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Background:
Systematic Review

Schwannomas of the Third Cranial Nerve: An Overview and Case Report

by
Antonello Curcio
1,*,
Shervin Espahbodinea
2,
Francesco Lacava
2,
Giovanni Raffa
2 and
Antonino Germanò
2
1
UOC di Neurochirurgia, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, 71013 Foggia, Italy
2
Division of Neurosurgery, BIOMORF Department, University of Messina, 98122 Messina, Italy
*
Author to whom correspondence should be addressed.
Neuroglia 2026, 7(1), 9; https://doi.org/10.3390/neuroglia7010009
Submission received: 22 January 2026 / Revised: 2 March 2026 / Accepted: 9 March 2026 / Published: 12 March 2026
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Abstract

Background: Schwannomas of the third cranial nerve are exceedingly rare benign tumors, and standardized management guidelines are lacking. Their close relationship with critical neurovascular structures makes diagnosis and treatment challenging, with a significant risk of postoperative neurological deficits. Methods: A systematic review of the literature was conducted according to the PRISMA guidelines, including case reports and clinical studies on oculomotor nerve schwannomas (ONSs). Demographic data, clinical presentation, tumor location, diagnostic methods, treatment strategies, and functional outcomes were analyzed. In addition, an illustrative case treated with a multimodal approach is presented. Results: Ninety-six cases met the inclusion criteria. The mean age at diagnosis was 34 years, with a slight female predominance. The most common presenting symptoms were diplopia and ptosis. Contrast-enhanced magnetic resonance imaging was the diagnostic modality of choice. Surgical resection was the primary treatment in most cases but was associated with worsening oculomotor nerve function in 43.1% of surgically treated patients. Stereotactic radiotherapy demonstrated favorable tumor control with lower neurological morbidity. In the presented case, subtotal resection followed by stereotactic radiotherapy resulted in sustained tumor stability at the one-year follow-up. Conclusions: Management of oculomotor nerve schwannomas should be individualized. For small or mildly symptomatic lesions, stereotactic radiotherapy appears to be an effective and less invasive option, while surgery should be reserved for large tumors causing a mass effect or progressive neurological deterioration.

1. Introduction

Schwannomas are benign, slow-growing tumors derived from Schwann cells, which are responsible for the myelination of peripheral nerves. Although they can occur along any myelinated nerve, cranial nerve schwannomas predominantly affect the vestibulocochlear nerve (VIII) [1]. ONSs, however, are exceedingly rare, with few cases reported in the literature [2].
The oculomotor nerve controls most of the eye’s movements and constriction of the pupil, and its involvement in a schwannoma can lead to significant clinical manifestations, such as diplopia, ptosis, and anisocoria. This article aims to synthesize existing knowledge, covering their epidemiology, pathophysiology, clinical features, diagnostic workup, and management strategies.

2. Materials and Methods

A systematic literature search was conducted in accordance with the PRISMA guidelines (see Supplementary Materials) using PubMed/MEDLINE, Scopus, and Web of Science (SCI-Expanded). Additional screening was performed using Google Scholar to identify potentially missed records. The search strategy included the following keywords: “third cranial nerve schwannoma,” “oculomotor schwannoma,” and “oculomotor neurinoma.” All databases were searched from inception to April 2025. Inclusion and exclusion criteria were defined using the PRISMA framework (Figure 1), which encompassed case reports, clinical studies, and reviews focusing on third cranial nerve schwannomas. Articles not available in English or lacking detailed clinical information were excluded. Additionally, each chosen manuscript’s references were examined, expanding our case collection. The data was analyzed to extract information on the presentation, diagnostic methods, treatment modalities, and outcomes.

3. Results

A total of 989 items were obtained. After examining the title and/or abstract, irrelevant and duplicate articles were discarded. A total of 96 cases fulfilled the inclusion criteria. The selected cases, along with all available demographic information, tumor location, and symptoms, are summarized in Table 1. The cohort’s mean age at diagnosis was 34 years, with a range of 2 months to 78 years. The ratio of men to women was 1:1.3 (overall 41:55 M:F). The cohort as a whole experienced symptoms for an average of 29 months, ranging from 3 days to 216 months (data collected from 37 patients). Following diagnosis, the average follow-up period was 34.7 months, with a range of 0.25 to 240 months (data collected from 59 patients).

3.1. Clinical Presentation

The analysis of reported cases revealed that the most common presenting symptoms of third cranial nerve schwannomas include ptosis, diplopia, and anisocoria. These symptoms result from the tumor’s compression or infiltration of the oculomotor nerve fibers. Some patients also reported headaches and periorbital pain. Few patients have also experienced hemiparesis/unilateral weakness or convulsion. Rarely, there have been reports of exophthalmos [3,4], dysarthria [5] and facial hypoesthesia [6].

3.2. Diagnostic Methods

Magnetic resonance imaging (MRI) with contrast enhancement is the preferred diagnostic modality, providing detailed images of the nerve and surrounding structures. Schwannomas typically appear as well-circumscribed, enhancing masses on MRI. In some cases, computed tomography (CT) scans and angiography have been utilized to assess bony involvement and vascular encasement.

