Upper motor neuron lesion is characterised by -

Correct option is B

Ans. (b) Hyperactive deep tendon reflexes
Explanation:
An Upper Motor Neuron (UMN) lesion affects the neurons in the central nervous system (brain and spinal cord), specifically the corticospinal or pyramidal tract. This results in a characteristic set of signs and symptoms:
1. Hyperactive Deep Tendon Reflexes (Hyperreflexia) → (Correct Answer)
· The upper motor neurons normally exert inhibitory control over reflex activity.
· When UMNs are damaged, this inhibitory control is lost, leading to exaggerated reflexes (hyperreflexia).
· This is a hallmark feature of UMN lesions seen in conditions like stroke, multiple sclerosis, and spinal cord injuries.
2. Hypotonia (Reduced Muscle Tone) → (Incorrect Choice)
· Hypotonia is typically a feature of Lower Motor Neuron (LMN) lesions, not UMN lesions.
· In UMN lesions, initial spinal shock may cause temporary hypotonia, but over time, spasticity and hypertonia develop due to loss of inhibitory control.
3. Flaccid Paralysis → (Incorrect Choice)
· Flaccid paralysis (loss of muscle tone with no resistance) is associated with LMN lesions, not UMN lesions.
· UMN lesions lead to spastic paralysis, where muscles are stiff and resistant to movement.
4. Fasciculations → (Incorrect Choice)
· Fasciculations (visible, involuntary muscle twitches) occur in LMN lesions due to the spontaneous discharge of degenerating motor neurons.
· UMN lesions do not cause fasciculations because the lower motor neurons remain intact.
Key Features of UMN Lesions: