A robot exoskeleton is revealing hidden sensory losses in stroke patients, helping explain why some survivors struggle to fully recover movement.
The technology can identify proprioception problems, the body’s sense of limb position and movement, without requiring patients to move the affected arm, making assessments easier in clinics.
Proprioception lets us know where our limbs are without looking.
When this sense is damaged after stroke, a person may not notice their arm has moved 10 centimetres, risking accidents such as touching a hot surface.
Jennifer Semrau is associate professor of kinesiology and applied physiology at the University of Delaware.
She said: “To simplify the concept, in class, I tell my undergraduates to close their eyes and touch their nose; if people can’t do that, it means they likely have impaired proprioception.”
Researchers at the university used a KINARM robotic exoskeleton that tracks upper-limb movement to study these often-overlooked sensory deficits.
The device moves a patient’s stroke-affected arm while they respond with their unaffected arm if they can feel the movement.
Healthy people can detect shifts as small as half a centimetre, but stroke survivors vary widely.
Signals between the brain and muscle receptors that detect movement can be disrupted after stroke.
People with proprioceptive loss may still feel pain or touch, as these travel along different nerve pathways.
Semrau said: “Pain is part of the somatosensory system and is relayed on a different set of nerves.
“After a stroke, some may have increased or decreased sensitivity to pain, and it’s the same with touch.”
She added: “Every person is a fingerprint; impairments each person has after a stroke are unique and require individualised treatment.”
The team found a gap in practice: only a tiny minority of clinicians currently assess proprioception in stroke patients.
Semrau said: “We found that just one per cent of clinicians assess proprioception in people with stroke.
“It’s a newer area, but research also shows that without sensory recovery, a person will not gain full recovery of function after a stroke.”
Untangling sensory from motor problems is difficult because they are closely linked.
The researchers said understanding both motor and sensory impairments is essential for personalised care.
