The parasitic synapse: How gliomas hijack the connectome for malignant gain

Gliomas, the most prevalent primary intrinsic tumors of the central nervous system, have historically been conceptualized as autonomous, space-occupying lesions that compromise neurological function through mass effect, tissue destruction, and peritumoral edema. However, contemporary research spanning molecular neuro-oncology, systems neuroscience, and clinical neurology has precipitated a fundamental paradigm shift, revealing that gliomas engage in complex, bidirectional, and dynamic interactions with the functional architecture of the brain. This review synthesizes a vast body of evidence to interrogate the provocative question of whether gliomas exert or aid brain functions. We systematically examine the evidence for glioma integration at synaptic, circuit, and large-scale network levels, scrutinize proposed mechanisms of neuron-glioma communication, and evaluate the clinical manifestations of this integration. A critical analysis concludes that while high-grade and low-grade gliomas demonstrate a remarkable capacity to integrate into and exploit the brain's structural and functional circuitry for proliferative advantage, there exists no substantive evidence that this integration confers any net beneficial or supportive function to the host brain. Instead, the apparent "functional integration" represents a sophisticated form of ecological niche adaptation and co-option of neurodevelopmental programs, characterized by direct synaptic coupling, activity-dependent paracrine signaling, and dynamic network remodeling. This refined understanding carries profound implications for developing novel therapeutic paradigms that target the tumor-brain interface, moving beyond cytotoxic strategies to include circuit-modulating and network-preserving approaches that disrupt the malignant synergy between neural activity and glioma progression while strategically bolstering the brain's innate capacity for functional resilience.