Neurological Pathology Indicated by Unequal Patellar Reflex

Causes of Unequal Reflexes

Lumbar radiculopathy from nerve root compression is the primary cause of diminished or absent patellar reflexes on one side, according to the American Academy of Pediatrics 1
Upper motor neuron lesions can cause increased reflexes on the affected side, while lower motor neuron disorders cause diminished or absent reflexes, as noted by the American Academy of Pediatrics 1
Asymmetric reflexes suggest lateralizing pathology requiring neurological evaluation rather than musculoskeletal treatment, as stated by the American Academy of Pediatrics 1

Diminished or absent reflex = lower motor neuron pathology (radiculopathy, peripheral neuropathy), according to the American Academy of Pediatrics 1
Increased reflex with abnormal plantar response = upper motor neuron pathology (spinal cord lesion, stroke), as noted by the American Academy of Pediatrics 1
Radiating leg pain, numbness, or weakness suggests nerve root compression, as reported by the American College of Cardiology and the American Heart Association 2, 3
Back pain worse with sitting and relieved when supine suggests spinal stenosis or disc disease, according to the American College of Cardiology 2

Sensory examination should test for dermatomal sensory deficits corresponding to L2-L4 distribution, as recommended by the American Academy of Pediatrics 1
Motor examination should assess for quadriceps weakness, which accompanies L3-L4 radiculopathy, as noted by the American Academy of Pediatrics 1

In patients presenting with asymmetric hyperactive patellar reflexes, the concurrent appearance of bowel or bladder dysfunction is a strong red‑flag sign of spinal cord compression and requires urgent neurological evaluation. 4

When hyperreflexia develops abruptly and is accompanied by a defined sensory level, this pattern signals an acute spinal cord emergency that demands immediate assessment and management. 4

The combination of hyperactive patellar reflexes and altered mental status suggests an underlying cerebral pathology (e.g., acute stroke or traumatic brain injury) and should prompt rapid neurological investigation. 5