The goal of this clinical study is to study sleep and its microstructure in neuropathic pain patients who have or who do not have a clinically significant sleep disturbance, before and during (after 1-month stabile dosage) pregabalin treatment. To find out whether reduced pain by pregabalin associates with improved sleep quality; to study, using resting state fMRI, brain network connectivity and the volume of the choroid plexus before and during pregabalin treatment (after dosage stable for one month) at baseline and during stabile treatment with pregabalin, and to compare the usability and reliability of sleep-related information collected with sleep diaries, actigraphy, iButtons, and ambulatory polysomnography in peripheral painful neuropathy patients. The main questions it aims to answer are: * Is pregabalin more efficacious in neuropathic pain patients who suffer from insomnia compared to those with no clinically meaningful sleep disturbance? * Does sleep disturbance due to pain associate with brain network connectivity and may these changes be reversed by pregabalin treatment? Participants will * Fulfill e-questionnaires and keep sleep diary before and after 1month stabile pregabalin intervention * Before and after 1-month stabile pregabalin medication: 1-week Actiwatch monitoring, iButton (1 day and night), ambulatory polysomnography (1 night), brain fMRI. Researchers will compare patients with high ISI score patients to see if they benefit more from pregabalin treatment than those with low ISI score.