Gray matter volumes of pain-related brain areas are decreased in fibromyalgia syndrome

Advances in functional neuroimaging in dementias and potential pitfalls

Neuroimaging is continuously advancing at a rapid rate and has progressed from excluding relatively uncommon secondary causes (stroke, tumor) to assisting with early diagnosis and subtype of dementia. Structural imaging has given way to functional, metabolic and receptor imaging.

Abnormal gray matter aging in chronic pain patients

Widespread brain gray matter (GM) atrophy is a normal part of the aging process. However, recent studies indicate that age-related GM changes are not uniform across the brain and may vary according to health status. Therefore the aims of this study were to determine whether chronic pain in temporomandibular disorder (TMD) is associated with abnormal GM aging in focal cortical regions associated with nociceptive processes, and the degree to which the cumulative effects of pain contributes to age effects. We found that patients have accelerated whole brain GM atrophy, compared to pain-free controls. We also identified three aberrant patterns of GM aging in five focal brain regions: 1) in the thalamus, GM volume correlated with age in the TMD patients but not in the control group; 2) in the anterior mid- and pregenual cingulate cortex (aMCC/pgACC), the TMD patients showed age-related cortical thinning, whereas the controls had age-related cortical thickening; and 3) in the dorsal striatum and the premotor cortex (PMC). Interestingly, the controls but not the patients showed age-related GM reductions. Finally, a result of particular note is that after accounting for the effects of TMD duration, age remained as a significant predictor of GM in the PMC and dorsal striatum. Thus, abnormal GM aging in TMD may be due to the progressive impact of TMD-related factors in pain-related regions, as well as inherent factors in motor regions, in patients with TMD. This study is the first to show that chronic pain is associated with abnormal GM aging in focal cortical regions associated with pain and motor processes.

Lacosamide for neuropathic pain and fibromyalgia in adults

BACKGROUND

Antiepileptic drugs have been used in pain management since the 1960s; some seem to be especially useful for neuropathic pain. Lacosamide is an antiepileptic drug that has recently been investigated for neuropathic pain relief, although it failed to get approval for painful diabetic peripheral neuropathy from either the Food and Drug Administration or the European Medicines Agency.

OBJECTIVES

To evaluate the analgesic efficacy and adverse effects of lacosamide in the management of chronic neuropathic pain or fibromyalgia.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register (2011, Issue 4), CENTRAL (2011, Issue 3), MEDLINE (January 2000 to August 2011) and EMBASE (2000 to August 2011) without language restriction, together with reference lists of retrieved papers and reviews.

SELECTION CRITERIA

We included randomised, double-blind studies of eight weeks duration or longer, comparing lacosamide with placebo or another active treatment in chronic neuropathic pain or fibromyalgia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data for efficacy and adverse events and examined issues of study quality, including risk of bias assessments. Where possible, we calculated numbers needed to treat to benefit from dichotomous data for effectiveness, adverse events and study withdrawals.

MAIN RESULTS

We included six studies; five (1863 participants) in painful diabetic neuropathy (PDN) and one (159 participants) in fibromyalgia. All were placebo-controlled and titrated to a target dose of 200 mg, 400 mg or 600 mg lacosamide daily, given as a divided dose. Study reporting quality was generally good, although the imputation method of last observation carried forward used in analyses of the primary outcomes is known to known to impart major bias where, as here, adverse event withdrawal rates were high. This, together with small numbers of patients and events for most outcomes at most doses meant that most results were of low quality, with moderate quality evidence available for some efficacy outcomes for 400 mg lacosamide.There were too few data for analysis of the 200 mg dose for painful diabetic neuropathy or any dose for fibromyalgia.In painful diabetic neuropathy, lacosamide 400 mg provided statistically increased rates of achievement of "moderate" and "substantial" benefit (at least 30% and at least 50% reduction from baseline in patient-reported pain respectively) and the patient global impression of change outcome of "much or very much improved". In each case the extra proportion benefiting above placebo was about 10%, yielding numbers needed to treat to benefit compared with placebo of 10 to 12. For lacosamide 600 mg there was no consistent benefit over placebo.There was no significant difference between any dose of lacosamide and placebo for participants experiencing any adverse event or a serious adverse event, but adverse event withdrawals showed a significant dose response. The number needed to treat to harm for adverse event withdrawal was 11 for lacosamide 400 mg and 4 for the 600 mg dose.

AUTHORS' CONCLUSIONS

Lacosamide has limited efficacy in the treatment of peripheral diabetic neuropathy. Higher doses did not give consistently better efficacy, but were associated with significantly more adverse event withdrawals. Where adverse event withdrawals are high with active treatment compared with placebo and when last observation carried forward imputation is used, as in some of these studies, significant overestimation of treatment efficacy can result. It is likely, therefore, that lacosamide is without any useful benefit in treating neuropathic pain; any positive interpretation of the evidence should be made with caution if at all.

Vitamin D deficiency in women with fibromyalgia in Saudi Arabia

BACKGROUND

The relation between low levels of 25-hydroxyvitamin D and nonspecific musculoskeletal pain, including fibromyalgia syndrome, is debatable. Many studies have reported "a positive relation" and others "found no relation."

OBJECTIVES

To determine the prevalence of vitamin D deficiency among patients with fibromyalgia in a neurology clinic in the Kingdom of Saudi Arabia (KSA).

