Which statement best describes positive signs in CNS lesions?

Which statement best describes positive signs in CNS lesions?

• A. Overactive motor behaviors, such as hyperactive stretch reflexes
• B. Muscle contractures and joint deformities
• C. Normal motor function
• D. Loss of proprioception

Answer: (A)

Positive signs in CNS lesions are new, abnormal motor phenomena created by a loss of inhibitory control from the brain, resulting in increased excitability of reflex pathways. An overactive stretch reflex is a classic example of this, reflecting hyperreflexia that occurs when upper motor neuron input to the spinal cord is diminished or lost. This is why the statement about overactive motor behaviors, such as hyperactive stretch reflexes, best describes positive signs. Muscle contractures and joint deformities arise from long-term spasticity and immobility rather than immediate abnormal reflex activity, so they’re not considered positive signs. Loss of proprioception is a sensory deficit, a negative sign rather than an added, abnormal motor response. Normal motor function, of course, does not reflect a positive sign.

Positive signs in CNS lesions are new, abnormal motor phenomena created by a loss of inhibitory control from the brain, resulting in increased excitability of reflex pathways. An overactive stretch reflex is a classic example of this, reflecting hyperreflexia that occurs when upper motor neuron input to the spinal cord is diminished or lost. This is why the statement about overactive motor behaviors, such as hyperactive stretch reflexes, best describes positive signs.

Muscle contractures and joint deformities arise from long-term spasticity and immobility rather than immediate abnormal reflex activity, so they’re not considered positive signs. Loss of proprioception is a sensory deficit, a negative sign rather than an added, abnormal motor response. Normal motor function, of course, does not reflect a positive sign.