Wearable microwave diagnostic systems could pave the way to providing an effective and continuous patient monitoring system in the future. To realise wearable systems for head diagnostics, a novel compact flexible antenna made from flexible textile materials is presented in this paper. The sensing antenna is fed with a microstrip transmission line incorporating a stepped monopole structure. Three patches of different sizes are excited to obtain a wideband performance. The conductive part and the substrate of the antenna is made from a flexible conductive textile and a 6 mm thick felt material respectively. The antenna operates from 1 GHz to 4.2 GHz when in direct contact with an artificial head phantom. Moreover, the antenna also exhibits directional radiation patterns with a simulated 6 dB front-to-back ratio at the center frequency of 2.5 GHz. Simulation results show that the antenna is suitable for wearable microwave head diagnostic systems. In addition, experimental results were performed using artificial head phantoms that mimicked the pathological effects of a human brain affected with neurodegenerative diseases, specifically, brain atrophy and ventricle enlargement. The results show that the textile-based antenna is capable of monitoring the pathological effects of the disease successfully.