Oculomotor Nerve Neurinoma: Report of two Cases

R. Kachhara1, S. Nair1, and V. V. Radhakrishnan2

1Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences & Technology Trivandrum, India

2Department of Pathology, Sree Chitra Tirunal Institute for Medical Sciences & Technology Trivandrum, India

Summary

Being motor nerves neurinomas originating from ocular nerves

are very rare, unless associated with neuro®bromatosis. Authors de-

scribe two cases of oculomotor nerve i.e. third nerve, Schwann cell

tumours. One of them presented as a cavernous sinus mass in a

middle aged lady while the other was a middle aged man with a large

cisterno-cavernous tumour. Surgical approach is discussed and the

relevant literature reviewed.

Keywords: Intracranial nerve sheath tumours; intracavernous

neoplasm; neurinoma; oculomotor nerve.

Introduction

Primary intracranial schwannomas constitute ap-

proximately 8% of all intracranial tumours [5, 19].

These tumours commonly arise from sensory division

of cranial nerves, chie¯y from the vestibular nerve and

less commonly from the trigeminal nerve root and

ganglion [19, 20]. Being purely motor nerves, neuri-

nomas arising from the ocular nerves i.e. third, fourth

and sixth, are very uncommon, unless associated with

von Recklinghausen's disease. A total of 28 cases of

neurinomas arising from the oculomotor nerve have

been reported in the literature. We report two addi-

tional cases of neurinomas originating from the

oculomotor nerve.

Case 1

This 55-year-old female presented with intermittent dull headache

for 3 years and double vision on looking to right along with para-

esthesia of upper part of face for 6 months. Four weeks prior to ad-

mission, she had rapid progression of drooping of right eye lid which

became complete within 48 hours. There were no neurocutaneous

markers. Neurological examination revealed right oculomotor and

trochlear nerve palsies and mild hypoaesthesia in the ophthalmic

division of right trigeminal nerve.

Routine investigations were normal. Computed tomography (CT)

scan showed hyperdense mass lesion in right parasellar region with

minimal contrast enhancement. Magnetic resonance imaging (MRI)

revealed a mass lesion in the right cavernous sinus which was hypo-

intense on T1 images and hyperintense on T2-weighted images. On

contrast administration, there was bright, homogenous enhancement

of the lesion causing medial displacement of cavernous carotid (Fig.

1a and b). Carotid angiography revealed medial displacement of

the cavernous carotid artery and the carotid siphon was opened up.

There was no tumour blush. Cross circulation was good. With a pre-

operative diagnosis of cavernous sinus meningioma, the patient was

operated on on February 21, 1997. After obtaining proximal control

of the carotid artery in the neck, a right frontotemporal craniotomy

with orbitozygomatic osteotomy and total excision of the tumour

was achieved. Anterior clinoid process was drilled intradurally and

the optic canal deroofed. At operation, the right third nerve was

thickened and pale looking and at the entrance to the cavernous

sinus it was becoming bulbous. After peeling away the outer layer

of the dura of the cavernous sinus the tumour was entered at its

maximum bulge. Tumour was soft to ®rm and moderately vascular.

The oculomotor nerve was impercetibly merging with the tumour

and could not be separately identi®ed. The Trochlear nerve was

stretched and pushed lateraly. Rootlets of the ophthalmic and

maxillary divisions were separate from the tumour. The postopera-

tive course was uneventful and she was discharged on 10th day. She

had persistent oculomotor and trochlear nerve palsies with partial

sixth nerve paresis and mild hypoaesthesia in the right ophthal-

mic division. Postoperative MRI did not show any evidence of re-

sidual tumour (Fig. 2a and b). Histopathological examination re-

vealed a benign nerve sheath tumour. At 2 months follow-up her

sixth nerve paresis had improved completely. She remained asymp-

tomatic except for persistent third and fourth nerve palsies at her

last follow up at 16 months after surgery.

