4.4.3 Electroencephalogram
Electroencephalogram (EEG) is a technique that measures changes in activity within brain systems and has been used to assess pain associated with evoked potentials (measurable electrical signals in the nervous system that originate from a controlled stimulus) and resting-state EEG166-168. EEG is readily available and relatively easy to use, although its uses in studies of OUD are limited169. EEG has been used to and evaluate OUD symptoms (e.g., impulsivity, emotional dysregulation, and reward sensitivity)170-172 and co-occurring chronic pain, as well as assess who may benefit most from analgesics173.
As sleep quality directly influences wellbeing and poor sleep worsens the experience of pain174, the use of EEG for assessment of pain in patients with OUD presents as a promising, largely unexplored opportunity. For example, Lewis and colleagues175 demonstrated, using EEG techniques, that heroin use suppressed REM sleep as well as deep non-REM sleep; notably, these findings were extended to methadone and morphine by Dimsdale and collaborators176. Discovery and validation of these abnormal sleep patterns in OUD patients through EEG provoked research into ameliorating these issues with novel treatments, subsequently reducing future risks of patient relapse177. EEG has proven to be a powerful tool in preclinical, human laboratory, and clinical research and has the potential to be a useful tool in diagnostics and risk assessment for patients with OUD in a clinical setting. The use of EEG in investigating how these measurements apply to pain for patients with OUD is limited and presents an opportunity for future biomarker research.