Prognosis factor in oculomotor schwannoma: a case of endoscopic endonasal approach and systematic review of the literature

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Prognosis Factor in Oculomotor Schwannoma: A Case of Endoscopic Endonasal Approach and Systematic Review of the Literature

Abad Cherif El Asri

^1,3

, Mohamed M. Arnaout

^1,4

, Mina M. Gerges

^1,5

, Miloudi Gazzaz

³

, Brahim El Mostarchid

³

, Theodore H. Schwartz

^1,2

INTRODUCTION

Intracranial schwannomas constitute approximately 8%e10% of all intracranial neoplasms, with vestibular schwannomas being the most common among them.

Nonvestibular schwannomas constitute only 10% of all schwannomas and include, in descending order of frequency, those arising from the trigeminal nerve, facial nerve, and lower cranial nerves.

^1-3

How- ever, oculomotor nerve (ON) schwanno- mas, with an equal predilection for the cisternal and cavernous sinus and orbital locations, are very rare, with only few re- ported cases in the literature.

^4-7

Consequently, very limited literature exists for the optimal management of oc- ulomotor schwannoma. Transcranial sur- gery was historically the most frequently used approach for managing this tumor.

There are no agreed-on criteria for when surgical or nonsurgical management is indicated, with little discussion of radio- surgery and no cases in which an endo- scopic endonasal approach (EEA) was used.

^4,5,8-10

We report the ﬁrst case in the literature of an expanded endoscopic skull-base approach for biopsy of an ocu- lomotor schwannoma. This case was extending into the cavernous sinus, and open surgery was considered to be unsafe.

The goal was biopsy for diagnosis with radiosurgery reserved for interval growth.

Function preservation was the motivation.

In addition to reporting our case, we also review the literature on oculomotor schwannoma to establish a consensus regarding best treatment options for this rare lesion.

METHODS

A literature search of the electronic PubMed databases up to December 2018 was conducted using subject headings (Medical Subject Headings) and key words, and limited to human studies. The terms oculomotor schwannoma and com- binations of the variables “schwannoma,”

“neurinoma,” “neurilemoma,” “oculomo- tor nerve,” “third cranial nerve,”

“cavernous sinus,” and “strabismus” were searched. To identify additional eligible

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BACKGROUND: We report the first case of oculomotor nerve (ON) schwan- noma treatment through an endonasal endoscopic approach. We also review the literature to determine prognosis factors of ON function after treatment.

-

METHODS: A complete MEDLINE search was undertaken for all articles reporting data for oculomotor schwannoma. We divided the patient population into 2 groups; Group I: patients who conserved or recovered good ON function and Group II: patients with either new, worsening, or unchanged third-nerve palsy at the last available follow-up. We conducted a comparative statistical analysis of data between the 2 groups.

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RESULTS: We identified 55 reported cases of ON schwannoma, all of whom were treated with open transcranial surgery, stereotactic radiosurgery, or observation. There were 22 patients in group I and 33 in group II. At admission, 29 patients had complete oculomotor nerve palsy (34.7% in group I and 67.7% in group II; P [ 0.02). Surgical treatment was performed in 36 cases. Radiosurgery was performed in 3 cases. Among patients with good preoperative ON function, 34.6% worsened at last follow-up (26.6% after surgery and 50% with observation;

P [ 0.03). In total, 31% of patients with total or near-total palsy at admission had an improvement of their ON function (all after surgical resection; P [ 0.05).

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CONCLUSIONS: ON function at admission and surgical resection of schwannoma appears to be a predictive factor of favorable prognosis regardless of location and tumor size. The endonasal endoscopic approach can be used to biopsy tumors in cases in which open surgery is considered too risky, such as cavernous sinus schwannomas.

