Rapidly progressive visual impairment and internal carotid artery stenosis caused by sphenoid sinus mucocele: illustrative case

Abstract

BACKGROUND

Sphenoid sinus mucocele is a rare type of paranasal sinus lesions that can occasionally cause neurological deficits such as optic and oculomotor nerve deficits. However, internal carotid artery (ICA) stenosis associated with sphenoid sinus mucocele is extremely uncommon.

OBSERVATIONS

A 36-year-old man with a history of craniotomy for Rathke’s cleft cyst in childhood presented with rapidly progressive right-sided retro-orbital pain, ptosis, and diplopia. CT and MRI revealed a cystic lesion occupying the sphenoid sinus with adjacent ICA stenosis that markedly worsened within 4 days. Emergency endoscopic transnasal cyst fenestration was performed, and the mucinous contents were evacuated. The cyst wall adhered tightly to the dura of the sella turcica and the wall of the ICA. Postoperatively, the patient’s visual and oculomotor nerve deficits resolved, and follow-up imaging demonstrated rapid improvement of the ICA stenosis.

LESSONS

This case illustrates that sphenoid sinus mucocele can lead to rapid progression of neurological deficits and ICA stenosis. Diagnosis based on imaging only may be challenging; however, timely recognition and prompt surgical intervention are crucial, as simple cyst fenestration can achieve complete neurological recovery and prevent severe major artery stenosis.

https://thejns.org/doi/10.3171/CASE25932

Sphenoid sinus lesions usually manifest as headaches or nasal congestion and only rarely extend to the skull base to cause neurological symptoms.¹ Differential diagnoses for mass lesions in the sphenoid sinus include pituitary neuroendocrine tumors, craniopharyngiomas, ectopic Rathke’s cleft cysts, and paranasal sinus cancers.^2–6 All these diseases rarely cause neurological deficits such as visual deficit if confined to the sphenoid sinus.⁷ We encountered a 36-year-old man with visual disturbance and oculomotor nerve palsy caused by a large sphenoid sinus mass lesion. He had previously undergone craniotomy for a sellar lesion at the age of 2 years, which had been diagnosed as a Rathke’s cleft cyst. More than 3 decades later, he developed progressive visual and oculomotor symptoms over several weeks. Imaging studies revealed asymptomatic mild internal carotid artery (ICA) stenosis adjacent to a sphenoid sinus lesion, which progressed to severe stenosis in 4 days. Following emergency endoscopic transnasal surgery, his visual symptoms improved markedly, with rapid resolution of the ICA stenosis. This case highlights that this rare condition of sphenoid sinus mucocele can progress rapidly, posing a risk of serious neurological complications, and that timely surgery can lead to a favorable outcome.

Illustrative Case

A 36-year-old man had been diagnosed with a sellar lesion at the age of 2 years, during evaluation for his short stature. He was found to have panhypopituitarism and underwent bifrontal craniotomy for removal of the sellar lesion, followed by initiation of hormone replacement therapy, which has been continued to the present. However, no neuroimaging examinations had been performed for more than 30 years. The pathological diagnosis at the time was a Rathke’s cleft cyst. Over the past 4 months, he had experienced progressively worsening headaches. One day, he suddenly developed severe retro-orbital pain accompanied by vomiting and was transferred to a regional hospital. He was alert on admission, but detailed examinations revealed a right-sided enlarged scotoma, right mild ptosis, and diplopia. On admission to our hospital, he was taking hydrocortisone (15 mg/day), desmopressin acetate hydrate (300 μg/day), levothyroxine sodium (75 μg/day), somapacitan (3.5 mg/wk), and human chorionic gonadotropin (5000 units/wk). CT revealed a sphenoid sinus mass and osteolytic changes in the right cavernous sinus, the floor of the sella turcica, and the clivus (Fig. 1A). MRI showed a 39-mm-diameter mass filling the sphenoid sinus with an obscure border with the sella turcica. The lesion extended toward the right oculomotor cistern on constructive interference in steady-state images (Fig. 1B) and displaced the normal pituitary gland superiorly. MR images showed the lesion as heterogeneous, with a mixture of high- and iso-intensity signals (Fig. 1C and D). These findings suggested hemorrhage or protein-rich contents. No contrast enhancement was observed (Fig. 1E). MR angiography revealed mild stenosis of the right ICA (Fig. 1F). No ischemic lesions were identified on diffusion-weighted imaging. Although the patient remained asymptomatic, the stenosis progressed markedly and appeared nearly occluded on follow-up MR angiograms obtained 4 days later (Fig. 1G). CT perfusion angiography showed severe stenosis of the right ICA (Fig. 2A). Cerebral blood flow and cerebral blood volume in the right middle cerebral artery territory were not reduced despite the stenosis of the right ICA. Nevertheless, mean transit time (MTT) and time to peak were prolonged, indicating widespread perfusion delay (Fig. 2B). In addition to the relatively rapid progression of optic and oculomotor nerve symptoms, he developed acute near occlusion of the ICA with cerebral hypoperfusion, prompting emergency surgical intervention. We did not administer antiplatelet or anticoagulant agents. Because there were no focal neurological symptoms, the underlying pathology was nonatherosclerotic, and the cerebral blood flow was still preserved. Therefore, surgical removal of the lesion was prioritized. Transnasal endoscopic cyst fenestration was performed using an endoscope (4-mm rigid scope, Olympus) with an EndoArm (Olympus) on the 6th hospital day. Bilateral rescue incisions were made to remove the posterior portion of the nasal septum. The anterior wall of the sphenoid sinus was opened widely, and a cystic lesion with a thick capsule occupying the sphenoid sinus was identified (Fig. 3A). Opening of the cyst wall allowed yellowish-white mucous material to escape (Fig. 3B). Based on these surgical findings, the lesion was diagnosed as a sphenoid sinus mucocele. The cyst wall was fenestrated adequately, and a sample was submitted for pathological examination. As the cyst wall was dissected from the sphenoid sinus, bone defects were observed in the right sella turcica and clivus. The cyst wall was strongly adherent to the dura mater at the sella turcica floor (Fig. 3C). Doppler sonography from the cyst cavity in the sphenoid sinus confirmed the flow of the right ICA. Dissection was considered high-risk because of the adhesion of the cyst wall to the ICA; therefore, the cyst wall was intentionally left in place.

