Lipomyelomeningocele: Pathology, Treatment, and Outcomes

A Review

Christina E. Sarris, B.S; Krystal L. Tomei, M.D., M.P.H; Peter W. Carmel, M.D; Chirag D. Gandhi, M.D.

Disclosures

Neurosurg Focus. 2012;33(4):e3 

In This Article

Radiological Assessment

Recent advances in both ultrasonography and MRI have substantially aided the diagnosis and treatment of spinal dysraphism, both prenatally and postnatally. Prenatal diagnosis of lipomyelomeningocele can be very challenging. A detailed examination of the fetal spine requires diligent scanning in various planes, with results that are very dependent on the position of the fetus. This examination has been aided by the utilization of 3D ultrasonography. The integrity of the neural canal is inferred by the regularity of the 3 ossification centers of the spine and the presence of soft tissue covering the spine; visualizing the conus medullaris in its normal location strengthens the likelihood of no abnormalities.[30] With higher frequency transducers, placode contents and cord tethering can be discerned.[7]

It may be difficult to detect lipomyelomeningocele by ultrasonography if the spine lies adjacent to the uterus, resulting in limited visualization of the subcutaneous mass. Magnetic resonance imaging is useful in demonstrating the presence of a fatty mass and cord tethering (Figs. 1 and 2>). Additionally, axial images are important in identifying splayed pedicles.[7]

Figure 1.

Sagittal T1- (left) and T2-weighted (right) MR images demonstrating a lipomyelomeningocele. Note the lipomatous component extending in the intradural and epidural spaces (arrows) as well as the subcutaneous space.

Figure 2.

Axial T2-weighted MR images demonstrating spina bifida occulta (left) with failure of fusion of the posterior elements at the midline, and the lipoma-placode interface (right, arrow).

While almost all open spinal dysraphisms are associated with an abnormal appearance of the posterior fossa on obstetric ultrasonography,[17] in a case of lipomyelomeningocele reported by Kim et al.,[37] the posterior fossa was completely normal. On ultrasonography, a well-demarcated subcutaneous mass was detected in the lower sacral area at 36 weeks. The spinal cord was observed to extend into the sacral area instead of being located in the upper lumbar spine, and an additional echogenic intraspinal mass contiguous with the lower spinal cord was identified. Kim et al.[37] reported that MRI revealed similar findings, but did not add new findings to the ultrasonography study.

Postnatally, MRI has aided in both the diagnosis and treatment of lipomyelomeningoceles. Lipomyelomeningocele features can vary substantially depending on the relative size of the lipoma and meningocele, along with the orientation of the neural placode.[64] Characteristically, imaging of lipomyelomeningocele reveals expansion of the spinal canal and subarachnoid space. The cord and the dura extend dorsally through the spinal dysraphism.[54] Most cases present with a deformed and stretched neural placode that is rotated toward the lipoma on 1 side. The meninges herniate on the opposite side. Spinal roots on the side of the lipoma emerge nearer to the neural foramina. These roots are shorter than the roots that emerge from the side where the meninges herniate, and these short roots serve to tether the spinal cord. The neural placode is frequently segmental.[64] A lipomatous dura mater can result if the lipoma surrounds the spinal cord or infiltrates the extradural space.[65]

After operation for lipomyelomeningocele, the cord may not be completely untethered, or after a short period may retether. Often this population will show imaging evidence of a tethered cord or low-lying conus despite the absence of symptoms.[2,44] As such, routine imaging may not be useful in evaluating patients after lipomyelomeningocele resection without clinical indication, unless the MRI is obtained in the immediate postoperative period to delineate a baseline. A study of 140 cases of tethered cord consisting of 48 cases of lipomyelomeningocele demonstrated no advantage in obtaining routine postoperative follow-up MRI scans.[24] In this study, only a single reoperation was performed on lipomyelomeningocele, and that was prompted by clinical evaluation rather than imaging. Determining the need for a tethered cord release after primary repair of a lipomyelomeningocele therein remains largely a clinical decision based on neurological function rather than on radiological findings. Additionally, because many pediatric patients may require sedation for MRI, the consideration for obtaining MRI must also include the risk and cost associated with this routine imaging. Tethered cord has been associated with progressive spinal deformities, and a series of 9 patients reported by Tubbs et al.[67] noted that tethered cord should be suspected in the presence of symptoms of tethered cord with an increasing lumbosacral angle.

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