Potential application of repetitive transcranial magnetic stimulation for apathy after traumatic brain injury: a narrative review

Apathy is a common sequela to traumatic brain injury affecting multiple aspects of the patient’s rehabilitation, recovery, domestic and social functioning, and quality of life. As a motivational disorder, it is distinct from depression, but shares many similar features. Anatomically, they both involve dysfunction in the ventral and medial prefrontal cortices and the anterior cingulate cortex; however, the dorsal anterior cingulate cortex may be more implicated in regulating motivation, while the subgenual anterior cingulate cortex may be more involved in regulating mood. Current treatment for apathy is limited, especially when standard pharmacotherapies for depression have not been shown to improve apathy. Repetitive transcranial magnetic stimulation is a neuromodulatory therapy effective for refractory depression. The mood modulatory effect was believed related to the anti-correlation between the subgenual anterior cingulate cortex and left dorsolateral prefrontal cortex. Studies have recently shown its safety and successful treatment of apathy in Parkinson’s disease, Alzheimer’s disease, and stroke, although the mechanism has not been fully elucidated. Repetitive transcranial magnetic stimulation has also been successfully applied in persons with traumatic brain injury for depression, dizziness, central pain, visual neglect, cognitive impairments, and disorders of consciousness. In this review, we aimed to summarize the current understanding of apathy and evidence of the clinical application of repetitive transcranial magnetic stimulation to explore the theoretical basis of potential therapeutic benefits of using repetitive transcranial magnetic stimulation for apathy after traumatic brain injury.