70 Chapter 3 size (n=56) may be considered small for cluster analyses, the significant cognitive differences observed and the meaningfulness of these differences, support the value of this exploratory cluster analysis and its potential relevance to reduce the cognitive heterogeneity in this population. No patient- nor clinical factors (e.g. number of BMs, primary tumor, previous treatment) were related to the clusters. In future studies we will assess whether cluster membership has predictive value for the trajectory of cognitive performance after treatment and whether they can be linked to biological substrates. If so, this could improve understanding of the pathophysiology of cognitive performance in these patients. Clinical implications Similar to previous studies, memory deficits were prominent in our sample11,12,22,23 with severe memory impairment in one out of every three patients. Moreover, in the cluster analysis the presence of memory deficits was a major determining factor. As declines in memory performance have been reported in up to 50% of patients one to four months after radiotherapy11,22,26, this highlights the cognitive vulnerability of this patient population. Additionally, in both the group- and individual analyses processing speed and psychomotor speed deficits were frequent. Processing speed relies on a widespread neural network, which can be altered by the presence of a tumor within that network.27,28 Psychomotor slowing is often experienced as a consequence of chemotherapy-induced neuropathy.29,30 Accordingly, a significant majority of patients with psychomotor impairment had received chemotherapy (68%), compared to half of those with processing speed impairments. Patients who reported sensory problems were more likely to have psychomotor speed impairments, regardless of whether sensory problems were attributed to neuropathy by patients themselves or not. Overall, this implies it is important to distinguish psychomotor from processing speed deficits within this population. Almost one third of the BMs patients showed impaired social cognition, specifically emotion recognition. This significantly impacts both patient and caregiver QoL as it enables us to process social information and respond appropriately in social contexts.31,32 Stress has been linked to worse emotion recognition33,34, and can also be a side-effect of dexamethasone.20 Nevertheless, neither self-reported stress levels nor dexamethasone use were related to emotion recognition in our sample. Social cognition has not received wide-spread attention yet, and thus only few studies in brain tumor patients exist.35–38 A recent study found that before surgery patients with low-grade glioma performed worse on emotion recognition tasks than healthy controls and these deficits remained stable after surgery.35 Further research
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