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George E. Carvell, PhD, PT   University of Pittsburgh
 
UPPER MOTOR NEURON SYNDROME: STROKE PATHOBIOLOGY I
 An upper motor neuron (UMN) pathology has a constellation of signs and symptoms resulting from loss of both pyramidal and non-pyramidal descending control of motor centers in the brainstem and spinal cord. For example, a lesion of the posterior limb of the internal capsule due to a stroke involving deep branches of the middle cerebral artery typically produces a 'classic' UMN disorder (capsular stroke). Damage to Cerebral Gray may involve other cerebral cortical brain dysfunction. Damage to white matter tracts in the spinal cord may result in an UMN Syndrome that may include all or some of the following signs and symptoms; the actual pattern depends on which tracts are involved. The UMN disorder includes both 'positive' and 'negative' sequelae.
    UMN Positive Signs and Symptoms: Spasticity, Hyperreflexia (hyperactive deep tendon reflexes, clonus, abnormal mass reflex response), Upgoing (positive) Babinski and positive Hoffmann Sign
    UMN Negative Signs and Symptoms: paresis/paralysis, loss of dexterity, poor muscle fractionation, abnormal motor unit recruitment, altered muscle synergy, shock (initially), no clinical or electrophysiological evidence of muscle denervation.
Pathological changes in the core and the ‘penumbra’ of the lesion evolve over time following a stroke. One can expect alterations in results of clinical testing and in an individual’s functional status as the lesion evolves (see next page).
U. Dirnagl, C. Iadecola, and M.A. Moskowitz, Pathobiology of Ischaemic Stroke: An Integrated View. TINS 22: 391-397, 1999
Dirnagl et al Fig 6 p 396
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