3.3. Treatment Modalities

Surgical resection remains the primary treatment for symptomatic third cranial nerve schwannomas. The approach depends on the tumor’s size, location, and involvement of surrounding structures. Microsurgical techniques aim to preserve the nerve function while ensuring complete tumor removal. Stereotactic radiosurgery has emerged as a non-invasive alternative, particularly for smaller tumors or patients unfit for surgery. Postoperative radiotherapy is considered for residual or recurrent tumors.
Surgery was used, as first-line treatment, to treat 49 of the reported cases, and in 2 case, after a first period of conservative treatment as a second-line choice [7,8]. Radiosurgery was used in just seven reports with 16 cases, and in 3 cases as adjuvant therapy after first-line surgical treatment [9,10]. We found that 41% (n = 21) of the surgical treated cases had a partial resection, whereas 48% (n = 25) of the cases had a complete resection. No description of the extent of resection was available in the remaining six cases. The majority of the time, the tumor was found in the cisternal region (n = 34) (Figure 2). Planning the extent of resection requires careful consideration of the tumor’s location and size.

3.4. Outcomes

There are five described recurrences following surgical treatment, treated respectively with re-surgery (STR) + RT (54 Gy) followed by a complete III nerve palsy [11], surgery with improvement [5], SRS without any outcome data [9], and without any other treatment reported, where over the course of the six-year follow-up, the tumor in the cavernous sinus has shown slight growth without any neurological deterioration [12].
Following treatment, a large number of surgical cases (22/51, 43.1%) reported worsening oculomotor function. Shuangshoti reported an unexpected death occurring on the eighth postoperative day [13]. A lesser percentage of the surgical cases evaluated indicated no change in oculomotor function (9/51, 17.6%) and enhanced oculomotor function (13/51, 25.5%). Among patients treated with radiotherapy, 16 cases were reported. Of these, one patient showed improvement [14], one experienced worsening of oculomotor function [2], and seven remained neurologically unchanged [2,15,16]; outcome data were not available for the remaining cases. In contrast, patients managed conservatively or with medical therapy, mainly corticosteroids, demonstrated a more heterogeneous outcome. Among these patients, oculomotor function remained unchanged in four cases [17,18,19,20], partial recovery was observed in nine [7,8,21,22,23,24], complete recovery in three [24,25], and worsening in five cases [26]. Notably, two patients who ultimately achieved partial recovery underwent surgical treatment as a second-line therapy [7,8]. In light of the heterogeneity of management strategies and outcomes identified in the literature, we present an illustrative case to further contextualize therapeutic decision-making and highlight the challenges associated with multimodal treatment of oculomotor nerve schwannomas.
Table 1. Reported cases of oculomotor schwannoma.
Table 1. Reported cases of oculomotor schwannoma.
AuthorYearAgeSexSiteOnsetFirst Line ManagementEORApproachFollow UpOutcome
Shuangshoti [13]197564FN/AHeadache and generalized seizureSurgeryN/APterional(months)N/A
Broggi e Franzini [27]198145MCisternalSlowly progressive R hemiparesis with mild central palsy of facial nerve for 5 yearsSurgeryN/ASubtemporalN/AN/A
Hiscott e Symon [28]198258FCisternocavernousDrowsiness, hemiparesis, minimal ptosis, dementia, headacheSurgerySTRFronto-temporalN/AIII nerve palsy
Leunda [29]198211MCisternalHeadaches, hemiparesis, ophthalmoplegiaSurgeryGTRSubtemporal4Worsened CN III palsy
Kansu [30]198215MCisternalOphtalmoplegia, ptosis, mydriasis. Recurrent III nerve palsy. Three-day history of periorbital pain and complete ptosis on the R sideSurgeryGTRSubtemporal108N/A
Takano [31]199065FCavernousPtosis, diplopiaSurgerySTRN/AN/ANo signs of involvement of other cranial nerves (non specifica il III nervo)
Kurokawa [32]199255MCavernousDiplopia (III, V and VI implicated), III nerve paresisSurgeryGTRPterional36III nerve palsy with complete recovery 5 days later
Shen [4]199343MOrbitocavernousProptosis with blurred vision for 7 yearsSurgeryGTRSubfrontal craniotomy5N/A
Niazi e Boggan [5]199413MCisternocavernousHemiparesis, diplopia, headache, dysarthria, anisocoriaSurgerySTRFronto-temporalN/AImproved
Kachhara [33]199861MCisternocavernousHeadache and diplopiaSurgeryGTRFTOZN/APersistent III and IV nerve palsy
