Chronic oculomotor nerve palsy secondary to a sphenoid–cavernous sinus lesion in an adolescent: a case report and literature review

Abstract

Background

Oculomotor nerve (cranial nerve III) palsy in children and adolescents is uncommon and typically suggests an underlying structural lesion rather than microvascular ischemia. Sphenoid sinus disease represents a rare cause of ocular cranial neuropathies and most frequently affects the abducens nerve. Consequently, isolated chronic oculomotor nerve palsy secondary to sphenoid sinus pathology is an unusual clinical presentation.

Case presentation

We report a 16-year-old male who presented with long-standing right ocular deviation and progressive limitation of eye movements beginning in early childhood. Neuro-ophthalmic examination demonstrated severe limitation of adduction, elevation, and depression of the right eye associated with a large-angle exotropia and a fixed dilated pupil, consistent with chronic oculomotor nerve palsy. Notably, no ptosis of the right upper eyelid was observed despite the severity of the motor deficit, a finding that is discussed in the context of divisional and fascicular nerve involvement. The patient had a prior history of a sphenoid sinus lesion treated with functional endoscopic sinus surgery and partial resection. Histopathological examination revealed a histiocyte-rich lesion with surrounding fibrosis. Magnetic resonance imaging obtained during the current evaluation demonstrated postoperative changes with arrested pneumatization of the right sphenoid sinus, with no evidence of residual or recurrent mass lesion, and diffuse fatty atrophy of the right medial and inferior rectus muscles consistent with long-standing denervation.

Conclusion

This case highlights a rare presentation of chronic isolated oculomotor nerve palsy associated with sphenoid–cavernous sinus pathology in an adolescent. The close anatomical relationship between the sphenoid sinus and the cavernous sinus provides a plausible mechanism for selective involvement of the oculomotor nerve. Early recognition of sphenoid sinus lesions in pediatric patients presenting with unexplained strabismus or cranial nerve deficits is essential to prevent irreversible neuro-ophthalmic sequelae.

Introduction

Oculomotor nerve palsy represents an important neuro-ophthalmic presentation because it may produce disabling diplopia, ptosis, and ocular misalignment, and can indicate pathology anywhere along the nerve’s long intracranial course [1]. In children and adolescents, however, ocular motor cranial nerve palsies are distinctly uncommon. Population-based pediatric cohorts report incidences on the order of only a few cases per million, making chronic third cranial nerve dysfunction an especially rare diagnostic challenge in this age group [2]. The etiological spectrum of pediatric CN III palsy also differs from that observed in adults. Congenital and traumatic causes predominate, whereas inflammatory, infectious, and neoplastic processes—although less frequent—remain critical considerations because they may require urgent targeted therapy and can initially present with subtle or progressive neurological findings [2, 3].

From an anatomical perspective, isolated involvement of CN III resulting from skull-base or paranasal sinus pathology is somewhat counterintuitive and may therefore be overlooked during early evaluation. After emerging from the midbrain, the oculomotor nerve traverses the subarachnoid space before entering the cavernous sinus, where it courses within the lateral dural wall prior to exiting through the superior orbital fissure [4]. Within the cavernous sinus, several cranial nerves and the internal carotid artery lie in close proximity. Importantly, CN III, together with CN IV and the ophthalmic and maxillary divisions of the trigeminal nerve (V1 and V2), is embedded within the lateral wall of the sinus, whereas the abducens nerve (CN VI) runs more freely within the sinus proper adjacent to the internal carotid artery. This anatomical configuration helps explain why many cavernous sinus lesions preferentially affect CN VI and often present with multi-nerve cavernous sinus syndrome rather than isolated chronic third nerve palsy [5].

The sphenoid sinus introduces additional anatomical complexity. Positioned centrally at the skull base, it lies in close proximity to the cavernous sinus and internal carotid artery, with variable bony thickness and occasional areas of dehiscence. These anatomical relationships allow expansile sphenoid sinus lesions to extend beyond the sinus boundaries and involve adjacent neurovascular structures [6, 7]. Nevertheless, ocular cranial neuropathies resulting from sphenoid sinus disease remain relatively uncommon and are typically acute in onset. When such neuropathies occur, the abducens nerve is most frequently affected, whereas involvement of the oculomotor nerve has been reported far less often [8, 9].

