Endoscopic Endonasal Fenestration of a Sellar and Suprasellar Arachnoid Cyst Mimicking a Rathke's Cleft Cyst: Diagnostic and Surgical Considerations

Background: Occasionally, sellar arachnoid cysts and Rathke's cleft cysts have overlapping clinical and radiologic features that create diagnostic uncertainty and demand intraoperative flexibility of approach. Patients presenting with signs of compression within the sella warrant surgical management, but the ideal surgical approach for each lesion differs significantly. Rathke's cleft cysts are routinely fenestrated into the sphenoid sinus through an endoscopic endonasal infrasellar approach, while arachnoid cysts are better managed with transcranial fenestration into the parasellar cisterns.

Presentation: We describe the case of a 73-year-old male presenting with progressive vision loss and hypopituitarism secondary to a sellar and suprasellar cystic lesion (preoperative imaging; [Fig. 1]). On imaging, the lesion lacked an intracystic nodule but was characteristically splitting the adenohypophysis and neurohypophysis, indicative of an epicenter within the pars intermedia, suggestive of a Rathke's cleft cyst. Further, the contents did not follow the signal intensity of cerebrospinal fluid on MRI, as would be expected for an arachnoid cyst. Although the differential diagnosis included an arachnoid cyst as a likely etiology, given the above findings, a Rathke's cleft cyst was thought more probable. As such, an endoscopic endonasal infrasellar approach was planned, with a suprasellar approach for fenestration into the parasellar cisterns as an alternative strategy if an arachnoid cyst were encountered. Bilateral rescue flaps were raised during the initial approach, preserving the posterior nasal branches of the sphenopalatine artery. Intraoperatively, the lesion proved to be an arachnoid cyst, and a suprasellar approach was utilized to fenestrate it into the surrounding cisterns ([Fig. 2]). Both the infrasellar and suprasellar defects were reconstructed with a single nasoseptal flap ([Fig. 3]). The patient had a favorable postoperative outcome that included resolution of his vision loss and hypopituitarism without complications.

Conclusion: This case highlights the diagnostic conundrum posed by select cystic lesions of the sellar region with overlapping features of both arachnoid and Rathke's cleft cysts and aims to review important points related to their differentiation, diagnosis, and management ([Table 1]). The surgical plan for such cases should include a flexible strategy, which often can be achieved with an endonasal approach.

Fig. 1

Fig. 2

Fig. 3

Table 1 Summary

Features	Sellar arachnoid cysts	Rathke's cleft cysts
Intracystic fluid	Homogeneous; CSF-like	Homogeneous; mucoid type or gelatinous type; intracystic nodule is sensitive and specific
Cyst wall	Not visible	Thin, peripheral rim of enhancement
Sellar localization	Rare; 1–3% of all ACs	Pars intermedia of pituitary; splits anterior and posterior lobes
T1-weighted MRI	Hypointense; nonenhancing	Hypointense or hyperintense; nonenhancing
T2-weighted MRI	Hyperintense; CSF like	Isointense to hyperintense
Classic surgical approach	Subfrontal open craniotomy; microscopic transphenoidal; endonasal transphenoidal	Endoscopic transnasal transphenoidal
EEA: treatment considerations	Requires collagen inlay and possible fat grafting; robust nasoseptal flap is critical for reconstruction	No inlay required; mucosal graft is sufficient if CSF leak occurs

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

Publication History

Article published online:
12 February 2021