Central post-stroke ('thalamic syndrome') and other central pains

Role of Brain Derived Neurotrophic Factor and Related Therapeutic Strategies in Central Post-Stroke Pain

Brain-derived neurotrophic factor (BDNF) is vital for synaptic plasticity, cell persistence, and neuronal development in peripheral and central nervous systems (CNS). Numerous intracellular signalling pathways involving BDNF are well recognized to affect neurogenesis, synaptic function, cell viability, and cognitive function, which in turn affects pathological and physiological aspects of neurons. Stroke has a significant psycho-socioeconomic impact globally. Central post-stroke pain (CPSP), also known as a type of chronic neuropathic pain, is caused by injury to the CNS following a stroke, specifically damage to the somatosensory system. BDNF regulates a broad range of functions directly or via its biologically active isoforms, regulating multiple signalling pathways through interactions with different types of receptors. BDNF has been shown to play a major role in facilitating neuroplasticity during post-stroke recovery and a pro-nociceptive role in pain development in the nervous system. BDNF-tyrosine kinase receptors B (TrkB) pathway promotes neurite outgrowth, neurogenesis, and the prevention of apoptosis, which helps in stroke recovery. Meanwhile, BDNF overexpression plays a role in CPSP via the activation of purinergic receptors P2X4R and P2X7R. The neuronal hyperexcitability that causes CPSP is linked with BDNF-TrkB interactions, changes in ion channels and inflammatory reactions. This review provides an overview of BDNF synthesis, interactions with certain receptors, and potential functions in regulating signalling pathways associated with stroke and CPSP. The pathophysiological mechanisms underlying CPSP, the role of BDNF in CPSP, and the challenges and current treatment strategies targeting BDNF are also discussed.

The Management of Poststroke Thalamic Pain: Update in Clinical Practice

Poststroke thalamic pain (PS-TP), a type of central poststroke pain, has been challenged to improve the rehabilitation outcomes and quality of life after a stroke. It has been shown in 2.7-25% of stroke survivors; however, the treatment of PS-TP remains difficult, and in majority of them it often failed to manage the pain and hypersensitivity effectively, despite the different pharmacotherapies as well as invasive interventions. Central imbalance, central disinhibition, central sensitization, other thalamic adaptative changes, and local inflammatory responses have been considered as its possible pathogenesis. Allodynia and hyperalgesia, as well as the chronic sensitization of pain, are mainly targeted in the management of PS-TP. Commonly recommended first- and second-lines of pharmacological therapies, including traditional medications, e.g., antidepressants, anticonvulsants, opioid analgesics, and lamotrigine, were more effective than others. Nonpharmacological interventions, such as transcranial magnetic or direct current brain stimulations, vestibular caloric stimulation, epidural motor cortex stimulation, and deep brain stimulation, were effective in some cases/small-sized studies and can be recommended in the management of therapy-resistant PS-TP. Interestingly, the stimulation to other areas, e.g., the motor cortex, periventricular/periaqueductal gray matter, and thalamus/internal capsule, showed more effect than the stimulation to the thalamus alone. Further studies on brain or spinal stimulation are required for evidence.

Tricyclic antidepressants and selective serotonin reuptake inhibitors but not anticonvulsants ameliorate pain, anxiety, and depression symptoms in an animal model of central post-stroke pain

Background

Central post-stroke pain (CPSP) is a type of neuropathic pain caused by dysfunction in the spinothalamocortical pathway. However, no animal studies have examined comorbid anxiety and depression symptoms. Whether the typical pharmacological treatments for CPSP, which include antidepressants, selective serotonin reuptake inhibitors (SSRIs), and anticonvulsants, can treat comorbid anxiety and depression symptoms in addition to pain remains unclear? The present study ablated the ventrobasal complex of the thalamus (VBC) to cause various CPSP symptoms. The effects of the tricyclic antidepressants amitriptyline and imipramine, the SSRI fluoxetine, and the anticonvulsant carbamazepine on pain, anxiety, and depression were examined.

Results

The results showed that VBC lesions induced sensitivity to thermal pain, measured using a hot water bath; mechanical pain, assessed by von Frey test; anxiety behavior, determined by the open-field test, elevated plus-maze test, and zero-maze test; and depression behavior, assessed by the forced swim test. No effect on motor activity in the open-field test was observed. Amitriptyline reduced thermal and mechanical pain sensitivity and anxiety but not depression. Imipramine suppressed thermal and mechanical pain sensitivity, anxiety, and depression. Fluoxetine blocked mechanical but not thermal pain sensitivity, anxiety, and depression. However, carbamazepine did not affect pain, anxiety, or depression.

