Can Musical Tones Played in the Ear Help With Gait-Freezing in Parkinson’s Patients?

Parkinson’s Disease is the second most common degenerative neurological disorder. The incidence of Parkinson’s Disease, let’s called it PD for short, is growing rapidly with an aging population. The fundamental cause of PD is the death of nerve cells that produce a chemical called dopamine. The loss of these dopamine producing cells occurs in a part of the brain known generally as the basal ganglia and specifically the substantia nigra.

This part of the brain, the basal ganglia, is known to influence movement and diseases or injury of the basal ganglia produces what are known collectively as movement disorders which include Parkinson’s Disease. Parkinson’s Disease is characterized by slow movements known as bradykinesia (brady = slow, kinesis = movements), tremor and other signs of abnormal muscle function. One of the more disturbing symptoms that can occur in patients suffering with PD is called freezing of gait.

Voluntary movement takes place in two basic steps. To move we create the intention to move in one part of the brain. Thus one part of the brain plans the movement and the actual movement commands that activate the muscles occur in a different part of the brain. So we plan a movement and that plan is carried out by other circuits in the brain which then execute that plan.

In many patients with Parkinson’s Disease, planned movements like walking have delayed or failed execution. This is called Freezing-of-gait and it can severely diminish the quality of life in a Parkinson’s patient. Although we call this symptom freezing of gait, it can actually occur with any voluntary movement, like reaching for a glass, brushing your hair or getting up from a seated position to stand. It often leaves the Parkinson’s patient unable to initiate a movement or stuck in the middle of a planned action. It should not be hard for you to imagine how freezing might severely diminish a patient’s functional abilities and interfere with his or her daily activities.

Not surprisingly, freezing has also been linked to falls and injuries in PD patients.

The medical treatments for PD include drugs that replace the dopamine that is lost with degeneration of the substantia nigra. As a general rule dopamine replacement therapies are quite effective for patients suffering with PD with two notable exceptions:

  1. They usually are not particularly effective for freezing-type symptoms and
  2. They usually loose their effectiveness over time

A number of research groups believe they have identified the specific part of the brain which malfunctions and causes freezing symptoms in Parkinson’s patients. It is known as the pedunculopontine nucleus (let’s call it the PPN for short) in the brainstem. This has lead to a number of trials of electrical stimulation of the PPN through the use of surgically implanted deep brain electrodes. There are a growing number of reports that suggest that electrical stimulation of the PPN may produce promising results for patients in the advanced stages of Parkinson’s Disease. This technique appears to activate the PPN and results in reduced gait-freezing in patients suffering from Parkinson’s Disease. While this is a promising surgical procedure, it does however, require brain surgery and all of the associated risks.

If only there was a way to stimulate the PPN in the brainstem non-invasively.

Some recent research suggests that non-surgical PPN stimulation may now be possible. What is even more encouraging is the possibility of stimulating the PNN and reducing freezing through the use of musical tones played through special bone conducting headphones. Let’s see how this might work.

Research has shown that structures in the inner ear called otoliths can be stimulated by tones of highly specific frequencies. These inner ear structures have direct connections with the PPN which as we have discussed are important brainstem structures related to freezing symptoms in Parkinson’s Disease. Stimulating the otoliths with a tone played through special bone-conducting headphones may activate the PPN and has the potential to reduce gait-freezing in patients suffering from Parkinson’s Disease. Other research suggests that neurological rehabilitation and cueing patients with auditory or visual signals can improve freezing symptoms in PD patients. Thus there is the potential to improve freezing of gait through the combination of rehabilitation with auditory cueing using sound frequencies known to stimulate the PPN which is implicated in freezing of gait in PD.

This is very encouraging news for patients suffering from gait freezing associated with Parkinson’s Disease.