Case 2

A 61-year-old male, a known diabetic for 12 years, presented with

defective vision in both eyes (left eye more than right), intermittent

headache and diplopia for 6 months. There was no evidence of

neurocutaneous markers. Neurologically, he was fully conscious

and alert. Visual acuity in the right eye was 6/60 and in the left eye

6/18 with left homonymous hemianopia. He had mild proptosis of

right eye. There was minimal ptosis and a slightly larger pupil on

Acta Neurochirurgica> Springer-Verlag 1998Printed in Austria

Acta Neurochir (Wien) (1998) 140: 1147±1151

a

b

Fig. 1. Gadolinium enhanced MRI (case 1), axial (a) and coronal (b)

views, showing brightly enhancing mass in the right cavernous sinus

a

b

Fig. 2. Post-operative contrast enhanced MRI (case 1) axial (a) and

coronal (b) views, showing no residual tumour

1148 R. Kachhara et al.

the right side with minimal restriction of adduction. He also had

trochlear nerve paresis.

Routine investigations were within normal limits. CT scan re-

vealed large, isodense suprasellar and right parasellar mass with

contrast enhancement. MRI scan revealed a well de®ned, lobulated,

extra-axial mass lesion in the suprasellar and right parasellar region,

iso-intense on T1 ± and heterogeneously hyperintense on T2 ±

weighted and proton density images. The tumour was occupying the

whole interpeduncular fossa with compression of the right cerebral

peduncle. The tumour was extending into optic canal and superiorly

up to the 3rd ventricle. There was bright homogeneous contrast

enhancement (Fig. 3). Carotid angiography revealed lifting up of

the right internal carotid bifurcation, right proximal anterior cere-

bral and middle cerebral arteries. There was good cross circulation.

With a pre-operative diagnosis of suprasellar meningioma, he was

operated on (25.6.97). A right frontotemporal craniotomy with

orbitozygomatic osteotomy and total excision of a large cisterno-

cavernous schwannoma was performed. The Optic chiasm was

pre®xed. Tumour was seen through right carotico-optic space and

lateral to the carotid artery. It was occupying the whole of the inter-

peduncular fossa pushing the optic chiasm and tracts upwards. The

right 3rd nerve could not be identi®ed. The cavernous sinus portion

and the part going to the optic canal was removed after drilling of the

clinoid process. The postoperative period was uneventful. He had

complete 3rd nerve and trochlear nerve palsies. Postoperative CT

scan revealed complete excision of the tumour (Fig. 4). Histo-

pathology con®rmed the diagnosis of schwannoma. On follow-up

after 12 months he was doing well with persistent III and IV nerve

palsies.

Discussion

Neurinomas arising from ocular nerves innervating

the extraocular muscles are very rare. Usually there is

Fig. 3. Gadolinium enhanced MRI (case 2), axial views, showing brightly enhancing, large right cisterno-cavernous tumour

Oculomotor Nerve Neurinoma 1149

an association of von Recklinghausen's disease if a

motor nerve is involved. Kovacs [13] was probably the

®rst to report an isolated oculomotor nerve sheath

tumour at autopsy in 1927. Celli et al. [4] had re-

viewed 38 cases of neurinomas arising from ocular

nerves i.e., third, fourth and sixth, including one of

their own cases of trochlear nerve neurinoma. Of

these, 22 originated from the third nerve. Other cases

have since been reported [1, 3, 7, 12, 14, 17] and to the

best of our knowledge, there have been only 28 cases

of neurinomas originating from the third nerve. We

add two more cases to the literature. None of the

reported cases had any manifestations of von Reck-

linghausen's disease including our two cases. The

transition of the oculomotor nerve from the central to

the peripheral nervous system is F 0:6 mm distal to

the brain stem [8]. Distal to this point, the schwann

cells cover the axon and serve as the anlage for

neurinomas. Therefore they can occur in the inter-

peduncular, prepontine, parasellar, cavernous region,

or the orbital apex. Celli et al. [4] divided these into 3

groups according to the site of the lesion. These are (i)

cisternal, (ii) cisternocavernous, and (iii) cavernous.

The third nerve neurinomas have fallen almost

equally into cisternal and cavernous groups (13 :15).

