Magnetic Resonance Imaging (MRI)

Rapid advances in brain imaging chronic pain patients have yielded exciting data sets that could provide the basis for the development of chronic pain biomarkers that could increase the probability of success in analgesic drug development, aid clinicians in understanding, tracking, and treating disease, and link patients to the most effective therapies for their pain conditions. This review explores the potential of brain imaging techniques to detect functional, morphometric, and chemical changes that could serve as biomarkers for disease state and therapeutic efficacy.

Complex regional pain syndrome (CRPS) in paediatric patients is clinically distinct from the adult condition in which there is often complete resolution of its signs and symptoms within several months to a few years. The ability to compare the symptomatic and asymptomatic condition in the same individuals makes this population interesting for the investigation of mechanisms underlying pain and other symptoms of CRPS. We used fMRI to evaluate CNS activation in paediatric patients (9-18 years) with CRPS affecting the lower extremity.

The discovery of cortical networks that participate in pain processing has led to the common generalization that blood oxygen level-dependent (BOLD) responses in these areas indicate the processing of pain. Physical stimuli have fundamental properties that elicit sensations distinguishable from pain, such as heat. We hypothesized that pain intensity coding may reflect the intensity coding of heat sensation during the presentation of thermal stimuli during fMRI.

BACKGROUND: With time, episodes of migraine headache afflict patients with increased frequency, longer duration and more intense pain. While episodic migraine may be defined as 1-14 attacks per month, there are no clear-cut phases defined, and those patients with low frequency may progress to high frequency episodic migraine and the latter may progress into chronic daily headache (> 15 attacks per month). The pathophysiology of this progression is completely unknown.

Substance P (SP) and neurokinin-1 receptors (NK-1R) are localized within central and peripheral sensory pain pathways. The roles of SP and NK-1R in pain processing, the anatomical distribution of NK-1R and efficacy observed in preclinical pain studies involving pain and sensory sensitization models, suggested that NK-1R antagonists (NK-1RAs) would relieve pain in patient populations. Despite positive data available in preclinical tests for a role of NK-1RAs in pain, clinical studies across several pain conditions have been negative.

OBJECTIVE: Focal somatic pain can evolve into widespread hypersensitivity to nonpainful and painful skin stimuli (allodynia and hyperalgesia, respectively). We hypothesized that transformation of headache into whole-body allodynia/hyperalgesia during a migraine attack is mediated by sensitization of thalamic neurons that process converging sensory impulses from the cranial meninges and extracephalic skin.

The habenula is a small bilateral structure in the posterior-medial aspect of the dorsal thalamus that has been implicated in a remarkably wide range of behaviors including olfaction, ingestion, mating, endocrine and reward function, pain and analgesia. Afferent connections from forebrain structures send inputs to the lateral and medial habenula where efferents are mainly projected to brainstem regions that include well-known pain modulatory regions such as the periaqueductal gray and raphe nuclei.

Functional MRI (fMRI) has provided new insights into brain mechanisms in chronic pain. However, unlike acute pain measures in healthy volunteers, there are additional concerns relating to mapping brain circuits in these patients. These include the ability to measure evoked versus spontaneous pain, background conditions such as medications, or comorbid diseases such as depression, anxiety, or addiction.

Functional imaging has revolutionized the neurosciences. In the pain field it has dramatically altered our understanding of how the brain undergoes significant functional, anatomical and chemical changes in patients with chronic pain. However, most studies have been performed in adults. Because functional imaging is non-invasive and can be performed in awake individuals, applications in children have become more prevalent, but only recently in the pain field.

Photophobia, or painful oversensitivity to light, occurs in a number of clinical conditions, which range from superficial eye irritation to meningitis. In this case study, a healthy subject with transient photophobia (induced by the overuse of contact lenses) was examined using functional magnetic resonance imaging (fMRI). While being scanned in a darkened environment, the subject was presented with intermittent 6-s blocks of bright light. The subject was scanned twice, once during his photophobic state and once after recovery.