Endoscopic endonasal transsphenoidal approach of pituitary macroadenoma and optic canal stenosis in a patient with McCune-Albright syndrome

Introduction

McCune-Albright syndrome (MAS) is a rare and complex disorder characterized by a triad of polyostotic fibrous dysplasia (FD), café-au-lait skin pigmentation, and endocrine abnormalities. The presence of at least two of these characteristics is sufficient for diagnosis. First described by Donovan James McCune and Fuller Albright in 1937, this genetic mosaic disorder arises from postzygotic mutations in the GNAS gene, leading to the activation of G protein signalling pathways. MAS manifests with skeletal deformities, including bone pain and fractures, as well as distinctive skin pigmentation, resulting in a mosaic pattern. Endocrine manifestations include precocious puberty, hyperthyroidism, hypercortisolism, growth hormone (GH) excess, or hyperprolactinemia.

Patients with MAS may present with visual impairment for different reasons. Craniofacial involvement by FD may cause acute or chronic vision loss due to progressive optic canal stenosis and can occur when bones surrounding the orbit are affected. However, optic canal involvement by FD may present without any visual compromise, so surgical decompression of the optic nerves is not always indicated, even prophylactically. Another possible cause of visual impairment in MAS patients is pituitary tumors that can compress the optic nerves or chiasm. Surgical excision of pituitary adenoma for MAS patients can be challenging due to FD, which thickens the bone at the skull base and sphenoid sinus, often showing a conchal type configuration. Due to its multifaceted nature, diagnosing MAS and managing those patients who present with visual impairment pose significant challenges. In this case report, the patient presented with optic neuropathy caused by bilateral compression of the optic canals due to FD and compression of the left optic nerve in its cisternal course by a pituitary macroadenoma. Visual field improvement was observed after transsphenoidal resection of pituitary adenoma and optic nerve decompression. This manuscript contributes to the growing body of literature, providing valuable insights into the clinical course, diagnostic approach, and therapeutic interventions for patients with MAS. Besides, this case illustrates a rare association of MAS and pituitary mammosomatotroph macroadenoma.

Case presentation

This case report details a compelling instance of MAS and pituitary mammosomatotroph macroadenoma. A 20-year-old male presented with a history of polyostotic FD involving the cranial bones, notably the sphenoid and skull base, leading to bilateral optic nerve compression in the optic canals, with an already amaurotic right eye and blurred vision in the left eye, with visual acuity of 0.3 and impairment of all visual fields. Besides optic canals constriction, neuroimaging revealed a pituitary macroadenoma in close contact with the cisternal segment of the left optic nerve (Figure 1). The patient denied precocious puberty and did not report other symptoms compatible with pituitary hypo- or hyperfunction. However, hormonal evaluations showed a significant increase in GH for 36 ng/mL (range, 0.02–1.23 ng/mL), insulin-like growth factor-1 (IGF-1) of 631.7 mg/mL (range, 127–428 mg/mL) and mild hyperprolactinemia of 32.11 ng/mL (range, 4–15 ng/mL) with normal thyroid, adrenal and testicular function, characterizing a probable GH-producing pituitary tumor.

Figure 1 Sagittal T2-weighted MRI illustrating a pituitary macroadenoma in the patient (red arrow). MRI, magnetic resonance imaging.

Although the patient showed a stable visual deficit in the left eye, surgical intervention was planned after multidisciplinary board case discussion. Before elective hospital admission could be carried out for the planned surgical procedure, the patient sought emergency attention due to acute visual worsening in the left eye. A computed tomography (CT) scan and magnetic resonance imaging (MRI) scans revealed extensive craniofacial involvement by FD and the presence of a macroadenoma in the left compartment of the sella turcica, with suprasellar extension and mild displacement of the left optic nerve (Figures 2-4).

Figure 2 Axial tomography imaging of facial bones. There is considerable osseous enlargement with regions of varied bone density ranging from sclerotic to lucent. The majority of affected bones exhibit a ground-glass appearance.

Figure 3 Axial T2-weighted MRI. Notice the involvement of the optic canal (red arrows). MRI, magnetic resonance imaging.