Against this background, we report a rare case of chronic isolated oculomotor nerve palsy in an adolescent secondary to a sphenoid sinus lesion that extended toward the cavernous sinus region, highlighting the diagnostic challenges, imaging findings, and clinical implications of this unusual anatomical pathway to third-nerve dysfunction.

Case presentation

A 16-year-old male was referred to the neuro-ophthalmology clinic for evaluation of long-standing limitation of right eye movements and progressive cosmetic misalignment. According to the patient and his family, the ocular deviation had been present since early childhood, beginning at approximately six years of age, and had gradually become more noticeable over time. The patient denied associated symptoms such as headache, facial numbness, diplopia, imbalance, or other neurological complaints.

The patient’s past medical history was notable for a right sphenoid sinus lesion, for which he had undergone functional endoscopic sinus surgery (FESS) with partial resection approximately three years prior to presentation. Histopathological examination of the excised sphenoid tissue revealed a histiocyte-rich lesion with surrounding fibrosis. The original preoperative MRI was not available for review, given the substantial interval since the initial evaluation; however, prior radiology reports documented a sphenoid sinus lesion extending toward the parasellar/cavernous sinus region. No original preoperative imaging could be retrieved for re-evaluation.

On neuro-ophthalmic examination, best-corrected visual acuity was 20/50 in the right eye and 20/20 in the left eye. Intraocular pressures were within normal limits in both eyes. Pupillary examination revealed a fixed, dilated pupil in the right eye that was nonreactive to both light and accommodation, whereas the left pupil was round and briskly reactive.

Ocular motility testing demonstrated marked limitation of extraocular movements in the right eye, most prominently affecting adduction, elevation, and depression, consistent with severe oculomotor nerve dysfunction. Ocular alignment testing revealed a large-angle right exotropia measuring approximately 60 prism diopters in the primary position. Importantly, despite the severity of the motility deficit and the presence of a fixed dilated pupil, no ptosis of the right upper eyelid was observed. A forced duction test was performed and was negative, confirming the absence of any restrictive mechanical component to the motility deficit and establishing that the limitation of extraocular movements was neurogenic rather than myogenic or restrictive in nature. Slit-lamp and fundus examinations were otherwise unremarkable in both eyes, demonstrating normal optic discs, maculae, and retinal vasculature.

To evaluate for persistent or recurrent pathology, high-resolution computed tomography (CT) and magnetic resonance imaging (MRI) of the brain and orbits were performed at the time of the current presentation. Imaging demonstrated postoperative changes including arrested pneumatization of the right sphenoid sinus, stable in appearance compared with previous postoperative reports. No residual or recurrent sphenoid sinus mass, cavernous sinus lesion, or intraorbital pathology was identified on current imaging. MRI revealed diffuse fatty atrophy of the right medial rectus and inferior rectus muscles, consistent with chronic denervation changes secondary to long-standing oculomotor nerve palsy. Atrophic changes of the superior rectus and inferior oblique muscles were not specifically identified or reported on the available MRI sequences; accordingly, involvement of these muscles cannot be confirmed or excluded on the basis of current imaging alone. Medial displacement of the right optic nerve was also noted. Mild mucosal thickening of the right maxillary sinus was present, likely representing postoperative changes related to prior sinus surgery. Representative MRI images are shown in Fig. 1.

Fig. 1.

Representative MRI images obtained during current neuro-ophthalmic evaluation, performed approximately three years after functional endoscopic sinus surgery. Left: Sagittal T2-weighted image demonstrating postoperative and arrested pneumatization changes of the right sphenoid sinus with no evidence of a residual or recurrent mass lesion. Right: Axial orbital MRI demonstrating diffuse fatty atrophy of the right medial rectus and inferior rectus muscles (arrow), consistent with chronic denervation changes attributable to long-standing oculomotor nerve dysfunction. No active cavernous sinus or parasellar mass is identified on the current examination. These findings reflect the sequelae of prior sphenoid sinus pathology—documented on prior radiology reports as extending toward the parasellar/cavernous sinus region—rather than active or ongoing compressive disease

Taken together, the clinical and radiological findings were consistent with chronic isolated right oculomotor nerve palsy resulting from previous sphenoid sinus pathology with extension toward the cavernous sinus region, with no evidence of active or residual disease on current imaging.

