In another procedure, after surgery to expose and drain the cysts, a flap of nearby muscle tissue is used to fill the cyst in order to prevent recurrence. A muscle flap is a portion of muscle that can be transferred along with its blood supply to an adjacent part of the body. The muscle flap is use to fill the decompressed cyst and to prevent it from refilling with cerebrospinal fluid. Results of treatment may be disappointing if irreversible nerve damage has already occurred.