Combined extradural-interdural-intradural approach to a trigeminal nerve cystic haemangiopericytoma with intra-operative cranial nerve monitoring

Objectives Haemangiopericytoma of the trigemimal nerve is extremely rare, with only two previous cases described to our knowledge. We present the surgical approach to this tumour, and describe a previously poorly reported method of monitoring the function of the branches of the trigeminal nerve: mapping of the sensory roots through transcranial somatosensory cortex sensory evoked potentials (SSEPs), motor evoked potentials (MEP) for the motor root and blink reflex. Design Case and technical reports Subjects 32 year-old male patient presenting with headaches and vomiting, found to have a mixed cystic-solid tumour of the left middle skull base region, in close relation with the foramen ovale and Meckel’s cave. Methods The radiological features of the tumour, technical aspects of the technical approach and neurophysiologic monitoring will be described. Results A pterional craniotomy with fronto-temporal extradural-interdural-intradural approach, and the tumour was debulked with MEP, SSEP and blink reflex monitoring of the branches of the trigeminal nerve. Complete tumour removal was achieved with no post-operative cranial nerve deficits. The histopathology revealed a cystic haemangiopericytoma. Conclusions Haemangiopericytoma is a rare entity. MEP and SSEP monitoring of the trigeminal nerve can be used to achieve complete and safe removal of the tumour.