Key words

-Cavernous sinus

-Endoscopic endonasal

-Extended approach

-Oculomotor nerve

-Palsy

-Schwannoma

-Surgery

-Transsphenoidal

Abbreviations and Acronyms EEA: Endoscopic endonasal approach F: Female

M: Male

MRI: Magnetic resonance imaging ON: Oculomotor nerve

From the Departments of¹Neurosurgery and²Otolaryngology and Neuroscience, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York, USA;

3Department of Neurosurgery, Mohamed V Military Hospital, Rabat, Morocco;⁴Department of Neurosurgery, Faculty of Medicine, Zagazig University, Sharqia, Egypt; and

5Department of Neurosurgery, Faculty of Medicine, Ain Shams University, Cairo, Egypt

To whom correspondence should be addressed:

Abad Cherif El Asri, M.D.

[E-mail:abad20031@gmail.com]

Citation: World Neurosurg. (2019) 129:72-80.

https://doi.org/10.1016/j.wneu.2019.05.170

Journal homepage:www.journals.elsevier.com/worldneurosurgery

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Literature Review

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Table 1. Summary of Cases of Oculomotor Nerve Schwannoma Reported in the Literature

Study

Age,

years Sex Main Symptoms

Mode of Installation of Symptoms

Onset of Symptoms,

months Tumor Location

Tumor Size,

mm Treatment and Approach

Prognosis of Oculomotor

Function

Oculomotor Function Outcomes

Follow-up, months Present case 56 M Recurrent partial oculomotor

palsy, diplopia and ophtalmologic migraine

Acute or subacute 0.17 Cavernous 24 STR or partial resection via endoscopic expanded

approach

Improved Partial recovery NA

Lee et al., 2018¹¹

10 F Acute intermittent headache and mild third-nerve palsy

Acute or subacute 12 Cisternal 3,4 No surgery: oral steroids Worsened Partial recovery 24

Mariniello et al., 2018¹²

38 M Partial third-nerve palsy, proptosis

NA NA Cavernous 20 GTR via pterional approach No change Unchanged third-nerve palsy

and improved proptosis 96

51 F Complete third-nerve palsy, proptosis

NA NA Cavernous 18 GTR via pterional approach No change Unchanged third-nerve palsy

and improved proptosis 132

16 F Complete third-nerve palsy, proptosis

NA NA Cisterno-cavernous 15 GTR via pterional approach with third nerve grafting

Improved Improved 240

Abo-shasha et al., 2018⁴

49 M Recurrent ophthalmoplegic migraine

Acute or subacute 240 Cisterno-cavernous 4 GKS No change Improved 18

Shin et al., 2015¹³

42 M Acute intermittent headache and mild third-nerve palsy

Acute or subacute 180 Cisternal 3 No surgery: analgesic Recurrent Partial recovery 10

Acute or subacute 192 Cisternal 4 No surgery: analgesic Recurrent Completely resolved but intermittent recurrent

84

41 F Acute Intermittent Headache and mild third-nerve palsy

Acute or subacute 144 Cisternal 3 No surgery: oral steroids Recurrent Resolved but intermittent recurrent

144

43 M Acute Intermittent Headache and mild third-nerve palsy

Acute or subacute 108 Orbital 4 No surgery: oral steroids Recurrent Partial recovery 108

Kumar et al., 2014¹⁴

29 M Diplopia Delayed 2 Cavernous 30 STR or partial resection Worsened Complete third-nerve palsy,

SRS treatment

24

Nonaka et al., 2014¹⁵

Acute or subacute 6 Cavernous 31 GTR via OZ-FT Unchanged

intermittent

No change NA

20 F Headache, dizziness, and vomiting

Delayed 6 Cisternal 65 GTR via OZ-FT Improved Partial third-nerve palsy NA

18 M Ptosis NA NA Cisternal 5 No surgery: observation NA No change 24

58 M NA NA NA Cisterno-cavernous 32 STR or partial resection via

FT-P approach

Unchanged complete palsy

Worsened NA

Kim et al., 2015¹⁶

31 F Diplopia, headache, and ptosis

Acute or subacute 60 Cisternal 3 No surgery: IV and oral prednisone

No change Partial third-nerve Palsy 12

M, male; STR, subtotal resection; NA, not available; F, female; GTR, gross total resection; GKS, Gamma-knife surgery; SRS, stereotactic radiosurgery; OZ-FT, orbito zygomatic-fronto-temporal; FT-P, fronto-temporo-pterional; IV, intravenous.

