Every patient with Parkinson’s disease does not experience the same problems. For example, some people have prominent tremors that interfere with daily activities, whereas others shake very little or not at all. One of the symptoms that might occur after many years after developing Parkinson’s disease is known as “freezing of gait”.
What is “freezing of gait”? This term is used to describe a phenomenon in which patients intermittently feel that their feet are “stuck to the floor as if held by magnets” when trying to walk. It is as if the motor function involved in ambulation is temporarily “blocked”. For some, there is brief trembling of the feet in place followed by short small steps, while others experience total immobility and are unable to move it all for a few moments.
What goes wrong in the nervous system that leads to “freezing of gait”? Normal ambulation requires a complex synchrony of action in numerous muscle groups that enable us to maintain posture and balance in order to begin stepping. In early childhood, the maturing brain develops circuits and feedback loops that automatically facilitate balance and ambulation. Consequently, we learn to walk without consciously thinking about the multiple individual motions that must occur harmoniously. The ability to quickly arise and begin walking is thus a semi-automatic function that most of us take for granted.
Parkinson’s disease alters the function of brain circuits that facilitate the automatic synchronous movements involved in ambulation and other complex motions. Most people with Parkinson’s disease have some reduction in step length and speed while walking, a symptom that is often observed at the time of initial diagnosis.
In the jargon of neuroscientists, freezing gait” is a disorder of “set switching” or “visuo-motor response”. Important components of motor control, including “amplitude generation” (inability to maintain effective speed and scaling of movement) and “rhythm generation” (a disordered timing of movement cycles) are impaired.
A simple way for laymen to conceptualize “freezing of gait” is to compare the function of the brain’s gait circuits to driving a car with an automatic transmission. When the automatic transmission is working, the car can begin moving, turn corners, or speed up effortlessly. However, if the automatic transmission (or brain gait circuit ) is not functioning normally, smooth continuous movement will be impaired.
“Freezing of gait” is often triggered by specific activities or circumstances that demand switching between motor actions. The earliest symptoms are noted when the patient finds that, for no apparent reason, upon arising they hesitate and are unable to immediately pick up their feet to begin moving forward. This transient inability to initiate locomotion is referred to as “gait initiation failure” or “start hesitation”. In a moment or two when this “motor block” is overcome, the patient can begin moving forward. Although significant “freezing of gait” is generally associated with longstanding Parkinson disease, a mild form of “gait initiation failure” can occur in patients in the early stages of the disease.
In addition to “start hesitation” there are several potential environmental triggers for “freezing of gait” (see table 1). Some patients might “freeze” when walking through narrow passages or doorways, trying to get on and off elevators, when turning or changing directions, and when walking in busy crowds. Emotional stimuli can also trigger “freezing of gait”, such as when being hurried, trying to cross a busy road, rushing to answer a ringing telephone, and when anxious or frightened. “Freezing of gait” is a distressing symptom, and in some cases the fear of “freezing” in social situations can become a potent trigger for this phenomenon.
“Freezing of gait” is not unique to Parkinson disease. Other, less common disorders, such as progresssive supranuclear palsy, corticobasal degeneration, multiple system atrophy, and normal pressure hydrocephalus, affect brain circuits and are often associated with “freezing of gait”. These conditions are often initially mistaken for Parkinson disease. If “freezing of gait” is a prominent symptom early in the course of the illness, one of these alternative diagnoses should be considered.
“Freezing of gait” makes walking slow and laborious, increasing the risk of falls. Impulsive patients who are unable or unwilling to delay walking, or do not request help when needed, put themselves at much greater risk of falling. The likelihood of falling is greatly increased in those with cognitive impairment and poor self-awareness of their limitations. Patients who experience “freezing” episodes on a frequent basis are likely to become more reluctant to walk, and thereby reduce their level of activity and social interaction. Consequently, it is important try to prevent or successfully manage episodes of “freezing of gait”.
