Does conus morphology have implications for outcome in lumbosacral lipoma?

Abstract

Lumbosacral lipomas (LSL) of the 'dorsal' type have been associated with more favourable outcomes compared with other conus region lipomas. We hypothesised that integrity of the conus on MRI underpins the improved prognosis in this subgroup of LSL patients. The definition of 'dorsal lipomas' included lipomas with attachment to the conus, but where the conus could be delineated on MRI (Morota type 1) as reported by Morota et al. (J Neurosurg Pediatr 19:428-439, 2017). Additional inclusion criteria included asymptomatic status at presentation, age >3 years at follow-up, and neurological and urological evaluation at presentation and at last follow-up. Lipoma extent and conus level were recorded. Outcome measures were the need for untethering surgery and neuro-urological status at last follow-up. Urological outcomes were defined by continence and efficacy of bladder emptying. Twenty-six children were included (median age 8.7 years). Conus level was low (at or below L2) in 92%. Nine required untethering surgery: 5 prophylactic, 4 because of clinical deterioration. Twenty-five children were continent at last follow-up, one had stress incontinence, and none required catheterisation. One had persisting ankle weakness after surgery requiring orthotic support. In LSL of the conus, visualisation of the conus on MRI is associated with good urological and motor outcomes. The integrity of the conus appears to be a more important prognostic factor than anatomical level. An observational approach to this group of LSL patients does not appear to compromise outcomes. These findings support a selective approach to untethering surgery.