Brain tumour surgery in the vicinity of short-term memory representation - results of neuronavigation using fMRI images

Objective. Functional information concerning the surrounding brain is mandatory for a good clinical outcome in brain tumour surgery. The value of fMRI to detect the motorcortex and Broca's area is widely accepted today. If an appropriate paradigm is used, short-term memory areas can be visualized as well. Obviously this information must be integrated into cranial neuronavigation for an appropriate intra-operative use. We report our first experiences with the direct integration of short-term memory fMRI into cranial neuronavigation. Method. From January 2001 to March 2002 14 patients were operated on for intracranial tumours with short-term memory fMRI imaging, using the "two-back-paradigm". Both pre- and postoperatively, the short-term memory of all patients was tested additionally by a standardized test battery including 16 different verbal and visuo-spatial items. Results. In all 14 patients the general level of working memory capacity was preserved after surgery. The visuo-spatial performance was kept unchanged or deteriorated slightly, the alertness slightly worsened as well, but we found an improvement in verbal test items. Conclusion. The two-back paradigm is able to visualize verbal memory tasks in fMRI. For visuo-spatial items, a new paradigm has to be designed. In contrast to deep seated brain lesions, focal cortical impairments do not lead to obvious and serious memory deficits. Therefore, the aim of gross total tumour removal has to be balanced against the aim of preservation of short-term memory fields. Nevertheless, the knowledge of the localization of cortical short-term memory fields may combine both aims during navigated brain tumour surgery, thus preserving the patient with a better quality of life.