CNR - Institute of Neuroscience CNR
Institute of Neuroscience
 

Project

Pain perception in the cognitively impaired older patients

Background

In modern pathophysiogical terms, pain corresponds to an "unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage" (Merskey, 1986). The experience of pain is the result of a complex integration of sensorial, cognitive and affective processes. Several studies have found a reduction in complaints concerning painful experiences - both with regards to intensity and frequency – and a diminished prescription of analgesics subjects with dementia. The results of studies reviewed show that, although the subtypes of dementia show common neuropathological features (such as atrophy and white matter lesions), the degree by which they occur and affect pain-related pathways and area, determine the pattern of changes in pain experience.

More specifically, in Alzheimer's Disease (AD) and even more so in frontotemporal dementia, a decrease in the motivational and affective components of pain is generally present, whereas vascular dementia might be characterised by an increase in affective pain experience. AD prevalently strikes the neocortex involved in the elaboration of the emotional-motivational component, leaving intact the somatosensory cortex, which is involved in the elaboration of the sensory-discriminative component. Benedetti et al.,(1999) has found a detection capacity and pain threshold within the normal range but an increased pain tolerance level in subjects with AD. But there are also other factors that could affect the pain experience in people with AD such as the progressive lose of the capacity to communicate and the mnesic deficit. Pain assessment and treatment, particularly for those with cognitive impairment and altered communication skills, constitute a major problem in geriatric medicine. The main questions that must be answered is how people with dementia experience pain. The major problem is represented by the assessment tools. In clinical settings most commonly used tools for measuring the subjective nature of pain are scales that measure the perceived pain. The Evoked Potentials are currently the most reliable assessment tools for the study of pain: potential evoked by pain are part of Somatosensorial Evoked Potentials (SEPs). Two cortical components that are particularly relevant to the pain have been identified, they correlate significantly with the self-assessments of subjects and are specifically attenuated by analgesics: a negative wave that appears at about 150 msec after the onset of the stimulus followed by a positive peak that appears at about 260 msec after the onset of the stimulus. The N150 and the P260, considered long latency components, depend on the activated sensory channel, on the neuronal distance to be conducted, on body area and fiber spectra stimulated but especially on the arousal level of the subject, on his vigilance, on attention and distraction. These two components are usually more pronounced in frontal areas and in associative temporo-parietal cortex, important areas for the interpretation, the modulation and control of pain. The P260 can be considered an index of cognitive evaluation of painful stimuli.

Aims of the project

Firstly, to quantify through SEPs, the experience of pain in patients with AD and in elderly subjects without cognitive deterioration; secondly, to evaluate possible differences between the psychophysiological response patterns in elderly patients without cognitive deficits and in subjects with AD.

Methodology

Participants were recruited from physicians working in a Nursing Home in Padua. After signing the informed consent, all subjects were examined by a trained neuropsychologist who administered a large set of neuropsychological tests. The experimental group consisted of 10 people with diagnosis of probable AD whereas the control group consisted of 17 elderly subjects with no cognitive deterioration. All participants were aged over 65 years. The study was approved by the Ethical Committee. Psychophysiological evaluation ( see Figure 1) included measurements of three threshold of pain (mechanical / thermic / electrical) and recording of evoked potentials of pain. In particular, three components have been identified and analyzed: the P100 and the N150, related to the discriminative-sensorial elaboration; and the P260 related to the affective-cognitive processing of pain. For each of the three components latency and amplitude were analyzed.

Psychophysiological procedure

 
 

Results

  1. No significant differences were found in thresholds between the healthy elderly group and the AD patients. Both groups discriminate painful stimuli in an adequate and similar way.
  2. With regards to the P100 and N150 components, no differences were found in the amplitude or in the latency between the two groups.
  3. An analysis of the positive P260 component has shown a significant Group Effect and a significant Condition Effect.

Grants

Grant: 70,000.00 from Pfizer SpA

 

no PI photo

Federica Limongi

Contact information

email  E-mail

email  049 8218898

Participating staff

Stefania Maggi

Marianna Noale

Paola Siviero