Astasis is a lack of

motor coordination Motor coordination is the orchestrated movement of multiple body parts as required to accomplish intended actions, like walking. This coordination is achieved by adjusting kinematic and kinetic parameters associated with each body part involved in t ...

marked by an inability to stand, walk or even sit without assistance due to disruption of muscle coordination. The term ''astasia'' is interchangeable with ''astasis'' and is most commonly referred to as ''astasia'' in the literature describing it. Astasis is the inability to stand or sit up without assistance in the absence of motor weakness or sensory loss (although the inclusion of 'the lack of motor weakness' has been debated by some physicians). It is categorized more as a symptom than an actual disease, as it describes a disruption of muscle coordination resulting in this deficit. The disturbance differs from cerebellar

ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...

in that with astasis the

gait Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed, terrain, the need to maneuver, and energetic efficiency. Di ...

can be relatively normal, with balance significantly impaired during transition from a seated to standing position. This balance impairment is similar to patients with

vestibulocerebellar syndrome Vestibulocerebellar syndrome, also known as vestibulocerebellar ataxia, is a progressive neurological disorder that causes a variety of medical problems. Initially symptoms present as periodic attacks of abnormal eye movements but may intensify t ...

, which is a progressive neurological disease with many symptoms and effects. Astasis has been seen in patients with diverse thalamic lesions, predominantly affecting the posterior lateral region of the brain. It is most frequently accompanied by

abasia Abasia (from Greek: ''a-'', without and ''basis'', step) is the inability to walk owing to impairment in motor coordination. The term covers a spectrum of medical disorders such as: * choreic abasia: caused by chorea of the legs * paralytic abas ...

, although not always. Abasia is a symptom very similar to it and is the inability to walk. The two are most commonly seen in

astasia-abasia Astasia-abasia refers to the inability to either stand or walk in a normal manner. Astasia refers to the inability to stand upright unassisted. Abasia refers to lack of motor coordination in walking. The term ''abasia'' literally means that the bas ...

, which is also called

Blocq's disease Blocq's disease was first considered by Paul Blocq (1860–1896), who described this phenomenon as the loss of memory of specialized movements causing the inability to maintain an upright posture, despite normal function of the legs in the bed. T ...

. It is more common for astasia and abasia to be seen together than it is to see either one or the other.

Signs and symptoms

Since astasis itself is more a symptom than a disease, it is more often seen associated with other signs and symptoms. People who have astasis often experience : * Odd gyrations * Tightrope balancing deficits (in which a person attempts to balance on a tightrope in order to test balance and motor coordination) * Near falling deficits (which is a test in which the patient is slightly pushed in order to check their ability to regain posture) * Exaggerated effort deficits (which is an overcompensation test used to determine motor coordination ability) * Atypical postures and weakness *

Paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...

* Jumping fits (in which motor control is partially or totally lost) *

Tremor A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, fa ...

s One study described a patient with astasis as lying in bed with a normal body posture. When the patient was sitting, he tilted his body to the left. When he was asked to stand up, the patient rotated his trunk axis to the left (left shoulder going backwards), and tilted his body to that same side, showing resistance to passive correction of posture in both of these planes. He was unable to stand and fell backwards and towards the left.

Causes

There are many speculations as to what is the main cause of astasis. A combination of weakness of the

triceps surae muscle The triceps surae consists of two muscles located at the calf – the two-headed gastrocnemius and the soleus. These muscles both insert into the calcaneus, the bone of the heel of the human foot, and form the major part of the muscle of the pos ...

peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...

, and irregular postural movements are the leading theories thus far.

Diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...

, spinal root or spinal cord lesions, and traumas or injuries to the

motor cortex The motor cortex is the region of the cerebral cortex believed to be involved in the planning, control, and execution of voluntary movements. The motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately a ...

of the brain can also cause similar symptoms that are seen in patients with astasis. However, none of these have been proven definite. Many scientists also believe that this is a

conversion disorder Conversion disorder (CD), or functional neurologic symptom disorder, is a diagnostic category used in some psychiatric classification systems. It is sometimes applied to patients who present with neurological symptoms, such as numbness, blindness ...

, in which patients exhibit symptoms without any neurological cause.

Peripheral neuropathy

Damage to the peripheral nerves coming from the legs to the

somatosensory area In neuroanatomy, the postcentral gyrus is a prominent gyrus in the lateral parietal lobe of the human brain. It is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch. Like other sensory areas, ...

is the leading candidate for the cause of astasis. These damaged nerves prevent feedback for stabilization of posture for patients with astasis. This causes a disturbance in postural movements, such as a swaying around the legs and hip joints. This swaying may be seen only when a patient in standing still, and may disappear before walking, indicating that these patients exhibit astasia without abasia. This impairment of sensation is not always required for the sensation to develop. However, impairment often worsens astasia.

