Recovery of Function

1. Clinical Implications “Best Practice” In Neurorehabilitation Factors In Recovery of Function Mechanisms of Motor Learning Transneuronal Lesion Effects Recovery of Function Stages of Recovery What Rule Governs Synaptogenesis Recovery Vs. Compensation Recovery Of Function Recovery Theories Map of Essential Course Concepts Fall 2006 DM McKeough

2. Recovery of Function • Mechanisms of motor learning • Recovery of function • Theories of the recovery of function • Transneuronal lesion effects • What rule governs synaptogenesis • Clinical Implications • Recovery vs compensation • Stages of recovery • Factors in recovery of function • Current “best practice” in neurorehabilitation Last Viewed Concept Map Exit

3. Jenkins et al, 1990 Mechanisms of Motor Learning Motor learning causes increased differentiation in cortical representation • Training effects • In an accomplished pianist, hand representation in S1 and M1 is bigger than normal • Focal Hand Syndrome • Use dependent hand dysfunction caused by repetitive fast alternating finger movements resulting in loss of differential digital representation in M1 (Byl et al, 1996) Last Viewed Recovery of Function Concept Map Exit

4. Recovery of Function • Do the same mechanisms that underlie motor learning also underlie recovery of function? • Looks like the answer is Yes Last Viewed Recovery of Function Concept Map Exit

5. Theories of theRecovery of Function • Resolution of diaschisis (edema) • Regenerative synaptogenesis (Wallerian re-generation-PNS) • Reactive synaptogenesis (Collateral sprouting - CNS) • Changes in cortical maps • Use of alternate pathways Regenerative synaptogenesis Last Viewed Recovery of Function Concept Map Exit

6. Cellular Response to Injury • What is diaschisis? • Temporary disruption of function produced by shock of damage to brain tissue (≈ spinal shock of the brain) • Includes loss of function of brain regions distant from primary site of injury • Possibly due to decreased blood flow, decreased metabolism or physiological disruption Last Viewed Theories of Recovery Exit

7. Regenerative Synaptogenesis • PNS Response to Injury • Begins 3-7 days post injury • Wallerian degeneration is the process whereby functional connections with target cells may be re-established following injury • Wallerian re-generation may permit recovery of lost function Last Viewed Theories of Recovery Exit

8. Reactive Synaptogenesis • CNS response to injury • No re-establishing functional connections with target cells occurs, any recovery of function occurs via collateral sprouting from intact neurons &/or reorganization (intact systems assume the lost function, neuroplasticity) collateral sprouting +/or reorganization = neuroplasticity Last Viewed Theories of Recovery Exit

9. Cortical Reorganization 1/2 • What mechanisms underlie the recovery of function? • Changes in cortical maps • Following peripheral injuries: (Amputation) • Intact adjacent areas of the cortex expand into quiet areas (due to unmasking of silent synapses) • Following central lesions: (Stroke) • Same • Following injury cortical mapping is responsive to training • Changes are progressive and reversible • Once the task was learned, mapping changes persist long-term Last Viewed Theories of Recovery Exit

10. Taub et al 1998 Cortical Reorganization 2/2 Use-Dependent Cortical Reorganization After Brain Injury Mechanisms of effectiveness of Constraint-Induced Movement Therapy(CIMT) Last Viewed Theories of Recovery Exit

11. Alternate Pathways • What mechanisms underlie the recovery of function? • Ipsilateral motor tracts take over Last Viewed Theories of Recovery Exit

12. Retrograde Orthograde Transneuronal Lesion Effects • Transneuronal (Transsynaptic) lesion effects • Orthograde: • Muscular atrophy • Denervation hypersensitivity (spasticity) • Retrograde: • Synaptic retraction • Atrophy of presynaptic cell • Glial ensheathment Last Viewed Recovery of Function Concept Map Exit

13. Synaptogenesis • What rule seem to govern synaptogenesis? • Use dependent competition such that if one area becomes silent, adjacent areas can re-program its use Last Viewed Recovery of Function Concept Map Exit

14. Clinical Implications • How is this information useful in the clinic? • Following injury cortical maps show: • Short-term changes (due to unmasking) • Long-term changes (due to adjacent areas take over the silent area) • Cortical mapping (re-mapping) is experientially dependent and requires willful intention Last Viewed Recovery of Function Concept Map Exit

15. Recovery vs Compensation • Recovery is achieving function through original processes, while compensation is achieving function through alternative processes • Should intervention strategies change for the two goals? Last Viewed Recovery of Function Concept Map Exit

16. Stages of Recovery • Spontaneous recovery • Recovery in the absence of intervention • Forced recovery • Achieved through specific intervention designed to affect neural mechanisms Last Viewed Recovery of Function Concept Map Exit

17. Factors Contributing to Recovery of Function • Age • Characteristics of the lesion • Effect of Experience • Effect of Pharmacology • Effect of Training Last Viewed Recovery of Function Concept Map Exit

18. Factors Contributing to Recovery of Function • Age • The brain reacts differently to injury at different stages of development • In general, the younger the age at the time of injury the better the outcome • Characteristics of the lesion • The smaller the lesion: smaller primary impairment • The longer it takes to develop: greater opportunity for collateral circulation and substitution • The better the outcome Last Viewed Recovery Factors Concept Map Exit

19. Factors Contributing to Recovery of Function • Effect of Experience • Enriched environment produces increased brain weight, dendritic branching, and enzyme activity • Postoperative enrichment is effective but does not allow the same extent of recovery as preoperative enrichment (Held 1985) • If environmental enrichment is to affect recovery of function, it must incorporate active participation of the patient for full recovery to occur (Stein 1995) Last Viewed Recovery Factors Concept Map Exit

20. Factors Contributing to Recovery of Function • Effect of Pharmacology • Amphetamine enhances the effects of neurotransmitters • Amphetamine plus PT produced significant improvement in motor performance on the Fugl-Meyer test (Crisostomo 1988) • GABA has harmful effects on recovery of function after brain damage • Cholinergic agents facilitate recovery of function after brain damage (vanWoerkom 1982) • Free radicals destroy the lipid membrane of the cell • Drugs used to treat common comorbidities (antihypertensives and sedatives) have deleterious effects on recovery of motor and language functions after stroke (Goldstein 1995) Last Viewed Recovery Factors Concept Map Exit

21. Factors Contributing to Recovery of Function • Effect of Training • Training has its greatest effect when performed as soon after the injury as possible • It is not likely that any single training approach will be as effective as a combination of interventions • Treatment strategies will be most effective when carefully considering the patient’s history, health status, age, and experience Last Viewed Recovery Factors Concept Map Exit

22. “Best Practice” • According to research results the current “best practice” approach to neurological rehabilitation is: • task-specific training • that requires willful intention • performed in an enriched environment • with facilitatory pharmacology • using a variety of treatment approaches • that soon after the injury and • is tailored to the individual patient’s history, health status, age, and experience • involving both physical and mental practice Last Viewed Recovery of Function Concept Map Exit

23. The End © DM McKeough 2006 Last Viewed Recovery of Function Concept Map Exit