Kachhara [33]199855FCavernousHeadache, diplopiaSurgeryGTRFTOZ16III and IV nerve palsy persistent. VI nerve palsy completely improved after 2 months
Asaoka [34]199964FCisternalChronic headacheSurgerySTRN/A36Partial III nerve palsy improved
Kawasaki [25]199923FCisternalDiplopia, nausea and headacheFollow upN/AN/A36Complete recovery
Mariniello [35]19998FCavernousDiplopia, ophthalmoplegia, ptosis, anisocoriaSurgeryGTRPterional24N/A
Katoh [36]200066FCisternocavernousAsymptomaticSurgerySTRPterional6Worsened, complete III nerve palsy
Lingawi [37]200053MCisternalHeadacheSurgeryGTRAnterior temporal approach6No change, oculomotor function intact
Norman [26]20018 monthsFCavernousAnisocoriaFollow upN/AN/AN/AWorsened, III nerve palsy
Norman [26]20013FCavernousExotropiaFollow upN/AN/AN/AWorsened, III nerve palsy, strabisums surgery
Norman [26]20012 monthsMCavernousIII nerve palsyFollow upN/AN/AN/AWorsened, III nerve palsy, strabisums surgery
Norman [26]20012 monthsMCisternalPtosisFollow upN/AN/AN/AWorsened, III nerve palsy
Norman [26]20012FCisternalPtosisFollow upN/AN/AN/AWorsened, III nerve palsy
Sarma [38]200236FCavernousDiplopiaSurgeryGTRFronto-temporal96Improved, III nerve palsy, strabisumus surgery
Hatakeyama [6]200333MCisternocavernousDiplopiaSurgeryGTRanterior petrosal approach with temporal craniotomy and zygomatic osteotomy7Complete recovery
Ohata [12]200663FOrbitocavernousDiplopia, ptosis, eye pain, chemosisSurgerySTROrbytozigomatic infratemporal epidural and subdural approach72N/A
Bisdorff e Wildanger [19]200614FCisternalHeadaches, ophthalmoplegia, ptosis, diplopiaFollow upN/AN/A4N/A
Tanriover [39]200734FOrbitocavernousAnisocoria, ptosis, headache, exotropiaSurgerySTRPterional5Improved
Santarius [8]200742FCisternalDiplopiaFollow upN/AN/A4III nerve palsy
Kim [16]200819FCisternalOphtalmoplegiaGKSN/AN/A36Unchanged
Kim [16]200829MCisternalPtosisGKSN/AN/A9Unchanged
Chewning [20]20083FCisternalPtosis, headaches, III nerve palsyFollow upN/AN/AN/AUnchanged
Shamim [40]200811FOrbitalTotal esotropia, gradual worsening of vision and concomitant limitation of eye movementSurgeryGTROrbital approach12Residual ptosis, mild to moderate esotropia. No recovery of vision
Prabhu e Bruner [41]200938FCisternocavernousHeadache, occasional diplopia, ptosis dizzinessSurgeryGTRPterional6Complete III nerve palsy
Goel e Shah [42]201016MCisternocavernousHeadache and ptosisSurgeryGTRPterional24III and IV nerve palsy persisted. The facial sensations had improved
Goel e Shah [42]201032MCisternalHeadache, ptosis and diplopiaSurgerySTRBasal temporal approach52Complete recovery of III nerve palsy
Hironaka [43]201058MOrbitocavernousNumbness of the foreheadSurgeryGTRFTOZ6Mild III paralysis
Furtado e Hegde [44]201221MCisternocavernousDiplopiaSurgerySTRPterional12Complete III nerve palsy
Furtado e Hegde [44]201225MOrbitocavernousIII nerve palsy, diplopiaSurgerySTROZ craniotomy15Proptosis had recovered, while III NC palsy remained stable
Wang [45]201330MCisternalHeadache, nausea, diplopia, ophthalmoplegiaSurgerySTRN/A0.27Unchanged III nerve palsy
Yang [46]20133MCisternalIrritability, convulsionSurgeryGTRPterional12Overall worse
Iijima [47]201437FCisternocavernousBehavioral changes, cognitive impairment, drowsy, disoriented, GCS 8, anisocoria, hydrocephalusSurgerySTRTwo-stage surgery: pterional approach + 6 weeks later subtemporal route3.5Improved, oculomotor function intact
Nonaka [17]201433FCavernousHeadache and III nerve palsySurgeryGTROZ-FTN/APartial III nerve palsy, improved
Kumar [11]201429MCavernousDiplopia and blurring visionSurgerySTROrbitozigomatic craniotomy24Worsened, complete III nerve palsy
Nonaka [17]201420FCisternalHeadache, dizziness and vomitingSurgeryGTRFTOZ12III nerve palsy completely recovered
Nonaka [17]201418MCisternalIntermittent oculomotor palsyFollow upN/AN/A24Intermittent symptoms
Nonaka [17]201458MCisternocavernousN/ASurgerySTRFT-PN/APartial III nerve palsy
Senapati [48]201424FCisternalDiplopia, ptosis, headache, vomiting, hypopituitarismSurgeryGTRPterional12Improving of hormonal status, complete III nerve palsy
Kauser [49]201432MOrbitocavernousProptosisSurgeryGTRFronto-orbitotomy4Worsened, complete III nerve palsy
Cho [50]201441FOrbitocavernousBlurred visionSurgerySTRFronto-temporal12Improved Partial III nerve palsy
Shin [24]201543MOrbitalHeadache and III nerve palsyFollow upN/AN/A108Partial recovery
Shin [24]201542MCisternalHeadache and III nerve palsyFollow upN/AN/A10Partial recovery
Shin [24]201523FCisternalHeadache and III nerve palsyFollow upN/AN/A84Completely resolved
