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The Hands-On Evaluation - Postural Reactions

Postural Reactions

The primary aim of postural reaction testing is to detect subtle deficits that were not obvious on gait evaluation.  In a patient which is recumbent with tetraplegia or paraplegia, evaluation of the postural reactions in the affected limbs is redundant.  However, evaluation of the thoracic limbs' postural reactions in a paraplegic patient will be important to detect an abnormality that could suggest a focal cranial thoracic lesion or a multifocal disorder. 

The postural reactions test the animal’s awareness of the precise position and movements of parts of its body and especially the limbs as well as the animal’s ability to generate movement in the part tested.  

How to perform

The postural reactions commonly tested are:

Paw placement:  evaluated by placing the paw in an abnormal position (turned over so that the dorsal surface is in contact with the ground) and determining how quickly the animal corrects the paw position.  It is fundamental to support the majority of the animal’s weight to improve test sensitivity. Paw replacement reaction can be very difficult to assess in cats that resent having their feet handled during this test.  Other postural reaction tests such as hopping, wheelbarrowing, and tactile placing are preferred in this species and should be considered in animals in which the paw placement reaction is equivocal or difficult to interpret.  

Thoracic limb paw placement

Pelvic limb paw placement

Hopping:  tested by holding the patient so that the majority of its weight is placed on one limb while the animal is moving laterally.  Normal animals hop on the tested limb to accommodate a new body position as their center of gravity is displaced laterally. 

Thoracic limb hopping

Pelvic limb hopping

Wheelbarrowing: the animal’s pelvic limbs are lifted off the ground by supporting the animal under the abdomen and forcing it to walk forward.  

Tactile placing response:  the animal is lifted and the distal part of the thoracic limb is brought in contact with the edge of a table while an attempt to visually impair the dog is made (cover up eyes with the hand).  When the dorsal surface of the paw makes contact with the edge of the surface, the animal should immediately place its foot on the surface

Normal tactile placing

Removing the visual impairment allows for testing of the role of vision in placing and is tested by bringing the animal to the table again and watching for the response of the front limbs before they touch the sides of the table.

Normal visual placing

How to interpret

Multiple components of the peripheral and central nervous system that affect limb function are tested with postural reactions.  These responses are complex in their pathways but generally involve an afferent arc 1) joint proprioceptor, 2) peripheral sensory nerve, 3) spinal cord and brainstem ascending pathways, 4) contralateral forebrain – and an efferent arc 1) contralateral forebrain, 2) descending motor pathways within the brainstem and spinal cord, 3) peripheral motor nerve and skeletal muscle.   Further information on the anatomical pathways involved in these tests can be found on our clinical neuroanatomy page.

Lesions affecting any of these components could potentially result in abnormal postural reactions.  Although these reactions are sensitive tests to detect neurological dysfunction, they do not provide specific information for lesion localization.  Their importance in localizing the lesion is dependent on the results of the rest of the neurologic examination.  In general, postural reactions remain normal in neuromuscular diseases as long as the animal has the strength to support its weight. 

For a more in-depth functional neuroanatomy review of postural reactions, head over to our neuroanatomy pages.

Abnormal paw placement - while the body weight is supported in this dog, there is a failure to return the paw to its normal position in both pevlic limbs.

Abnormal tactile placing - note in this cat, the asymmetrical reduced response to this test in the thoracic limbs

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