Continues

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Table 1. Continued

Study

Age,

years Sex Main Symptoms

Mode of Installation of Symptoms

Onset of Symptoms,

months Tumor Location

Tumor Size,

mm Treatment and Approach

Prognosis of Oculomotor

Function

Oculomotor Function Outcomes

Follow-up, months Kim et al.,

2015¹⁶

52 M Diplopia, headache, and ptosis

Acute or subacute 0.1 Cisternal 3 No surgery: IV and oral prednisone

No change Partial third-nerve Palsy 12

Suenaga et al., 2014⁷

79 F Oculomotor nerve palsy NA NA Cisternal 15 STR or partial resection via

pterional transsylvian approach

Improved Complete third-nerve palsy 58

Kauser et al., 2014¹⁷

32 M Proptosis Delayed 6 Orbito-cavernous 43 GTR Worsened Complete third-nerve Palsy 4

Senapati et al., 2014¹⁸

24 F Diplopia, ptosis Delayed 24 Cisternal 62 GTR No change Complete third-nerve Palsy 12

Cho et al., 2014¹⁹

41 F Blurred vision Acute or subacute 0.25 Orbito-cavernous 24 STR or partial resection via FT-P approach

Improved Partial third-nerve palsy 12

Iijima et al., 2014²⁰

37 F Cognitive impairment, hydrocephalus

Delayed 3 Cisterno-cavernous 50 STR or partial resection Improved Oculomotor function intact 2

Scheller et al., 2013²¹

42 F Anisocoria, exophthalmos Acute or subacute 1.67 Orbital 17 GTR Improved No change 48

Yang et al., 2013²²

3 M Convulsion, ptosis Acute or subacute 0.33 Cisternal 13 GTR Worsened Near-complete third-nerve

palsy

12

Wang et al., 2013²³

30 M Headache, nausea, diplopia, ophthalmoplegia

Acute or subacute 60 Cisternal NA STR or partial resection No change Third-nerve palsy NA

Nagashim et al., 2012²⁴

58 M Ocular pain, blindness Delayed 24 Orbito-cavernous NA GTR No change Complete third-nerve palsy 6

Furtado et al., 2012⁹

21 M Diplopia Delayed 6 Cisterno-cavernous 15 GTR No change Complete third-nerve palsy 12

Furtado et al., 2012⁹

25 M Third-nerve palsy, diplopia Delayed 4 Orbito-cavernous 50 GTR No change Complete third-nerve palsy 15

Prabhu et al., 2010²⁵

38 F Recurrent headache, dizziness, diplopia, ptosis

Acute or subacute NA Cisternal 35 GTR Worsened Complete third-nerve palsy 6

Goel et al., 2010³

32 M Headache, ptosis, diplopia Delayed 3 Cisternal 41 GTR Improved Oculomotor function intact 52

Chewning et al., 2008²

14 F Ptosis, headaches, third- nerve palsy

Acute or subacute 0.33 Cisternal 4 No surgery: observation No change No change NA

Shamim et al., 2008²⁶

11 F Total esotropia Delayed 36 Orbital NA GTR Improved Esotropia, improved NA

Kim et al., 2008⁶

29 M Ptosis NA NA Cisternal 3 GKS No change Unchanged 9

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Kim et al., 2008⁶

19 F Ophthalmoplegia NA NA Cisternal 4 GKS No change Unchanged 36

Tanriover et al., 2007²⁷

34 F Complete third-nerve palsy, proptosis headache

Acute or subacute 0.67 Cavernous 10 STR or partial resection via pterional approach

