Hyperreflexia is an exaggerated briskness of the tendon reflexes. This may be physiological in an anxious patient (reflexes often denoted ++), or pathological in the context of corticospinal pathway pathology (upper motor neurone syndrome, often denoted +++). It is sometimes difficult to distinguish normally brisk reflexes from pathologically brisk reflexes. Hyperreflexia (including a jaw jerk) in isolation cannot be used to diagnose an upper motor neurone syndrome, and asymmetry of reflexes is a soft sign. On the other hand, upgoing plantar responses are a hard sign of upper motor neurone pathology; other accompanying signs (weakness, sustained clonus, absent abdominal reflexes) also indicate abnormality.
Hyperreflexia reflects an increased gain in the stretch reflex. This may be due to impaired descending inhibitory inputs to the monosynaptic reflex arc. Rarely pathological hyperreflexia may occur in the absence of spasticity, suggesting different neuroanatomical substrates underlying these phenomena.
"Hyperreflexia" of the bladder detrusor muscle may be a cause of urinary urge incontinence.
Sherman SJ, Koshland GF, Laguna JF. Hyper-reflexia without spasticity after unilateral infarct of the medullary pyramid. Journal of theNeurological Sciences 2000; 175: 145-155