Chiasmal Herniation after Suprasellar Tumor Resection

Introduction: Endoscopic endonasal approach (EEA) is an elegant and minimally invasive access to the anterior skull base. This technique is most commonly utilized in the resection of sellar/suprasellar lesions. We present a patient who developed a downward chiasmal herniation syndrome with visual decline following EEA resection of a large dermoid tumor and was eventually treated with a ventriculoperitoneal shunt (VPS).

Case Presentation: A 33-year-old male with a history of prior resection of a large sellar/suprasellar dermoid cyst via an orbitozygomatic approach in 2014 developed tumor recurrence with superior displacement of the optic chiasm. Despite his stable neurological status, reoperation and decompression to protect remaining vision was planned. His preoperative formal visual testing showed OD 20/70 and OS 20/25, and dense bitemporal hemianopsia.

The patient underwent EEA for tumor resection with residual adherent capsule left. In addition to increasing headaches, formal testing the next morning revealed a visual decline, measuring 20/200 bilaterally. Emergent CT scan and MRI showed hydrocephalus and downward herniation of the third ventricle and optic chiasm into the resection cavity and sella ([Fig. 1]). CSF diversion through an external ventricular drain (EVD) allowed immediate improvement of his left eye to 20/70. Serial CT scans were obtained to monitor ventricular size and location of the chiasm, which revealed reversal of his chiasmal herniation. Eventually a VPS was placed. He continued to have improvement of his vision: OD 20/150 and OS 20/25.

Six weeks following surgery, the patient re-presented with headache and blurry vision after blowing his nose. An MRI showed isolated pneumocephalus within the resection cavity with upward displacement of the chiasm. His vision had declined to OD 6/200 and OS 20/70. In response, his shunt setting was increased. During emergent exploration, his skull base closure was intact. Repeat imaging revealed that the chiasm descended to normal anatomical position. On discharge, the patient had visual improvement to OD 20/200 and OS 20/40.

Discussion: Visual deterioration following EEA is potentially reversible and emergent investigation is warranted. Our patient had preoperative arrested radiographic hydrocephalus, which eventually caused a herniation syndrome of the chiasm when the large tumor was removed. Pre- and postoperative measurements of the chiasm level relative to the skull supported our hypothesis. Additionally, CSF diversion improved his visual acuity with a more anatomic placement of the optic chiasm. A second incident of pneumocephalus created an upward herniation that was treated by dialing up the shunt. Literature review reveals rare cases of chiasmal descent treated with VPS or chiasmoplexy.

We present this case to highlight the importance of evaluating for preoperative hydrocephalus in patients with large sellar/suprasellar lesions, which may contribute to herniation of the optic chiasm. This complication was mostly reversible with CSF diversion.

Fig. 1 Sagittal MRIs. Red asterisk (*) marks the level of the anterior communicating artery (Acomm), which corresponds with level of optic chiasm in sellar/suprasellar cases. Preoperative (A), intraoperative (B), immediately postoperative (C), and pneumocephalus (D) scans are shown. Note the downward herniation into the sella on the postoperative scan (C).

No conflict of interest has been declared by the author(s).