Despite the recent advances in continuum robots for minimally invasive surgery or interventions, their applications to endovascular neurosurgery have remained technically challenging due to the difficulty of miniaturization. Aimed at enabling robotic applications to neurovascular interventions for endovascular treatments of stroke or brain aneurysms, we present a telerobotically controlled magnetic soft continuum robot capable of active steering and navigation under externally applied magnetic fields. For magnetic steering, a seven-degree-of-freedom (7-DOF) serial manipulator is employed to place an actuating magnet that can be manipulated via real-time teleoperation of the robot arm. A motorized linear drive is used to advance or retract the magnetic soft continuum robot, the distal tip of which is steered by the actuating magnet to enable endovascular navigation in the complex cerebral vasculature. We demonstrate the system's ability to guide selective navigation in different branches of cerebral arteries using anatomical models under visual feedback. We also compare the navigational performance of our system with that of a manually controlled passive guidewire and a conventional magnet-tipped guidewire. We found that the telerobotically controlled magnetic soft continuum robot allows for safer and quicker access to hard-to-reach areas in clinically challenging anatomies by enabling smooth navigation in narrow and winding pathways.