Spectrum of cutaneous hyperalgesias/allodynias in neuropathic pain patients

A Korean nationwide investigation of the national trend of complex regional pain syndrome vis-à-vis age-structural transformations

Background

The present study employed National Health Insurance Data to explore complex regional pain syndrome (CRPS) updated epidemiology in a Korean context.

Methods

A CRPS cohort for the period 2009-2016 was created based on Korean Standard Classification of Diseases codes alongside the national registry. The general CRPS incidence rate and the yearly incidence rate trend for every CRPS type were respectively the primary and secondary outcomes. Among the analyzed risk factors were age, sex, region, and hospital level for the yearly trend of the incidence rate for every CRPS. Statistical analysis was performed via the chi-square test and the linear and logistic linear regression tests.

Results

Over the research period, the number of registered patients was 122,210. The general CRPS incidence rate was 15.83 per 100,000, with 19.5 for type 1 and 12.1 for type 2. The condition exhibited a declining trend according to its overall occurrence, particularly in the case of type 2 (P < 0.001). On the other hand, registration was more pervasive among type 1 compared to type 2 patients (61.7% vs. 38.3%), while both types affected female individuals to a greater extent. Regarding age, individuals older than 60 years of age were associated with the highest prevalence in both types, regardless of sex (P < 0.001).

Conclusions

CRPS displayed an overall incidence of 15.83 per 100,000 in Korea and a declining trend for every age group which showed a negative association with the aging shift phenomenon.

Complex regional pain syndrome and functional neurological disorders - time for reconciliation

There have been many articles highlighting differences and similarities between complex regional pain syndrome (CRPS) and functional neurological disorders (FND) but until now the discussions have often been adversarial with an erroneous focus on malingering and a view of FND as 'all in the mind'. However, understanding of the nature, frequency and treatment of FND has changed dramatically in the last 10-15 years. FND is no longer assumed to be only the result of 'conversion' of psychological conflict but is understood as a complex interplay between physiological stimulus, expectation, learning and attention mediated through a Bayesian framework, with biopsychosocial predisposing, triggering and perpetuating inputs. Building on this new 'whole brain' perspective of FND, we reframe the debate about the 'psychological versus physical' basis of CRPS. We recognise how CRPS research may inform mechanistic understanding of FND and conversely, how advances in FND, especially treatment, have implications for improving understanding and management of CRPS.

Complex regional pain syndrome-significant progress in understanding

Research into complex regional pain syndrome (CRPS) has made significant progress. First, there was the implementation of the official IASP "Budapest" diagnostic criteria. It would be desirable to also define exclusion and outcome criteria that should be reported in studies. The next step was to recognize the complex pathophysiology. After trauma, some inflammation is physiological; in acute CRPS, this inflammation persists for months. There is an abundance of inflammatory and a lack of anti-inflammatory mediators. This proinflammatory network (cytokines and probably also other mediators) sensitizes the peripheral and spinal nociceptive system, it facilitates the release of neuropeptides from nociceptors inducing the visible signs of inflammation, and it stimulates bone cell or fibroblast proliferation, and endothelial dysfunction leading to vascular changes. Trauma may also expose nervous system structures to the immune system and triggers autoantibodies binding to adreno- and acetylcholine receptors. In an individual time frame, the pain in this inflammatory phase pushes the transition into "centralized" CRPS, which is dominated by neuronal plasticity and reorganization. Sensory-motor integration becomes disturbed, leading to a loss of motor function; the body representation is distorted leading to numbness and autonomic disturbances. In an attempt to avoid pain, patients neglect their limb and learn maladaptive nonuse. The final step will be to assess large cohorts and to analyze these data together with data from public resources using a bioinformatics approach. We could then develop diagnostic toolboxes for individual pathophysiology and select focused treatments or develop new ones.

Ulnar nerve impairment at the wrist does not contribute to extramedian sensory symptoms in carpal tunnel syndrome

OBJECTIVE

Extramedian spread of sensory symptoms is frequent in carpal tunnel syndrome (CTS) but its mechanisms are unclear. We explored the possible role of subtle ulnar nerve abnormalities in the pathogenesis of extramedian symptoms.

METHODS

We recruited 350 CTS patients. After selection, 143 patients (225 hands) were included. The hand symptoms distribution was graded with a diagram into median (MED) and extramedian (EXTRAMED) pattern. We tested the correlation of ulnar nerve conduction measures with the distribution and the severity of symptoms involving the ulnar territory. The clinical significance of ulnar nerve conduction findings was explored with quantitative sensory testing (QST).

RESULTS

EXTRAMED distribution was found in 38.7% of hands. The ulnar neurographic measures were within normal values. Ulnar nerve sensory measures were significantly better in EXTRAMED vs MED hands and not significantly correlated to ulnar symptoms severity. Ulnar and median nerve sensory measures were significantly correlated. QST showed normal function of ulnar nerve alphabeta-fibers.

CONCLUSIONS

Ulnar nerve sensory abnormalities do not contribute to the spread of sensory symptoms into the ulnar territory.