Discussion

This report focuses on the etiological mechanism of oculomotor nerve palsy rather than its surgical management. The aim is to highlight why a lesion involving the sphenoid and cavernous sinuses selectively affected the third cranial nerve while sparing the fourth and sixth cranial nerves, particularly in a pediatric patient, and to address several unusual clinical features of this case.

Anatomical basis for selective CN III involvement

The sphenoid sinus occupies a central position at the skull base and demonstrates highly variable pneumatization patterns. Its lateral walls lie in close proximity to several critical neurovascular structures, including the cavernous sinus, internal carotid artery, optic nerve, and superior orbital fissure, while its superior wall borders the sella turcica. Within the cavernous sinus, cranial nerves III, IV, V1, and V2 course within the lateral dural wall, whereas cranial nerve VI travels freely within the sinus proper adjacent to the internal carotid artery. This anatomical configuration explains why the abducens nerve is particularly vulnerable to inflammatory, infectious, or expansile sphenoid and cavernous sinus pathology and why CN VI palsy is the most frequently reported ocular motor deficit associated with sphenoid sinus disease [8–10].

The occurrence of chronic oculomotor nerve palsy in pediatric patients should raise strong suspicion for an underlying structural or compressive lesion rather than an ischemic etiology, as microvascular causes are distinctly uncommon in this age group [11–13]. In our patient, long-standing right exotropia, a fixed dilated pupil, and severe limitation of extraocular movements were consistent with chronic oculomotor nerve dysfunction. MRI findings at the current evaluation demonstrated diffuse fatty atrophy of the medial rectus and inferior rectus muscles (Fig. 1), indicating chronic denervation rather than active inflammation or neoplasia. These radiographic findings support irreversible neuromuscular injury secondary to long-standing compression of the oculomotor nerve.

As illustrated in Fig. 2, the sphenoid sinus lesion in this case is conceptualized as originating from or expanding along the lateral wall of the sphenoid sinus and extending superiorly and laterally toward the cavernous sinus, where it encountered the oculomotor nerve within the superior aspect of the lateral dural wall. This trajectory—from the lateral sphenoid sinus wall toward the cavernous sinus—provides an anatomically coherent explanation for the compressive injury sustained by CN III. The oculomotor nerve occupies the superior portion of the lateral wall of the cavernous sinus and has the largest caliber among the cranial nerves in this region, making it particularly susceptible to early compression from lesions extending along this route [4, 5]. In contrast, the trochlear nerve lies more inferiorly within the lateral wall, and the abducens nerve runs medially within the cavernous sinus proper adjacent to the internal carotid artery. This spatial arrangement may explain why the lesion selectively affected CN III while sparing adjacent cranial nerves.

Fig. 2.

Schematic illustration of the proposed anatomical trajectory of the sphenoid sinus lesion in relation to the cavernous sinus and adjacent cranial nerves. The lesion is depicted as originating from the lateral wall of the right sphenoid sinus and extending directly toward the cavernous sinus through the sphenoid–cavernous anatomical corridor. Within the cavernous sinus, cranial nerves III, IV, V1, and V2 course within the lateral dural wall, whereas the abducens nerve (CN VI) runs within the cavernous sinus proper adjacent to the internal carotid artery (ICA). Because the oculomotor nerve (CN III) occupies the superior aspect of the lateral wall and has the largest caliber among the cranial nerves in this region, it may be particularly susceptible to early compression by lesions extending from the sphenoid sinus. The continuous anatomical relationship between the sphenoid sinus and cavernous sinus illustrated here provides a plausible explanation for the selective involvement of CN III observed in this patient

Similar patterns of isolated third cranial nerve palsy secondary to sphenoid sinus pathology have been reported in association with mucoceles, inflammatory disease, and other skull-base lesions [14–16]. These reports highlight the close anatomical relationship between the sphenoid sinus and the cavernous sinus, which allows compressive or inflammatory processes to extend to adjacent cranial nerves. El-Mograbi and colleagues reported that ocular cranial nerve palsies occur in approximately 6–12% of patients with sphenoid sinus disease, with the abducens nerve being the most frequently affected [17]. This distribution reflects the inherent vulnerability of CN VI within the cavernous sinus.