Figure 4 Coronal T1-weighted Gd MRI illustrating a pituitary macroadenoma touching the optic chiasm, with left parasellar extension (left side). Gd, gadolinium; MRI, magnetic resonance imaging.

In the face of acute visual loss, an urgent endoscopic endonasal transsphenoidal approach (EETA) was carried out. Left optic canal unroofing with optic nerve decompression and resection of the pituitary macroadenoma were performed. The EETA technique was slightly modified to address peculiarities of the patient’s anatomy caused by the diffuse skull base FD, with the aid of neuronavigation. The nasal cavity was narrow, compromising the movement of instruments. The nasal turbinates were markedly hypertrophied and covered by thin mucosa. To enlarge the intranasal space, the inferior and middle turbinates on the left side and both superior turbinates were resected with the aid of endonasal shavers and diamond burr drills (Figure 5). Removing the thick bone of the ethmoids and sphenoid was a major challenge due to the lack of anatomical references. Hence, neuronavigation was essential until normal skull base structures could be recognized. After removing the lamina papyracea on the left side, ipsilateral optic canal identification was possible by advancing posteriorly from the left periorbit. The canal was progressively unroofed at least 180 degrees circumferentially, from the orbit to the tuberculum sellae, using fine diamond burrs with continuous saline irrigation, to decompress the left optic nerve. The sphenoid drilling continued contralaterally to delineate the floor of the sella turcica, where the dura mater of the sella was identified (Figure 6). A star-shaped dural opening was performed and the tumor was resected in its entirety. The optic chiasm and left optic nerve were identified. They were completely free in their cisternal trajectory to the left optic canal that which was already opened. Sellar reconstruction was performed with intraselar fat, a pedicled nasoseptal mucosal flap, and fibrin glue (Figures 7-10).

Figure 5 Intraoperative endoscopic view demonstrating a narrowed left nasal fossa. *, indicates inferior turbinate; #, indicates nasal septum.

Figure 6 Endoscopic intraoperative image depicting the surgical drilling of the extensively ossified sphenoid sinus.

Figure 7 Endoscopic intraoperative images illustrating the exposure of the dura mater overlying the sellar region and the optic canal, following drilling of the sphenoid sinus (A); the initiation of pituitary adenoma resection (B) and the final aspect of the sellar region after gross total resection of the pituitary adenoma (C). *, indicates optic canal; #, indicates sellar region.

Figure 8 Endoscopic intraoperative image illustrating the exposure of the dura mater overlying the sellar region and the optic canal, following drilling of the sphenoid sinus. *, indicates optic canal; #, indicates sellar region.

Figure 9 Endoscopic intraoperative image showing the initiation of pituitary adenoma resection.

Figure 10 Endoscopic intraoperative image showing the final aspect of the sellar region after gross total resection of the pituitary adenoma.

Postoperative course was unremarkable, and the patient was discharged on the 6^th postoperative day with no surgical complications. Anatomopathological and immunohistochemical analysis revealed a mammosomatotroph adenoma, with a Ki-67 score of 1–5%. Despite some nasal crusting observed in the first postoperative visits to the ear, nose, and throat (ENT) clinic, the nasal mucosa has completely re-epithelialized and the nasoseptal flap was well integrated. Most importantly, there was a significant improvement in visual fields and visual acuity in the left eye, which was 0.8 in the 6^th month of follow-up. Currently, the patient is receiving hormone replacement with levothyroxine due to central hypothyroidism and the rest of the pituitary function is normal including GH, IGF-1, and prolactin levels.

All procedures performed in this article were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

MAS is a clinical syndrome with a low incidence in clinical practice and its concurrence with pituitary macroadenoma is very rare. This genetic disorder is characterized by a clinical triad of polyostotic FD, café-au-lait skin spots, and single or multiple endocrinopathies (1,2). The complexity of MAS arises from its somatic mosaic pattern due to a post-zygotic mutation in the GNAS gene during embryogenesis, affecting various tissues. The craniofacial FD present in MAS has potential complications such as progressive narrowing of the optic canals, which can lead to visual loss (3,4).