FIG. 1.

A: Axial CT scan showing osteolytic changes in the right cavernous sinus, the floor of the sella turcica, and the clivus. B: Constructive interference in steady-state MR image obtained on admission showing that the right oculomotor nerve is compressed by the cyst (arrowhead). C–E: T1-weighted (C), T2-weighted (D), and gadolinium-enhanced T1-weighted (E) MR images obtained on admission. F: MR angiogram obtained on admission showing mild stenosis at the C3 portion (arrowhead). G: MR angiogram obtained 4 days after admission showing the right ICA is nearly occluded (arrowheads) and the right middle cerebral artery is weaker.

FIG. 2.

A: CT perfusion angiogram showing that the right ICA is poorly depicted. B: Preoperative CT perfusion study showing perfusion delay in the right hemisphere on MTT.

FIG. 3.

Operative findings. A: Viscous cystic contents leaked out through the anterior wall of the sphenoid sinus. B:The cyst cavity was isolated from the sella turcica. C: The cyst wall (white arrowheads indicate cyst wall edge) was strongly adhered to the dura mater (black arrowhead).

The visual field defects and oculomotor nerve palsy were resolved within 2–3 days after operation. MRI performed the day after surgery demonstrated sufficient shrinkage of the mass lesion (Fig. 4A), and MR angiography revealed rapid improvement of the right ICA stenosis (Fig. 4B). CT perfusion angiography on the 4th day after surgery also demonstrated improvement in prolongation of MTT in the right middle cerebral artery territory (Fig. 4C). Pathological examination revealed tissue covered by either stratified squamous or multifid ciliated epithelium. Inflammatory cell infiltration, vascular proliferation, and fibrous proliferation were observed on the cyst walls, which indicated granulomatous change, consistent with the diagnosis of mucocele. The patient was discharged from the hospital on the 8th postoperative day in stable condition. Ophthalmological evaluation on the 15th postoperative day revealed resolution of the scotoma in the right eye and improvement of the right oculomotor nerve palsy. At the 3-month follow-up, no obvious signs of recurrence were observed, and improvement of right ICA stenosis was maintained (Fig. 4D).

FIG. 4.

A: Postoperative T2-weighted MR image showing complete removal of the tumor. B: Postoperative MR angiogram showing significant improvement of the right ICA stenosis. C: Postoperative CT perfusion study showing no perfusion difference between the hemispheres on MTT. D: MR angiogram obtained at 3 months after surgery showing complete resolution of the right ICA stenosis.

Informed Consent

The necessary informed consent was obtained in this study.

