Understanding an EEG

Hi, I'm the carer to a guy who underwent an EEG several years ago, He received a clinic letter explaining the results, but as might be expected neither he or I can understand the gobbledygook!

It reads "Rhythmic activity is fairly well formed, on several occasions during the recording there are runs of slow components seen scattered over both cerebral hemispheres. These slower waveforms persist from time to time. They are slightly accentuated with hyperventilation. No paroxysmal are noted and no spikes or complex waveforms are seen. Conclusion: There is a scattered excess of slower components  No evidence of eleptiform disturbance." 

Can anybody help? Could this be related to the brain tumour that he was diagnosed with some years later?

Thanks

Fewkes