Brain tumors, abnormalities, and malignancies are considered fatal. Early detection techniques could save lives if they are utilized effectively for brain cancers. They should have remarkable mobility, high accuracy, high response speed, and low losses. The presented study shows what is believed to be a step toward achieving these objectives. A novel biomedical photonic crystal fiber sensor that can accurately detect and discriminate between different brain cells is proposed. The anomalous brain cells include injuries, tumors, and malignant cells. The proposed sensor can detect these various types with high relative sensitivity and negligible losses in comparison to other photonic crystal fiber-based biomedical sensors. The presented sensor exhibits a relative sensitivity of 97.5%, an effective area of 4.17 × 10 −8  m 2 , a negligible confinement loss of 1.76 × 10 −11  cm −1 , a remarkably low effective material loss of 0.005942 cm −1 , and a numerical aperture of 0.3524. The presented sensor is eligible to work in the terahertz regimes with a wide range of 1–3 THz. Also, a detailed comparison between the presented sensor and associated photonic crystal fiber literature is carried out to authenticate the effectiveness and veracity of the presented structure.