Technical note: pre-positioning lower limb SSEP during semi-sitting positioning in posterior fossa surgery- does it matter?

Intra-operative monitoring has been a crucial tool in modern neurosurgery as it allows to optimize surgical outcome whilst reducing neurological deficits. Somatosensory evoked potentials are routinely monitored in most spinal and brain surgeries due to providing invaluable information regarding the functional integrity of sensory pathways. The use of this neurophysiological technique is particular useful when positioning patients in semi-sitting position during posterior fossa surgery. However, there is general agreement within the intra-operative neuromonitoring community that either upper or lower limb SSEPs monitoring typically suffice. Nonetheless, we report a case study of a patient in whom lower limb SSEPs were independently affected from upper limb SSEPs during positioning. In this respect, we suggest that both upper and lower limb SSEPs monitoring should be considered during semi-sitting positioning in patients undergoing posterior fossa surgery.