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Photoacoustics can image spreading depolarization deep in gyrencephalic brain.

ABSTRACT: Spreading depolarization (SD) is a self-propagating wave of near-complete neuronal depolarization that is abundant in a wide range of neurological conditions, including stroke. SD was only recently documented in humans and is now considered a therapeutic target for brain injury, but the mechanisms related to SD in complex brains are not well understood. While there are numerous approaches to interventional imaging of SD on the exposed brain surface, measuring SD deep in brain is so far only possible with low spatiotemporal resolution and poor contrast. Here, we show that photoacoustic imaging enables the study of SD and its hemodynamics deep in the gyrencephalic brain with high spatiotemporal resolution. As rapid neuronal depolarization causes tissue hypoxia, we achieve this by continuously estimating blood oxygenation with an intraoperative hybrid photoacoustic and ultrasonic imaging system. Due to its high resolution, promising imaging depth and high contrast, this novel approach to SD imaging can yield new insights into SD and thereby lead to advances in stroke, and brain injury research.

SUBMITTER: Kirchner T

PROVIDER: S-EPMC6572820 | biostudies-other | 2019 Jun

REPOSITORIES: biostudies-other

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Photoacoustics can image spreading depolarization deep in gyrencephalic brain.

Kirchner Thomas T Gröhl Janek J Herrera Mildred A MA Adler Tim T Hernández-Aguilera Adrián A Santos Edgar E Maier-Hein Lena L

Scientific reports 20190617 1

Spreading depolarization (SD) is a self-propagating wave of near-complete neuronal depolarization that is abundant in a wide range of neurological conditions, including stroke. SD was only recently documented in humans and is now considered a therapeutic target for brain injury, but the mechanisms related to SD in complex brains are not well understood. While there are numerous approaches to interventional imaging of SD on the exposed brain surface, measuring SD deep in brain is so far only poss ...[more]

PMID: 31209253

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Project description:OBJECTIVERetrospective clinical data and case studies support a therapeutic effect of ketamine in suppression of spreading depolarization (SD) following brain injury. Preclinical data strongly support efficacy in terms of frequency of SD as well as recovery from electrocorticography (ECoG) depression. The authors present the results of the first prospective controlled clinical trial testing the role of ketamine used for clinical sedation on occurrence of SD.METHODSTen patients with severe traumatic brain injury (TBI) or aneurysmal subarachnoid hemorrhage (SAH) were recruited for this pilot trial. A standard ECoG strip was placed at the time of craniotomy, and the patients were then placed on an alternating every-6-hour schedule of ketamine or other sedation agent. The order of treatment was randomized. The ketamine dose was adjusted to clinical effect or maintained at a subanesthetic basal dose (0.1 mg/kg/hr) if no sedation was required. SD was scored using standard criteria, blinded to ketamine dosing. Occurrence of SD was compared with the hourly dose of ketamine to determine the effect of ketamine on SD occurrence.RESULTSSuccessful ECoG recordings were obtained in all 10 patients: 8 with SAH and 2 with TBI. There were a total of 1642 hours of observations with adequate ECoG: 833 hours off ketamine and 809 hours on ketamine. Analysis revealed a strong dose-dependent effect such that hours off ketamine or on doses of less than 1.15 mg/kg/hr were associated with an increased risk of SD compared with hours on doses of 1.15 mg/kg/hr or more (OR 13.838, 95% CI 1.99-1000). This odds ratio decreased with lower doses of 1.0 mg/kg/hr (OR 4.924, 95% CI 1.337-43.516), 0.85 mg/kg/hr (OR 3.323, 95% CI 1.139-16.074), and 0.70 mg/kg/hr (OR 2.725, 95% CI 1.068-9.898) to a threshold of no effect at 0.55 mg/kg/hr (OR 1.043, 95% CI 0.565-2.135). When all ketamine data were pooled (i.e., on ketamine at any dose vs off ketamine), a nonsignificant overall trend toward less SD during hours on ketamine (χ2 = 3.86, p = 0.42) was observed.CONCLUSIONSKetamine effectively inhibits SD over a wide range of doses commonly used for sedation, even in nonintubated patients. These data also provide the first prospective evidence that the occurrence of SD can be influenced by clinical intervention and does not simply represent an unavoidable epiphenomenon after injury. These data provide the basis for future studies assessing clinical improvement with SD-directed therapy.Clinical trial registration no.: NCT02501941 (clinicaltrials.gov).

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Photoacoustics can image spreading depolarization deep in gyrencephalic brain.

Publications

Photoacoustics can image spreading depolarization deep in gyrencephalic brain.

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