Why are some people who do not reach the Westmead PTA Scale's criteria pronounced out of PTA ?

Remember, the Westmead PTA Scale is a clinical research tool to aid in the determination of the length of PTA and for some patients it may not be appropriate (see the sections on Who to Test and Alternative Explanations). Therefore, the Clinical Neuropsychologist can choose to use a clinical estimate of the length of PTA.

How long do we have to test patients if there appears to be no change in their score - for example, the patient always scores 6 and has never reached 12 out of 12 ?

'We believe it is not unreasonable to ask that the PTA examiner continue to test a patient for 3 months on the scale when they find that the patient's score has reached a plateau.'