REVERSIBLE VISUAL DEFICIT FOLLOWING DEBULKING OF A RATHKES CLEFT CYST- A TETHERED CHIASM - CASE-REPORT

Delayed chiasmal syndromes after emptying of a Rathke's cleft cyst hav e not been reported previously. When these deficits occur following th e treatment of parasellar lesions they are usually associated with the descent of a scarred optic system into an empty sella, and vision oft en improves promptly when the optic system is elevated. Two months aft er transsphenoidal surgery with emptying of a large intrasellar cyst, a 22-year-old man developed recurrent bitemporal visual field deficits over a 3-day period. Sagittal magnetic resonance images demonstrated an enhancing band of tissue extending anteriorly from the normally pla ced chiasm down to the anterior portion of the sella turcica. At crani otomy the enhancing tissue was found to be scar extending from the ant erior border of the chiasm to the diaphragma sellae. The anterior port ion of the diaphragm was resected as widely as possible without dissec ting the scar itself from the chiasm. A membrane consistent with the w all of a Rathke's cleft cyst was found attached to the resected tissue . The patient's vision was improved 2 days after surgery. This case il lustrates that traction by scar extending from the chiasm to the diaph ragm, even when the chiasm is in its normal anatomical location, may c ause progressive visual loss; and that untethering of the chiasm by re secting the diaphragm while leaving the scar intact can result in impr oved vision.