Improved Improved NA

Ohata et al., 2006²⁸

63 F Headache, ptosis, diplopia Acute or subacute 1 Cavernous 25 STR or partial resection No change Complete third-nerve palsy 72

Bisdorff et al., 2006²⁹

14 F Headache, ptosis, diplopia Delayed 144 Cisternal 7 No surgery: observation No change No change 4

Kozic et al., 2006³⁰

9 M Ptosis, hemiparesis Acute or subacute NA Cisternal 27 STR or partial resection Worsened

(malignant tumor)

Aggression with malignant- nature third-nerve palsy,

strabismus surgery

NA

Murakami et al., 2005³¹

11 F Recurrent ptosis, diplopia, headache

Acute or subacute 60 Cisternal 5 GTR Worsened Third-nerve palsy,

strabismus surgery

1

Netuka and Benes, 2003³²

12 F Headaches Delayed 10 Cisternal 28 GTR Recovered after

worsening

Third-nerve palsy 12

Hatakeyama et al., 2003³³

33 M Diplopia, ptosis Delayed 8 Cisterno-cavernous 40 GTR Improved Oculomotor function intact 7

Sarma et al., 2002³⁴

36 F Diplopia, third-nerve palsy NA NA Cavernous 7 GTR Improved Third-nerve palsy,

strabismus surgery

96

Norman et al., 2001³⁵

0,17 M Third-nerve palsy NA NA Cavernous 3 No surgery: observation Worsened Third-nerve palsy,

strabismus surgery

96

0,75 F Anisocoria NA NA Cavernous 3 No surgery: observation Worsened Third-nerve palsy 8

2 F Anisocoria NA NA Cisternal 3 No surgery: observation Worsened Third-nerve palsy 11

0,17 M Ptosis NA NA Cisternal 3 No surgery: observation Worsened Third-nerve palsy 48

3 F Exotropia NA NA Cavernous NA No surgery: observation Worsened Third-nerve palsy,

strabismus surgery

84

Katoh et al., 2000³⁶

66 F Asymptomatic NA NA Cisterno-cavernous 15 GTR Worsened Complete third-nerve palsy 6

Lingawi et al., 2000³⁷

53 M Headache Delayed 3 Cisternal 5 GTR No change Oculomotor function intact 6

Kawasaki, 1999³⁸

23 F Diplopia, nausea, and headache

Acute or subacute 216 Cisternal 4 No surgery: oral steroids No change Episodic third-nerve palsy and migraine

36

Asaoka et al., 1999⁸

64 F Headache Delayed NA Cisternal 15 STR or partial resection Recovered after

worsening

Partial third-nerve palsy 36

8 F Third-nerve palsy Delayed 96 Cavernous 10 GTR Improved Partial third-nerve palsy 24

M, male; STR, subtotal resection; NA, not available; F, female; GTR, gross total resection; GKS, Gamma-knife surgery; SRS, stereotactic radiosurgery; OZ-FT, orbito zygomatic-fronto-temporal; FT-P, fronto-temporo-pterional; IV, intravenous.

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studies, the reference lists also were screened for articles. An analysis of the published studies concerning clinical and radiologic characteristics, treatment, and outcomes was performed. Articles written in a language other than English were excluded, as were abstracts, editorials, letters, or comments.

The data extraction included the following parameters: 1) year of publica- tion and author; 2) age and sex; 3) onset of symptoms; 4) signs on admission; 5) tu- mor location; 6) tumor size; 7) treatment;

and 8) outcomes. At the last reported follow-up we divided the outcomes of patients according to improvement, dete- rioration or stability of third nerve func- tion compared with before treatment.

The aim of our study was to compare treatment options for third-nerve schwannoma and compare functional outcomes with the endonasal endoscopic case we present. According to the results reported by the investigators, we divided the patient population into 2 groups:

Group I: patients who conserved or recovered good third-nerve function at the last available follow-up.

Group II: patients who had worsening or unchanged third-nerve palsy at the last available follow-up.

