María J. García-Rubio, PhD in clinical health psychology, together with Nancy Navarro, specialist in clinical neuropsychology and major cognitive disorder, explain in this article dementia and its neuropsychological assessment through the GDS scale.
This article aims to describe dementia from a neuroanatomical and psychobiological perspective in order to justify the application of the GDS scale during the neuropsychological assessment of patients diagnosed with dementia.
Although it is a validated scale and frequently used by neuropsychologists and other health professionals, it is required to be defined and appropriate to the diagnosis in order to extract the maximum of its evaluative value.
What is dementia?
Dementia is a general term that identifies conditions whose set of signs and symptoms are characterized by a progressive decrease in mental and executive capacity of cognitive domains.
This neurological disease reduces the degree of autonomy and independence of people who suffer from it, thus affecting their ability to perform instrumental activities of daily living and therefore, the patient usually requires continued support from their caregiver (Alzheimer ‘s Association, 2014).
From a psychobiological perspective, nerve cells or neurons are the first to be affected during the evolutionary pattern of dementia, although the key marker is the existence of neurofibrillary tangles, and also the formation of senile plaques observed in cortical dementia (Goriely et al., 2020).
It has also been shown that the presence of cerebral microinfarcts adversely affects the subcortical area of the brain, leading in most cases to the onset of vascular dementia (Bir et al., 2021).
As a consequence, this results in massive destruction of neurons in the cerebral cortex, leading to changes in their structure and function.
At the neuroanatomical level, the development of dementia involves an anatomical pathological process of the brain in which, as a common factor in all types of dementia, the temporal poles are disseminated, with damage also existing in the gray matter of the parietal and prefrontal neocortex, in the case of Alzheimer’s disease and frontotemporal disease (Kang et al., 2019).
Other neurological diseases such as Lewy Body dementia, neuronal damage is more focused in the brainstem regions (Rodriguez, 2020).
What is the neuropsychological assessment of dementia like?
Dementia has been the focus of much research, with the aim of understanding its pathophysiology and physical and cognitive consequences, in most cases. Subsequently, groups and lines of research became interested not so much in the concept but in its evaluation and treatment.
The number of cases with dementia was growing, so there had to be at least one neuropsychological assessment tool to complete the medical protocol dedicated to the approach of the patient with dementia.
The Global Deterioration Scale (GDS)
In 1982 Barry Reisberg and colleagues published an assessment tool now known as the “Global Deterioration Scale or GDS”.
What is the GDS scale?
This instrument aims to provide an alternative neuropsychological measure for each neurodegenerative stage associated with dementia.
Thus, it takes into account cognitive ability specifically, executive function, attentional and memory processes, from the onset of the first characteristics of cognitive impairment until its last stage (Custodio et al., 2017).
In turn, the GDS scale takes into account the limits of each evolutionary stage of dementia that follow each other as a slow and continuous process. With these characteristics, the GDS scale aims to provide guidance support to professionals, neuropsychologists or other healthcare professionals working with patients diagnosed with dementia.
According to Reisberg et al. (1999), the concept of retrogenesis is a fundamental basis for the development of the scale, as it explains that the course of dementia is accompanied by a reduction in cognitive ability.
Moreover, the decrease in cognition is completely inverse to the process of learning acquisition that is achieved from childhood and adulthood, which is reflected not only in higher cognitive processes but also in brain development (Strikwerda-Brown et al., 2019).
For example, the person with a diagnosis of dementia may initially lose information from short-term memory, in intermediate stages will have problems with access to long-term memories, while in the final stages will be unable to control physiological processes that are acquired in early childhood such as autonomy for feeding or sphincter control.
GDS scale stages
The original version of the GDS scale by Reisberg et al. (1982) includes 7 stages linked to the development of dementia. Thus, each of them explains the alteration corresponding to the physical, cognitive and mental course of the disease.
Also, the description of cognitive status by stage is accompanied by an approximate rating in the minimental (MEC) of Lobo et al. (1999) in order to link both instruments in the same patient. The following is a brief review of each of them and their scores:
- GDS 1. Absence of cognitive deficit. In this phase the person shows no impairment at subjective or objective level, which means that he/she presents an ideal state at cognitive level. It corresponds to a score of 30-35, in the MEC evaluation.
- GDS 2. Very mild cognitive deficit. During this period the person presents complaints regarding memory with respect to the misplacement of objects or forgetfulness of names that usually go unnoticed in the family, work and social environment. At the same time, no cognitive deficit is objected by clinical examination. It corresponds to a score of 25-30 in the MEC evaluation.
- GDS 3. Mild cognitive deficit. Changes are observed in the performance of occupational, labor and social tasks such as: semantic difficulty, decrease in retaining new information or remembering new people already known, forgetfulness in spatial location, decreased concentration. It may be accompanied by moderate anxiety. Corresponds to a score of 20-27 on the MEC assessment.
- GDS 4. Moderate cognitive deficit. The person presents difficulty in elaborating tasks with respect to planning aspects such as: finances, cooking, travel, calculation operations. At the same time, the location in time and person, recent events, possible prosopagnosia and emotional lability are diminished. It corresponds to a score of 16-23 in the MEC evaluation.
- GDS 5. Moderately severe cognitive deficit. In this stage, the person’s executive capacity decreases in the following activities: choice of clothing, remembering addresses, telephones, names of relatives, however, he/she recognizes his/her own name and that of his/her closest family. Corresponds to a score of 10-19 on the MEC assessment.
- GDS 6. Severe cognitive deficit. For this stage, the person needs support to perform instrumental activities of daily living, such as dressing, bathing, remembering names of close family or caregivers. It may also show decreased urinary continence, personality and affective changes. Corresponds to a score of 0-12 on the MEC assessment.
- GDS 7. Very severe cognitive deficit. The person at this stage presents loss of verbal and motor skills such as walking without help, sitting, standing up and keeping the head upright. Loss of smile. He/she needs assistance for personal hygiene. Neurological signs are observed. Corresponds to a score of 0 on the MEC assessment.
Clinical applicability of the GDS scale
As anticipated, the GDS scale has the particularity of complementing cognitive assessment instruments, such as the MEC, increasing the evaluative potential of these cognitive screening tools in a neurological disease as complex as dementia (Peña-Casanova et al., 2014).
Moreover, this potential is more relevant in advanced stages of dementia in which there is great individual variability among patients. Therefore, it is so important to have tools such as the GDS scale, as it fulfills the function of guiding the evolutionary process of dementia for the professional responsible for the patient.
Thus, based on the deterioration indicated by the GDS scale, the professional can establish new intervention guidelines adapted to the characteristics of the patient’s stage of dementia, as well as design other support strategies according to the needs of daily living, care and treatment.
It should also be noted that although the application of the GDS scale has been properly associated with Alzheimer’s disease due to its progressive evolution, this neuropsychological screening tool can be applied to other cases such as Lewy Body disease or vascular dementia (Sousa et al., 2020).
The GDS scale has proven to be valid and reliable for the specification of the evolutionary process of dementia, especially for its ability to differentiate and describe the course and progression of the disease with clinical observations. In addition, it is associated with other clinical implications such as improved patient prognosis from new and individualized intervention plans.
In fact, GDS scores not only serve to determine the degree of cognitive impairment, but also to optimize therapeutic decision-making and pharmacological choices necessary to contribute to the improvement of the quality of life of these patients.
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