Hey, how are you guys? Interesting what the discussion is about. Although the description of the assessment is not complete but you mentioned that rapid head turns causes abnormal gait and loss of balance. my guess is that your client has issues with coordination and disturbances in vestibular function.

i would reassess him for vestibular function and consider vestibular rehabilitation. the good thing is you know provocative factors to this abnormal loss of balance, this is where I would focus my treatment to encourage habituation.

exercises such as standing ...one hand or both on a table then gradually turning head left to right...increasing speed as the client is able to maintain his balance, then progressing to one hand or no hands...regulating speed of head turns as able

i would consider...walking parallel to a wall in a straight line, progressing to walking and turning head left and right

i would consider also, exercises done with eyes closed

but i would assess vestibular function first, looking out for signs of nystagmus and vertigo...

i would add coordination exercises...walking in a straight line, waking in a straight line and moving arms etc