We study the problem of decentralized monitoring of stream runtime verification specifications. Decentralized monitoring uses distributed monitors that communicate via a synchronous network, a communication setting common in many cyber-physical systems like automotive CPSs. Previous approaches to decentralized monitoring were restricted to logics like LTL logics that provide Boolean verdicts. We solve here the decentralized monitoring problem for the more general setting of stream runtime verification. Additionally, our solution handles network topologies while previous decentralized monitoring works assumed that every pair of nodes can communicate directly. We also introduce a novel property on specifications, called decentralized efficient monitorability, that guarantees that the online monitoring can be performed with bounded resources. Finally, we report the results of an empirical evaluation of an implementation and compare the expressive power and efficiency against state-of-the-art decentralized monitoring tools like Themis.