Nevertheless, isolated involvement of the oculomotor nerve remains distinctly uncommon. Sethi and Lau [18] described patients with sphenoid sinus mucoceles presenting with isolated CN III palsy, demonstrating that localized sphenoid sinus expansion may selectively compress the oculomotor nerve without affecting adjacent cranial nerves. Similarly, Lee and colleagues reported a patient with a large sphenoid sinus mucocele presenting with acute isolated third nerve palsy, in whom surgical decompression resulted in neurological improvement [19].

When lesions extend beyond the sphenoid sinus into the cavernous sinus, they more commonly produce cavernous sinus syndrome characterized by simultaneous involvement of cranial nerves III, IV, V, and VI [20, 21]. In contrast, our patient demonstrated selective chronic involvement of the oculomotor nerve, highlighting an unusual presentation of sphenoid–cavernous sinus pathology.

The absence of ptosis in severe CN III palsy

A noteworthy finding in this case was the absence of ptosis despite the presence of a fixed dilated pupil, marked limitation of adduction, elevation, and depression, and a large-angle exotropia consistent with severe CN III dysfunction. Because the levator palpebrae superioris is innervated by the superior division of the oculomotor nerve, preservation of eyelid elevation in this setting is unusual.

The oculomotor nerve divides into superior and inferior divisions before entering the orbit through the superior orbital fissure. The superior division innervates the levator palpebrae superioris and superior rectus muscles, whereas the inferior division supplies the medial rectus, inferior rectus, inferior oblique, and parasympathetic fibers to the ciliary ganglion. Consequently, selective involvement of specific fascicles or divisions may produce atypical clinical presentations.

One possible explanation is preferential involvement of fibers destined for the inferior division, resulting in severe motility deficits and pupillary involvement while relatively sparing levator function. In addition, partial aberrant regeneration following long-standing compressive injury may have contributed to preservation or recovery of eyelid elevation despite persistent deficits in other CN III-innervated muscles.

The chronic nature of the lesion may also have allowed differential susceptibility or recovery among individual fascicular groups. Nevertheless, the absence of ptosis remains atypical and cannot be fully explained from the available retrospective data. It is possible that ptosis was present during an earlier phase of the disease and subsequently improved, or that selective fascicular involvement occurred. Therefore, the mechanism underlying levator sparing in this patient remains speculative.

Extraocular muscle denervation: imaging findings and completeness of assessment

MRI demonstrated diffuse fatty atrophy of the right medial rectus and inferior rectus muscles, consistent with chronic denervation. These muscles are innervated by the inferior division of CN III and represent the most conspicuously atrophied muscles reported on available imaging sequences. Atrophic changes of the superior rectus and inferior oblique—also innervated by CN III (superior and inferior divisions, respectively)—were not specifically identified or reported on the available MRI sequences; the imaging status of these muscles therefore cannot be confirmed or excluded from this record alone. Fatty replacement of extraocular muscles on T1-weighted MRI sequences constitutes a reliable marker of chronic denervation, as opposed to T2/STIR hyperintensity which may reflect subacute or edematous changes [22]. The medial displacement of the right optic nerve is attributable to the volume loss of the medial rectus muscle, consistent with the chronic denervation pattern observed in this case.

Differential diagnosis of the histiocyte-rich fibrotic sphenoid lesion

The histopathological description of a histiocyte-rich lesion with surrounding fibrosis is nonspecific and warrants consideration of several entities in the pediatric population. Potential differential diagnoses include xanthogranulomatous inflammatory lesions, Rosai–Dorfman disease, Langerhans cell histiocytosis [23], and chronic granulomatous fungal disease, all of which have been reported to involve the paranasal sinuses and occasionally present with cranial neuropathies. However, the available pathological material and clinical records did not include sufficient histological or immunohistochemical information to permit a more specific retrospective diagnosis. Therefore, the precise nature of the original sphenoid lesion remains uncertain.

