Changes in Motor Cortical Representation After Stroke: Correlations Between Clinical Observations and Magnetic Stimulation Mapping Studies
Eric P. Bastings, David C. Good
Thursday April 17 3:00 pm / Exhibit Hall A

Neuroimaging Studies (PET Scan And FMRI) After Stroke Have Suggested A Reorganization Of Motor Systems Including Increased
Activity Of The Motor Cortex Ipsilateral To The Paretic Limb. These Observations However Reflect Changes In Cerebral Blood Flow, And
Do Not Prove A Direct Participation Of These Regions In Motor Control, Which Is Functionally Accessible To Transcranial Magnetic
Stimulation (TMS) Mapping Studies.

Ten Patients With Cortical Or Subcortical Hemispheric Stroke And Initial Severe Motor Deficit Were Studied From 1 To 28 Months After
Onset (mean: 14 Months). Sites 1 Cm Apart Were Stimulated Using A Grid (1cm X 1cm Squares) Placed Over The Scalp. Intensity Of
Stimulation Was 110% Of Response Threshold. Motor Evoked Potentials (MEPs) Were Recorded From Both First Dorsal Interosseous
Muscles. Extensive Evaluation Of Motor Function Included NIH Stroke Scale, MRC Scale, Frenchay Hand Test, And Hand/arm
Motricity Scores. Surface Area And "weight" (integrated Amplitude Of Individual Responses For Each Hemisphere) Of The Motor
Representation Was Calculated. Correlations Between Clinical And Electrophysiological Data Were Determined Using Spearman's Rank
Correlation Test. Anatomical Location Of Infarct By CT Or MRI Was Available In All Patients.

Patients Fell Into Three Categories Of Functional Hand Recovery: A) Poor Outcome (scores Of Zero On Both Frenchay And Hand
Motricity Index); B) Good Outcomes (scores Of 5 On The Frenchay Test); C) Intermediate Outcome (zero On Frenchay And 22 Or
Greater On Hand Motricity Index). Different Patterns Of MEPs Mapping Were Also Observed: No Map In Patients With Poor Outcome,
Contrasting To A Striking Enlargement Of The Motor Map And Shift Into Adjacent Regions, Especially Anterolaterally In Patients With
Good Outcome, Even With Large Infarcts. A Strong Correlation (p<0.005) Was Found Between All Measures Of Improvement In Affected
Hand Strength And Function And The Relative Increase Of Surface And Weight Of The Motor Representation In The Injured Hemisphere.
No Ipsilateral Response Was Obtained After Stimulation Of The Healthy Or Stroke Hemisphere.

Our Data Support A Strong Association Between Expansion Of Motor Cortical Representation In The Stroke Affected Hemisphere And
Good Motor Outcome. Contrasting To Neuroimaging Data, No Evidence Of Participation Of The Intact Hemisphere Was Observed.
Further Studies Associating FMRI And TMS Mapping In The Same Patient Should Help To Better Understand Cortical Reorganization
After Stroke.




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