Two new visual methods for generating phantom sensations

in amputees and normal subjects: multiple reflections from three-panel mirrors, and mirror images flickering in

counterphasePeterzell, D.H.1,2,3, Cone, R.E..2, McQuaid, J.R.3, & Ramachandran, V.

S.1 1UCSD Center for Brain & Cognition

2Alliant International University, San Diego3Veteran’s Administration Hospital, San Diego

THIS IS A DRAFT:Abstract submitted to ECVP 2006

Abstract

A mirror box apparatus has been used previously to reduce or eliminate phantom limb pain in amputees and to generate phantom sensations (e.g., tingling) in normal subjects. We have created two new apparati that generate intense phantom sensations in two patients (missing left arms) who experienced little relief following standard mirror box treatment. One uses three vertical mirrors, with panes oriented at angles that enable viewers to see unusual reversed mirror images of themselves from the side. The other uses a real-time video image of the individual, and flickers the image between a normal image and a mirror image. When both subjects move their remaining arm and hand while viewing the modified images, they experience sensations and movement in the missing limb. One subject reports complete and permanent cessation of phantom pain following use of the tri-partite mirror. Both methods induce sensations of tingling, movement, and temperature change in the hands and arms of some normal subjects. We speculate that the human mirror neuron system plays a role in producing these effects.

Phantom limbs and pain

• People who lose a limb often perceive sensations in the limb that has been lost.

• The phantom limb is often accompanied by feelings of pain, pressure, and burning in the missing limb.

• Phantom limb pain can be severe and disabling. It continues to be experienced by two thirds of amputees, eight years post-amputation.

• Usually, but not always, the phantom is “paralyzed,” “frozen stiff,” “in cement”, or “won’t budge an inch”

Merzenich’s finding of neural plasticity in non-humans

• Following amputation, considerable re-arrangement of the neocortex takes place

Merzenich (cont)

V.S. Ramachandran

• Rearrangement of sensory cortex is responsible for phantom limb pain in humans

Representation of fingers on cheek and stump of a right limb amputee.

(From Ramachandran, 2000)

Representation of fingers on cheek and stump of a right limb amputee.

These points on the body surface yield referred sensations in the phantom hand.

(From Ramachandran, 2000)

Representation of fingers on cheek and stump of a right limb amputee.

These points on the body surface yield referred sensations in the phantom hand.

“My phantom hand sometimes itches like crazy… But now, I know exactly where to scratch” --”Tom”

(From Ramachandran, 2000)

Representation of fingers on cheek and stump of a right limb amputee.

These points on the body surface yield referred sensations in the phantom hand.

“My phantom hand sometimes itches like crazy… But now, I know exactly where to scratch” --”Tom”

(From Ramachandran, 2000)

Magnetoencephalography (MEG) image superimposed on a magnetic resonance (MR) image a right limb amputee, revealing a re-arrangement the left hemisphere’s somatosensory cortex in a right limb amputee

(From Ramachandran, 2000)

Classic mirror treatment phantom limb pain - Ramachandran (1993)

• If the patient gets visual feedback that the phantom is obeying the brain’s commands, the learned paralysis is sometimes unlearned.

• Mirror imaging of limbs using a mirror box

Classic mirror treatment phantom limb pain - Ramachandran (1993)

• If the patient gets visual feedback that the phantom is obeying the brain’s commands, the learned paralysis is sometimes unlearned.

• Mirror imaging of limbs using a mirror box

“Look into side of the mirror so that you see the reflection of your intact hand superimposed on the felt location of your phantom hand.”

“Then try to make symmetrical motions using both hands (e.g., conducting an orchestra).”

Classic mirror treatment phantom limb pain - Ramachandran (1993)

• This method has positive therapeutic value for some patients

Classic mirror treatment phantom limb pain - Ramachandran (1993)

• This method has positive therapeutic value for some patients

In some patients, the procedure animates the phantom as never before, allowing it to “move.” The sudden sense of voluntary control and movement reduces and sometimes permanently removes phantom pain.

Classic mirror treatment phantom limb pain - Ramachandran (1993)

• Although the mirror box method reduces some patients’ pain, it is ineffective for others.

Classic mirror treatment phantom limb pain - Ramachandran (1993)

• Although the mirror box method reduces some patients’ pain, it is ineffective for others.

• Individual differences are related to patients’ abilities to “immerse” themselves and feel “present” in the illusion that the reflected arm was in fact their own. There is great variability in the experienced authenticity of the mirror box illusion.

Classic mirror treatment phantom limb pain - Ramachandran (1993)

• Although the mirror box method reduces some patients’ pain, it is ineffective for others.

• Individual differences are related to patients’ abilities to “immerse” themselves and feel “present” in the illusion that the reflected arm was in fact their own. There is great variability in the experienced authenticity of the mirror box illusion.

• Each amputee has his/her own individual perception of the phantom limb. The phantom limb may be shorter, or longer, have some parts thicker or thinner, be continuous, or have gaps in it, in comparison to the original limb. This may explain why the mirror box is so successful for some, yet ineffective for others.

Optimal Mirror Treatment• The classic mirror box may not offer the most effective

mirror intervention possible for all patients.

• Case study - R.C. – History of amputation, pain– Tried single mirror intervention of Ramachandran, little activation– Created mirror enviroment– Cured phantom pain…

• We (actually, the second author, R.C.) have developed an alternative three-mirror environment in which upper limb amputees can have their phantom limbs individually tailored to represent their own perception of their missing limb

• The image that stimulates the phantom is very strange. The subject sees a side view of him/herself, and that image is itself a mirror image.

Roberta Cone’s Technique(Peterzell, Cone, McQuaid, Ramachandran, 2005)

Roberta Cone’s Technique(Peterzell, Cone, McQuaid, Ramachandran, 2005)

Peterzell’s (2005) Phantom Pulse Effect

Peterzell’s (2005) Phantom Pulse Effect

NOTE:

• Controlled studies of these new techniques have not yet been performed.

• N=2 (More by Aug, 2006)• Both methods evoke strong sensations in many

normal subjects. The stationary hand and arm feels tingling, movement, heaviness, and temperature change. The fingers in the non-active hand sometimes move involuntarily.