Clinical Neuropsychology. Recovery & Rehabilitation. Alan Sunderland School of Psychology

Transcription

1 Clinical Neuropsychology. Recovery & Rehabilitation Alan Sunderland School of Psychology 1

2 The Changing Role of Clinical Neuropsychology HISTORY The Origins of Clinical Neuropsychology Emergence as a profession during the second world war. A diagnostic, assessment role supervised by neurologists. A shift towards greater independence and more involvement in rehab from the 1980s onwards. The Rehabilitation Professions Physiotherapy, occupational therapy, speech therapy. By far the greatest input into rehab programmes. Practical emphasis without a clear scientific foundation. 2

3 The Changing Role of Clinical Neuropsychology TODAY Rehabilitation Professions Remain the mainstay of rehabilitation services. Still practically oriented but increasing evidence-based practice. Many examples of collaborative work with neuropsychologists. Clinical Neuropsychologists Continuing importance of neuropsychological assessment. But most now have at least an advisory role in rehabilitation. Primary scientific base is cognitive neuroscience. Need for more development of a scientific rationale for intervention. 3

4 Overview What principles should guide clinical assessment? Recovery & rehabilitation What processes explain recovery? How might therapy build on these recovery processes? 4

5 Functional Recovery After Human Brain Damage The brain does not regenerate after damage due to stroke or head injury. But long-term functional improvements do occur over months or years. I year after a stroke 5

6 Long-term Recovery After Stroke Percentage of Patients with Normal or Near-Normal Ability Adapted from Wade, 1992 and Sunderland et al., Months since stroke Self-care Walking Use of both hands Language

7 Cognitive Recovery After Head Injury. Wong et al. (2001) A database containing 319 patients with a broad range of coma duration was used to construct recovery curves for performance IQ. Recovery is influenced by severity, but is always faster early, with slower changes apparent over many months. 7

8 Case Example - Neal 17 years old. Traffic accident (bicycle car). In a coma for 17 days (= a very severe injury). No brain damage seen on CT brain scan ( = most damage may be diffuse axonal injury). At 3 months no physical disability. He is very forgetful. Results of neuropsychological assessment: Pattern of impairment is like a mild amnesia Longer-term episodic memory is impaired for both verbal & nonverbal material. Implicit memory and reasoning ability are not significantly impaired. An additional cognitive problem is slowed rate of information processing. 8

9 Cognitive Recovery After Head Injury All cognitive abilities show improvement over the first year. A decline at 18 months is probably due to medication for epilepsy. 9

10 Different views on the extent of recovery. Kolb & Whishaw describe cases of no recovery on cognitive tests after surgery for epilepsy. But where ability is measured carefully in cases without additional complications, a degree of recovery is always expected. This spans at least months, and in cases where the initial injury is very severe, recovery may progress slowly over many years. 10

11 Two routes to recovery Long-term recovery after brain damage is still poorly understood, but it is seems that two different processes contribute:restitution = restoration of a lost function by intact areas of the brain taking over the functions of the damaged areas. Compensation = an adaptive change to circumvent persistent impairment. - External compensation through use of aids. Internal compensation e.g. through change in cognitive strategy. 11

12 Changing Views on Restitution The traditional clinical belief (e.g. Wilson, 1999) The restitution component is restricted to the early stages and is spontaneous or natural recovery largely unaffected by therapy. More recent neuroscience evidence suggests That brain remapping* is heavily influenced by therapeutic input. That this can happen years after brain damage not just in the first months. This evidence comes mostly from studies of motor control : * Also termed cortical reorganisation or neuroplasticity. 12

13 Background: Arm paresis after stroke Reduced use of one hand and arm (paresis) is a common long term problem after stroke. This is due to damage to the contralateral motor cortex or descending pathways. When there is complete paralysis in the arm and leg it is called hemiplegia, but where there is some movement the correct term is hemiparesis. 13

14 Therapy promotes early restitution. Evidence from an animal study Nudo et al. (1996) 8 squirrel monkeys were trained to use precise finger movements of one hand to retrieve food from a small well 14

15 Evidence from an animal study Nudo et al. (1996) Under light anaesthetic, the primary motor cortex was stimulated with a microelectrode. This allowed the areas of cortex producing movements in the digits, wrist and arm to be mapped. A small stroke was caused by tying-off the blood vesseis feeding an area representing finger movements 15

16 Nudo et al. (1996) Rehabilitation Therapy The stroke caused loss of fine control of finger movement and impairment on the food retrieval task. Half of the monkeys were given 30 days of training on the task and regained ability to retrieve the food rapidly. The control group were given no training. 16

