[Osteoporosis, arachnoid cyst and conus medullaris compression].

The authors report the case of a 75-year-old woman with an osteoporotic vertebral crush fracture of L1, without detectable vertebral necrosis, with signs of conus medullaris compression. The outcome at 2 years was satisfactory with complete recovery of neurological impairment after laminectomy from T12 to L2 and evacuation of a compressive arachnoid cyst overlying L1. This rare case is remarkable because of the presence of an arachnoid cyst. The role of the latter in the pathogenesis and progression of the neurological lesions is discussed.