Conclusion

In summary, antidepressants and SSRIs but not anticonvulsants can effectively ameliorate pain and comorbid anxiety and depression in CPSP. The present findings, including discrepancies in the effects observed following treatment with anticonvulsants, antidepressants, and SSRIs in this CPSP animal model, can be applied in the clinical setting to guide the pharmacological treatment of CPSP symptoms.

Ultrasound-Guided Stellate Ganglion Block for Central Post-Stroke Pain: A Case Report and Review

Background

Central post-stroke pain (CPSP) is refractory to pharmacotherapy (eg, NSAIDs, opioids, antidepressants, and anticonvulsants), and may require transcranial or deep brain stimulation.

Case Presentation

A 67-year-old woman presented with severe paroxysmal cramp-like pain on the right side, including the head and both upper and lower extremities. The pain started 5 years earlier, was initially mild and occasional, but gradually intensified to an unbearable degree with an average of 10–15 daily episodes, each lasting for 5–10 mins. The patient disclosed “hemorrhagic stroke” 10 years ago that resulted in hemiplegia on the right side. CT examination verified the lesion. The patient received daily injection of 2-mL 2% lidocaine under ultrasound guidance to block the stellate ganglion. Pain subsided rapidly in both intensity and frequency. On the seventh day, the patient no longer had pain episodes. At the last follow-up, 9 months later, the patient was free from pain.

Conclusion

Ultrasound-guided stellate ganglion block is a viable alternative for CPSP that is refractory to pharmacotherapy.

Deficient pain modulatory systems in patients with mild traumatic brain and chronic post-traumatic headache: implications for its mechanism

Although the prevalence rate of chronic post-traumatic headache (CPTHA) after mild traumatic brain injury (TBI) reaches up to 95%, its mechanism is unknown, and little is known about the characteristics of the pain system in this condition. Our aim was to investigate the capabilities of two pain modulatory systems among individuals with CPTHA and study their association with CPTHA, here for the first time. Forty-six subjects participated; 16 with TBI and CPTHA, 12 with TBI without CPTHA, and 18 healthy controls. Testing included the measurement of heat-pain (HPT) and pressure-pain (PPT) thresholds in the forehead and forearm, pain adaptation to tonic noxious heat, and conditioned pain modulation (CPM).The participants completed a post-traumatic stress disorder (PTSD) questionnaire. The two TBI groups did not differ in the TBI and background characteristics. However, TBI patients with CPTHA had significantly higher HPT and lower PPT in the cranium and higher PTSD symptomatology than TBI patients without CPTHA and healthy controls. Adaptation to pain and CPM were diminished in the CPTHA group compared with the two control groups. The intensity of CPTHA correlated negatively with cranial PPT, magnitude of pain adaptation, and CPM. CPTHA intensity correlated positively with PTSD symptomatology. CPTHA appears to be characterized by cranial hyperalgesia and dysfunctional pain modulation capabilities, which are associated with CPTHA magnitude. It is concluded that damage to pain modulatory systems along with chronic cranial sensitization underlies the development of CPTHA. PTSD may reinforce CPTHA and vice versa. Clinical implications are discussed.

A Comprehensive Review of Central Post-Stroke Pain

Although central post-stroke pain is widely recognized as a severe chronic neuropathic pain condition, its consolidated definition, clinical characteristics, and diagnostic criteria have not been defined due to its clinically diverse features. The present study was undertaken to comprehensively review current literature and provide a more complete picture of central post-stroke pain with respect to its definition, prevalence, pathophysiology, clinical characteristics, and diagnostic problems, and to describe the range of therapies currently available. In particular, nursing care perspectives are addressed. It is hoped that this review will help nurses become knowledgeable about central post-stroke pain and provide valuable information for the drafting of effective nursing care plans that improve outcomes and quality of life for patients with central post-stroke pain.

Capturing brain metrics of neuropathic pain using nuclear magnetic resonance

SUMMARY Neuropathic pain is typically caused by a lesion or dysfunction in the nervous system that results in both negative (i.e., reduced sensitivity) and positive symptoms (i.e., paraesthesia, spontaneous ongoing pain with shooting, electric shock-like sensations and abnormal responses to evoked pain). Intriguingly, chronic pain disorders manifest profound alterations in brain structure and function, and thus, modern nuclear magnetic resonance (NMR) techniques have allowed us to begin to dissect the complexities of how neuropathic pain affects the brain. NMR approaches can be used as an independent measure to improve our understanding of key changes in brain structure, function and chemistry in chronic neuropathic pain. Accordingly, NMR techniques provide neurobiological metrics that allow us to understand the neurobiological basis of chronic neuropathic pain. Additionally, although at an early stage, NMR methods can also be useful to define clinical metrics to predict chronification of neuropathic pain and responses to drugs. This article provides a review of NMR techniques and their capacity to study spontaneous pain and evoked pain, as well as structural, functional and neurochemical alterations that have repeatedly been associated with chronic neuropathic pain. Finally, the importance for quantifying disease state and treatment efficacy in neuropathic pain using NMR techniques is discussed.

