Introduction: Acute brain swelling after head trauma is generally believed to be caused by impaired cerebrovascular autoregulation (vaso–paralysis), cellular edema, and vasogenic edema. Brain swelling caused by vaso–paralysis after repeated head trauma has gained attention as "second impact syndrome" and is frequently reported. However, reports of cer­ebral edema following concussion are rare.

Case: A 24–year–old male soccer player with no history of concussion experienced facial head trauma by impact with an opponent player’s knee during a match. Immediately after the injury, the patient presented with disorientation, amnesia, and headache, and a concussion was sus­pected, and the patient was admitted to our hospital. At examination 3 h post–injury, the patient’s orientation improved, but the headache persisted, along with mild antegrade amnesia, sluggish thinking, impaired memory, and concentration. Magnetic resonance imaging (MRI) of the head ruled out intracranial hemorrhage. However, fluid–attenuated in­ver­sion recovery, diffusion–weighted imaging, and ADC revealed a high–intensity area in the right temporo–occipital cortex. Arterial spin label­ing ruled out increased blood flow to this site. With rest and treatment, MRI signal changes disappeared the next day, and subjective symptoms improved 3 days after presenting to our hospital. Following a graduated return to play protocol, the patient returned to play within 1 week and did not experience any recurrence of symptoms.

Discussion: This case was diagnosed clinically as a concussion as head MRI revealed vasogenic edema localized to the right temporo–occipital cortex. Since no increase in cerebral blood flow was observed, the cause was determined to be transient hyperpermeability rather than vaso–paralysis. The MRI signal resolved one day post–injury, and the patient returned to sports smoothly. Based on these results, the concus­sion diagnosis may not have been clinically severe.

Conclusion: Concussions may result from vasogenic edema due to in­creased vascular permeability.