SIGNIFICANCE

Our data favour the hypothesis that spinal and supraspinal neuroplastic changes may underlie extramedian spread of symptoms in CTS.

Pregabalin for neuropathic pain based on recent clinical trials

Pregabalin is a ligand for the alpha-2-delta subunit of voltage-gated calcium channels with anticonvulsant, analgesic, and anxiolytic properties. It has predictable absorption across the gastrointestinal tract, is neither metabolized nor protein-bound, and has minimal drug-drug interactions. It is effective with two or three-times daily dosing in a dose range of 150 to 600 mg daily. Seven published prospective, randomized clinical trials in postherpetic neuralgia (PHN) and painful diabetic peripheral neuropathy (DPN) demonstrate pain relief, decreased sleep interference, and improvements in several secondary outcome measures. The 50% responder rates for PHN and DPN compare favorably with other first-line agents for neuropathic pain. Pregabalin is well tolerated in most patients with infrequent severe adverse effects. Pregabalin is an important addition to the treatment armamentarium for neuropathic pain.

Streamlined classification of psychopathological hand disorders: A literature review

In the surgical hand clinic, psychopathological hand disorders can be sorted into one of the following four categories: (1) factitious wound creation and manipulation; (2) factitious edema; (3) psychopathological dystonias, and (4) psychopathological sensory abnormalities and psychopathological Complex Regional Pain Syndrome. This article introduces these four categories. Pertinent literature that includes descriptions of each category's syndromes and diseases, demographic and psychological profiles, differential diagnoses, and appropriate treatment recommendations is reviewed.

Migraine with unilateral motor symptoms: a case-control study

OBJECTIVE

To characterise the clinical features of non-familial migraine with unilateral motor symptoms (MUMS) and compare these features with those of migraine without weakness.

METHODS

24 patients with MUMS and 48 matched controls were identified from a tertiary care headache centre. Using a structured interview, the migraine symptoms of both groups were characterised. Results of previously administered Beck Depression Inventories (BDI), Minnesota Multiphasic Personality Inventories and psychiatric diagnoses were collected, when available, and compared between groups.

RESULTS

9 patients had episodic migraine and 15 had chronic migraine. Patients with MUMS always had weakness involving the arm subjectively, and both arm and leg objectively. A give-way character was always present. Only 17% of patients with MUMS reported facial weakness; 58% reported persistent interictal weakness; 92% reported sensory symptoms. A rostrocaudal march of sensory and motor symptoms was frequently reported. Weakness was ipsilateral to unilateral headache in two thirds of the patients. Compared with controls, patients with MUMS had had similar pain intensities, but were more likely to report other migrainous symptoms, including allodynia. 38% of patients with MUMS were told they had had a stroke, and 17% believed they had had a stroke despite normal brain imaging. Patients with MUMS reported fewer affective disorders and more adjustment disorders than controls, and had similar BDI scores.

CONCLUSIONS

A syndrome of severe migraine with accompanying give-way weakness is common in tertiary care headache centres. It is accompanied by other neurological symptoms.

Dysynchiria is not a common feature of neuropathic pain

Patients with chronic neuropathic pain (non-CRPS) and brush-evoked allodynia watched a reflected image of their corresponding but opposite skin region being brushed in a mirror. Unlike complex regional pain syndrome Type 1, this process did not evoke any sensation at the affected area ('dysynchiria'). We conclude that central nociceptive sensitisation alone is not sufficient to cause dysynchiria in neuropathic pain. The results imply a difference in cortical pain processing between complex regional pain syndrome and other chronic neuropathic pain.

Patients initially diagnosed as 'warm' or 'cold' CRPS 1 show differences in central sensory processing some eight years after diagnosis: a quantitative sensory testing study

We used quantitative sensory testing (QST) to gain further insight into mechanisms underlying pain in CRPS 1. Specific goals were: (1) to identify altered patterns of sensory processing some 8 years after diagnosis, (2) to document differences in sensory processing between 'warm' and 'cold' diagnostic subgroups, (3) to determine relationships between changed sensory processing and disease progression regarding pain. The study was performed on a cohort of patients (n=47) clinically diagnosed with CRPS 1 of one upper extremity approximately 8 years previously. Pain was quantified by VAS and MacGill Pain Questionnaire (MPQ), and all subjects underwent electrical and mechanical QST. Cold patients (n=13) had poorer MPQ scores than warm ones (n=34), and more pain on electrical stimulation. Their evoked pain increased with disease progression and correlated with clinical pain measures. For both diagnostic subgroups, thresholds to pressure pain were lower on the affected extremity and with disease progression. Eight years after original diagnosis, cold CRPS 1 patients have poorer clinical pain outcomes and show persistent signs of central sensitisation correlating with disease progression. The latter is not the case for warm CRPS 1 patients. Both diagnostic subgroups show greater pressure hyperalgesia on the affected limb and with disease progression. QST may prove useful in the subdiagnosis of CRPS 1 and in quantifying its progression, with both applications warranting further investigation for clinical and research use.