in the rate of OSD based on dimple location. Those with OSD had a mean dimple position of 15 mm (SD 11.8) above the coccyx. Those without OSD had a mean dimple position of 12.2 mm (SD 19) above the coccyx (p = 0.25). CONCLUSIONS The prevalence of OSD identified with modern high-resolution MRI screening is significantly higher than that reported with US screening, particularly in patients with dimples. The majority of OSD lesions identified are FFT and low conus. The clinical significance of such lesions remains unclear.