Dermoid cyst of the lateral wall of the cavernous sinus presenting with isolated abducens nerve palsy

Dear Editor,Dermoid cysts are rare congenital slow growing neoplasmsaccounting for less than 1 % of intracranial tumors [2].Dermoid cysts confined to the lateral wall of the cavernoussinus are extremely unusual and clinical symptoms general-ly occur late in the course of tumor growth, due to localirritative effects of the space-occupying lesion. The mostcommon clinical presentation results from involvement ofthe cranial nerves contained in the lateral wall of the cav-ernous sinus. Accordingly, while trigeminal nerve dysfunc-tion, oculomotor and trochlear nerve palsies with dermoidorigin have been widely described [1, 5], isolated abducensnerve deficit, to the best of our knowledge, has not beenpreviously reported.A 37-year-old man presented with a 1-week history ofprogressive diplopia. On the first examination, a remarkablelimitation in abduction in his right eye was observed (Fig. 1).Magneticresonanceimaging(MR)demonstratedacysticovalshaped lesion in the right parasellar space hypointense tohyperintense on T1- and T2-weighted images, whichpresented a slight rim of enhancement after contrast injection(Fig. 1). The posterior vertical segment and the posteriorbend of the intracavernous carotid artery were displacedantero-medially (Fig 1). Analysis of MR images suggestedthat the tumor was an interdural dermoid cyst of the lateralwall of the cavernous sinus.The patient underwent a right fronto-temporal cranioto-my for intradural resection of the tumor, which was ob-served bulging into and deforming the lateral wall of thecavernous sinus. The outer (or meningeal) layer of thelateral wall was incised over the most prominent part ofthe tumor, and its greasy content associated with hair tuftswas progressively removed. The capsule adherent to theinner (or membranous) layer of the lateral wall of the cav-ernous sinus was dissected and removed in a piecemealfashion.Histopatological examination confirmed that the tumorwas a dermoid cyst.The patient’s postoperative recovery was uneventful. Atthe 1-month follow-up examination, diplopia had resolvedand MR images obtained at this time revealed total tumorresection (Fig. 1).Interdural dermoid cysts of the lateral wall of the cavern-ous sinus have been rarely reported in the literature [1, 5].The lateral dural wall of the cavernous sinus is composed oftwo layers, the outer layer (meningeal layer or dura propria)and the inner membranous layer (or endosteal layer), whichis formed by the dural sleeves of CN III, IVand V1 [3, 7].According to this meningeal architecture, interduraldermoid cysts generally induce symptoms due to involve-ment of the ophthalmic division of the trigeminal nerve,oculomotor nerve and trochlear nerve [1, 5]. In the present