Aneurysmal bone cyst of the lumbar spine: a case report
The present case has been reported in the Asian Journal of Neurosurgery.

A 17-year-old female presented with one week history of severe localized lower back pain at fourth lumbar vertebral level which increases on lying supine. On examination, she had left dorsiflexion and EHL weakness of grade 4/5 with sensory impairment in left L5 dermatome. Local tenderness on palpation was present. Her bladder and bowel habits were normal. There was no previous history of trauma. X-rays showed osteolytic lesion involving the L4 vertebral body with winking owl sign on AP views.

CT scan of lumbar spine with reconstruction showed lytic expansile lesion involving the L4 vertebral body and left pedicle. MRI revealed characteristic findings of aneurysmal bone cyst with multiple fluid-fluid levels. There was extension of the lesion into the spinal canal and pressure on the left sided nerve roots. She underwent left transpedicular approach and complete excision of the lesion followed by pedicle screw fixation. The lesion had a dark red fleshy appearance with moderate vascularity.

The lesion was encasing the nerve root on the left side, which was carefully dissected and excised. Multiple blood filled cysts involving the L4 vertebral body were encountered. The tumor was totally extradural and was completely excised. Histopathology of the lesion revealed uniformly distributed osteoclast type giant cells having multiple nuclei. There were few cysts containing hemorrhage and were lined by histiocytes and osteoclast giant cells. These features were suggestive of secondary aneurysmal bone cyst.

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