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ULY CLINIC
ULY CLINIC
24 Septemba 2025, 14:04:09
Grasset’s phenomenon
Grasset’s phenomenon refers to the inability to raise both legs simultaneously, even though each leg can be lifted individually.
In adults: Indicates complete organic hemiplegia or significant upper motor neuron lesion.
In infants: A normal reflex observed until 5–7 months of age, reflecting immature motor control.
Pathophysiology
Infants: Motor pathways are immature, and bilateral leg coordination is not yet fully developed.
Adults: Occurs due to upper motor neuron lesions, typically from:
Stroke
Cerebral palsy
Spinal cord injury
The phenomenon results from contralateral inhibition and loss of descending motor control, causing the unaffected leg to drop when attempting simultaneous elevation.
Examination Technique
Patient positioning: Place the patient supine on a firm surface.
Single leg assessment: Lift and support one leg at a time to ensure both legs can be raised independently.
Bilateral leg assessment: Attempt to raise both legs simultaneously.
Observation: In a positive Grasset’s phenomenon:
The unaffected leg drops when the affected leg is lifted (in adults).
Documentation: Record side affected, ability to lift individually versus simultaneously, and any associated spasticity or weakness.
Clinical features
Feature | Manifestation |
Bilateral leg elevation | Inability to raise both legs simultaneously |
Single leg elevation | Each leg can be lifted independently |
Adult pathology | Suggests upper motor neuron lesion, usually hemiplegia |
Infant normal variant | Present until 5–7 months due to immature motor pathways |
Associated findings | Spasticity, weakness, increased reflexes on affected side |
Differential Diagnosis
Condition | Key Feature | Notes |
Adult hemiplegia | Positive Grasset’s phenomenon with unilateral weakness | Often post-stroke or CNS lesion |
Infant normal motor development | Present until 5–7 months; disappears spontaneously | Normal developmental phenomenon |
Severe peripheral neuropathy | Weakness in both legs, but no contralateral dropping | Lesion is peripheral, not UMN |
Spinal cord lesion | Bilateral deficits with reflex changes | Usually other sensory or motor signs present |
Pediatric considerations
Normal until 5–7 months, reflecting coordination development.
Persistence beyond this age may indicate neurological impairment.
Geriatric/Adult Cconsiderations
A positive Grasset’s phenomenon in adults indicates a serious upper motor neuron lesion, such as hemiplegia from stroke.
Assessment helps determine functional limitations and rehabilitation needs.
Limitations
Requires patient cooperation and proper positioning.
May be difficult to assess in infants with irritability or poor muscle tone.
Must distinguish from bilateral weakness due to peripheral causes.
Patient counseling
Infants: Explain that inability to lift both legs simultaneously is normal and temporary.
Adults: Explain that this sign indicates neurological impairment and the need for further evaluation and rehabilitation.
Emphasize physical therapy and functional recovery planning if hemiplegia is present.
Conclusion
Grasset’s phenomenon is a developmental reflex in infants and a pathological indicator of upper motor neuron lesions in adults, particularly hemiplegia. Careful assessment can help differentiate normal development from neurological injury and guide early intervention and rehabilitation.
References
Ropper AH, Samuels MA. Adams and Victor’s Principles of Neurology. 11th ed. New York: McGraw-Hill; 2021.
Campbell SK, et al. Physical Therapy for Children. 5th ed. Philadelphia: Elsevier; 2018.
Nelson WE, et al. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia: Elsevier; 2021.
Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science. 6th ed. New York: McGraw-Hill; 2021.