Hyperreflexia refers to overactive reflex responses. It is a symptom, not a disease, often indicating an underlying neurological condition. Overly responsive reflexes signal disrupted body control mechanisms, warranting medical attention to identify the cause.
What Hyperreflexia Is
Reflexes are involuntary actions your body performs in response to specific stimuli, serving as protective mechanisms. An example is quickly pulling your hand away from a hot stove without conscious thought. This process involves sensory neurons sending signals to the spinal cord, which then rapidly communicates with motor neurons to trigger a muscle response.
In a normal reflex, the response is swift but proportionate. Hyperreflexia occurs when this response becomes abnormally heightened, meaning the muscle contraction is more forceful or prolonged than expected. This overactivity often points to issues within the central nervous system, particularly involving upper motor neurons, which transmit signals from the brain to the spinal cord. Damage to these neurons can lead to a loss of inhibitory control from higher brain centers, resulting in increased reflex activity.
Underlying Conditions It May Signal
Hyperreflexia often indicates issues with upper motor neurons. Spinal cord injuries are a common cause, as damage disrupts communication between the brain and the spinal cord below the injury level. This can lead to exaggerated responses to stimuli, such as bladder filling.
Focal brain lesions, such as those caused by a stroke or a tumor, can also result in hyperreflexia. These lesions interfere with the brain’s ability to modulate reflex activity, leading to an overactive response. Multiple sclerosis (MS), a chronic disease affecting the central nervous system, can cause hyperreflexia due to damage to the myelin sheath that protects nerve fibers. Similarly, Amyotrophic Lateral Sclerosis (ALS), a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord, can manifest with hyperreflexia as upper motor neurons degenerate.
Conditions not directly impacting the nervous system can also lead to hyperreflexia. Hyperthyroidism, an overactive thyroid gland, can increase nervous system excitability, contributing to exaggerated reflexes. Severe electrolyte imbalances, such as those involving calcium or magnesium, can disrupt nerve and muscle function, leading to hyperreflexia. Certain medications, particularly stimulants, can also have hyperreflexia as a side effect.
Associated Symptoms and Autonomic Dysreflexia
Hyperreflexia can be accompanied by other physical signs of neurological dysfunction. These include muscle twitching, known as fasciculations, which are small, involuntary muscle contractions visible under the skin. Spastic tendencies, characterized by muscle stiffness and involuntary spasms, are also common. Muscle weakness may also be present.
It is important to distinguish hyperreflexia from autonomic dysreflexia (AD), which is a distinct and potentially life-threatening condition primarily associated with spinal cord injuries, especially those at or above the sixth thoracic vertebra (T6). Autonomic dysreflexia involves an overreaction of the autonomic nervous system to a noxious stimulus below the level of injury. This overreaction leads to a sudden and dangerous rise in blood pressure, which can cause symptoms such as a severe headache, sweating above the injury level, and a slowed heart rate. Unlike generalized hyperreflexia, autonomic dysreflexia is an emergent situation requiring immediate medical intervention to identify and remove the triggering stimulus, such as a full bladder or bowel impaction, to prevent serious complications like stroke or seizure.
Diagnosis and Treatment Approaches
Hyperreflexia is identified during a neurological examination. A healthcare provider tests deep tendon reflexes, such as the patellar (knee jerk) or Achilles reflex, by gently tapping specific tendons with a rubber hammer. An exaggerated response indicates hyperreflexia.
Once hyperreflexia is detected, further diagnostic tests pinpoint the underlying cause. These may include imaging studies like Magnetic Resonance Imaging (MRI) of the brain or spinal cord to detect lesions or structural abnormalities. Blood tests may also check for electrolyte imbalances, thyroid dysfunction, or other systemic conditions. Treatment for hyperreflexia focuses on addressing the underlying medical condition. For instance, treatment might involve medications for neurological disorders, physical therapy for muscle spasticity, surgical interventions for spinal cord issues, or hormone regulation for conditions like hyperthyroidism.