Lipomyelomeningocele, is a closed neural tube defect, that usually occurs in the lumbosacral area as a single lesion but can be associated with other spinal dysraphism 1) and Caudal regression syndrome.
Represent a unique population within the spectrum of spinal dysraphism.
Premature separation of the neuroectoderm from the ipsilateral surface ectoderm allowing mesenchymal tissue to invade into the central canal, or “premature dysjunction” theory, was proposed for the pathogenesis of dorsal type lumbosacral lipoma. To test this theory, the unilateral neural fold was incised using Hamburger and Hamilton stage 12 or 13 chick embryos. Among 35 embryos evaluated, 15 showed abnormal findings, and of these one showed findings which suggested lumbosacral lipoma: a back lump, blending of the neuroepithelium and mesenchyme through indistinct basement membrane and vertebral body abnormalities. The other 14 embryos showed abnormalities including blunt tails, open neural tube defects, incomplete closure of the dorsal neuroepithelium with intact skin, skin dimples, disorganized gray matter, scoliosis, ectopic neuroepithelium and an accessory spinal cord. The results revealed that the incision of the unilateral neural fold in the early chick embryo may produce a lesion suggestive of lumbosacral lipoma, a finding which supports the premature dysjunction theory. This method needs further refinement to overcome technical difficulties, high mortality, and a low yield before being adopted as an experimental model for lumbosacral lipoma 2).
A subcutaneous lipoma that passes through a midline defect in the lumbodorsal fascia, vertebral neural arch, and dura, and merges with an abnormally low tethered cord 3).
The natural history of LMMC remains poorly defined. The description and prevalence of the presenting orthopaedic clinical signs and symptoms for LMMC have been infrequent and often documented only in general terms.
Many patients with lumbosacral lipoma are asymptomatic; however, a significant proportion will have neurological deficits present at birth and most develop neurological symptoms over time.
Implication of these deficits with respect to natural history and management are not well understood.
New dynamic MRI-based parameters to establish the presence and magnitude of tethered cord syndrome (TCS) have been defined. oscillatory frequency (OF) measured the extent of loss of translational cord displacement in supine and prone positions; delta bending angle (ΔBA) defined the relative angulation of conus with lower spinal cord, and sagittal and axial root angles represented ventral nerve root stretching. The difference in OF or ΔBA was minimum in the group with thick filum terminale and progressively increased in the groups with lipomyelomeningocele and meningomyelocele 4)
Butterfly vertebra may be associated.
From Naidich TP, McLone DG, Mutluer S. A new understanding of dorsal dysraphism with lipoma (lipomyeloschisis): radiologic evaluation and surgical correction. AJNR. 1983; 4:103–116 5)
- mobilize the subcutaneous mass, it funnels down through the deep fascia
- open last intact vertebral arch (work from normal dura)
identify the fibrovascular band that crosses the most cephalic widely bifid lamina
sectioning the fibrovascular band frees the dural tube and releases the sharp kink in the superior surface of the meningocele
taking care to preserve dorsal nerve roots, the dura is incised anterior to the dura-lipoma junction
similar procedure is carried out with arachnoid membrane
dural/arachnoid incisions are continued around entire extent of tethered conus
cord and placode are untethered;
Lipoma is then trimmed as completely as possible, intentionally leaving some fat behind to avoid injury to dorsal surface of placode. Superior extension along dorsal surface of cord or into central canal is debulked as much as is safely possible
the placode is reformed into a closed neural tube
close the pial margins
the dura is closed (primarily if possible, or using fascia lata graft if too much tension is placed on folded placode)
An expansile dural graft should be incorporated in cases of lipomyelomeningocele in which primary dural closure does not permit free flow of CSF 6).
Continuous eCUSA-based stimulation of the cauda equina during LMMC resection is a feasible mapping technique with potential added value improving safety of untethering. Future studies evaluating extension of untethering, as well as the rates of retethering and long-term neurological and urological outcomes, are warranted 7).
The aim of a study is to compare the outcomes of surgical and conservative treatments of pediatric asymptomatic lumbosacral lipomas, and to address whether the patients can benefit from prophylactic surgeries. The literature reports of surgical and conservative treatments of child asymptomatic lumbosacral lipomas were reviewed and collected, and a meta-analysis of the reports regarding the incidence of sphincter and lower limb dysfunctions was performed. A total of five literatures were collected, containing a total of 403 patients, among which 124 patients received conservative treatments with 32 (25.81%) cases developing neurological dysfunctions during follow-up, and 279 received prophylactic surgical treatments with 30 (10.75%) patients developing neurological dysfunctions in follow-up, the difference being statistically significant (P ≤ 0.05). For pediatric asymptomatic lumbosacral lipomas of the three major subtypes, the limited source of literature so far suggests that prophylactic surgery is superior to conservative strategy in preventing the patients from neurological deterioration. Larger patient cohorts, randomized studies, and longer length of follow-ups are needed for further corroboration 8).
Lumbosacral lipomyelomeningocele case series.
Lumbosacral Lipomyelomeningocele with Lateral Attachment to Neural Placode 9).
Fetal lipomyelomeningocele was suspected during the second-trimester ultrasound and confirmed by magnetic resonance imaging. The pregnancy took its course and a term neonate was delivered. At 2 years of age lipomyelomeningocele surgical removal was performed. The patient is now 4 years old and, despite neurogenic bladder, is a healthy boy with normal psychomotor development for his age. This case illustrates the favorable prognosis of this entity and the importance of prompt diagnosis and multidisciplinary counseling 10).
A patient with lipomyelomeningocele (known in utero) presented for MRI characterization prior to surgical procedure at three months of age. Cross-sectional imaging revealed a spinal dysraphism of the lower lumbar spine, with a posterior spinal defect spanning L4 to S2 subcutaneous fat intrusion, and distal spinal cord extrusion. An osseous excrescence was also appreciated, articulating with the left iliac bone. This case demonstrates the youngest known lipomyelomeningocele with accessory limb and the abnormal growth of multiple tissue types at the site of spinal dysraphism-a potential consequence of dedifferentiated cell proliferation originating from a secondary neural tube defect or rachipagus parasitic twinning 11)