An implantable device can help restore natural facial movement in patients with unilateral facial paralysis, scientists say.
According to a study published in the journal Plastic and Reconstructive Surgery, animal experiments show promising results with a “bionic face” approach to facial resuscitation, using electrical signals from the uninjured side of the face to trigger muscle movement in the paralyzed side.
This approach would represent a paradigm shift in the management of hemifacial paralysis, according to Nate Jowett of Harvard Medical School in the US, who led the research.
Hemifacial paralysis is a “devastating clinical condition” that leads to functional, aesthetic and communication problems.
While reconstructive surgery methods, such as nerve and muscle transfer, can restore some facial movements, these techniques have significant shortcomings. For example, while patients may regain some ability to smile, it requires a conscious effort to do so.
The development and “proof of principle” of a new technique that uses functional electrical stimulation to restore movement of the face in hemifacial paralysis.
To evoke more natural and appropriate movements, stimulation of the paralyzed side is linked to electrical activity on the unaffected side to produce paired muscle contractions.
The researchers implanted tiny electrically-shielded cuff electrodes around the facial nerve of rats with experimentally induced hemifacial palsy. Electrical stimulation was given to produce blinks and whisker movements of different durations and amplitudes.
The movements were evoked by linking stimulation of the paralyzed side led to movements on the uninjured side. The “paired muscle contractions” produce more natural, normal-looking movements. The researchers note that most facial expressions, especially positive ones, are symmetrical.
Previous studies reported the basic concept of using signals from the healthy side of the face to drive functional electrical stimulation of paralyzed facial muscles.
The new research addressed some key technical challenges that affect the long-term success of this approach, including providing a more natural, spontaneous smile and other facial movements while blocking unwanted and involuntary movements.
While preliminary experiments in rats are encouraging, there is a long way to go before the “bionic face” can be refined enough for testing in human patients with hemifacial paralysis, the researchers said.
They plan further studies to develop a fully implantable, miniaturized neuroprosthetic device for hemifacial resuscitation.
“Although the ultimate goal of resuscitation is to restore dynamic movement to the entire facial musculature, restoring just three symmetrical facial movements (brow lift, blink, and smile) would dramatically improve outcomes,” Jowett said.
Researchers believe that the combination of proximal neural block with distal functional electrical stimulation could also be helpful in treating other peripheral nerve disorders, such as abnormal muscle contractions or nerve pain. PTI