Parkinson disease patients are greatly helped by carbidopa/levodopa and other dopamine-enhancing medications, but after many years of treatment may find the degree of benefit fluctuates throughout the day. For example, the medication might be beneficial much of the day (the patient feels “on”), but parkinsonian symptoms worsen (the patient feels “off”) if doses are missed, inadequate, or if the interval between doses is too long.
“Freezing gait” is most often encountered in patients who experience fluctuating responses to the dopamine enhancing medications. If the “freezing of gait” occurs predominantly when the patient is “off”, readjusting the timing and doses of medication to prevent or decrease “off” spells can help prevent the symptoms. Close patient – physician cooperation, and conscientious compliance, are required in order to determine the optimal dosings and time schedule and avoid over-medication or under-medication.
Unfortunately, these measures often do completely solve the problem. “Freezing of gait” is not entirely attributable to diminished brain dopamine levels. Neural circuits not reliant on dopamine are also important for locomotion and balance, and are altered in Parkinson disease. Thus “freezing of gait” may also occur when patients are “on”, and the dopamine enhancing medications appear to be working. In this situation, medication adjustment is less likely to be beneficial in preventing the problem. Deep brain stimulation (DBS), a surgical treatment used to reduce fluctuating motor symptoms in Parkinson disease when medication adjustment is not sufficient, does not eliminate “freezing of gait” for patients who experience this phenomenon in the “on” state.
It is important for patients who experience “freezing of gait” to have a strategy for dealing with these situations (see table 2). There is no fool-proof way of re-initiating movement that works for everyone. However, whenever the feet become “stuck”, it is important for the patient to immediately recognize the problem and come to a complete halt. Continuing to try to move the body forward while the feet are “frozen” in place is likely to precipitate a fall. After standing still for several seconds, many patients with “freezing of gait” are able to re-initiate ambulation by using tricks such as counting to three, and then lifting one foot high off the floor as if marching.
Multi-tasking and distractions (eg talking and walking) can trigger “freezing” and should be avoided. Loud rhythmical counting, or stepping in time to a musical beat or metronome, are potentially helpful auditory cues for overcoming freezing. Visual cues, such as an inverted walking stick, stepping over a small object, or striped lines on the floor, can reduce “freezing” in some cases. Patients who “freeze” in a particular place, such as a doorway, should try to visualize the area beyond the obstacle. Once the object is passed, freezing generally resolves.
Physiotherapists and other health professionals offer important gait rehabilitation programs to enable people with Parkinson’s disease to improve their movements and safety. Assistive devices such as a wheeled walker can prevent falls for some patients, but are not always effective for “freezers”.
Preventing and treating “freezing of gait” is a major unmet need for patients with Parkinson’s disease. Fortunately, research into rehabilitation, medical, and surgical therapies that might specifically help “freezing of gait” is being performed at centers around the world. Innovative therapies (such as external anodal electrical stimulation of the motor cortex of the brain and deep brain stimulation of new targets in the brainstem) are exciting avenues of investigation that might eventually help patients with “freezing of gait”.
Table 1: Potential “triggers” for “freezing gait”
Gait initiation (“start hesitation”)
Turning or changing directions
Obstacles in the path
Multi-tasking / distractions
Being startled (“startle hesitation”)
Table 2: Treating “freezing of gait”
• Optimize carbidopa/levodopa therapy to reduce or eliminate “off” times
• When “freezing” occurs the patient must recognize the problem and come to a complete stop to abort the malfunctioning automatic gait program
Visual and auditory cues to re-initiate gait after coming to a stop:
• count to 3 and take a large high step (like marching) with one foot
• march to a cadence or tune
• step over a target (eg a line in the floor or a laser beam)
additional helpful options:
• Participate in physical therapy and rehabilitation programs
• Assistive devices (eg rolling walkers) for selected cases
Dr. Howard Weiss, is a member of PFNCA’s Medical Advisory Board.
Note: Dr. Weiss presented two lectures at the 2016 PFNCA Symposium. These lectures are part of more than 11 hours of video content that is now available online. To learn more, please click here.