SPS will begin insidiously in the axial muscles.

Motor symptoms occur predominantly in distal limb muscles rather than axial muscles.

This abnormal posturing is an extrapyramidal effect and is caused by spasm of the axial muscles along the spinal column.

The anterior horn contains motor neurons that affect the axial muscles while the posterior horn receives information regarding touch and sensation.

Typically the paralysis starts in the pelvic limbs and subsequently ascends to affect the pectoral limbs and then the axial muscles.

Reptile lungs are typically ventilated by a combination of expansion and contraction of the ribs via axial muscles and buccal pumping.

In birds, tendon ossification primarily occurs in the hindlimb, while in ornithischian dinosaurs, ossified axial muscle tendons form a latticework along the neural and haemal spines on the tail, presumably for support.

Additional features include bradykinesia, early-onset postural instability, increased rigidity in axial muscles, dysautonomia, alien limb syndrome, supranuclear gaze palsy, apraxia, involvement of the cerebellum including the pyramidal cells, and in some instances significant cognitive impairment.

Lesions to this area can result in multiple deficits in visual tracking and oculomotor control (such as nystagmus and vertigo), integration of vestibular information for eye and head control, as well as control of axial muscles for balance.