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We describe a unique case of intrathecal baclofen overdose mimicking brainstem death, during bilateral anterior cingulate cortex deep brain stimulation (DBS) for pain. A 37-year-old man with chronic regional pain syndrome requiring an intrathecal baclofen pump underwent DBS under general anaesthesia and experienced an intraoperative generalised tonic-clonic seizure on dural opening. Once the operation was completed, the patient was noted to have fixed, dilated pupils bilaterally and was transferred for an emergency computed tomography scan of the head, which did not reveal any acute intracranial pathology. The patient was transferred to the intensive care unit for management of concurrent hypotension, bradycardia and supportive management of his low Glasgow Coma Scale (GCS) score. A trial of atropine to counter the bradycardia was unsuccessful. Intrathecal baclofen toxicity was suspected as a diagnosis of exclusion, necessitating urgent aspiration of the baclofen pump. The patient's GCS score improved after pump aspiration and he was discharged home several days later. It was noted that the intrathecal baclofen pump had been refilled several days previously and the patient had reported intermittent episodes of somnolence. In perioperative patients with intrathecal baclofen pumps in situ, baclofen toxicity should always be considered as a differential in perioperative complications, even if it is considered a rare event.

Chronic neuropathic pain affects 7%-10% of the population. Deep brain stimulation (DBS) has shown variable but promising results in its treatment. This study prospectively assessed the long-term effectiveness of DBS in a series of patients with chronic neuropathic pain, correlating clinical results with neuroimaging. Sixteen patients received 5 years' post-surgical follow-up in a single center. Six had phantom limb pain after amputation and 10 had deafferentation pain after traumatic brachial plexus injury. Patient-reported outcome measures were completed before and after surgery, using VAS, UWNPS, BPI and SF-36 scores. Neuroimaging evaluated electrode location and effective volumes of activated tissue (VAT). Two subgroups were created based on the percentage of VAT superimposed upon the ventroposterolateral thalamic nucleus (eVAT), and clinical outcomes were compared. Analgesic effect was assessed at 5 years and compared to preoperative pain, with an improvement on VAS of 76.4% (p=0.0001), on UW-NPS of 35.2% (p=0.3582), on BPI of 65.1% (p=0.0505) and on SF-36 of 5% (p=0.7406). Eight patients with higher eVAT showed improvement on VAS of 67.5% (p=0.0017) while the remaining patients, with lower eVAT, improved by 50.6% (p=0.03607). DBS remained effective in improving chronic neuropathic pain after 5 years. While VPL-targeting contributes to success, analgesia is also obtained by stimulating surrounding posterior ventrobasal thalamic structures and related spinothalamocortical tracts., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)