Described here are systems and methods for evaluating the extent of brain-skull tethering, which may also be referred to as loss of trabecular reserve, in subjects using magnetic resonance elastography (“MRE”). The present disclosure describes a method for assessing progressive damage to arachnoid space (“SAS”) trabeculae. The method generally includes measuring the relative movement between the brain and the skull using MRE. As one example, an MRE-based method named slip interface imaging (“SII”) can be implemented. By measuring trabecular reserve in subjects who have a history of prior head trauma, the susceptibility of a given subject to future injury can be assessed.