From the Guidelines
Brisk reflexes, or hyperreflexia, are typically caused by upper motor neuron damage, which can occur in conditions such as stroke, multiple sclerosis, spinal cord injury, or amyotrophic lateral sclerosis, as well as certain metabolic disorders like hyperthyroidism or electrolyte imbalances 1. The causes of brisk reflexes can be multifaceted, involving various neurological and metabolic conditions.
- Upper motor neuron damage is a primary cause, often resulting from conditions like stroke, which can lead to spasticity and significant pain and functional disturbances, as discussed in the management of adult stroke rehabilitation care 1.
- Other conditions such as multiple sclerosis, spinal cord injury, or amyotrophic lateral sclerosis can also lead to upper motor neuron damage and subsequently brisk reflexes.
- Metabolic disorders, including hyperthyroidism or electrolyte imbalances, may also contribute to the development of hyperreflexia.
- It is essential to evaluate brisk reflexes in the context of other neurological findings, as they alone do not always indicate disease.
- A comprehensive neurological examination, possibly including imaging studies or laboratory tests, is necessary for proper diagnosis and treatment, which depends on the underlying cause rather than the reflex itself.
- Treatment options, such as those discussed for spasticity in stroke patients, including medications like tizanidine, baclofen, dantrolene, and diazepam, may be considered based on the specific cause of the hyperreflexia 1.
From the Research
Causes of Brisk Reflexes (Hyperreflexia)
- Brisk reflexes, also known as hyperreflexia, can be caused by a variety of neurologic conditions, including stroke, brain injury, spinal cord injury, multiple sclerosis, and cerebral palsy 2
- Hyperreflexia is a component of the upper motor neuron (UMN) syndrome, which is characterized by a velocity-dependent increase in resistance, i.e., hypertonia 2
- Spasticity, which is often associated with hyperreflexia, is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex as one component of the UMN syndrome 3
- The underlying mechanisms of hyperreflexia are complex and involve the interplay of various factors, including the loss of inhibition from the brain to the spinal cord, leading to an increase in the excitability of the stretch reflex 4
- Hyperreflexia can also be caused by other conditions, such as upper motor neuron lesions, which can result in spasticity and clonus, a type of involuntary muscle contraction 5
Clinical Assessment of Hyperreflexia
- The clinical assessment of hyperreflexia involves a thorough physical examination, including the evaluation of muscle tone, muscle strength, and reflexes 6
- The examination of reflexes is typically divided into several categories, including myotatic reflexes, cutaneomucous reflexes, spinal cord or defence automatism reflexes, and posture and attitude reflexes 6
- The assessment of hyperreflexia also involves the evaluation of primitive pathological reflexes, remote reflexes, synkinesias, and signs of meningeal irritation 6