Final answer:
Abnormal UMN or pyramidal tract signs include muscle weakness, pronator drift, heightened reflexes, the clasp-knife response, and other symptoms like spasticity. These are tested by resistance-based muscle strength assessments and reflex testing to indicate potential UMN lesions.
Step-by-step explanation:
Indications of abnormal upper motor neuron (UMN) or pyramidal tract signs include muscle weakness, pronator drift, and the clasp-knife response. Muscle strength is assessed by having a patient perform movements, like lifting an arm, against resistance. A difference in strength between limbs suggests a unilateral corticospinal tract issue, whereas global weakness might imply a widespread motor system problem. Conditions like cerebral palsy, multiple sclerosis (MS), or a stroke can cause UMN lesions.
For diagnosing UMN lesions, the pronator drift test is used. In this test, a patient extends their arms forward with palms up, and upon closing the eyes, if one arm pronates, it suggests motor system impairment. Other UMN lesion indicators include heightened deep tendon reflexes, decreased movement control, positive Babinski sign, spasticity, and hyperflexia. The clasp-knife response is when resistance to passive muscle movement abruptly gives way, resembling a pocket knife closing.