Vascular anatomical considerations for preoperative planning

Surgical and endoscopic approaches to lesions involving the sphenoid sinus and cavernous sinus require careful consideration of adjacent vascular structures, particularly the internal carotid artery. In addition, rare anatomical variations of the ophthalmic artery have been described and may alter the vascular risk profile during skull-base surgery. Although no vascular anomaly was identified in our patient, awareness of such variations and appropriate preoperative vascular assessment may help minimize ischemic and neuro-ophthalmic complications when operating within this anatomically complex region.

Chronicity, prognosis, and management considerations

Compared with previously reported cases, our patient demonstrated several distinctive features. First, the patient belongs to the adolescent age group, whereas most reported cases occur in adults. Second, the presentation was chronic rather than acute, with imaging findings demonstrating long-standing neural compression and secondary extraocular muscle atrophy. The history of a sphenoid sinus lesion with prior endoscopic resection and histopathological evidence of a histiocyte-rich fibrotic process further suggests a prolonged low-grade compressive mechanism.

Delayed diagnosis or incomplete resolution of sphenoid sinus disease may result in permanent orbital and neuro-ophthalmic sequelae even after successful surgical management [24]. In our patient, follow-up imaging demonstrated no recurrent mass or active sinus disease; however, persistent extraocular muscle atrophy highlighted the limited potential for functional recovery once chronic structural changes have occurred [24, 25]. These findings underscore the importance of early recognition and management of sphenoid sinus pathology to prevent irreversible cranial nerve injury.

Management of such complex cases requires a multidisciplinary approach involving otolaryngology, neuro-ophthalmology, and pediatric ophthalmology. Although endoscopic sinus surgery remains the cornerstone of treatment for sphenoid sinus disease, residual ocular misalignment may persist and require strabismus surgery for cosmetic rehabilitation. Nevertheless, restoration of normal ocular motility is often limited in cases with long-standing denervation [24, 26].

This case emphasizes the importance of considering sphenoid sinus pathology in children and adolescents presenting with unexplained strabismus or cranial nerve dysfunction and illustrates an unusual pathway to isolated chronic CN III palsy, contrasting with the more typical abducens nerve involvement observed in sphenoid sinus disease.

Conclusion

This case illustrates an uncommon presentation of chronic isolated oculomotor nerve palsy secondary to sphenoid–cavernous sinus pathology with pediatric onset. Although sphenoid sinus disease most frequently affects the abducens nerve, localized or slowly progressive lesions extending along the lateral sphenoid sinus wall toward the cavernous sinus may selectively compress the oculomotor nerve due to its superior position within the lateral dural wall and its relatively large caliber. The negative forced duction test in this patient confirmed a purely neurogenic mechanism, excluding restrictive myopathic disease. The absence of ptosis in the setting of otherwise severe CN III dysfunction raises important considerations regarding divisional and fascicular involvement, partial compressive injury within the cavernous sinus, and the possibility of aberrant regeneration in this chronic case. In our patient, long-standing compression resulted in irreversible neuromuscular changes, including fatty atrophy of the medial and inferior rectus muscles consistent with chronic denervation, with the status of other CN III-innervated muscles not fully characterized on available imaging. These findings emphasize the importance of early neuroimaging and prompt recognition of sphenoid sinus pathology in children presenting with unexplained strabismus or cranial nerve dysfunction. The histiocyte-rich fibrotic pathology in this case also warrants awareness of a broad differential, including xanthogranulomatous sinusitis, Rosai–Dorfman disease, Langerhans cell histiocytosis, and chronic fungal granulomatous disease, though definitive retrospective reclassification is not possible from the available pathological data. Early diagnosis, thorough histopathological evaluation, and multidisciplinary management are essential to minimize permanent neuro-ophthalmic sequelae.

Author contributions

RAA collected the clinical data and assisted in drafting the manuscript. SST contributed to the literature review and manuscript preparation. FA supervised the study, managed the patient, and critically revised the manuscript. All authors read and approved the final manuscript.

Funding

The authors received no specific funding for this work.

Data availability

All data generated or analyzed during this study are included in this published article.

Declarations

Ethics approval and consent to participate

Ethical approval was obtained from the Institutional Review Board of King Khaled Eye Specialist Hospital. The study adhered to the tenets of the Declaration of Helsinki.

Consent for publication

Written informed consent for publication of clinical details and images was obtained from the patient and the patient’s legal guardian.

Competing interests

The authors declare no competing interests.