Discussion

Observations

Among paranasal sinus cysts, sphenoid sinus mucocele is the rarest entity, representing only 1%–2% of all cases.⁸ It is characterized by mucus accumulation within the cyst cavity, which can lead to thinning or osteolytic changes in the surrounding bone.⁹ The most common symptom is headache, which is thought to result from stretching of the skull base dura mater by the expanding cyst.¹⁰

The primary cause of paranasal sinus cyst is generally considered to be obstruction of the paranasal ostium following inflammation, tumors, or trauma, including paranasal sinus surgery.⁹ However, mucous gland–derived primary cysts or submucosal hematomas have been proposed in the presence of patent natural ostia, and these cases suggest that the mucocele can be considered to have originated from a primary cyst.¹¹ In this case, the previous surgery was performed via the transcranial approach without manipulation of the sphenoid sinus, suggesting that the present lesion is unlikely to represent a secondary mucocele. However, because the histopathological specimens from the initial surgery more than 30 years ago were not preserved, it is impossible to definitively determine whether the original lesion was truly a Rathke’s cleft cyst. Rather, as previously reported,¹² the presence of bony defects in the sellar floor and the slow enlargement over more than 30 years suggest that the initial lesion might have been an intrasellar mucocele that had extended intracranially. Although sphenoid sinus mucocele is rare in childhood because the sinus is not yet pneumatized,¹³ intracranial extension may occur considering the fragility of the developing bone and the osteolytic nature of mucoceles.

Neurological symptoms associated with sphenoid sinus mucocele include visual impairments, such as loss of visual acuity and eye movement impairments in 47% of cases.⁷ Cranial nerve symptoms include visual acuity impairment in 5%–57% of cases, oculomotor nerve palsy in 19%–21%, and trochlear nerve palsy in 5%–16%.⁷ Patients with ocular motor impairment had a better prognosis than those with visual impairments.¹⁴ Although visual symptoms caused by sphenoid sinus mucocele are often irreversible,¹⁴ visual recovery depends on the preoperative visual acuity and the time duration between the onset of symptoms and surgical intervention.¹⁵ According to a previous study,¹⁶ the likelihood of visual improvement markedly decreases when surgery is delayed beyond 6–10 days after symptom onset. Another study on visual impairment due to inflammatory sphenoid sinus disease stated that visual acuity improved in 87.5% of patients following appropriate surgical intervention.¹⁷ In the present case, surgery was performed on the 6th day after the rapid progression of symptoms, leading to a favorable recovery. This clinical course highlights the necessity of prompt surgical intervention.

In the present case, we also observed a rapidly progressive near occlusion of the ICA, which is an extremely rare occurrence. To the best of our knowledge, only 3 previous cases of intracranial arterial stenosis caused by a paranasal mucocele have been reported.^13,18,19 These previously reported cases were diagnosed by angiography or MRI, whereas the present case is the first in which detailed preoperative evaluation was performed using both CT angiography with perfusion study and MRI, demonstrating prompt postoperative improvement of the major artery stenosis. Diagnosing mucoceles based on imaging only can sometimes be challenging, as they may be mistaken for other slow-growing lesions such as ectopic pituitary neuroendocrine tumors or Rathke’s cleft cysts. However, as demonstrated in our case, sphenoid sinus mucoceles have the potential to cause rapid progression of cranial nerve deficitsand stenosis of major arteries. Therefore, when a mucocele is considered in the differential diagnosis for symptomatic sphenoid sinus lesion, timely recognition and prompt surgical intervention are warranted.

For the management of sphenoid sinus mucoceles, endoscopic transnasal cyst fenestration is generally recommended as a safe surgical procedure with low recurrence rates.^20,21 The present case, which was characterized by bone erosion around the cyst and rapid progression of cranial nerve deficits or severe ICA stenosis, and the 3 previously reported cases demonstrate that only simple cyst fenestration may be sufficient and effective even in high-risk cases.

Lessons

Diagnosis of sphenoid sinus masses can be challenging. Among the possible differential diagnoses, mucoceles are particularly important because they can cause rapidly progressive cranial nerve deficits, including optic and oculomotor dysfunction. Moreover, they may lead to critical ICA stenosis with rapid progression. Endoscopic cyst fenestration and drainage, a relatively simple surgical procedure, generally achieves high cure rates. Therefore, prompt recognition and timely surgical intervention are essential.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Yamaguchi, Nakazato. Acquisition of data: Nakazato. Analysis and interpretation of data: Yamaguchi, Nakazato. Drafting the article: Yamaguchi, Nakazato, Tosaka. Critically revising the article: Yamaguchi, Nakazato, Oya. Reviewed submitted version of manuscript: Yamaguchi, Tosaka, Oya. Approved the final version of the manuscript on behalf of all authors: Yamaguchi. Statistical analysis: Nakazato. Administrative/technical/material support: Mukada. Study supervision: Mukada, Oya.

Correspondence

Rei Yamaguchi: Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan. rei.yamaguchi@gunma-u.ac.jp.