Central poststroke pain: current diagnosis and treatment

Central post-stroke pain syndrome (CPSP) is a debilitating sequel that can follow thalamic sensory stroke. Less well recognized, CPSP follows lateral medullary stroke and parietal cortical stroke and may develop anywhere along the spinothalamic or trigemino-thalamic pathways. Patients describe sharp, stabbing, or burning pain and experience hyperpathia and especially allodynia. Although CPSP was first described over 100 years ago, CPSP is too frequently underrecognized. It is treatable disorder. Pharmacological therapy, magnetic stimulation, and invasive electrical stimulation are reviewed and recommendations made.

Central poststroke pain: an abstruse outcome

Central poststroke pain (CPSP), formerly known as thalamic pain syndrome of Déjerine and Roussy, is a central neuropathic pain occurring in patients affected by stroke. It is one manifestation of central pain, which is broadly defined as central neuropathic pain caused by lesions or dysfunction in the central nervous system. Thalamic pain was first described 100 years ago by Déjerine and Roussy and has been described as "among the most spectacular, distressing, and intractable of pain syndromes". CPSP is characterized by constant or intermittent pain and is associated with sensory abnormalities, particularly of thermal sensation. While the pain is frequently described as burning, scalding, or burning and freezing, other symptoms are usually vague and hard to characterize, making an early diagnosis particularly difficult. In fact, those who develop CPSP may no longer be under the care of health care professionals when their symptoms begin to manifest, resulting in misdiagnosis or a significant delay before treatment begins. Diagnosis is further complicated by cognitive and speech limitations that may occur following stroke, as well as by depression, anxiety and sleep disturbances. Patients may also exhibit spontaneous dysesthesia and the stimulus-evoked sensory disturbances of dysesthesia, allodynia and hyperalgesia. The present study offers a historical reference point for future clinical and basic research into this elusive type of debilitating pain.

Prevalence and predictors of pain and fatigue after stroke: a population-based study

Pain and fatigue are two often overlooked symptoms after stroke. Their prevalence and determinants are not well understood. In this study patients with first-ever stroke (n=377) were examined at baseline and after 1 year. General characteristics of the patients, as well as stroke type, stroke severity and risk factors were registered at baseline. After 1 year survivors (n=253) were examined with respect to residual impairment, disability, cognition and depression. They were asked whether they had experienced pain and/or fatigue which had started after the stroke, and which the patient felt to be stroke related. Twenty-eight patients (11%) had stroke-associated pain and 135 (53%) had stroke-associated fatigue. Pain was associated with depression and different manifestations of stroke severity, especially degree of paresis at baseline. Fatigue was more associated with physical disability. In univariate analysis, fatigue was also associated with sleep disturbances. In conclusion, it is important to be aware of the occurrence of pain and fatigue after stroke, because these symptoms are common, they impair quality of life and they are potentially treatable. Post-stroke depression may coexist with pain and fatigue. The detection of one symptom should lead to consideration of the others. Follow-up and individual assessment of stroke patients is crucial.

Post-stroke pain case study: clinical characteristics, therapeutic options and long-term follow-up

Central post-stroke pain (CPSP) is a syndrome characterized by sensory disturbances and neuropathic pain. In 40%-60% of CPSP patients, the onset of central pain following a stroke occurs more than 1 month after the stroke, creating a source of diagnostic uncertainty or significant delay in treatment since healthcare providers familiar with CPSP may no longer be caring for the patient when the symptoms occur. In addition to chronic pain, the presence of somatosensory abnormalities is the most important diagnostic corollary of CPSP. Neuropathic or central pain has been estimated to occur in up to 8% of patients after a stroke, and about 18% of stroke patients with a somatosensory disturbance will develop CPSP. Although largely a matter of conjecture, it is generally agreed that damage to spinothalamic sensory pathways plays a significant role in the pathogenesis of CPSP. A comprehensive examination of the patient for sensory deficits is essential before treatment can be initiated. Functional disturbances such as depression, anxiety and sleep disturbances are significant comorbid conditions associated with CPSP; the physician should incorporate an assessment of these potential comorbidities into the examination. Treatment options for CPSP are limited; at present, amitriptyline is the drug of first choice. Other drugs including antidepressants, anticonvulsants, antiarrhythmics, opioids and N-methyl-d-aspartate antagonists may provide relief for some patients who do not respond to amitriptyline. Included in this review is a case study outlining the challenges of managing the patient with CPSP.

