Purpose: The study explored the direction of change (decline vs. improvement) after diffuse axonal injury (DAI) in the domains of the ICF: body structure, body function, and activity.

Methods: Thirteen patients with DAI were assessed by using diffusion tensor imaging (DTI) to measure body structure, the Barrow Neurological Institute Screen for Higher Cerebral Functions (BNIS) to measure body function, and the Assessment of Motor and Process Skills (AMPS) to measure activity. The DTI, BNIS, and AMPS were applied at the acute phase (A1), and at 6 and 12 months post-injury (A2 and A3). Visual and statistical analyses were conducted to explore time-dependent changes in the ICF domains.

Results: Improvements were observed for most patients in all ICF domains from injury until six months. Thereafter, the results diverged, with half of the subjects showing a decline in DTI and BNIS scores between A2–A3, and all but one of the patients exhibiting identical or better A2–A3 AMPS process skill scores.

Conclusions: From 6 to 12 months post-injury, some patients underwent an ongoing degenerative process, causing a decline in cognitive function. The same decline was not observed in the activity measure, which might be explained by the use of compensatory strategies.

• Implications for rehabilitation

• In rehabilitation it is essential to be aware that in some cases with TBI, an ongoing degenerative process in the white matter can be expected, causing an adverse late effect on cognitive function.

• The cognitive decline, caused by DAI, does not necessarily mean a concurrent decrease in activity performance, possibly explained by the use of compensatory strategies. This suggests that, after the post-acute phase, rehabilitation offering strategy training may be beneficial to enhance every-day functioning.

• Strategy use requires awareness, which imply the need to assess level of awareness in order to guide rehabilitation.