Pain and Dementia

Question 1

Statistic of older people experiencing pain?

Answer 1

Above 85years = 70%

Question 2

Which studies support reduced pain processing in AD?

Answer 2

1. Study in the lecture by Benedetti, 1999 shows that patients with AD have normal stimulus detection and pain thresholds - but much lower pain tolerance (measured as the point where pain becomes ‘unbearable’. This correlated with EEG measurements and mini-mental state examination measures of cognitive impairment. However, the experiment relies on verbal report for all three measures. However, more recent studies have found that verbal reports may only be appropriate in early stages of cognitive impairment where individuals can still recognize and verbalize pain. Other studies relying on the verbal report have found entirely contradictory findings. Measurements which rely on reflexive withdrawal from pain stimulus report reduced thresholds indicating increased spinal processing. Most findings are also only representative of mild-moderately impaired patients, due to an ethical dilemma in inducing experimental pain in severely cognitively impaired individuals.
2. Clinical findings show that AD patients in nursing homes are prescribed less analgesics than compos mentis residents. However, people with AD commonly suffer from comorbid conditions associated with pain.
3. TASTPM (crossbreed of two strains of AD mutation) show reduced sensitivity to thermal heat as measured by withdrawal reflex, increased endogenous enkephalin expression. Normal sensitivity is restored by naloxone.

Question 3

What is the effect of AD on pain report?

Answer 3

Ability of AD patients to correctly complete visual analogue scales such as the VAS scale declines with degree of cognitive impairment

Question 4

How can pain be alternatively measured in AD patients?

Answer 4

As opposed to measuring pain report, pain response can instead be measured. This can be done using

• Facial expression
• Nociceptive flexion reflex. This is a reflex response that indirectly measures spinal processing of pain signals
• Autonomic e.g., heart rate, skin conductance
• Brain responses

Question 5

What do facial expression reveal about patients with AD?

Answer 5

Most studies find that patients with AD show increase facial responses to pain. This may mean that they have an augmented pain processing, or just that they have an increased tendency for facial expression

Question 6

What do nociceptive flexion reflexes reveal about patients with AD?

Answer 6

This measure has been shown to correlate highly with pain thresholds for cognitively normal patients.
One study has used this measure in patients with AD, finding that the threshold was significantly decreased. This may indicate increased spinal pain processing in AD.

Question 7

What do fMRI studies reveal about AD patients?

Answer 7

They reveal similar activations in response to pain, and possibly even increased in some pathways. However these types of studies should be taken with a pinch of salt, because evidence for pain specific processing regions and activations of the brain are controversial and many people believe that the supposed ‘pain matrix’ is more of stimulus salience matrix in general.

One study has shown that in an advanced subgroup of dementia patients, pain-evoked potentials were unable to be produced. It is important to remember that many experimental studies reflect that of mild to moderate populations, due to ethical issues with invoking pain in advanced groups.

Question 8

What do autonomic responses reveal about AD patients?

Answer 8

Studies show a decline in autonomic responses to pain for AD patients. However, even in early stages dementia is associated with decline in autonomic responses, possibly due to loss of cholingeric central processing. Autonomic responses may not be appropriate measures of pain in AD.

Question 9

What is known about the placebo response in AD patients?

Answer 9

Studies have shown that there is a loss of placebo analgesia in AD patients, which occurs when prefontal connectivity to other brain regions is lost. Placebo effect is mediated by descending inhibitory control, which may therefore be reduced in AD. Alongside this, placebo analegesia has been shown to be mediated by same receptors as opioid drugs - therefore loss of sensitivity in this system may be occuring. This could lead to a need for a higher dose of analgesic. This is confounded by potential adverse effects, however.