Astasia

"Astasia" redirects here. This term was also applied to chlorophyll-less Euglena.

Astasis is a lack of motor coordination 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 in the fact that with astasis the gait 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, 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, 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, which is also called Blocq's disease. It is more common for astasia and abasia to be seen together than it is to see either one or the other.

Paul Oscar Blocq 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's disease". 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 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.

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