Please select the eligibility criteria that correspond to the clinical trial below.
Title: Randomized Controlled Double-blind Cross-over Trial Evaluating the Role of Frequencies on Spinal Cord Stimulation in the Management of Failed Back Surgery Syndrome (SCS Frequency Study)
Brief Summary: The purpose of this study is to evaluate the role of frequency settings on spinal cord stimulation in the management of Failed Back Surgery Syndrome (SCS Frequency Study).


Options:
A: Inclusion Criteria:

1. A diagnosis of primary or idiopathic erythromelalgia
2. Patients ≥18 years who have developed chronic pain that has remained refractory to medical treatment for ≥6 months.
3. Minimum pain intensity of 5/10 on a numeric rating scale NRS at baseline.
4. Successful two-week SCS testing period with tonic stimulation (≥2 points reduction in pain NRS from baseline). This means patients will experience paresthesia during the trial period of spinal cord stimulation.

Exclusion Criteria:

1. Coexisting conditions that would increase procedural risk (e.g., sepsis, coagulopathy).
2. History of laminectomy or posterior fusion at the thoracolumbar junction, where percutaneous electrode end tips are routinely placed.
3. Abnormal pain behavior and/or unresolved psychiatric illness.
4. Unresolved issues of secondary gain or inappropriate medication use.
5. Unfit for participation for any other reason as judged by the study physician.
B: Inclusion Criteria:

* At least 18 years old at the time of informed consent
* Willing and able to provide a signed and dated informed consent
* Capable of comprehending and consenting in English
* Willing and able to comply with all study procedures, study visits, and be available for the duration of the study
* On a stable dose (no new, discontinued or changes in) of all prescribed pain medications and willing/able to maintain or only decrease the dose of all prescribed pain medications
* Tried appropriate conventional medical management for their pain
* Not indicated for additional surgical treatment in the opinion of the referring physician or spinal surgeon
* Undergone previous spinal surgery
* Diagnosed with FBSS with appropriate pain score
* Primary pain at appropriate spinal level

Exclusion Criteria:

* Has an active implanted device, whether turned on or off
* Displays current signs of a systemic infection
* Pregnant or lactating, inadequate birth control, or the possibility of pregnancy during the study
* Has untreated major psychiatric comorbidity
* Has serious drug-related behavioral issues
* Has neurological abnormalities unrelated to Failed Back Surgery Syndrome
* Diagnosed with Raynaud disease
* Diagnosed with Fibromyalgia
* Has any active malignancy or has been diagnosed with cancer and has not been in remission for at least 1 year prior to screening
* Has secondary gains which, in the opinion of the investigator, are likely to interfere with the study
* Participating or planning to participate in another clinical trial
* Has characteristics/limits of household or close contacts involved in study (eg, family member already a study participant where blind could be broken)
C: All patients were selected after multidisciplinary discussion with a specialized pain physician, a psychological and psychiatric evaluation was performed to rule out psychogenic pain as well as other psychiatric morbidity contraindicating an implant. After authorization by the psychologist and psychiatrist an implant was offered.

Inclusion Criteria

* Patients enrolled in this study must meet the following inclusion criteria:
* Patients able to provide informed consent to participate in the study;
* Patient is between the age of 18 and 75;
* Patient has Failed Back Surgery Syndrome;
* Patient has a simulator implanted at the dorsal column spinal cord powered by an EON/EON Mini® internal pulse generator.
* Patient medication has remained stable for at least 4 weeks prior to baseline data collection;
* Patient agrees not to add or increase medication throughout the randomization trial period of the study;
* Patient is willing to cooperate with the study requirements including compliance with the treatment regimen and completion of all office visits.

Exclusion Criteria

A patient will be excluded from participation in this study if they meet any one of the following criteria:

* Patient has current evidence of any psychiatric disorder, as documented by the DSM-IV-TR criteria with psychotic characteristics;
* Patient has a history of life-threatening severe illness or is suffering from severe chronic disease other than the indication for the study;
* Patient has history of substance abuse or substance dependency in the past 6 months prior to baseline data collection;
* Patient currently participating in another clinical study;
* Patient with demand-type cardiac pacemakers, an infusion pump or any other implantable neurostimulator device except for the spinal cord stimulator under study;
* Patient is not willing to maintain current medication regimen;
* Female candidates of child bearing potential who are pregnant (confirmed by positive urine/blood pregnancy test), not using adequate contraception as determined by the investigator, or nursing (lactating) a child.
D: Inclusion criteria:

* Patients 18 - 70 years old. For patients who only participate in the clinical RCT (without fMRI) no upper age limit.
* CRPS affecting one single upper or lower limb diagnosed by the IASP (2012) Budapest research criteria (Harden et al., 2010).
* Triggering trauma or the onset of pain \>3 months ago.
* If possible drugs that can influence the fMRI scans should be avoided. Documentation if used.

Exclusion criteria

* Drug abuse.
* Malignant/progressive, systemic or neurodegenerative disease.
* Other severe pain conditions.
* Severe clinical anxiety or depression, symptoms of fatigue or ME of a disabling level.

For patients who participate in the MRI related analyses:

* Metallic implants incompatible with the MR technology or medical condition not recommended for fMRI.
* Pregnancy.
* Phobia for MRI examination.
* Diseases that can cause structural changes and interfere with the interpretation of the MRI-scans (like severe diabetes mellitus, heart disease, ischemic stroke and vascular conditions).

Answer: B