The most common diseases causing cognitive impairment include Alzheimer's disease, dementia with Lewy bodies, and vascular dementia. There are also dementias that can be cured or ameliorated through the treatment of the underlying diseases. In the field of neurosurgery, representative underlying diseases are normal pressure hydrocephalus, chronic subdural hematoma, and brain tumors. Another treatable dementia somewhat unfamiliar to neurosurgeons is cognitive impairment caused by endocrine disorders. Such cognitive impairment caused by abnormalities in the hypothalamus-pituitary axis, thyroid gland, adrenal gland, and gonadal system can be improved by appropriate adjustment of the endocrine environment. Detailed examination of endocrine function is also essential in dementia treatment.

Purpose: We organized the methods for calculating the global score (GS) of the clinical dementia rating (CDR) and clarify the points to be noted when using publicly available calculators for calculating GS.

Methods: We investigated and organized the literature on the methods for GS calculation. We examined specific issues of the two calculators.

Results: There are two main rules for calculating GS set, one proposed by Morris and the other by Gelb. It is necessary to clarify which method is the basis for calculating GS. Note that the calculator from the National Alzheimer's Coordinating Centre (NACC) gives different results from the rules set by Morris.

Conclusion: Although the use of CDR is becoming essential in clinical practice, care must be taken when calculating GS. We have developed our own calculator and would like many people to use it.