Weakness of the triceps surae muscle

Weakness of the

has been seen in many patients who have been diagnosed with astasis. This weakness can be caused by a

myopathy In medicine, myopathy is a disease of the muscle in which the muscle fibers do not function properly. This results in muscular weakness. ''Myopathy'' means muscle disease (Greek : myo- ''muscle'' + patheia '' -pathy'' : ''suffering''). This meani ...

to that muscle group. The bilateral triceps surae muscle, made up of the

gastrocnemius The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtalar ...

and the

soleus In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg (the calf). It runs from just below the knee to the heel, and is involved in standing and walking. It is closely connected to the gastrocnemius mu ...

, is essential to maintain a straight posture while standing. This indicates that weakness to this muscle is the cause of the swaying and impaired posture in patients with astasis. This weakness is seen regardless of whether somatosensory feedback from the legs is impaired, suggesting it is one of the main causes of astasia without abasia.

Diabetes

Many patients who suffer from

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...

can have damage to a single nerve or groups of nerves in the body. Some patients experience damage to the nerves coming from the somatosensory area controlling postural stability, which can cause symptoms similar to those seen in patients with astasia. These patients exhibit trouble standing and hip swaying. This damage can be caused by a wide array of things, such as high blood glucose levels, or decreased blood flow to the brain.

Spinal cord/root lesions

Lesions A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...

in the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

or the

spinal root Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolo ...

can cause damage to a nerve or nerve root. Depending on where the abnormality is in a patient they can experience a wide range of symptoms, including those that are found in patients with astasis. It has been seen that patients with spinal atrophy who have astasia without abasia have neither sensory disturbances of the lower limbs or weakness in the hip extensor flexor muscles. This helps to indicate that one of the main causes of astasia without abasia is weakness in the triceps surae muscle.

Other causes

Many other causes for astasia have been reported, such as temporal hypoperfusion in the left hemisphere and posterior cingulate infarction. However, there have only been one or two cases in which these causes have been reported. There has also been one case that reported a patient showing a hemorrhage in the right thalamo-mesencephalic junction. This region involves important structures for the control of postural stability, motor control, ocular movements and vestibulo-ocular integration. This region of the brain is not yet well understood and according to current knowledge, this is the first reported case with the simultaneous combination of astasis, pretectal syndrome, and asymmetrical asterixis.

Diagnosis

Therapy

The most effective treatment of astasia seems to be a removal of stress inducing stimuli and allowing the patient to rest and regain strength. Despite the lack of a direct prescribable cure for the effect of astasia on the motor system of the legs, in almost all documented cases physical rehabilitation and relief from mental stressors have led to a full recovery. Although astasia is not expressly associated with any neurological disorders, due to the efficacy of stressor removal treatment, it is believed that mental illnesses, such as depression, anxiety, as well as acute stressors, are potential factors for development of this condition. Therefore, isolation of the patient from their current stressors has been shown to be the most efficient way to rid them of disabling motor symptoms. Another method for treatment for patients who experience astasia is to have therapy for the triceps surae muscle. This therapy can help strengthen these muscles to help maintain an upright posture. It has also been suggested that

ankle-foot orthoses Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...

be prescribed for these patients. This would help patients with astasia maintain balance by preventing ankle

dorsiflexion Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

. Currently, physical therapy and rehabilitation are widely accepted as the best treatments for the symptoms of astasia. There is, however, evidence to suggest that regulation of a patient's social situation and behavioral influences can influence the effectiveness of rehabilitation. A 1975 study shows that when a patient is given direct encouragement and social distractions, their physical recovery proceeds much faster than when only basic instructions are provided to them.

History

Paul Oscar Blocq Paul Oscar Blocq (1860–1896, page 1.) was a French pathologist who is remembered for his neuropathological work done with Jean-Martin Charcot (1825-1893) and Gheorghe Marinescu (1863-1938) at the Salpêtrière in Paris. Blocq and Marinescu w ...

was the first to describe astasis as the inability to maintain an upright posture despite normal function of the legs while sitting. He recognized that paralysis and other deficits could all be observed along with the syndrome astasia-abasia. Jean-Martin Charcot, Charles Lasègue, and other physicians prior to Blocq's description described astasis as "a special variety of motor feebleness of the legs from want of coordination in standing position.” Astasia-abasia is also known as "

". Blocq is credited with diagnosing the first eleven cases and is credited with inventing the chair test for diagnoses. This test involves each patient first walking for 20–30 feet forward then 20–30 feet backward. The patients were then to sit in a

swivel chair A swivel, spinny, or revolving chair is a chair with a single central leg that allows the seat to rotate 360 degrees to the left or right. A concept of a rotating chair with swivel castors was illustrated by the Nuremberg patrician Martin Löf ...

that had wheels and to push the chair forward and backward. In a follow-up study, these trials were compared with a control group of 9 patients with movement disorders with regard to the gait that were non-psychogenic.

References

{{Reflist, 35em Neurological disorders