Long-term functional outcome after stroke: the impact of MRI-detected lesion characteristics

Abstract

The objective of this thesis was to gain a better understanding of the relationship between ischemic lesion characteristics and long-term functional outcome of stroke survivors. The relationship between volume and localization of the ischemic cerebral lesion and the long-term functional outcome of first-ever ischemic middle cerebral artery stroke survivors was studied. Volume and localization was obtained with conventional Magnetic Resonance Imaging (MRI) scans. Outcome was assessed at the levels of body functions, activities and participation according to the International Classification of Functioning, Disability and Health (ICF). (1) In a systematic review, we found that previous studies showed a strong relationship between lesion volume and short-term outcome. However, earlier studies investigated only short follow-up periods up till 3-6 months, although functional improvement still occurs after 6 months. Furthermore, it was not clear if lesion volume related to all different levels of functional outcome (ICF) . (2) In the second week after stroke a strong relationship between lesion volume and neurological deficits was found as well as moderate correlations between lesion volume and body functions and limitations in activities. (3) Moderate relationships between lesion volume and functional outcome and quality of life after one year poststroke were demonstrated. A clinical model with clinical variables only predicted outcome of Activities of Daily Living of the stroke survivor after one year with an accuracy of 77%. Adding neuro-imaging variables to the clinical model increased the accuracy to 83%, but this difference was not statistically significant. (4) Involvement of structures with a greater density of corticofugal fibres (internal capsule) was associated with poor recovery of hand motor function after 1-year poststroke. The probability of recovery of some or all of the hand function ranged from 51% for those patients in whom the motor cortex was affected, to only 13% for those patients in whom both motor cortex and internal capsule were affected. (5) Our study showed that hemispheric lesion side, level and volume were weak to moderate predictors of verbal memory. Performance on visual recognition could not be predicted by lesion characteristics. (6) Stroke volume is a reflection of damaged brain tissue. A larger infarction leads to more deterioration of body functions, more activity limitations and a lesser capacity to participate, as well as an impaired Quality of Life. The strength of correlation between lesion characteristics and functional outcome weakens after a longer follow-up period post stroke. (7) Besides to its volume, the location of the lesion is important, especially for the outcome of motor function of the upper paretic limb. Long-term poststroke, the effect of localization was seen for hand motor recovery as well as for long-term episodic memory disorders