I know it’s a bit gauche to name a test after oneself, but I’ve grown fond of a sensory/COR version of the Parks Three Step for cyclovertical motor anomalies and what the heck – Press is also a name with five letters that begins with “P” and ends with “S”, so let’s have a go at it.
This is a patient who I evaluated yesterday. His leftward habitual head tilt is rather obvious, but he has no discernible hyper deviation on primary gaze with cover testing when he holds his head straight. The sensory test using a three step is conducted using a Worth-4-Dot or similar target in the same way the motor there step is done, but in this instance we’re using diplopia as the key variable rather than hyperdeviation.
The patient fuses in primary gaze, seeing only one circle at the bottom.
Step 1: Compare fusion on head tilt to the left vs. right shoulder
Step 2: Compare fusion on head rotation to the right vs. left
Step 3: Compare fusion on chin-up vs. chin-down position
A negative response is the patient reporting a lustrous single circle in all three planes of rotation, oblique, horizontal, and vertical. A positive response is diplopia in any plane of head rotation. Typically the patient’s habitual head tilt or face turn is in the field of action that adaptively improves fusion, so if the patient habitually tilts toward the left shoulder, a forced tilt to the right of equal or greater magnitude will elicit diplopia.
I refer to this as a sensory/COR analog of the Parks Three Step because the Parks only activates head and neck reflexes in its third step. I’ll elaborate on the significance of the COR (Cervico-Ocular Reflex) in this context in Part 2, which is particularly relevant for patients with a history of torticolis as well as patients with a history of mTBI/whiplash.