We conducted a comparative statistical analysis of the epidemiologic, clinical, radiologic, and therapeutic parameters between the 2 groups. Qualitative param- eters were compared using the c

²

^{test, and} quantitative parameters were compared using the independent samples t test. All statistical results were considered as sig- niﬁcant if P < 0.05. The analysis was performed with the SPSS 21 package software (IBM Corp., Armonk, New York, USA).

RESULTS

A MEDLINE search resulted in 55 cases of oculomotor schwannoma. The data of all 55 patients, including those of the current case, are summarized in Table 1.

2-4,6-9,11-40

There were 22 patients in group I and 33 in group II.

Case Illustration

A 56-year-old male patient complained of 5 months of acute ocular pain, diplopia, and proptosis in the right eye. Examina- tion revealed near-complete right eye

ptosis, symmetric pupils, and deﬁcits of supraduction and adduction. Magnetic resonance imaging (MRI) was completed, which showed a 24 8 6-mm lesion extending from the right cavernous sinus into the right orbit (Figure 1). The patient was treated with intravenous and oral steroids, and he had improvement in the eye pain as well as the double vision.

Repeat MRI 4 months later showed no change in the appearance of the lesion, and his symptoms began to recur. Given the location of the tumor, open transcranial surgery thought felt to be too risky. EEA was used in a stepwise manner; after performing a right uncinectomy, a middle turbinate resection, and a wide maxillary antrostomy and ethmoidectomy, the sphenoid sinus was entered and widely enlarged. This provided a panoramic view before we exposed the medial aspect of the superior orbital ﬁssure.

Guided by navigation and vascular Doppler probe, the drilling of the lateral wall of the sphenoid sinus between the cavernous sinus and the orbital apex allowed the exposition of the medial part of the superior orbital ﬁssure, and then the dura and the annulus of Zinn were opened.

After retracting upward the medial rectus muscle, we discovered a grayyellow ﬁrm tumor, which was partially excised. The patient awoke with a worsening of his partial third-nerve palsy with limited adduction and supraduction but preserved eyelid movement and pu- pillary reaction. At a follow-up visit 4 months later, the ptosis and oculomotor palsy had dramatically improved. MRI showed a small residual located infer- olaterally in the cavernous sinus (Figure 2).

Treatment at this point will include serial imaging and stereotactic radiosurgery at the ﬁrst sign of growth.

Literature Review Analysis

Demographic Data. Age distribution of 55 patients with oculomotor schwannoma is shown in Table 2. The median of the age was 31.5 years, 36 years for the patients in group I and 27 years for those in group II. No signiﬁcant difference of age was found between both groups (P ¼ 0.17). The male (M)-to-female (F) ratio was 0.77 (24 M/31 F), 0.46 in group I (7 M/15 F), and 1.13 in group II (17 M/15 F).

Table 1. Continued

StudyAge, yearsSexMainSymptoms Modeof Installation ofSymptoms Onsetof Symptoms, monthsTumorLocation Tumor Size, mmTreatmentandApproach Prognosisof Oculomotor Function

Oculomotor Function OutcomesFollow-up, months Kachhara etal.,19983955FHeadache,diplopia,ptosisDelayed36Cavernous20GTRWorsenedThird-andfourth-nervepalsy16 Kachhara etal.,19983961MHeadache,diplopiaDelayed6Cisterno-cavernous40GTRWorsenedThird-andfourth-nervepalsy12 Niaziand Boggan, 199440

13MDiplopia,headache,ptosisAcuteorsubacute0.67Cisterno-cavernous50STRorpartialresectionImprovedThird-nervepalsy,diplopia improvedNA M,male;STR,subtotalresection;NA,notavailable;F,female;GTR,grosstotalresection;GKS,Gamma-knifesurgery;SRS,stereotacticradiosurgery;OZ-FT,orbitozygomatic-fronto-temporal;FT-P,fronto-temporo-pterional;IV,intravenous.

