Parkinsonian gait

Parkinsonian gait (or festinating gait, from Latin festinare [to hurry]) is the type of gait exhibited by patients with Parkinson's disease (PD).^[2] It is often described by people with Parkinson's as feeling like being stuck in place, when initiating a step or turning, and can increase the risk of falling.^[3] This disorder is caused by a deficiency of dopamine in the basal ganglia circuit leading to motor deficits. Gait is one of the most affected motor characteristics of this disorder although symptoms of Parkinson's disease are varied.

Parkinsonian gait (indoor)

Parkinsonian gait (outdoor)

Features of PD gait are more obvious in the side view.^[1]

Parkinsonian gait is characterized by small shuffling steps and a general slowness of movement (hypokinesia), or even the total loss of movement (akinesia) in extreme cases.^[4][5][6] Patients with PD demonstrate reduced stride length, walking speed during free ambulation and cadence rate, while double support duration is increased.^{[7][8][9][10]} The patient has difficulty starting, but also has difficulty stopping after starting. This is due to muscle hypertonicity.^[11]

Abnormal gait characteristics

Parkinson's disease patient showing a flexed walking posture pictured in 1892, from Nouvelle Iconographie de la Salpètrière, vol. 5

Patients with Parkinson's disease exhibit gait characteristics that are markedly different from normal gait. While the list of abnormal gait characteristics given below is the most discussed, it is certainly not exhaustive.

Heel to toe characteristics

Whereas in normal gait, the heel strikes the ground before the toes (also called heel-to-toe walking), in Parkinsonian gait, motion is characterised by flat foot strike (where the entire foot is placed on the ground at the same time)^[12] or less often and in the more advanced stages of the disease by toe-to-heel walking (where the toes touch the ground before the heel). In addition, PD patients have reduced foot lifting during the swing phase of gait, which produces smaller clearance between the toes and the ground.^[13]

Patients with Parkinson's disease have reduced impact at heel strike and this mechanism has been found to be related to the disease severity with impact decreasing as the disease progresses. Also, Parkinson patients show a trend towards higher relative loads in the forefoot regions combined with a load shift towards medial foot areas. This load shift is believed to help in compensating for postural imbalance. The intra-individual variability in foot strike pattern is found to be surprisingly lower in PD patients compared with those with a typical gait.^[14]

Vertical ground reaction force

In normal gait, the vertical ground reaction force (GRF) plot has two peaks – one when the foot strikes the ground and the second peak is caused by push-off force from the ground. The shape of the vertical GRF signal is abnormal in PD.^[15][16] In the earlier stages of the disease, reduced forces (or peak heights) are found for heel contact and the push-off phase resembling that of elderly subjects. In the more advanced stages of the disorder where gait is characterized by small shuffling steps, PD patients show only one narrow peak in the vertical GRF signal.^{[citation needed]}

Falls and freezing of gait

Falls and freezing of gait are two episodic phenomena that are common in Parkinsonian gait. Falls and freezing of gait in PD are generally thought to be closely intertwined for several reasons, most importantly: both symptoms are common in the advanced stages of the disease and are less common in the earlier stages, with freezing of gait leading to falls in many instances. Both symptoms often respond poorly and sometimes paradoxically to treatment with dopaminergic medication, perhaps pointing to a common underlying pathophysiology.^[17] It is possible to demonstrate poor and paradoxical dopaminergic medication response through a challenge paradigm in which gait is assessed after withdrawal from medication and in the full ON medication state.^[18]

Freezing of Gait: Freezing of Gait (FOG) is typically a transient episode – lasting less than a minute, in which gait is halted and the patient complains that his/her feet are glued to the ground. When the patient overcomes the block, walking can be performed relatively smoothly. The pathophysiology of the phenomenon is poorly understood but likely extends across a disseminated functional-anatomic network.^[19] Current treatments for FOG offer only limited benefits but a range of novel approaches are being actively explored,^[20] and thought is being given to how future research strategies are best coordinated.^[21]

The most common form of FOG is 'start hesitation' (which happens when the patient wants to start walking) followed in frequency by 'turning hesitation'^[22][23] FOG can also be experienced in narrow or tight quarters such as a doorway, whilst adjusting one's steps when reaching a destination, and in stressful situations such as when the telephone or the doorbell rings or when the elevator door opens. As the disease progresses, FOG can appear spontaneously even in an open runway space.^[17] It is proven that psychological interventions can help reduce negative effect of psychosocial factors, like anxiety or depression, that can worsen freezing of gait or tremor in Parkinson's patients.^[24] Based on that, every patient could benefit from psychological intervention, not only to reduce anxiety, depression, pain, and insomnia, but also to reduce effect of psychosocial factors in worsening of motor symptoms.

Falls: Falls, like FOG are rare in the earlier stages of the disorder and becomes more frequent as the disease progresses. Falls result mainly due to sudden changes in posture, in particular turning movements of the trunk, or attempts to perform more than one activity simultaneously with walking or balancing. Falls are also common during transfers, such as rising from a chair or bed. PD patients fall mostly forward (45% of all falls) and about 20% fall laterally.^[17] Falls that occur frequently very early in the disease course may signify that another diagnosis (such as progressive supranuclear palsy) should be considered.^[25]

Postural sway

Postural instability in upright stance is common in end-stage PD and compromises the ability to maintain balance during everyday tasks such as walking, turning and standing up from sitting. An inability to adequately balance the body's center of mass over the base of support combined with inflexibility in body movements (due to increased rigidity) causes patients with advanced PD to fall. Whereas postural sway in normal stance usually increases in patients with balance disorders arising from stroke, head injury and cerebellar ataxia it is often reduced in patients with PD. This is because in PD, the problem appears to be a lack of flexibility in shifting postural responses. This inflexibility increases the tendency to fall in these patients.^[26][27]

Electromyographic studies

Electromyographic (EMG) studies of the leg muscles in PD patients have shown an extreme reduction in the activation of the tibialis anterior muscle in the early stance and in the early and late swing phases, and a reduction in triceps surae muscle bursting at push-off. The quadriceps and hamstring muscles on the other hand, show prolonged activation in the stance phase of gait.^[28] This implies that PD patients have higher passive stiffness of ankle joints, show larger background EMG activity and more co-contraction of leg muscles in stance. Stiffer joints lead to abnormal postural sway in the PD patients.^[29][30]