brought to you by the nerve stimulation experts at Neurosign

May 28, 2024

CPA Ependymoma



A woman in her 30’s with a large cerebellopontine angle (CPA) suspected ependymoma. She has mild ataxia and reports difficulty in swallowing recently. She had a tumour removed from the pineal gland as a child. The MRI shows a large mass in the CPA which looks like an ependymoma, although this would be rare.

The surgeon will debulk it but will probably leave tumour overlying the lower cranial nerves, followed up with radiosurgery.

I am monitoring VII, IX, X, XI and XII.

VII is monitored using 4 channels and with the needles in the nerve branches of the face, IX is a pair of needles ipsilateral to the uvula in the soft palate, X is done using the Lantern Laryngeal Electrode on the endotracheal tube, XI is a pair of needles in the trapezius, and XII a pair of needles in the lateral aspect of the tongue. All electrodes are ipsilateral to the tumour.

As there is also significant brainstem compression, I am running SSEPS from the tibial nerve and collected responses from cz- fz. I have a robust SSEPS on the right side, and poor on the left which correlates to her preoperative clinical neurological assessment.

The lower cranial nerves are particularly at risk, with the tumour extending to the foramen magnum. IX and X have been identified as soon as the tumour was exposed, but the tumour has grown around the nerves instead of pushing the nerves away, as in an acoustic neuroma. In the last few minutes, the surgeon thinks these nerves may have been damaged by cautery.

The SSEP has remained stable on the right and poor on the left.

Surgeon has identified the place on the IXth nerve where conduction stops. There is a definite cautery burn on the nerve which stimulates on the distal side but not on the proximal. The nerve looks intact so it may recover, but not during the surgery.

The tumour bleeds whenever it is touched, so the surgeon is considering options before continuing. One possibility is that this is a glossopharyngeal schwannoma.

Surgery is continuing, XII has been identified.

Histology has come back and confirmed the tumour as a glossopharyngeal schwannoma,  so the loss of the IXth was inevitable.

Surgeon is continuing to debulk and remove tumour.

Surgeon has now reached a stage where most of the tumour is out but some remains, either attached to cranial nerves or to the brainstem. After discussion,  the surgeon has decided to achieve haemostasis and close.

There is some facial weakness, loss of IXth activity, but this was a very difficult and extensive tumour which was severely compressing the brainstem. The goal of decompressing the brainstem has been achieved, and the patient will be sent for radiosurgery to treat the remainder of the tumour.

Her SSEP On the left remains poor, that on the right has remained stable throughout the operation.