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ABAD CHERIF EL ASRI ET AL. PROGNOSIS FACTOR IN OCULOMOTOR SCHWANNOMA

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No signiﬁcant difference of sex was found between both groups (P ¼ 0.1).

Clinical Presentation. The characteristics and clinical presentations of patients in each group are shown in Table 2. The median delay until onset of symptoms was 7 months (9 months in group I and 6 months in group II), without signiﬁcant difference (P ¼ 0.33).

Symptom presentation was acute to subacute (less than 4 weeks) in 41.6% of patients (57.1% of patients in group I and in 52.6% of patients in group II; P ¼ 0.75). At admission, 29 patients had complete ON palsy (34.7% in group I

and 67.7% in group II) and 24 patients had partial palsy (47.4% in group I and 17.6% in group II), and 2 cases were asymptomatic. The difference between groups was signiﬁcant (P ¼ 0.02).

Diplopia was the main symptom in 40 cases. Proptosis was reported in 32 cases.

Twelve patients complained of recurrent ophthalmologic migraine, whereas exophthalmos, hemiparesis, blurred vision, or seizures were reported in some cases.

Radiologic Findings. Most cases used MRI to accurately determine the size and loca- tion of the lesions. MRI in these cases

demonstrated that oculomotor schwan- nomas are most frequently located in the interpeduncular cistern in 26 cases (47%);

strictly located in the cavernous sinus in 13 cases (24%); cisterno-cavernous in 9 cases (16.4%), orbito-cavernous in 4 cases (7.3%); and intraorbital in 3 cases (5.5%).

Given the complexity of the surgical management of lesions invading the cavernous sinus, we regrouped all tumors located or extending into the cavernous sinus as a cavernous schwannoma;

consequently, the number of cavernous sinus schwannomas represented was 26 cases (50% of patients in both group I and in group II). The median diameter was 18 mm in group I and 19.3 mm in group II (P ¼ 0.8).

Treatment. Surgical treatment was per- formed in 65.4% of cases (36 patients);

74% in group I and 59.3% in group II with a P ¼ 0.53 (Table 3). Gross total resection was achieved in 66.6% of cases (64.7% of patients in Group I and 68.4% in Group II;

P ¼ 0.82), subtotal resection was achieved in 7 cases, and a biopsy or partial resection in 4 cases. All cases were performed through a craniotomy. Our case is the ﬁrst EEA. Sixteen patients were observed or received steroid therapy. Radiosurgery was performed in 3 cases.

Outcomes. Follow-up was variable, ranging from 1 month to 20 years, with a mean of 38 months. An analysis of the reported outcomes demonstrated that 15 patients (27.3%) had worsening of their previously oculomotor function, 23 (41.8%) were stable, and 17 (31%) improved after treat- ment (Table 3). Among patients with preoperative good oculomotor function 34.6% (9 patients) worsened at last follow-up (26.6% after surgery and 50%

with observation, P ¼ 0.03). In total, 31%

with total or near-total palsy at the admission had an improvement of their oculomotor function (all after surgical resection; P ¼ 0.05) (Table 4). The 3 patients treated with radiosurgery had an unchanged oculomotor function at the last follow-up.

DISCUSSION

Our study shows a surprising result.

Surgical management of schwannomas appears to result in better long-term function preservation compared with

Figure 1. Preoperative cranial magnetic resonance imaging showing a 2486-mm right cavernous lesion (arrows) that is moderately enhanced with gadolinium on axial T1-weighted (A) and coronal T1-weighted imaging (B).

Figure 2. Cranial magnetic resonance imaging at 4 months postoperatively showing a small residual lesion located inferolaterally in the right cavernous sinus (panelA: axial T1WI with gadolinium and panelB: coronal T1WI with gadolinium).

