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November 12, 2019

Acoustic

 

Description

This lady in her 40’s has a small acoustic schwannoma of about 2cm, but has severe trigeminal pain and a loss of sensation in the side of the face – although she describes it as being the whole face. The MRI scan shows the tumour invading the internal auditory canal and erosion of the meatus. As it leaves the meatus, it appears to go superiorly and there is a small tip extending into the cerebellum.

Tumours of this size can be treated using radiosurgery – as this is non-invasive, this treatment is usually chosen by patients rather than the actual removal of the tumour. However, as radiosurgery simply kills the tumour cells so that it no longer grows, for patients with trigeminal pain, or brainstem compression, just killing the cells will not alleviate the pain nor solve problems due to the brainstem compression. For this reason, this patient is having the tumour excised – to relieve her symptoms of trigeminal pain.

I am using my standard acoustic montage – 4 channels for VII, V, IX, X and XI. I had some difficulty inserting needles into the soft palate for IX – a combination of a small aperture, the temperature probe in the way, and I seemed to keep finding the hard palate. Eventually got needles in, although not the whole needle, throatpack inserted. After positioning, all traces were flat.

1030 – patient positioned on operating table

1150 – craniotomy completed, dura opened, cerebellum retracted and surgeon exploring down side of the tumour. Lower cranial nerves seen and stimulated (IX and X). Electrodes for IX are correctly inserted!

1220 – after checking with the stimulating probe, the CUSA is being used to debulk the tumour.

1230 – ENT surgeon has arrived to take down the internal auditory canal wall and remove tumour in the IAC.

1300 – canal wall is down and facial nerve identified in the IAC. Surgeon now removing tumour from inside the canal.

1325 – tumour is all removed from the meatus and IAC, although he is having difficulty in actually seeing it. Neurosurgeon is taking over again to remove remainder of tumour and capsule.

1445 – remainder of tumour is out and facial nerve stimulates at 0.025mA, though not as well as at the meatus. The patient is likely to have some temporary facial weakness, especially around the eye, for some time following surgery. Her trigeminal symptons are likely to resolve, although facial sensation may not fully recover.