Intraosseous Petrous Apex Schwannoma: Case Report

Intraosseous petrous apex schwannomas are an exceedingly rare entity; little is known about their epidemiology, natural history, and postoperative outcomes. We present the fourth known case of a primary intraosseous schwannoma of the petrous apex and identify unifying radiographic and clinical characteristics to aid in future diagnostic considerations of lesions of the petrous apex.

A 68-year-old woman presented with progressive intermittent vertigo, tinnitus, facial numbness, diminished hearing, diplopia, and ataxia. She was found to have deficits of cranial nerves V2, V3, and VI, vocal cord dysfunction, and ataxia. Imaging demonstrated a 5.1-cm mass centered at the petrous apex, extending from the cavernous sinus to the jugular foramen and involving the petrous and cavernous segments of the internal carotid artery ([Fig. 1]).

The patient underwent a combined right posterior fossa and transtemporal approach for extradural resection of the tumor. The facial nerve was fully skeletonized within the mastoid after removing tumor circumferentially. The vertical segment of the petrous carotid artery was also skeletonized by removing tumor which had displaced it ventrally. The inferior portion of the tumor was left behind after frozen section revealed schwannoma without aggressive features so as to preserve neurologic function. The tumor was noted to be heterogeneous in texture, with a soft, grayish, vascular component as well as a firm and hypovascular component. Permanent section demonstrated a WHO grade 1 schwannoma. The patient’s symptoms improved postoperatively with no new deficits ([Fig. 2]). At 16-month follow-up, moderate growth of the residual tumor was demonstrated with the patient experiencing onset of facial pulling. She subsequently underwent stereotactic radiosurgical treatment of the residual tumor ([Fig. 3]).

Symptoms of primary intraosseous petrous apex schwannomas are governed by the compression of nearby cranial nerves, and are thus relieved with debulking of the tumor. The treatment strategy should be to (1) obtain a diagnosis, (2) debulk and relieve mass effect, and (3) preserve neurologic function. We avoided significant postoperative deficits by accomplishing our expected subtotal resection after confirming the pathology was benign. Our close follow-up demonstrating slow growth is the longest currently available in the literature. Our multimodal management includes stereotactic radiosurgery to address residual tumor prior to recurrence of symptoms. Longer follow-up will be necessary to comment on the long-term efficacy of radiosurgical treatment for residual or recurrent intraosseous schwannomas.

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No conflict of interest has been declared by the author(s).