Gait Disorders

Stroke – A Major Health Problem

Many stroke survivors will suffer from long-term gait disorders. A stroke is a cardiovascular disease that occurs when a blood vessel carrying oxygen and nutrients to the brain becomes obstructed or bursts, causing the affected portion of the brain to die. In 2005, the overall prevalence of stroke in the U.S. population for people ? 20 years of age was 2.6% and it generally increases with age and the addition of risks factors such as high blood pressure, smoking and diabetes. According to the American Heart/Stroke Association, approximately 780,000 people in the U.S. will annually experience a new (first time) or recurrent stroke or an average of one stroke every 40 seconds. This results in just over 150,000 deaths annually, making stroke the third leading cause of death in the U.S. behind heart disease and cancer.

The Aftermath of a Stroke

For survivors, the aftermath of a stroke can mean a lifetime of physical as well as psychological challenges. While approximately 50 to 70% of those who survive a stroke event will recover and regain functional independence, another 15 to 30% will not fully recover and will remain permanently disabled. Although the number and types of gait disorders following a stroke are not well documented, it is generally accepted that they vary depending upon the severity of the stroke event and the existence of other health problems such as heart disease, diabetes, etc.

Many stroke survivors will be left with hemiparesis, or weakness to one side of their body, while others may suffer the complete paralysis to one side called hemiplegia. Data collected from the Framingham Heart Study showed that 6 months after having their stroke, in patients who were 65 years of age or older, 50% or half of this group had some hemiparesis. Furthermore, 30% reported that they were not able to walk without some assistance. Finally, the economic costs associated with treating and dealing with the aftermath of a stroke are estimated to be a staggering $65 billion U.S. dollars in 2008.

Gait Disorders

How you walk is called your gait. Many health care professionals consider any slowing of gait speed, smoothness, symmetry and synchrony to be indicators of some gait disorder or abnormality. Many of us probably take walking with a normal gait for granted or believe that it “just comes naturally” when in fact it is the result of a complex interaction between our bones, muscles and nervous system. Therefore, it should come as no surprise that, when any part of this complex system is affected by injury or disease, we can develop any number of gait disorders. Data collected by the CDC, or Centers for Disease Control, showed that in 2000 over 381,000 Americans reported receiving help in walking. Some commonly diagnosed gait disorders and prominent characteristics include:

  • Propulsive gait – a rigid posture with the head and neck bent forward or stooped;
  • Scissor gait – walking with a crouch or legs bent at knees and hips where the knees and thighs touch or cross in a scissor-like movement;
  • Spastic gait – usually one leg is stiff from some chronic or long-term muscle spasm and the foot is dragged across the ground;
  • Steppage gait (foot drop) – partial or complete loss of control of the muscles of the foot and ankle, causing it to point down, resulting in toes dragging or scrapping across the ground during the swing phase of walking;
  • Waddling gait – a distinctive “duck-like” walk.

The risk of acquiring some type of gait disorder generally increases as we grow older. In fact, a recent study showed that at least 20% of non-institutionalized adults reported some difficulty in walking that required some assistance from others or some sort of devices to walk. However, many others will experience changes in their normal gait as result of a stroke, multiple sclerosis, Parkinson’s disease, traumatic brain injury, unanticipated accidents or surgical injury.

Foot Drop – A Type of Gait Disorder

Foot drop is not a disease but a chronic condition caused by weakness or paralysis of the muscles that lift the foot, causing the toes to drag across the ground during the swing phase of gait. Foot drop typically occurs when the signal from the peroneal nerve that controls the muscles of the foot is interrupted due to some primary condition such as stroke, multiple sclerosis or other unanticipated injury. When the foot no longer flexes upwards or dorsiflexes, the foot drop sufferer will compensate by making changes to their normal gait, by raising their leg and foot higher and swinging their hip in an exaggerated movement known as circumduction in an attempt to clear their toes off the ground. These abnormal changes to the gait can further lead to poor balance, pain, fatigue and increased anxiety about walking.

Current Therapies for Foot Drop

There are several types of therapies in use today that can be used individually or in combination in an attempt to offset some of the effects of foot drop. They include:

Physical Therapy

Physical therapy employs a series of exercises and motivational techniques in an attempt to strengthen the affected limb. Although usually with the consistent application of physical therapy some benefits are achieved over time, many foot drop sufferers reach a “plateau” or state where additional benefits are no longer realized.

