Does Multiple Sclerosis Cause Hyperreflexia?
Yes, multiple sclerosis commonly causes hyperreflexia as a manifestation of upper motor neuron dysfunction from demyelinating lesions in the central nervous system.
Mechanism and Clinical Significance
Hyperreflexia in MS results from disruption of descending inhibitory pathways due to demyelinating lesions in the brain and spinal cord. This leads to disinhibition of spinal reflex arcs, resulting in exaggerated tendon reflexes that are commonly observed on neurological examination.
Evidence from Research Studies
MS patients demonstrate significantly increased reflex responses compared to healthy controls 1. Specifically, research has documented:
- Higher reflex gain (p = 0.0002) - indicating hyperexcitability of motoneurons
- Faster contraction rates (p = 0.0002) - suggesting greater recruitment of fast-twitch muscle fibers
- Shorter reflex loop delays (p = 0.0046) - reflecting enhanced peripheral receptor sensitivity
- Lower threshold for triggering reflexes (p = 0.026) despite producing higher reflex torque (p = 0.033)
These findings demonstrate that hyperreflexia in MS involves both increased sensitivity to stimulation and amplified reflex responses 1.
Clinical Patterns
Detrusor Hyperreflexia
Beyond somatic reflexes, detrusor hyperreflexia is the most common urological finding in MS patients 2. In a neurourologic evaluation of 86 MS patients:
- 76% demonstrated detrusor hyperreflexia on cystometry
- 97% had symptomatic voiding dysfunction
- 50% showed vesico-sphincter dyssynergia on electromyography
This bladder hyperreflexia represents another manifestation of the same upper motor neuron pathology affecting spinal reflex circuits 3, 2.
Spasticity and Hyperreflexia
Hyperreflexia is closely associated with spasticity in MS. Research characterizing reflex changes in spastic MS patients found:
- Increased phasic stretch reflex gains compared to controls
- Paradoxically lower tonic stretch reflex gains
- Altered joint viscosity properties
This suggests that hyperreflexia in MS involves complex changes in both reflex and non-reflex mechanisms 4.
Clinical Examination Findings
Bilateral extensor plantar reflexes (Babinski signs) in MS patients indicate the possibility of vesico-sphincter dyssynergia and suggest multilevel spinal cord involvement 2. The presence of hyperactive tendon reflexes correlates with:
- Ashworth scale scores for spasticity
- Clinical tendon reflex scales
- Degree of functional impairment
Important Caveats
While hyperreflexia is common in MS, the absence of hyperreflexia does not exclude the diagnosis. The diagnostic criteria for MS focus on demonstrating dissemination of lesions in space and time through clinical and paraclinical findings, particularly MRI 5, 6. Hyperreflexia is a supportive clinical finding but not a required diagnostic criterion.
Neurourologic patterns can change over time - 4 of 9 MS patients re-evaluated showed different patterns, emphasizing that reflex findings may evolve with disease progression or treatment 2.