Is the Volume of the Caudate Nuclei Associated With Area of Secondary Hyperalgesia?

Is the Volume of the Caudate Nuclei Associated With Area of Secondary Hyperalgesia? - A Study of Healthy Volunteers

The purpose of this prospective study is to investigate the degree of association between the volume of important pain-relevant structures in the brain and the size of the areas of secondary hyperalgesia.

The healthy study participants will be included from the cohort of a previous study (NCT02527395) where areas of secondary hyperalgesia, heat pain detection thresholds, pain during 1 min. thermal stimulation and test results from the Pain Catastrophizing Scale and the Hospital Anxiety and Depression Score will be retrieved. The study consists of 1 study day. The study day will be conducted at a maximum of 2 months and a minimum of 2 weeks after the completion of the previous study (NCT02527395).The results of the previous study (NCT02527395) will be blinded until all participants have completed the study day.

All study participants will complete a MRI-scan of the brain.

The MRI scans will be performed with a Siemens MAGNETOM Verio 3 tesla, with b17 software, and a 32-channel head coil. The MRI-scan sequence is as follows:

• 3D Localiser
• 3D T1 weighted iso
• AX Diffusion tensor imaging
• AX Epi resting state fMRI
• AX Gre field map
• AX Epi ASL
• AX T2-weighted blade
• AX T2-weighted flair
• AX T2-weighted* Gre

Total MRI-scan time is estimated to approximately 40 minutes.

Inclusion Criteria:

• Age >18 years and <35 years
• Speak and understand Danish
• Male sex
• Study participants who have understood and signed the informed consent
• No prescription medicine during the last 30 days.
• Have participated and completed the study with the identifier: NCT02527395.

Exclusion Criteria:

• Study participants that cannot cooperate to the test.
• Study participants who have a weekly intake of >21 units of alcohol, or a have consumed >3 units of alcohol within 24 hours before experimental day.
• Study participants with a substance abuse, assessed by the investigator.
• Study participants, who have consumed analgesics less than 3 days before experimental day.
• Study participants, who have consumed antihistamines less than 48 hours before experimental day.
• Study participants, who have consumed antidepressant medication during the last 30 days before experimental day.
• Study participants with chronic pain.
• Study participants with neurological illnesses.
• Study participants with psychiatric diagnoses.
• Study participants with a Body Mass Index of >30 kg/m2 or <18 kg/m2
• Study participants with Contraindications to MRI
• Study participants that decline information regarding potential pathological findings in relation to the MRI.
• Study participants that have any kind of trauma resulting in pain and administration of analgesics in the period between experimental pain testing and MRI-scan.
• Study participant that experience a head trauma in the period between the experimental pain testing and the MRI-scan.