There are many speculations as to what is the main cause of astasis. A combination of weakness of the triceps surae muscle, peripheral neuropathy, and irregular postural movements are the leading theories thus far. Diabetes, spinal root or spinal cord lesions, and traumas or injuries to the motor cortex 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, in which patients exhibit symptoms without any neurological cause.

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.

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 abasia: caused by paralysis of the leg muscles

- spastic abasia: caused by spastic stiffening of the leg muscles

- trembling abasia: caused by trembling of the legs

Abasia is frequently accompanied by astasis, an inability to stand, see Astasia-abasia.