17 . Nudo et al., Re-mapping Animals in the control group showed a reduction of the hand representation compared to before their stroke. Animals who were re-trained showed no loss of representation and some increase of hand representation in formerly elbow/shoulder areas. This animal study suggests that neuroplasticity may allow restitution of function but only if intensive rehabilitation training is given. 17

18 Does therapy promote restitution of after human brain damage? It is difficult to study brain changes during human recovery because of the timescale involved and individual differences in brain damage and type of rehabilitation therapy. Functional brain imaging shows widespread changes but it is hard to say if these reflect restitution, compensation, or unrelated changes in brain physiology. A clearer picture emerges by studying a radical, intensive technique of improving hand function which can have an effect even years after a stroke. 18

19 Constraint Induced Movement Therapy (Taub et al., 2002) In this therapy a sling is worn on the other arm throughout the waking day. This overcomes the tendency to use the other hand by forced use. This is maintained for 2 weeks of normal activities and combined with with intensive graded training in the use of the paretic limb for everyday functional tasks. A number of studies have shown that in some cases this results in a permanent increase in use of the affected arm. This well controlled and rapid therapy offers opportunities to do a human study similar to that by Nudo et al. 19

20 Mapping human cortical representation with TMS (transcranial magnetic stimulation). Motor representation can be mapped by moving the TMS coil across the scalp in 1 cm steps and recording muscle twitches in the thumb. Muscle twitch detected by EMG. 20

21 Does therapy promote restitution of after human brain damage? (Liepert et al., 2000) 13 patients more than 6 months after a stroke. Before constraint induced therapy there was an average off 40% fewer TMS active sites across the damaged hemisphere than the intact hemisphere. After therapy, the situation was reversed, with 37% more active sites on the damaged side. This effect diminished over time but the paretic side remained more responsive than at baseline, and at 6 months after therapy. Black bars = Number of active TMS positions in the damaged hemisphere. *P<0.05 Grey bars = Active sites in the intact hemisphere. Line = Patient s reports of the amount of use of the paretic hand. 21

22 Liepert et al. (2000) interpreted these results as evidence of restitution of cortical representation of the paretic limb. The reduced excitability of the damaged hemisphere before therapy was consistent with diminished representation of the paretic limb. The increased number of active sites after therapy was seen as a resolution of this abnormality and recovery of a normal balance between the hemispheres. In addition to enlargement of the excitable area there was a shift in its location suggesting recruitment of adjacent cortical areas paralleling the animal study by Nudo et al. (1996). which demonstrated the formation of a new hand representation neighbouring the cortical lesion. 22

23 Two routes to recovery These studies of recovery from paresis suggest that intensive therapy can promote restitution of function early or late after brain damage. This may indicate general rules of recovery that also apply to more complex functions such as recovery from memory impairment. Deciding between aiming for restitution or compensation is important if we are to have a scientific basis for rehabilitation therapy: Do we provide stimulation to restore memory e.g. computer games? Or teach strategies and provide aids to compensate for persistent memory impairment? At present, most clinical interventions do not specify clearly which they are aiming for. The process tends to be intuitive rather than scientific. 23

24 Restitution = Subtle compensation? Luria observed soldiers recovering from bullet wounds to the brain and suggested that long-term cognitive recovery occurred by people learning to use new strategies for tackling cognitive tasks. The damaged area of the cerebral cortex could not be restored. Hence when he tried to think, his mind had to detour round these scorched areas and employ other faculties to recover some lost skills. Luria (1972), quoted by Kolb & Whishaw In fact, even in motor recovery there are at least slight changes in how the fingers are used when ability is regained. Friel and Nudo (1998) note that it is difficult to be sure if true motor recovery ever occurs after motor cortex injury. 24

25 Processes of Recovery. Key Points. There is usually a significant return of functional ability over the months or years after head injury or stroke. The brain does not heal but there is reorganisation of cortical representations (neuroplasticity) which may allow restitution of some functions. Recovery may occur by restitution or compensation. It is often difficult to distinguish between them. 25

26 Long-term Recovery After Stroke Percentage of Patients with Normal or Near-Normal Ability Adapted from Wade, 1992 and Sunderland et al., Months since stroke Self-care Walking Use of both hands Language

27 Further Study Taub, E., Uswatte, G., & Elbert, T. (2002). New treatments in neurorehabilitation founded on basic research. Nature Reviews Neuroscience, 3(3),