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Large acoustic schwannoma
This lady has a 3.5cm acoustic schwannoma, presenting with deafness in the affected ear and now with facial pain, but otherwise no observed neurological deficits. The MRI scan shows considerable brainstem compression, and the Vth nerve can be seen being compressed by the tumour. This relates to the facial pain, as the trigeminal nerve provides sensory information from the face, rather than the facial nerve.
Given her age and state of health, the plan is to do for a complete clearance, including the tumour within the internal auditory canal, although some tumour capsule is likely to be left over the facial nerve.
The scan shows a solid tumour with no cystic component. It’s going to be a long day!
I shall be using my normal acoustic protocol; 4 branches of facial, trigeminal, glossopharyngeal, vagus and accessory.
After positioning and draping, the craniotomy is almost complete. IX, X and XI are all firing, indication lower cranial nerve involvement with the tumour. I would expect this activity to cease as the tumour is debulked and/or when CSF is drained off (lumbar tap in place).
Dura opened and cerebellum retracted, surgeon investigating down side of tumour. Stimulated surface of tumour to check for VII, at 0.5mA, no response as expected. CSF being drained to create more room.
Tumour our debulked with occasional stimulation before further debulking. Facial nerve identified down side of capsule near porus. Trigeminal nerve mechanically stimulated.
Lower cranial nerves have now stopped firing as pressure is relieved.
ENT surgeon is now drilling down wall of internal auditory canal.
The canal wall is down and the tumour our in the canal has been teased out very easily, almost in a single piece – very unusual! The facial nerve is exposed and stimulates well at 0.05mA. The vestibular nerve can be seen and appears free of tumour.
The neurosurgeon is coming back to start removing the capsule.
Capsule is now removed with a strip remaining over the facial nerve. Nerve stimulates well at the brainstem at 0.05mA. Surgeon is ensuring haemostasis and will then close.