Kim [21]201531FCisternalDiplopia, headache and ptosisFollow upN/AN/A12Partial improvement III nerve palsy
Kim [21]201552MCisternalDiplopia, headache and ptosisFollow upN/AN/A12Incomplete recovery of the ophtalmoplegia
Shin [24]201541FCisternalHeadache and III nerve palsyFollow upN/AN/A144Resolved in 6 months. Just another one episode
Yulek e Demer [51]201660MOrbitalDiplopiaN/AN/AN/AN/AN/A
Yulek e Demer [51]201660MOrbitocavernousDiplopiaN/AN/AN/AN/AN/A
Yulek e Demer [51]201621FOrbitalDiplopiaN/AN/AN/AN/AN/A
Yulek e Demer [51]201655FCisternalN/AN/AN/AN/AN/AN/A
Yulek e Demer [51]20166FOrbitalN/AN/AN/AN/AN/AN/A
Lee [22]201810FCisternalHeadache and III nerve palsyFollow upN/AN/A24Ptosis and headache improved. Exotropia with limitation of ocular movement remained
Mariniello [52]201816FCisternocavernousIII nerve palsy, proptosisSurgeryGTRPterional240Improved prognosis and outcome of III nerve
Mariniello [52]201851FCavernousIII nerve palsy, proptosisSurgeryGTRPterional132Unchanged III nerve palsy and improved proptosis
Muhammad e Niemela [3]201864MN/AExophthalmos and blurry visionN/AN/AN/AN/AN/A
Abo-Shasha [14]201849MCisternalOphthalmoplegic migraineRT (25 Gy in 5 daily fractions)N/AN/AN/ASix months later, the patient reported a reduction in symptoms
Mariniello [52]201838MCavernousIII nerve palsy, proptosisSurgeryGTRPterional96Unchanged III nerve palsy and improved proptosis
Marutirao [53]201827MCisternalHeadache, vomiting and blurring visionSurgeryGTRFronto-temporal craniotomy with zigotomy; transsyilvian and subtemporal approach2Improvement in headache with partial recovery of the III nerve palsy
El Asri [7]201956MOrbitocavernousOcular pain, diplopia and proptosisFollow upSTREndoscopic endonasal approach8Partial recovery
Bentley [18]201969FCisternalDiplopiaFollow upN/AN/A3Stable disease
Fadel [15]201910FCisternocavernousHeadaches, ophthalmoplegia, ptosis, diplopia, III palsyRT (45 Gy over 25 fractions)N/AN/A58Unchanged III palsy. She underwent strabismus correction surgery with subsequent resolution of her diplopia
Petruzzelli [54]201916MCisternalHeadache, photophobia, nausea and ptosisFollow upN/AN/A0.25Improvement of headache symptoms in about one week
Fadel [15]20198MCavernousOphtalmoplegia, exotropiaRT (50 Gy over 25 fractions)N/AN/A56Unchanged III palsy. After 12 months, he underwent strabismus correction and ptosis repair
Wesolosky [55]20206MOrbitalProptosisSurgeryN/AUrgent lateral orbitotomyN/AUnable to fully elevate in adduction and persistent mydriasis
Mrabet [23]202118FN/AHeadaches, intermittent III nerve palsyFollow upN/AN/AN/ANo longer presented additional episodes
Chen [56]202121FN/AIII nerve palsy after resection of a schwannoma located in the left cavernous sinus 7y priorN/AN/AN/AN/AN/A
Langlois [9]202122FN/ADiplopiaSRSN/AN/AN/AN/A
Langlois [9]202148MN/ADiplopiaSRSN/AN/AN/AN/A
Langlois [9]202120FN/ADiplopia, ptosisSRSN/AN/AN/AN/A
Langlois [9]202111FN/ADiplopia, ptosisSRSN/AN/AN/AN/A
Langlois [9]202171MN/ADiplopia, ptosis, trigeminal painSurgeryN/AN/AN/AN/A
Langlois [9]202157MN/ADiplopia, ptosis, visual lossSRSN/AN/AN/AN/A
Langlois [9]202119FN/ADiplopia, ptosis, visual lossSurgeryN/AN/AN/AN/A
Langlois [9]202130FN/ADiplopia, ptosis, visual lossSurgeryN/AN/AN/AN/A
Langlois [9]202122MN/ADiplopia, ptosisSurgeryN/AN/A9N/A
Langlois [9]202145MN/ADiplopia, ptosisSRSN/AN/AN/AN/A
Tian [57]202137FOrbitalExotropia, diplopiaN/AN/AN/AN/AN/A
Shah [58]202121FCisternalHeadache, imbalance on walking and slurring of speechSurgeryGTRLateral supracerebellar transtentorial approach14III nerve palsy persisted
Tian [57]202128FCavernousPtosisN/AN/AN/AN/AN/A
Margolin [59]202178FCisternocavernousIII nerve palsy, ptosisFollow upN/AN/AN/A-
Rutkowski [60]202133FOrbitocavernousRetro-orbital pain, diplopia and III nerve palsySurgerySTRExtended pterional craniotomy with pretemporal transcavernous0.5Improved
Langlois [9]202140FN/AVisual lossSRSN/AN/AN/AN/A
Douglas [2]202242FOrbito-cisternocavernousDiplopiaSRS (27 fraction of 1.8 Gy)N/AN/A120No residual diplopia after strabismus reparative surgery
Douglas [2]202263FN/AEnlarged right pupilPBT (26 fraction of 1.8 Gy)N/AN/A60Right eye fixed in abduction
Douglas [2]202250FN/AExotropiaGKS (12 Gy single dose)N/AN/A12Strabismus repaired with surgery
Murali [61]202271FCisternalOne episode of seizureSurgerySTRPterionalN/AN/A
Douglas [2]202246FCisternalMigraineGKS (12 Gy single dose)N/AN/A72Diplopia treated with prism glasses
Ishino [10]20247FCisternalDiplopiaSurgerySTRPterional20Improved ON function. Ptosis remained