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observation. These ﬁndings imply that over time, as the schwannomas grow, they cause irreversible damage to the third nerve. The only hope of preserving function is to operate early, before func- tion is lost. Since there was also a cor- relation between preoperative function and outcome, the earlier the operation, the better the long-term outcome. For tumors that cannot be completely removed, a biopsy or partial resection followed by radiosurgery appears pru- dent, since the 3 patients who had radi- osurgery demonstrated preserved oculomotor function. Other than in our case report, the surgical approaches in all reported cases were transcranial

(orbitozygomatic, transzygomatic fronto- temporal, and the transzygomatic sub- temporal). This allowed enough exposure of the tumor and around the inter- peduncular cistern. In fact, most intra- cavernous schwannomas have an extradural (“interdural”) location and are well separated from the cranial nerves and the internal carotid artery by the in- ternal dural layer.

In this report, we demonstrate for the ﬁrst time that EEA can be used to access oculomotor schwannomas since the medial aspect of the superior orbital ﬁssure can be more easily accessed through an endonasal approach then through a craniotomy.

^10,41

Although EEA may, in some cases, allow

complete resection of the tumor, the exposure is limited and in our cases only partial resection could be achieved. How- ever, once a deﬁnitive diagnosis is made, radiosurgery can be offered soon after to prevent further growth and functional deterioration. During the last decade, similar to the approach used for small- and medium-size vestibular schwannomas, radiosurgery and particularly Gamma Knife surgery have emerged as valuable, safe, and long-term effective, minimally invasive ap- proaches for nonvestibular schwanno- mas.

^6-42

This approach has been suggested as upfront therapy and an effective treat- ment option for patients with oculomotor schwannomas.

Oculomotor schwannomas may grow anywhere along the course of the ON. The diagnosis of a schwannoma often is made by imaging evaluation and clinical symp- toms that correlate with distribution of the involved nerve. The schwannoma might be strictly located in the interpeduncular cistern, the cavernous sinus, the orbit, or more likely involving more than one of these compartments.

²⁷

Schwannomas arising from the ONs almost invariably present with diplopia and objective signs of eye movement dysfunction. Acute and subacute onset are observed in more than one half of reported cases. The very thin structure and vulnerability of these nerves may explain their early anatomic and functional involvement during tumor growth. Sometimes, the clinical presentation may be deceptive, and oculomotor palsy be associated with pain.

^4,29,43

This has been observed in 23.6% of cases and causes confusion with recurrent migraine. However, the mechanism of intermittent unilateral headaches and ipsilateral ophthalmoplegia can be explained by intermittent release of a chemical substance from the tumors and resultant stimulation of the trigeminal nerve receptors or by repeated inﬂammation

leading to demyelination

andremyelination.

^16,29,31

Furthermore, as the tumor grows in size, it compresses surrounding neurovascular structures, causing worsening neurologic deﬁcits such as contralateral or sometimes ipsilateral hemiparesis because of the mass effect on the brainstem posteriorly.

¹⁵

Both ON and small ON schwannomas are difﬁcult to visualize on conventional Table 2. Epidemiologic and Clinical Characteristics of Reported Cases of Oculomotor

Nerve Schwannoma

Data

All Patients (55 Patients)

Group I (22 Patients)

Group II

(33 Patients) PValue

Age, years, median 31.5 36 27 0.17

Sex

Male 24 7 17 0.1

Female 31 16 15

Onset of symptoms, months 7 9 6 0.33

Mode of installation of symptoms

Acute or subacute 41.6% 57.1% 52.6% 0.75

Progressive 58.4% 42.9% 47.4%

Main symptoms

Diplopia 72.7% 63.6% 78.8% NA

Proptosis 58.1% 22.7% 81.8%

Recurrent ophthalmologic migraine 21.8% 22.7% 21.2%

Other symptoms 12.7% 13.6% 12.1%

Oculomotor function at admission

Good function 46.3% 63.6% 33% 0.03

Poor function 53.7% 36.4% 67%

Site of tumor

Cisternal 47.2% 40.9% 51.5% 0.77

Cavernous 52.8% 58.1% 48.5%

Intracavernous 23.6% 22.7% 24.2%

Cisterno-cavernous 16.3% 18.1% 15.1%

Intraorbital 5.4% 13.6% 0%

Orbito-cavernous 7.2% 4.5% 9.1%

Mean of great diameter, mm 18.8 18 19.3 0.8

NA, not available.

