Filum Terminale Lipoma Presenting as Painful Monoparesis in Adolescents: A Case Series of Chronic Progressive Lumbosacral Radiculopathy

A bstract Lumbosacral radiculopathy due to structural lesions of the filum terminale or cauda equina is uncommon but may present with progressive lower-limb pain and weakness. Filum terminale lipomas are frequently incidental magnetic resonance imaging (MRI) findings, and only few are symptomatic. When they do, the presentations may be atypical and lack classical red-flag signs such as saddle anesthesia. We report a case series of two adolescents with symptomatic filum terminale/cauda equina lipoma presenting predominantly with painful asymmetric monoparesis. The first case was a 17-year-old girl with a 1-year history of progressive unilateral radicular pain followed by distal-to-proximal lower-limb weakness and later bladder and bowel symptoms, but without saddle anesthesia. The second case was a 16-year-old boy who presented with a 2-month history of low back pain and painful unilateral monoparesis without sphincter involvement, consistent with lumbosacral radiculopathy secondary to filum terminale lipoma. In both cases, spinal MRI revealed a fat-intensity lesion in the filum terminale/cauda equina region, causing nerve root compression and displacement. Both patients were referred for neurosurgical evaluation at the time of reporting and received symptomatic neuropathic pain management. Symptomatic filum terminale lipoma can rarely present during adolescence with chronic, progressive, painful monoparesis and lumbosacral radiculopathy. Although many patients do not initially show the classical features of cauda equina syndrome, progressive neurological deficits and sphincter dysfunction may eventually develop.