Abstract
AimsLumbosacral lipomas (LSL) are congenital disorders of the terminal spinal cord region that have the potential to cause significant spinal cord dysfunction in children. They are of unknown embryogenesis with variable clinical presentation and natural history. It is unclear whether the spinal cord dysfunction reflects a primary developmental dysplasia or whether it occurs secondarily to mechanical traction (spinal cord tethering) with growth. While different anatomical subtypes are recognised and classified according to radiological criteria, these subtypes correlate poorly with clinical prognosis. We have undertaken an analysis of surgical specimens in order to describe the spectrum of histological changes that occur and have correlated the histology with the anatomical type of LSL to determine if there are distinct histological subtypes.Methods and resultsThe histopathology was reviewed of 64 patients who had undergone surgical resection of LSL. The presence of additional tissues and cell types were recorded. LSLs were classified from pre‐operative magnetic resonance imaging (MRI) scans according to Chapman classification. Ninety‐five per cent of the specimens consisted predominantly of mature adipocytes with all containing thickened bands of connective tissue and peripheral nerve fibres, 91% of samples contained ectatic blood vessels with thickened walls, while 22% contained central nervous system (CNS) glial tissue. Additional tissue was identified of both mesodermal and neuroectodermal origin.ConclusionsOur analysis highlights the heterogeneity of tissue types within all samples, not reflected in the nomenclature. The diversity of tissue types, consistent across all subtypes, challenges currently held notions regarding the embryogenesis of LSLs and the assumption that clinical deterioration is due simply to tethering.
Highlights
Lumbosacral lipomas (LSL) of the conus medullaris are a common form of spinal malformation
The role of resection of the lipoma and untethering of the spinal cord in averting neurological and urological deterioration is controversial.[5,6]. The essence of this controversy is whether the neurological and urological disability is a result of secondary injury to the terminal spinal cord and cauda equina through a process of mechanical tethering – and potentially amenable to surgery – or whether dysfunction is a result of a primary inherent malformation
Of the 64 specimens, 95.3% consisted predominantly of mature adipocytes, while the other specimens had a greater proportion of immature adipocytes
Summary
Lumbosacral lipomas (LSL) of the conus medullaris are a common form of spinal malformation. Diagnosis is made typically in infants on the basis of a midline lumbosacral swelling, sometimes accompanied by local cutaneous manifestations including dermal sinus, skin appendage and capillary haemangioma.[1] At the time of diagnosis there may already be features of distal spinal cord dysfunction, including distal lower limb weakness and asymmetry, talipes deformities and features of neurogenic sphincter impairment; as many as 40% of cases are ostensibly asymptomatic at birth. Over time all patients are at risk of new or progressive neurological deterioration.[2,3,4] The role of resection of the lipoma and untethering of the spinal cord in averting neurological and urological deterioration is controversial.[5,6] The essence of this controversy is whether the neurological and urological disability is a result of secondary injury to the terminal spinal cord and cauda equina through a process of mechanical tethering – and potentially amenable to surgery – or whether dysfunction is a result of a primary inherent malformation
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