Why upper limb flexion and lower limb extension in a stroke?

Answer 1

The key to understandis the red nucleus situated in the mesencephalon.

These bilateralnucleiinfluence onlythe upper limbs increasing, if working properly, the muscular flexor tone.

Strokes sparing the brainstem, and so the red nuclei,will cause upper limb flexion.By contrast, lesionsinvolving the red nucleus or itsprojectionswill cause upper limb extension.

The lower limbs are not affected by the red nuclei. They undergo just the control of the cortex, that normally inhibits the extensor tone of the lower limbs. A stroke blocking this control will cause lower limbs extension.

Depending on the location, different results are so expected.

Answer 2

Upper limb flexion and lower limb extension are common patterns seen in stroke patients due to the differential involvement of motor pathways in the brain. The upper limb flexion typically results from the loss of inhibitory control from the stroke-affected hemisphere, while the lower limb extension can occur due to spasticity and abnormal reflexes in the lower extremities. These patterns are a result of the disruption in the brain's ability to control movement and are often seen in the acute phase of a stroke.