Sacral aneurysmal bone cyst in a child presenting with radiculopathy

Abstract

A13-year-old girl with complaints of difficulty in walking, left leg pain, and lower back pain of 1 month duration was admitted to our pediatric neurology department. Having the symptoms of lumbosacral radiculopathy, a magnetic resonance imaging (MRI) was ordered to exclude any herniated disc, spinal stenosis, or arthritic and degenerative changes of the facet joints. Lumbosacral MRI demonstrated a 4-cm×3.5cm×3.5-cm well-defined, expansile lesion of the left side of the sacral bone at the level of the S1–S2 vertebrae extending to the left sacroiliac joint (Figs. 1 and 2). The lesion was hypointense on T1WI and hyperintense on T2WI containing cysts with internal septations and characteristic fluidfluid levels representing blood of variable ages that was compatible with aneurysmal bone cyst (Fig. 2a and 2b). At the level of S1 and S2 the nerve roots at the left side were compressed by this expansile lesion. After contrast administration, we did not observe any enhancement or solid component distinctively. The left piriformis muscle had denervation-related muscle atrophy because of entrapment neuropathy of the piriformis nerve, originating in the sacral plexus and arising from the posterior division of the ventral rami of the first and second sacral nerve (Fig. 2c).An open bone biopsy confirmed the diagnosis of aneurysmal bone cyst which