Anatomopathological and immunohistochemical analysis revealed a mammosomatotroph adenoma: a pituitary neuroendocrine tumor composed of acidophilic cells that produce both GH and prolactin. Immunohistochemical studies also reveal the presence of these two hormones localized in the same cell. Its biological behavior is similar to that of well-differentiated GH or mixed adenomas. As most of these tumors are well-demarcated intrasellar neoplasms with variable suprasellar extensions, surgical resection is expected to provide very satisfactory long-term control (5).

The incidence of MAS-associated pituitary adenoma cases is low. A recent review of the published literature reported 57 cases from 36 articles. Clinical manifestations included visual deficits in 29 cases (50.9%): 17 cases were caused by bone compression from FD, three cases were due to pituitary tumor compression, and nine cases could not be completely distinguished. This review reports significant postoperative visual improvement, especially in patients with giant adenomas. Transsphenoidal approaches to pituitary adenomas were performed in nine patients and gross total resections were achieved in eight of them. The authors concluded that transsphenoidal approach is appropriate to treat pituitary adenomas in MAS. Study of optic nerve compression in MAS patients requires thorough neuroophthalmological evaluation and dedicated neuroimaging, usually combining CT and MRI techniques, that complement each other. While the CT scan provides a detailed perspective of the bone involvement by the FD, MRI is crucial for a comprehensive evaluation of soft tissue involvement, especially within the sellar region and optic nerves, being able, for example, to depict hyperintensity signs of edema or ischemia of the optic nerves. Understanding the structural intricacies highlighted by CT and MRI scans is the cornerstone for surgical planning and for guiding surgeons in navigating the challenging terrain posed by the unfavorable bone architecture associated with MAS (6).

The management of optic nerve compression in MAS is variable. While surgical intervention is crucial in cases of acute vision loss, the prophylactic decompression based solely on imaging should be avoided (7,8). The Fibrous Dysplasia/McCune-Albright Syndrome International Consortium suggests a multidisciplinary approach with the collaboration of various specialists for comprehensive patient care and does not recommend prophylactic optic nerve decompression (9). On the other hand, therapeutic decompression has shown good outcomes in improving vision. Cutler et al. compared the outcomes of six prophylactic optic nerve decompressions with 13 therapeutic decompressions in patients with craniofacial FD (8). While one case presented bilateral severe visual loss and five cases showed a stable status after prophylactic surgery, six patients showed visual improvement after therapeutic decompression. Therefore, they suggested that optic nerve decompression should be offered only to patients with some degree of visual impairment (10).

This present case report involves a MAS patient with amaurosis in the right eye who progressed with visual worsening in the left eye. The cranial CT scan showed bone changes, mainly in the sphenoid bone, which contributed to the compression of the optic nerve. MRI demonstrated T2 hyperintensity in both optic nerves. MRI also showed a pituitary macroadenoma abutting the optic chiasm. Like Li et al., who reported nine cases of MAS-associated pituitary adenomas without precisely defining the cause of visual deficits, we could not completely distinguish the main cause of visual loss in the left eye of our patient (6). It may have been due to the combination of left optic nerve compression by the pituitary adenoma and left optic canal narrowing by FD.

Finally, this report highlights that despite the increased technical difficulty caused by FD, it is possible to successfully access the pituitary adenoma and decompress the optic nerve in the optic canal using the EETA. It is a less invasive approach with reduced perioperative morbidity that generally allows for faster recovery, less operative stress, and more acceptable cosmetic outcomes than transcranial approaches.

Conclusions

Treating patients with visual impairment secondary to optic nerve compression and/or pituitary macroadenomas in MAS poses intricate challenges. The transsphenoidal approach of pituitary adenoma and optic nerve decompression under neuronavigational guidance is a safe and effective management for MAS patients in experienced hands. This case report emphasizes the need for a tailored, multidisciplinary approach, considering the variable nature of MAS presentations. The discussion surrounding decompression highlights the importance of clinical correlation and imaging assessment in optimizing patient outcomes.

Acknowledgments

None.

Footnote

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-176/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this article were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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