Objective: Axonal injury (AI) after traumatic brain injury (TBI) is often overlooked as an explanation for cognitive complaints when no damage is detected by computed tomography. The purpose was to assess cognition during the 12 months following a TBI and suspected traumatic axonal injury (TAI)., Methods: The sample included 17 patients younger than 65 years old, however one died. In the acute phase and at 6 and 12 months, cognition, reaction time, psychomotor performance and finger tapping speed were assessed. Working memory and work status were added at 12 months. Acute MRI findings were recorded., Results: After 1 year, all patients still showed cognitive dysfunction. A recovery had been noted at 6 months, but a cognitive decline was indicated for the majority at 12 months. The sick-listed patients had TAI located in the corpus callosum and the brainstem. They were cognitively more impaired and in more areas than the four patients who had returned to work., Conclusion: Cognitive screening can identify the long-term impact of TAI identified by conventional MRI, used as a routine clinical technique. For rehabilitation and for insurance-related matters, these injuries must be taken seriously, as a deterioration over time might occur. Further research is needed.