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Hypokinesia refers to decreased bodily movement. One of the two categories of movement disorders, hypokinesia is characterized by a partial or complete loss of muscle movement due to a disruption in the basal ganglia. Patients with hypokinetic disorders like Parkinson’s Disease experience muscle rigidity and an inability to produce movement. It is also associated with mental health disorders and prolonged inactivity due to illness, amongst other diseases.

The other category of movement disorder resulting from damage to the basal ganglia, hyperkinesia, features an exaggeration of unwanted motion, like twitching or writhing in Huntington’s disease or Tourette's Syndrome.

Spectrum of Disorders
Hypokinesia describes a variety of more specific disorders:



Neurobiology
Hypokinetic symptoms arise from damage to the basal ganglia, which plays a role in producing force and computing the effort necessary to make a movement. There are two possible neural pathways enabling the basal ganglia to produce movement. When activated, the direct pathway sends sensory and motor information from the cortex to the first structure of the basal ganglia, the putamen. That information directly inhibits the globus pallidus internal and allows free movement. The indirect pathway, traveling through the putamen, globus pallidus external, and subthalamic nucleus, activates the globus pallidus internal threshold and inhibits the thalamus from communicating with the motor cortex, producing hypokinetic symptoms.

When levels of dopamine decrease, the normal wave firing pattern of basal ganglia neural oscillations changes and the tendency for oscillations increases, particularly in the beta wave of the basal ganglia. Recent research indicates that when oscillations fire simultaneously, processing is disrupted at the thalamus and cortex, affecting activities such as motor planning and sequence learning as well as causing hypokinetic tremors.

Treatments
Treatment for Parkinson’s Disease has involved the surgical destruction of the globus palidus internal, effectively activating the direct pathway in the basal ganglia and allowing for greater possibilities for muscle movement.

Dopaminergic Drugs
Some Parkinson's patients are unable to move during sleep, prompting the diagnosis of "nocturnal hypokinesia." Physicians have experienced success treating this sleep disorder with slow-release or night-time dopaminergic drugs, and in some cases, continuous stimulation by the dopamine agonist rotigotine. Despite improved mobility during sleep, many Parkinson's patients report an extremely uncomfortable sleeping experience even after dopaminergic treatments.

Deep Brain Stimulation
Posteroventral pallidotomy (PVP) is a specific kind of deep brain stimulation that destroys a small part of the globus pallidus by scarring the neural tissue, reducing brain activity and therefore tremors and rigidity. It is suspected that PVP recalibrates basal ganglia activity in the thalamocortical pathway. PVP in the dominant hemisphere has been reported to disrupt executive function verbal processing abilities, and bilateral PVP may disturb processes of focused attention.



Many akinesia patients also form a linguistic akinesia in which their ability to produce verbal movements mirrors their physical akinesia symptoms, especially after unsuccessful PVP deep brain stimulation. Patients are usually able to maintain normal levels of fluency, but often stop mid-sentence, unable to remember or produce a desired word. According to a study of Parkinson's patients with articulatory hypokinesia by Caligiuri (1989), subjects with faster rates of speech experienced more problems trying to produce conversational language than those who normally spoke at slower rates.

Stem Cells
New treatments include increasing the number of dopamine cells by transplanting stem cells into the basal ganglia or stimulating endogenous stem cell production and movement to the basal ganglia. The successful integration of stem cells can relieve hypokinetic symptoms and decrease the necessary dosage of dopaminergic drugs. However, a variety of complications, including possible tumor formation, inappropriate cell migration, rejection of cells by the immune system and cerebral hemorrhage are possible, causing many physicians to believe that the risks outweigh the possible benefits.

Symptoms
Stress causes alterations of cerebral circulation, increasing blood flow in the supramarginal gyrus and angular gyrus of the parietal lobe, the frontal lobe and in the superior temporal gyrus of the left hemisphere. There is also an increase in cardiac activity and change in the tonus of the heart vessels, which is an elementary indication of stress development. In patients with normal stress, an adaptive fight-or-flight response is usually triggered by sympathetic nervous system activation. Hypokinesia patients experience these typical stress symptoms on a regular basis because of damage to the basal ganglia system. Therefore, when a hypokinesia victim is under stress, he or she does not display a typical fight-or-flight response, placing the patient under greater danger from potentially harmful stimuli. Low-impact exercise, elimination of drug and alcohol use, and regular meditation can help to restore normal stress responses in hypokinesia patients.

Connections to Other Medical Conditions
Though it is often most associated with Parkinson's disease, hypokinesia can be present in a wide variety of other conditions.