Medical assessor guidance note 23

Nervous system impairment: assessment of disturbances of mental status and integrative functioning using the clinical dementia rating

This material is issued by the State Insurance Regulatory Authority (SIRA) under s65(2) of the Motor Accidents Compensation Act 1999 (the Act) in the interests of promoting accurate and consistent medical assessments. The interpretation provided here is not legally binding but represents the clinically recommended interpretation in an area where more than one interpretation of existing provisions may be possible. This recommended interpretation is publically available. Any medical assessment which does not adopt this interpretation should be accompanied by clinical justification for the interpretation adopted, supported by full, robust reasons.


  1. The Permanent Impairment Guidelines – Guidelines for the assessment of permanent impairment of a person injured as a result of a motor vehicle accident 1 October 2007 (PI Guidelines, 2007): Chapter 5 Nervous System Impairment pages 30-34, clauses 5.11- 5.13 and Tables 5.1 and 5.2.
  2. The American Medical Association Guides to the Evaluation of Permanent Impairment, 4th Edition (AMA 4 Guides): Chapter 4 pages 139 to 152 and Table 2.


The PI Guidelines direct that the assessment of Mental Status and Integrative Functioning are assessed according to clauses 5.9 to 5.13.

Clause 5.11 states that:

The assessor should use Table 5.1 of these Guidelines, the Clinical Dementia Rating (CDR) which combines cognitive skills and function.

Clause 5.12 of the PI Guidelines states that:

When using the CDR the individual’s cognitive function for each category should be scored independently. The maximum CDR score is 3. Memory is considered the primary category, the other categories are secondary. If at least three secondary categories are given the same numeric  score as memory then the CDR = M. If three or more secondary categories are given a score greater or less than the memory score, CDR = the score of the majority of secondary categories unless three secondary categories are scored less than M and two secondary categories are scored greater than M. In this case CDR = M. Similarly if two secondary categories are greater than M, two are less than M and one is the same as M, CDR=M.

Issue requiring clarification

According to Table 5.1 Personal Care (PC) the level of impairment is the same for CDR score 0 and CDR score 0.5, being “Fully capable of self care”. However, the method for differentiating between assigning a score of 0 or 0.5 for PC is not outlined and this could affect the final CDR score.

Preferred interpretation

Assessment of impairment:

Medical Assessors should use the following approach when assigning a CDR score for PC (if the impairment level is found to be fully capable of self care).  This approach includes assigning a rating that best fits with the pattern of the majority of other categories.

When the PC rating is “Fully capable of self care” and at least 3 other components of the CDR are scored at 0.5 or higher, the PC should be scored at 0.5. Conversely, if 3 or more ratings are less than 0.5 then a rating of 0 should be assigned. Assessors should exercise their clinical judgment in allocating the appropriate category.

The Medical Assessor should provide reasons to support all ratings allocated and reference the presence and description of all impairment categories.

Justification for preferred interpretation

The preferred interpretation and methodology as outlined above is suggested to promote consistency of assessment.


Injury Strategy Branch
October 2016