Causes of Exaggerated tendon reflex

In hyperactive stretch reflex there is increased speed of response, duration and amplitude of movement.

• Hyperreflexia can be either exaggerated or brisk response.it is very difficult to differentiate between the two. The term exaggerrated reflex means tbe amplitude and duration of the limb movement is more and brisk rellex means an increase in amplitude but not increase in duration,Brisk reflex may be a normal variant its presence may confuse us as abnormal but  is only of pathological significance when it is asymmetrical (comparing with the other side) or if associated with other signs of UMN lesion (spasticity. Babinski’s sign etc.)

Brisk       = Increase in amplitude of muscle contraction
Exaggerated = Increase in amplitude and duration of musle contration

• Hyperactivity of muscle indicate an interruption of corticospinal and other descending pathways that influence the reflex arc due to a suprasegmental lesion, that is, a lesion above the level of the spinal reflex pathways.

Hyperactivity of muscle reflex is seen in the following conditions

• As a sign of UMN lesion - pyramidal lesion and associated damage of reticulospinal and vestibulo spinal tract.
• Psychoneurosis - anxiety -amplitude of movement is increased.Reflexes may be brisk if the patient is agitated, frightened, or anxious.
• Tetany
• Tetanus
• Early phase of neuritis - increased irritability of peripheral nerve
• Paralysis of antagonist - increased knee jerk in paralysis of antagonist hamstring muscle
• Extrapyramidal lesion - increased tension of muscle (not always). MSR slightly increased
• Thyrotoxicosis.
• Strychnine poisoning 

When the reflexes are exaggerated, always look for clonus