3.5. Our Case

A patient presented with episodic headache and blood pressure fluctuations in September 2024. During radiological investigations, a brain MRI incidentally revealed a cystic expansive lesion located in the right tuberculum sellae/suprasellar region. A follow-up contrast-enhanced MRI performed one month later demonstrated lesion growth, prompting hospital admission for further management. An ophthalmological evaluation performed elsewhere was reviewed and reported no ocular deficit.
Preoperative MRI showed an irregular extra-axial mass measuring approximately 27 × 18 × 17 mm, located between the right suprasellar cistern and the adjacent Sylvian fissure (Figure 3). The lesion appeared to originate from the right cavernous sinus, which was diffusely infiltrated, with inferior extension toward the upper portion of Meckel’s cave. It was characterized by a solid component with contrast enhancement and internal cystic areas. Medially, the lesion displaced and elevated the right optic chiasm and was in close contact with the pituitary stalk. The mass showed intimate relationships with adjacent vascular structures, including the right internal carotid artery siphon, the M1 segment of the right middle cerebral artery, the P1–P2 segments of the right posterior cerebral artery, and the ipsilateral superior cerebellar artery. Posteriorly, it compressed and deviated the course of the right oculomotor nerve at its mesencephalic emergence.
Preoperative CT confirmed the extra-axial sellar–parasellar lesion without evidence of intracranial hemorrhage or hydrocephalus (Figure 4).
Biphase CT angiography demonstrated no early arterial enhancement and only minimal delayed contrast uptake, with all adjacent vessels patent but indented by the lesion.
The patient underwent right pterional craniotomy with a subfrontal microsurgical approach. Intraoperatively, the lesion appeared soft, whitish-yellow, and moderately vascularized, showing tight adherence to the cavernous sinus, internal carotid artery, right middle cerebral artery, and the second and third cranial nerves. Given the high risk of neurological morbidity associated with radical resection, a subtotal excision was deliberately performed. Despite a limited partial resection of the lesion, consisting primarily of decompression of the cystic component, the patient developed a complete right third cranial nerve palsy. The histological examination reported a schwannoma (Grade 1, WHO 2021) [62]. Postoperative CT demonstrated expected surgical changes, including pneumocephalus and a small extra-axial fluid–blood collection, as well as partial removal of the lesion, with a residual mass measuring approximately 19 × 18 × 17 mm. Early postoperative MRI revealed acute ischemic lesions involving the right hypothalamus with extension to the posterior limb of the right internal capsule, as well as smaller acute ischemic foci in the right temporo-mesial cortico-subcortical regions and periventricular white matter, adjacent to the surgical site. The proximal intracranial arterial circulation remained patent. Clinically, the patient was mobilized on postoperative day two. Due to the development of a postoperative cerebrospinal fluid leak at the surgical wound site, a lumbar drain was placed on postoperative day five and removed six days later, with subsequent satisfactory wound healing.
At the three-month follow-up MRI, the residual lesion showed a further reduction in size (approximately 14 × 13 × 12 mm vs. 27 × 18 × 17 mm) with disappearance of the cystic components and homogeneous, intense contrast enhancement (Figure 5).
Imaging also demonstrated a cavitary gliotic lesion in the right nucleo-capsular region, consistent with the evolution of the prior ischemic insult, along with a mild increase in supratentorial ventricular volume.
Stereotactic radiation treatment was performed with a robotic-arm Linac on the heteroplasia located in the right cavernous sinus. A total dose of 24 Gy was administered, divided into four fractions. No significant side effects were observed or reported. Cortisone therapy was recommended for another nine days.
At one-year follow-up, the lesion remained stable in size (maximum anteroposterior diameter of 22 mm) but exhibited a large central non-enhancing area consistent with extensive necrosis, with persistent peripheral enhancement (Figure 6).
The mass continued to encase and compress adjacent vascular structures, including the intracavernous segment of the right internal carotid artery and the proximal segments of the right middle and posterior cerebral arteries. Chronic ischemic changes in the right nucleo-capsular and anterior temporal regions were unchanged.