Ankle-Foot Orthotics

Ankle-foot orthotics or “AFO” refers to a category of braces worn on the lower leg and designed to fix or brace the foot and ankle at a predetermined angle so the toes clear the ground while walking. AFOs are utilized as assistive devices for patients with mild to moderate foot drop, but their use can be limited by certain physical characteristics such as a person’s height and weight.

Surgery

Depending upon the cause, surgery may be indicated in some patients with foot drop. The goal of most foot drop surgeries is to permanently fix the foot into position so the toes no longer drag on the ground. For others whose foot drop condition results from an injury where pressure is being applied to nerves, surgery is performed to decompress or relieve that pressure in an attempt to restore normal nerve and muscle function.

Neurostimulation Devices

Neurostimulation, also known as Functional Electrical Stimulation (FES), works by delivering low-voltage electrical impulses to a targeted nerve in order to stimulate a desired response. When used for foot drop, currently available devices are worn just below the knee and deliver electrical energy through the skin to stimulate the peroneal nerve, thereby raising the foot during the swing phase of gait. Some devices may also employ a separate gait sensor that communicates with the control unit, providing information about specific events such as when the heel makes contact with the ground. Unlike current therapies like AFOs, which only mitigate the effects of foot drop, neurostimulation devices have the potential to bring greater movement and mobility to gait disorder patients by actually restoring more normal physiological function.

External Neurostimulation Systems

Most foot drop stimulators in use today are completely external, i.e., worn outside the body. These are battery-operated, single or multi-channel stimulation units strapped to the patient’s leg just below the knee. These external stimulators are designed to deliver momentary stimulation energy through electrodes placed on the skin, in the area near the peroneal nerve, to activate the muscles of the ankle and foot during walking. Most systems require the use of a separate wired or wireless “gait” sensor worn in the shoe that sends signals to the stimulator unit when the heel lifts off or strikes the ground. While external neurostimulation systems have been shown to be effective in restoring some level of physical function in certain foot drop patients, they also have known practical limitations in daily use. These include:

  • External devices can be bulky and therefore aesthetically unattractive;
  • They must be turned off and removed before going to sleep, bathing or swimming;
  • Hemiplegic patients may experience difficulty securing and removing the devices;
  • Some patients may experience sensitivity, skin irritation or even minor burns from the skin electrodes;
  • Skin electrodes require periodic removal and replacement;
  • Accuracy of electrode placement is required for good quality of nerve stimulation and muscle contraction;
  • Single-channel operation may require periodic office visits for system adjustment.

Benefits of Neurostimulation Devices

The potential benefits of neurostimulation devices for foot drop sufferers continue to capture the attention of health care providers and patients as digital technologies continue to trend towards improved sophistication, functionality and user-friendliness. Researchers from the Harvard Medical School studied 24 patients suffering from foot drop by measuring several gait parameters, including speed and symmetry, with and without a neurostimulation device. The study results showed that patients immediately demonstrated gains in gait speed, rhythm and steadiness when using an externally fitted neurostimulation device versus patients without stimulation. Furthermore, the authors pointed out that these gains in gait symmetry, speed and steadiness increased over time with continued use of a device.

Neurostream Innovative Approach to Neurostimulation for Gait Disorders

Neurostream’s goal is to develop and bring to market the “next generation” of implantable neurostimulation devices aiming to treat gait disorders by focusing on demonstrating the following innovative capabilities through clinical study:

  • Fully implantable system that integrates in the body and assists the patient invisibly
  • Stimulation technology that gives patients more natural movement
  • Internal sensing technology that eliminates the need for external gait sensors
  • “Always on” functionality providing therapy at all times
  • “Smart technology” that delivers function at the right time, complementing patient’s gait
  • Device long-term reliability
  • Internal memory provides the health care professional access to information about patient’s gait activities outside of the clinical setting
  • Exercise capability to potentially assist in maintenance of muscle mass, tone and function
  • Custom programmability to match the therapy to the individual patient’s gait and needs

Neurostream has incorporated these design goals into a medical investigational device, the Neurostep®, an implantable neurostimulation device designed to restore the mobility and independence of foot drop sufferers.

CAUTION: INVESTIGATIONAL DEVICE, LIMITED BY THE UNITED STATES FEDERAL LAW TO INVESTIGATIONAL USE.

Gait Disorder Resources and Links

The following non-Neurostream links are provided as a courtesy to the user. Please note that Neurostream Technologies G.P. does not monitor these sites and therefore, cannot be held responsible for the accuracy of their content.