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MRI. Three-dimensional MRI sequences have become widely available for clinical use in evaluating the intricate structures of cranial nerves.

^23,37

Steady-state free pre- cession sequences of MRI evidence small- and mid-size parasellar schwannomas as a hypo- or isointense mass, well deﬁned by the high signal intensity of the cerebro- spinal ﬂuid. MRI with diffusion tensor tractography recently has been introduced to identify the cranial nerves, mainly the facial-acoustic complex around vestibular schwannomas. This technique seems useful for identifying the nerve of origin in large ON schwannoma. In total, 34% of

ON schwannomas are less than 5 mm when they are discovered. Careful imaging evaluation is needed to identify schwan- noma due to its small size, location in the brain, and infrequent presentation.

^16,37

ON schwannoma typically are described as a parasellar or suprasellar mass, often mimicking a medial sphenoid wing or a posterior clinoid meningioma, especially when they occur in a cisternal loca- tion.

^2,12,42

Lesions tend to be hypo-to iso- intense on T1-weighted images and are invariably hyperintense on T2-weighted studies.

³⁷

These features, although relatively nonspeciﬁc, may be helpful for

differentiating schwannomas from other tumors such as lymphoma, metastasis, or aneurysm, whereas the differential diagnosis in orbital location includes neuroﬁbroma, hemangiopericytoma, extraconal meningioma, rhabdomyo- sarcoma, pleomorphic adenoma of the lacrimal gland, and venous varix.

^24,37

CONCLUSIONS

We report the ﬁrst EEA for management of an oculomotor schwannomas, Oculo- motor nerve function at admission and surgical resection of schwannoma appear to be predictors of favorable prognosis regardless of location and tumor size.

Whenever the ON function is not compromised at diagnosis, we think that radiosurgery could be a valid option, avoiding any surgical risks. Otherwise, a combined approach with planned subtotal removal followed by Gamma Knife surgery should be further explored to determine whether the results compare favorably with open surgical resection.

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Table 3. Management and Outcomes of Reported Cases of Oculomotor Nerve Schwannoma

Data

All Patients (55 Patients)

Group I (22 Patients)

Group II

(33 Patients) PValue

Management

Observation or steroid therapy 30% 23% 33% 0.65

Surgical procedure 65% 73% 67%

Gross total resection 51% 49% 58%

Partial or subtotal removal 28% 19% 42%

Radiosurgery 5% 5% 7% 0.43

Mean follow-up, months 38 55 29

Oculomotor function outcomes NA

Worsened 27% 0% 46%

Unchanged 42% 36% 52%

Improved 31% 64% 3%

NA, not available.

Table 4. Comparison of Oculomotor Function According to Its Preoperative Statue

Oculomotor Function Outcomes Worsened Unchanged Improved PValue

Patients admitted with good oculomotor function

Nonoperated patients (10 patients) 50% 50% 0 0.03

Operated patients (15 patients) 26.6% 26.6% 46.8%

Gamma knife surgery (1 patient) 0 100% 0

All patients (27 patients) 34.6% 38.4% 27%

Patients admitted with poor oculomotor function

Nonoperated patients (6 patients) 0 100% 0 0.05

Operated patients (21 patients) 23.9% 33.3% 42.8%

Gamma knife surgery (2 patients) 0 100% 0

All patients (29 patients) 20.6% 48.2% 31%

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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Received 21 February 2019; accepted 20 May 2019 Citation: World Neurosurg. (2019) 129:72-80.

https://doi.org/10.1016/j.wneu.2019.05.170

Journal homepage:www.journals.elsevier.com/worldneurosurgery

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Prognosis factor in oculomotor schwannoma: a case of endoscopic endonasal approach and systematic review of the literature