4. Discussion

Due to the infrequency of ONS, most centers lack experience in its treatment, and there are no published guidelines or consensus statements regarding the management of patients with these tumors.
Our literature review identified 96 reported ONS cases. Considering the extended timeframe during which these cases were published and the varied geographic distribution of treatment sites, it is unsurprising that techniques and therapies differed significantly. The fact that imaging methods (CT and MRI) and treatment approaches (surgical and radiosurgery) have changed significantly over time adds to the difficulty of analyzing treatment-related morbidity. This accounts for the diverse methods employed within the surgical subgroup. In more recent cases, MRIs were used to characterize tumors and ascertain the size and extent of lesions. MRI with gadolinium contrast remains the gold standard for diagnosing schwannomas of the oculomotor nerve. MRI provides superior soft tissue contrast and can clearly delineate the tumor from surrounding neural and vascular structures. Characteristically, these tumors appear well-circumscribed, enhancing masses that may show heterogeneity due to cystic changes or hemorrhage within the tumor. In patients with ONS, MRIs show the precise extent of the tumor in the skull base cisterns or along the nerve’s path in parasellar spaces within the cavernous sinus. Some schwannomas were observed to extend from one compartment into another and were subsequently referred to as “cisterno-cavernous” [49]. Finally, ONSs may be located solely within the orbit or extending into it, as many cases documented in the literature [44,49,63,64]. High-resolution MRI sequences, such as T1-weighted, T2-weighted, and contrast-enhanced images, are crucial for accurate assessment. Additionally, diffusion-weighted imaging (DWI) can be helpful in distinguishing schwannomas from other entities like metastatic lesions or meningiomas. In some cases, magnetic resonance angiography (MRA) may be necessary to evaluate the relationship between the tumor and adjacent blood vessels, particularly if there is suspicion of vascular encasement or compression. The differential diagnosis for oculomotor nerve schwannomas includes various other conditions that can present with similar clinical features, such as aneurysms, particularly those involving the posterior communicating artery, posterior cerebral artery and superior cerebellar artery, which can compress the oculomotor nerve and present with a painful third nerve palsy, along with meningiomas and metastatic lesions, as well as inflammatory and infectious processes. Although schwannomas exhibit a rather distinct radiographic appearance as hyperintense lesions in gadolinium-enhanced MRIs, only histopathology can definitively identify cranial nerve schwannomas. Schwannomas are characterized histologically by a highly cellular Antoni A zone with palisading cells and a distinctively less cellular, mucin-filled Antoni B zone [65]. Schwannomas are characterized immunohistochemically by the overexpression of protein S-100 [66].
With the exception of one asymptomatic patient reported by Kato et al. [36], every patient found through our literature review as well as those described in our case series exhibited at least one or both of the usual common signs of third nerve palsy: diplopia (42 patients) and ptosis (40 patients). Another common clinical manifestation resembled ophthalmoplegic migraines (34 patients), marked by short episodes of ptosis and diplopia during or after a headache [67]. This pooled cohort also reported other symptoms, such as hydrocephalus [47], cognitive decline [47], periorbital pain [19,24,30], and nausea [21,22,23,25,45,54]. The majority of these symptoms were caused by the mass effect of a displaced or compressed brain due to especially large lesions that required surgery [45,47]. Our literature review uncovered several statistically significant findings, despite the considerable variability in follow-up duration, symptom duration, and the various treatments administered to patients. Patients with large tumors (average diameter of 25.5 mm) generally underwent surgical intervention, while those with small tumors (average diameter of 7.34 mm) typically did not have resection and were treated with radiotherapy or underwent follow-up.
Due to the manipulation of a lesion that is intrinsic to the small nerve during resection, surgical intervention often led to a complete third nerve palsy (Table 2), which is expected because the oculomotor nerve is quite delicate. The possibility of irreversible oculomotor nerve damage during surgery has led some providers to take a less aggressive approach for patients who do not show significant or life-threatening symptoms, such as those with only partial third nerve palsy, elderly patients, or those with stable tumors [36]. Considering the morbidity linked to third nerve palsy, the alternative approach could be subtotal resection [34,39]. If the tumor is situated more anteriorly toward the superior orbital fissure than in the cisternal region, the likelihood of nerve injury rises [39].
Several surgical approaches can be utilized depending on the tumor’s size, location, and extent:
Transcranial Approach: This is often the preferred approach for tumors located in the cavernous sinus or those extending into the posterior fossa. It allows for direct visualization and access to the nerve and tumor.
Endoscopic Endonasal Approach: Minimally invasive, this approach can be used for tumors situated anteriorly or in the sellar region, providing a route to the nerve without the need for extensive brain retraction.
Combined Approaches: In cases of extensive tumors, a combination of transcranial and endoscopic approaches may be required to achieve complete resection.
Intraoperative neurophysiological monitoring, including electromyography (EMG) and somatosensory evoked potentials (SSEPs), can be invaluable in preserving nerve function during surgery. Advances in microsurgical techniques and tools, such as high-powered microscopes and precision instruments, have significantly improved surgical outcomes.
Two cases documented the application of SRS to attain local control. Both cases indicated a decrease in tumor size and no deterioration of symptoms [16]. These findings align with earlier research that documented the effectiveness of SRS in handling other intracranial skull base schwannomas [16,68]. It is worth mentioning that Langlois and colleagues conducted a study that assessed the safety and efficacy of SRS in 11 patients with ONS. The results showed that SRS can be safely applied and offers a good tumor control rate [9]. Furthermore, most patients exhibited an improvement in diplopia. The authors of this study propose that this can be viewed as a first-line treatment in ONS, as it poses lower injury risks than other methods. There are two reports of surgically managed ONS in which SRS demonstrated effectiveness as an adjunct treatment for tumor size control following incomplete tumor resection [5,10].
The prognosis for patients with third cranial nerve schwannomas is generally favorable, particularly when tumors are diagnosed early and managed appropriately. The extent of preoperative nerve involvement is a key determinant of postoperative outcomes. Patients presenting with minimal neurological deficits and those undergoing complete tumor resection typically have better functional recovery. However, complete functional recovery of the oculomotor nerve is not always achievable, especially in cases of significant preoperative deficits or extensive nerve involvement. Residual symptoms such as mild diplopia or ptosis may persist, necessitating ongoing management and rehabilitation. Regular follow-up with MRI is crucial to monitor for tumor recurrence, particularly in cases where subtotal resection was performed or radiosurgery was employed. The risk of malignant transformation is extremely low, given the benign nature of schwannomas [8,69].
To maintain any residual oculomotor functions, we recommend treating smaller tumors that pose a lower risk of compressing nearby structures with a combination of SRS and strabismus repair. If SRS does not manage to achieve local control of the lesion and oculomotor function deteriorates further, conventional microsurgical resection seems appropriate for suitable patients. However, considering that most surgically treated ONS patients experienced complete third nerve palsies post-surgery, we recommend reserving surgical resection for those with large tumors that compress surrounding tissues at diagnosis.
Research into the molecular and genetic basis of schwannomas may offer new insights into their pathogenesis and potential therapeutic targets. Advances in imaging techniques, such as functional MRI and tractography, could improve diagnostic accuracy and preoperative planning [70,71,72,73]. Furthermore, developments in minimally invasive surgical techniques and precision radiotherapy hold promise for enhancing treatment outcomes and reducing morbidity.