In most patients whose clinical history is known,

oculomotor nerve involvement was present in nearly

80% (22/28). Other presenting signs include decreased

visual acuity and hemiparesis. Mehta et al. [15] de-

scribed a case of oculomotor schwannoma presented

with signs and symptoms of a posterior fossa space

occupying lesion with minimal involvement of the

third nerve. Of the cases of cavernous neurinomas

described in the literature [4], in one group of patients

[6, 7, 10, 16, 21, 23] where the tumour was mainly

con®ned to parasellar area, there was de®cit of the

nerve hosting the tumour as an isolated sign or occa-

sionally with involvement of one of the other cranial

nerves governing eye movements or of the ophthalmic

nerve. Another group of patients [2, 9, 11, 18], with

third nerve neurinoma who had extension into the

orbit, presented with exophthalmos and oculomotor

nerve de®cit with involvement of the nerves of the

superior orbital ®ssure and of the optic nerve (orbital

apex syndrome). While one of our cases with intra-

cavernous neurinoma had invovement of third and

fourth nerves with mild disturbance of the ophthalmic

division of ®fth nerve, the other with large cisterno-

cavernous tumour had involvement of the optic nerve

and minimal third and trochlear nerve paresis. MRI is

the investigation of choice for these neoplasm [12]. It

also provides information about the displacement of

the cavernous carotid artery.

In the majority of cisternocavernous and cavernous

neurinomas, the pre-operative diagnosis was meningi-

oma as in our cases. Sindou et al. [22] in a review,

quoted a 50% chance of complete removal of para-

sellar neurinomas of ocular nerves similar to that re-

ported for parasellar neurinomas of the ®fth nerve.

With the present microsurgical techniques, these

tumours can be removed totally with minimal brain

retraction using frontotemporal craniotomy, with

orbitozygomatic osteotomy. It is not always possible

to determine the nerve of origin at operation, espe-

cially with large tumours, because these cranial nerves,

as well as the ophthalmic nerve, come close to each

other in the parasellar region. In the ®rst case, the

right third nerve was bulbous at the entrance to

cavernous sinus and beyond that it was imperceptibly

merging with the tumour and could not be traced

further. In the other case, the cisternal course of the

third nerve could not be identi®ed. Both the patients

had palsy of the oculomotor and trochlear nerves

postoperatively which has continued to persist during

the follow up.

Fig. 4. Postoperative contrast enhanced CT (case 2), showing no

residual tumour

1150 R. Kachhara et al.

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Comments

This article adds two cases to the literature on oculomotor nerve

neurinomas, which is a rare eventuality. The authors have to be

congratulated for having achieved a total resection of the tumours,

without having created any new neurological de®cits. It is likely that

the orbito-zygomatic removal associated with the frontotemporal

craniotomy which was performed in both patients, helped in pro-

viding an optimal approach to the cavernous sinus, and also to the

interpeduncular cistern for the second case.

For attributing the tumour origin to the oculomotor nerve (in the

®rst case), the authors relied on the fact ``the third nerve was thick-

ened and pale looking, and at the entrance to cavernous sinus

was becoming bulbous''. Although such a thickening pleads for the

origin of the tumour on the increased-in-diameter nerve, we would

like to emphasize that this may not always correspond to a tumorous

process of the nerve. As a matter of fact such a segmental thickening

can also be seen, as a ``pseudo-neuromatous'' reaction of the nerve,

proximal to a localized and severe chronic compression. We have

observed this phenomenon in a number of cases, at the level of

cranial nerves as well as of spinal roots or peripheral nerves, in non-

tumorous compressions. We also observed it on nerves compressed

by tumours extrinsic to the nerve, especially on cranial nerves at

their entrance into the roof of the cavernous sinus, just before

passing through the dural wall. We remember such cases with

bulbous thickening of the oculomotor nerve accompagning intra-

cavernous meningiomas. This must make the surgeons very cau-

tious before deciding to sacri®ce any neural structures.

M. Sindu

This is a nice review of a most unusual pathology. I had, a few

years ago, a third nerve neurinoma presenting as a parasellar tumour

without evidence of an intracavernous extension. At the time of sur-

gery the tumour was thought to have been totally removed, but two

years later she developed a recurrence within the cavernous sinus.

The re-operation was extremely di½cult, and I elected to give radio-

surgery with gamma, Knife (Steiner) and she has remained stable for

the last four years. This modality of treatment should therefore be

considered as an alternative in these cases.

The authors are to be congratulated for calling our attention to the

various types of presentation of these rare tumours.

J. Lobo-Antunes

Correspondence: Dr. Rajneesh Kachhara, Department of Neuro-

surgery, Sree Chitra Tirunal Institute for Medical Sciences & Tech-

nology, Trivandrum 695 011, India.

Oculomotor Nerve Neurinoma 1151