Conus medullaris intramedullary arachnoid cyst- case report and review of the literature

BACKGROUND: Spinal intramedullary cysts present a radiological dilemma. We present a rare case of a conus intramedullary arachnoid cyst and report on its differentiating features and management. CASE DESCRIPTION: We report a case of a 30-month-old child who presented with decreased gluteal sensation and urinary dribbling for 6 months. Apart from some slowness in walking, the power was normal in all four limbs. Imaging showed a non-enhancing, T2-weighted hyperintense 12 × 8 mm conus intramedullary cyst without any edema. A T12-L1 laminotomy followed by marsupialization of the cyst was done. Histopathology was suggestive of an arachnoid cyst. The postoperative course was uneventful with improvement in muscle strength and achievement of regular milestones. We also present the pertinent review of the literature to date. CONCLUSION: Intramedullary arachnoid cysts are a rare entity and should form the differential diagnosis for cysts presenting in the conus medullaris. Simple decompressive options may suffice for symptomatic cases and radical excision may be avoided. A high index of suspicion is essential considering the subtle nature of presenting symptoms.