METHODS

This study was done at a neurology clinic of Bugshan Hospital, Jeddah, KSA, from January to April 2011. Thirty female patients were diagnosed with fibromyalgia according to new clinical fibromyalgia diagnostic criteria; their serum vitamin D levels were screened. Vitamin D deficiency is defined as <20 ng/mL, vitamin D insufficiency is defined as 21-29 ng/mL, and vitamin D sufficiency is equal to or >30 ng/mL.

RESULT

Thirty female patients were included in the study. The mean age was 34.56 ± 8.1 years. Mean vitamin D level was 4.76 ± 1.46 ng/mL. A significant negative correlation between vitamin D level and widespread pain index was found. Thirty percent of the patients were Saudi Arabian of whom 100% were veiled; 70% were non-Saudi Arabian of whom 47.6% were veiled and 52.4% wore long pants and/or full sleeved clothes. Vitamin D deficiency was equally prevalent among veiled (4.77 ± 1.37 ng/mL) and nonveiled (4.75 ± 1.68 ng/mL). Treatment with high-dose vitamin D resulted in clinical improvement in all patients.

CONCLUSION

Vitamin D deficiency is often seen in patients diagnosed with fibromyalgia in our population. This was equally true in veiled and nonveiled, but conservatively dressed populations. Effective treatment with high-dose vitamin D could lead to resolution of almost all symptoms. Further study of these populations and fortification of foods with vitamin D may be essential.

Strategy-dependent dissociation of the neural correlates involved in pain modulation

BACKGROUND

Cognitive strategies are a set of psychologic behaviors used to modulate one's perception or interpretation of a sensation or situation. Although the effectiveness of each cognitive strategy seems to differ between individuals, they are commonly used clinically to help patients with chronic pain cope with their condition. The neural basis of commonly used cognitive strategies is not well understood. Understanding the neural correlates that underlie these strategies will enhance understanding of the analgesic network of the brain and the cognitive modulation of pain.

METHODS

The current study examines patterns of brain activation during two common cognitive strategies, external focus of attention and reappraisal, in patients with chronic pain using functional magnetic resonance imaging.

RESULTS

Behavioral results revealed interindividual variability in the effectiveness of one strategy versus another in the patients. Functional magnetic resonance imaging revealed distinct patterns of activity when the two strategies were used. During external focus of attention, activity was observed mainly in cortical areas including the postcentral gyrus, inferior parietal lobule, middle occipital gyrus, and precentral gyrus. The use of reappraisal evoked activity in the thalamus and amygdala in addition to cortical regions. Only one area, the postcentral gyrus, was observed to be active during both strategies.

CONCLUSIONS

The results of this study suggest that different cognitive behavioral strategies recruit different brain regions to perform the same task: pain modulation.

Neurobiology underlying fibromyalgia symptoms

Fibromyalgia is characterized by chronic widespread pain, clinical symptoms that include cognitive and sleep disturbances, and other abnormalities such as increased sensitivity to painful stimuli, increased sensitivity to multiple sensory modalities, and altered pain modulatory mechanisms. Here we relate experimental findings of fibromyalgia symptoms to anatomical and functional brain changes. Neuroimaging studies show augmented sensory processing in pain-related areas, which, together with gray matter decreases and neurochemical abnormalities in areas related to pain modulation, supports the psychophysical evidence of altered pain perception and inhibition. Gray matter decreases in areas related to emotional decision making and working memory suggest that cognitive disturbances could be related to brain alterations. Altered levels of neurotransmitters involved in sleep regulation link disordered sleep to neurochemical abnormalities. Thus, current evidence supports the view that at least some fibromyalgia symptoms are associated with brain dysfunctions or alterations, giving the long-held “it is all in your head” view of the disorder a new meaning.

The development and psychometric validation of the central sensitization inventory

Central sensitization (CS) has been proposed as a common pathophysiological mechanism to explain related syndromes for which no specific organic cause can be found. The term "central sensitivity syndrome (CSS)" has been proposed to describe these poorly understood disorders related to CS. The goal of this investigation was to develop the Central Sensitization Inventory (CSI), which identifies key symptoms associated with CSSs and quantifies the degree of these symptoms. The utility of the CSI, to differentiate among different types of chronic pain patients who presumably have different levels of CS impairment, was then evaluated. Study 1 demonstrated strong psychometric properties (test-retest reliability = 0.817; Cronbach's alpha = 0.879) of the CSI in a cohort of normative subjects. A factor analysis (including both normative and chronic pain subjects) yielded 4 major factors (all related to somatic and emotional symptoms), accounting for 53.4% of the variance in the dataset. In Study 2, the CSI was administered to 4 groups: fibromyalgia (FM); chronic widespread pain without FM; work-related regional chronic low back pain (CLBP); and normative control group. Analyses revealed that the patients with FM reported the highest CSI scores and the normative population the lowest (P < 0.05). Analyses also demonstrated that the prevalence of previously diagnosed CSSs and related disorders was highest in the FM group and lowest in the normative group (P < 0.001). Taken together, these 2 studies demonstrate the psychometric strength, clinical utility, and the initial construct validity of the CSI in evaluating CS-related clinical symptoms in chronic pain populations.