Neurinoma of the oculomotor nerve

Pierpaolo Lunardi, Giovanni Rocchi, Antonella Rizzo, Paolo Missori*

Introduction

Nerve-sheath tumors of the nerves governing eye movement are rare, only 23 cases having so far been reported. We report a case of cranial nerve III nerve-sheath tumor, which resembled a brainstem tumor.

Case report

A 60 year old woman was admitted to our De- partment in 1982 because of headache, diplopia and increasingly severe right hemiparesis. Five years before she had begun to have frontal head- ache, which responded to routine analgesics, and one year before increasing weakness of the right limbs. A week before admission she sud- denly developed a horizontal diplopia.

Examination. Neurological examination showed a right hemiparesis and mild left pal- pebral ptosis but no other neurological signs, and general physical examination did not elicit the typical features of von Recklinghausen’s dis- ease. A CT brain scan imaged a partly solid- partly cystic lesion in the brain stem, the solid portion enhancing markedly after injection of contrast medium (Fig. 1). Vertebral and left carotid angiography showed posterior displace- ment of the basilar artery but no new-formed pathological circulations. Although the CT scan seemed to point to an intrinsic brainstem lesion

Summary

A rare case of neurinoma of cranial nerve III is described. Preoperative diagnosis of such tu- mors is difficult because they may be mistaken for brainstem tumors.

Key words: schwannoma, oculomotor nerve, nerve-sheath tumor, brainstem neoplasm.

with central necrosis, the angiogram left room for the possibility that the lesion might be extrin- cis.

Operation. After a left temporal craniotomy the temporal lobe was retracted and the free margin of the tentorium incised, revealing a cir- cumscribed lesion the size of a walnut. The le- sion was emptied of its cystic content and then easily separated from the brainstem and basilar artery. The third cranial nerve was incorporated in the tumor close to the posterior cerebral ar- tery. The lesion was completely removed to- gether with the incorporated portion of the nerve.

After an uneventful postoperative course the patient was discharged on day IO with a left cranial nerve palsy. Histological examination revealed a typical neurinoma. At 6-years follow- up the patient presented only the left cranial nerve III deficit.

* Department of Neurological Sciences, Neurosurgery. University of Rome ‘La Sapienza’, Italy

Address for correspondence and reprint requests: Paolo Missori, M. I). , Neurochirurgia, viale dell’univer~i~~ 30 A, 00185 Roma - Italia

Accepted 26.61989

Clin Neural Neurosurg 1990. Vol. 92-4

333

Fig. 1. CT scan after contrast enhancement showing a partly cystic (left), partly solid lesion (right: arrow) with hyper- dense rim involving the midbrain and compressing the third ventricle.

Discussion

Neurinomas of the cranial nerves account for about 8% of intracranial tumors’. Except in von Recklinghausen’s disease, these tumors tend to originate from sensory nerves and the vestibular nerve is the one most often affected. Rarely are the nerves governing eye movement affected. we have collected 23 published cases of nerve- sheath tumors of these motor nerves: in thirteen cases the oculomotor nerve was affect- ed2,3,4,5,6,7,9,10,11,12, in seven cases the troch- learS~‘3~‘4~15~16~17 and in three cases the abducent nerves~‘s~ly.

The oculomotor nerve may be affected either along its course in the lateral wall of the ca- vernous sinus or in the segment running from there to the brainstem. In the former case differ- ential diagnosis is from meningioma, aneurysm and other parasellar tumors, and in the latter case from intrinsic brainstem neoplasms or oth- er benign lesions like dermoid and epidermoid cysts or neuroepithelial cysts. Correct diagnosis is essential to the choice of treatment: radioth- erapy for malignant brainstem tumors and surgi- cal removal for benign lesions. Diagnosis may be established by means of serial stereotactic biopsy6 and magnetic resonance imaging, which

may help to dispel doubt by showing ;1 wcli- defined lesion extrinsic to the brainstern!“.

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