5. Conclusions

Third cranial nerve schwannomas, though rare, are significant due to their potential to cause debilitating symptoms. Early diagnosis and appropriate management are crucial to preserving nerve function and improving quality of life. Future research should focus on refining diagnostic criteria, enhancing surgical techniques, and exploring innovative therapeutic options to further improve patient outcomes. Collaborative research efforts and the establishment of multicenter registries could facilitate the accumulation of larger datasets, aiding in the development of evidence-based guidelines for the management of these rare tumors.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/neuroglia7010009/s1, the PRISMA Checklist.

Author Contributions

Conceptualization, A.G. and S.E.; methodology, G.R.; software, F.L.; validation, A.G. and A.C.; investigation, S.E. and A.C.; data curation, S.E., F.L. and A.C.; writing—original draft preparation, A.C., S.E. and F.L.; writing—review and editing, A.C.; visualization, A.C.; supervision, G.R.; project administration, A.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Written informed consent has been obtained from the patient(s) to publish this paper.

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Acknowledgments

The authors have reviewed and edited the output and take full responsibility for the content of this publication.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
ONS Oculomotor nerve schwannoma
STRSubtotal resection
GTRGross total resection
RTRadiation therapy
SRSStereotaxic radiosurgery
CTComputed tomography
MRIMagnetic resonance imaging

