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

Diagnosis and Presentation

The diagnosis of a lipomyelomeningocele largely depends on an understanding of the pathology. Lipomyelomeningocele is characterized by a subcutaneous lipoma that is generally located in the lumbar or sacral region.[25] The subcutaneous lipoma extends through a defect in the lumbodorsal fascia, vertebral neural arch, and dura, attaching to an elongated and tethered spinal cord.[27] The most common presenting symptom is a fatty mass positioned in the midline or just off the midline in the lumbosacral region. Additionally, the majority present with other skin lesions associated with the lipoma, including a hairy nevus, skin dimples, and cutaneous hemangiomas.[27,34,61] Because the fatty mass is clinically apparent at birth, those affected are generally diagnosed before neurological symptoms present, and as many as 48% have been found to be neurologically intact on initial diagnosis.[25,64]

Three categories of lipomyelomeningocele exist, based on the relative anatomy of the lipoma and neural components: dorsal, transitional, and caudal. The dorsal-type lipomas have an area of attachment to the dorsal spinal cord at the area of myeloschisis in the lower lumbar or lumbosacral levels of the spinal cord and are continuous with the subcutaneous tissue. The lipoma passes through a fascial defect, and may extend into and expand the central canal. A dural defect is present and the placodelipoma interface may lie in the extradural space. Transitional lipomas have an attachment that extends beyond the area of myeloschisis down to the conus, with a less distinct lipoma-cord interface. The lipoma again extends through a dural defect. The caudal-type lipomas arise predominantly from the caudal end of the conus medullaris. These lipomas may extend through a dural defect or may be encased in the dura.[49,69]

As the subcutaneous lipoma is restricted by the defect in the lumbodorsal fascia, the upward movement of the conus medullaris during axial growth may be limited and thus may lead to progressive neurological and urinary deficits, the sequelae of a tethered cord.[29] Loss of neurological function has been found to increase with age because of progressive conus tethering and injury to nervous tissue. Loss of neurological function has also been demonstrated to have a logarithmic association with increasing patient age and is believed to be secondary to increased stretch on the spinal cord with axial growth spurts.[26,27,33,52] Other theories regarding the mechanism of progression of symptoms include decreased perfusion secondary to stretch on the spinal cord, increased mass effect from progressive deposition of fat, and stretching effects on the spinal cord.[51,52,71] Hoffman et al.[27] observed that 62.5% of patients were neurologically asymptomatic prior to 6 months of age, while only 29.3% were asymptomatic after 6 months of age. Furthermore, Koyanagi et al.[39] reported progressive neurological symptoms with age in patients with tethered cord, with no children remaining asymptomatic after age 5. A series of 80 patients reported by Kanev et al.[34] demonstrated that bowel and bladder function deteriorates prior to motor function or sensation. Patients in their series demonstrated complete paralysis of bowel and bladder prior to the appearance of motor or sensory loss on physical examination. The disease progression can result in frequent urinary tract infections and neurogenic bladder and bowel incontinence or constipation, as well as leg length discrepancy, foot deformities, gait abnormalities, scoliosis, spasticity, and back and leg pain.[27,34]

Urinary complaints in these children are secondary to the impaired innervation of the urinary system, either from malformation during embryogenesis, or a tethered cord as a result of the lipomyelomeningocele. Urinary dysfunction can be due to detrusor paresis, external sphincter dysfunction, or most commonly, detrusorsphincter dyssynergy.[15] Urinary dysfunction may cause symptoms such as urinary incontinence, frequent urinary tract infections, urinary urgency, and in severe cases of urological dysfunction, hydronephrosis or pyelonephritis may cause upper urinary tract damage. The initial symptom of a neurogenic bladder is frequently a change in micturition pattern.[12] Urodynamic testing aimed at evaluation of urological dysfunction may help with evaluation of the severity of dysfunction. Additionally, abnormality of bladder function may be the only evidence of neurological compromise in these children.[20]

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