Pharmacologic Management Part 2: Lesser-Studied Neuropathic Pain Diseases

This second part of a review of the pharmacologic management of neuropathic pain diseases describes the current treatment options for three lesser-studied neuropathic syndromes: Central poststroke pain, spinal cord injury, and complex regional pain syndrome II. Diagnosis can be difficult in patients with these syndromes, because the pain experienced is much greater and of a different type than would normally be expected following a stroke or injury to the spinal cord or a peripheral nerve. Even when an accurate and timely diagnosis is made, treatment options are limited and frequently suboptimal. However, the results of published trials do support the use of anticonvulsants and/or tricyclic antidepressants as first-line pharmacotherapy in these three neuropathic pain syndromes. To maximize treatment outcomes, future research must: Continue to more fully elucidate the relationship between the signs and symptoms of pain and the underlying pathophysiology; Delineate the natural history of central poststroke pain, spinal cord injury, and complex regional pain syndrome; Identify patient-related factors that may indicate an increased risk of developing neuropathic pain following stroke or nerve injury; Investigate emerging treatments that target underlying pain mechanisms.

Does parenchymal brain injury affect biobehavioral pain responses in very low birth weight infants at 32 weeks' postconceptional age?

OBJECTIVE

Children with neurologic impairments have shown diminished pain response compared with control subjects; however, it remains unclear what mechanisms underlie this response or when it develops. If this were also true with premature infants who undergo neonatal intensive care, then infants with parenchymal brain injury (PBI) would be at increased risk of underrecognition and undertreatment of procedural pain. The purpose of this study was to determine whether infants with PBI display altered responses to acute procedural pain at 32 weeks' postconceptional age (PCA), compared with control subjects.

METHODS

We compared responses to blood collection by heel lance at 32 weeks' PCA in 12 very low birth weight infants (mean [range] birth weight: 876 g [630-1240 g]; gestational age: 26.3 weeks (24-28 weeks) who had sustained PBI in the neonatal period, with 12 control subjects matched for gestational age at birth and gender (838 g [625-990 g]; 26.3 weeks [24-28 weeks[) who had normal neonatal brain imaging. PBI was defined as cerebral parenchymal infarction (grade 4 intraventricular hemorrhage) or cystic periventricular leukomalacia on serial cranial ultrasound scans conducted in the neonatal period. Biobehavioral responses to pain were measured using facial activity (Neonatal Facial Coding System) and measures of heart rate (HR) variability (low-frequency [LF] power [0.04-0.15], high-frequency [HF] power [0.15-0.8 Hz], and LF/HF ratio) as a measure of cardiac autonomic modulation. Neurodevelopmental follow-up was undertaken at 18 months.

RESULTS

The infants with PBI had significantly higher illness severity scores at day 1 compared with day 3 (Score of Neonatal Acute Physiology II: 32.1 vs 19.8) but similar previous pain experiences (109 vs 115) and total morphine exposure (0.29 vs 0.30 mg/kg). Both groups of children mounted similar responses to heel lance at 32 weeks' PCA with no difference in facial response or HR variability. Mean HR and facial action scores increased from baseline to the lance, whereas LF, HF, and the LF/HF ratio decreased significantly. No group differences were found. The only statistically significant difference between groups was that infants with PBI had more tongue protrusion at lance. Neurodevelopmental follow-up showed 8 of 11 toddlers with PBI had cerebral palsy compared with 0% of control toddlers. Psychomotor Developmental Index score on the Bayley Scales of Infant Development II was significantly lower in the PBI group. Five of 11 toddlers with PBI had Mental Developmental Index score <2 standard deviations below mean compared with 0% of the control toddlers.

CONCLUSION

Contrary to expectations, we did not find any evidence of an altered pain response pattern in infants with proven brain injury in the neonatal period. Although most infants with PBI developed cerebral palsy, these findings suggest that cerebral injury predominantly to the central white matter leaves brainstem responses intact in the neonatal period. Furthermore, it seems that the injured brain of the preterm infant has not yet expressed the identifiable differences in pain display and the functional impairment observed at later ages.

Treatment of central post-stroke pain with oral ketamine

Case report of 68 year old female with central post-stroke pain successfully treated with oral ketamine. The patient's pain was refractory to conventional pain treatments and she had persistent right hemi-body neuropathic pain with allodynia and hyperalgesia. An intravenous ketamine trial, followed by oral ketamine with titration to 50mg three times a day was beneficial in decreasing allodynia and hyperalgesia, as well as improving functional capabilities. Known side effects including dysphoria, hallucinations, and paranoid feelings were attenuated with benzodiazepines.