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Figure 1. PRISMA flow diagram illustrating the study selection process. A total of 989 records were identified through database searching. After removal of duplicates and screening of titles and abstracts, full-text articles were assessed for eligibility. Ninety-six cases met the inclusion criteria and were included in the final qualitative synthesis. Reasons for exclusion included non-English language, lack of clinical data, and unrelated pathology.
Figure 1. PRISMA flow diagram illustrating the study selection process. A total of 989 records were identified through database searching. After removal of duplicates and screening of titles and abstracts, full-text articles were assessed for eligibility. Ninety-six cases met the inclusion criteria and were included in the final qualitative synthesis. Reasons for exclusion included non-English language, lack of clinical data, and unrelated pathology.
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Figure 2. Distribution of reported oculomotor nerve schwannomas according to anatomical location. Bar chart illustrating the number of cases involving the cisternal, cavernous, orbitocavernous, orbital, and cisternocavernous regions, based on the 96 cases identified in the literature review.
Figure 2. Distribution of reported oculomotor nerve schwannomas according to anatomical location. Bar chart illustrating the number of cases involving the cisternal, cavernous, orbitocavernous, orbital, and cisternocavernous regions, based on the 96 cases identified in the literature review.
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Figure 3. Preoperative brain MRI of a 51-year-old female diagnosed with oculomotor nerve schwannoma. CISS (top) and contrast-enhanced T1-weighted (bottom) axial, coronal and sagittal images demonstrate a 27 × 18 × 17 mm irregular extra-axial mass located between the right suprasellar cistern and the Sylvian fissure. The lesion shows heterogeneous enhancement with internal cystic components. It infiltrates the right cavernous sinus and extends toward Meckel’s cave. Medially, the mass displaces the optic chiasm and abuts the pituitary stalk. Posteriorly, it compresses the right oculomotor nerve at its mesencephalic emergence.
Figure 3. Preoperative brain MRI of a 51-year-old female diagnosed with oculomotor nerve schwannoma. CISS (top) and contrast-enhanced T1-weighted (bottom) axial, coronal and sagittal images demonstrate a 27 × 18 × 17 mm irregular extra-axial mass located between the right suprasellar cistern and the Sylvian fissure. The lesion shows heterogeneous enhancement with internal cystic components. It infiltrates the right cavernous sinus and extends toward Meckel’s cave. Medially, the mass displaces the optic chiasm and abuts the pituitary stalk. Posteriorly, it compresses the right oculomotor nerve at its mesencephalic emergence.
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Figure 4. Preoperative CT scan (axial sagittal–coronal view). Non-contrast computed tomography confirms the presence of an extra-axial sellar–parasellar mass without evidence of acute hemorrhage or hydrocephalus. The lesion produces a mild mass effect on adjacent structures.
Figure 4. Preoperative CT scan (axial sagittal–coronal view). Non-contrast computed tomography confirms the presence of an extra-axial sellar–parasellar mass without evidence of acute hemorrhage or hydrocephalus. The lesion produces a mild mass effect on adjacent structures.
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Figure 5. Three-month follow-up MRI. CISS (top) contrast-enhanced T1-weighted (bottom) axial, coronal and sagittal images demonstrate a reduction in the residual lesion (approximately 14 × 13 × 12 mm) with disappearance of the cystic component and homogeneous contrast enhancement. Postoperative gliotic changes are visible in the right temporal region.
Figure 5. Three-month follow-up MRI. CISS (top) contrast-enhanced T1-weighted (bottom) axial, coronal and sagittal images demonstrate a reduction in the residual lesion (approximately 14 × 13 × 12 mm) with disappearance of the cystic component and homogeneous contrast enhancement. Postoperative gliotic changes are visible in the right temporal region.
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Figure 6. One-year follow-up MRI after stereotactic radiotherapy. CISS (top) and contrast-enhanced T1-weighted (bottom) axial, coronal and sagittal images show stable lesion size with development of a large central non-enhancing area consistent with radiation-induced necrosis and persistent peripheral enhancement. The mass continues to encase the intracavernous segment of the right internal carotid artery without evidence of vascular occlusion.
Figure 6. One-year follow-up MRI after stereotactic radiotherapy. CISS (top) and contrast-enhanced T1-weighted (bottom) axial, coronal and sagittal images show stable lesion size with development of a large central non-enhancing area consistent with radiation-induced necrosis and persistent peripheral enhancement. The mass continues to encase the intracavernous segment of the right internal carotid artery without evidence of vascular occlusion.
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Table 2. Post-treatment results compared between surgical treatment, radiation therapy and pure conservative treatment.
Table 2. Post-treatment results compared between surgical treatment, radiation therapy and pure conservative treatment.
III c.n. FunctionSurgery (n = 51)Radiotherapy (n = 16)Conservative (n = 20)
Improved13 (25.5%)1 (6.2%)10 (50%)
Unchanged9 (17.6%)7 (43.7%)4 (20%)
Worsened22 (43.1%)1 (6.2%)5 (25%)
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Curcio, A.; Espahbodinea, S.; Lacava, F.; Raffa, G.; Germanò, A. Schwannomas of the Third Cranial Nerve: An Overview and Case Report. Neuroglia 2026, 7, 9. https://doi.org/10.3390/neuroglia7010009

AMA Style

Curcio A, Espahbodinea S, Lacava F, Raffa G, Germanò A. Schwannomas of the Third Cranial Nerve: An Overview and Case Report. Neuroglia. 2026; 7(1):9. https://doi.org/10.3390/neuroglia7010009

Chicago/Turabian Style

Curcio, Antonello, Shervin Espahbodinea, Francesco Lacava, Giovanni Raffa, and Antonino Germanò. 2026. "Schwannomas of the Third Cranial Nerve: An Overview and Case Report" Neuroglia 7, no. 1: 9. https://doi.org/10.3390/neuroglia7010009

APA Style

Curcio, A., Espahbodinea, S., Lacava, F., Raffa, G., & Germanò, A. (2026). Schwannomas of the Third Cranial Nerve: An Overview and Case Report. Neuroglia, 7(1), 9. https://doi.org/10.3390/neuroglia7010009

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