Safety of Indocyanine Green Microdosing for Clinical Imaging of CSF Ventricular Dynamics and Extracranial Outflow.
Miriam Zamorano, Banghe Zhu, Ahmed T Massoud, Jonathan Hendricks, H Alex Choi, Pedram Peesh, Brandon A Miller, Xinhai Robert Zhang, Manish N Shah, Eva M Sevick-Muraca
Journal of neuroimaging : official journal of the American Society of Neuroimaging 2025 DOI: 10.1111/jon.70028 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Nonclinical safety study with in vitro and in vivo components, plus a human observational component Peer reviewed |
|---|---|
| Sample size | 10 |
| Population | Brain-injured adults with external ventricular drain catheters; juvenile rat pups; mixed primary CNS cell cultures |
| Interventions | Indocyanine green (ICG) intraventricular injection |
| Dose | 100 µg (intraventricular microdose in neonatal model) |
| Duration | 1 hour and 24 hours (in vitro); behavioral tests and immunohistochemical analyses (rat study, duration not specified); CSF collection after intravenous administration (adults, timing not specified) |
| Measures | Novel Object Place Recognition Test, rotarod behavioral tests, TNF-α immunohistochemistry, oxidative DNA damage, microglial activation, neuronal density, lactate dehydrogenase assay |
| Topics | Microdosing |
| Keywords | Brain injury Cervical lymphatics Indocyanine green Near‐infrared fluorescence Oligomer‐induced neurotoxicity Pediatric hemorrhagic hydrocephalus |
| Key findings | Microdosing ICG directly into CSF is safe at the tested concentrations, with no evidence of neurotoxicity in cell cultures, juvenile rats, or surrogate measures in adults. |
Abstract
Intravenous administration of indocyanine green (ICG) has been approved in brain surgeries for decades, yet concerns about neurotoxicity prevent its direct administration into the cerebrospinal fluid (CSF). Armed with prior animal studies demonstrating the feasibility of using ICG microdosing into the CSF, we sought to evaluate its nonclinical safety profile and obtain surrogate measures in adults prior to its use in human neonates. Evaluation of ICG toxicity was conducted in mixed primary CNS cell cultures and in an extended safety study of juvenile rat pups deploying intraventricular injections of saline (as control) or ICG. Analysis of animal behavior included Novel Object Place Recognition Test and rotarod behavioral tests. Immunohistochemical analysis of tumor necrosis factor-alpha (TNF-α), oxidative deoxyribonucleic acid damage, microglial activation, and neuronal density was performed on collected brains. We measured ICG levels (before and after intravenous administration) in collected CSF from external ventricular drain catheters of 10 brain-injured adults. TNF-α and lactate dehydrogenase assay for cytotoxicity showed transient elevations after 1 h of incubation with 1291 µM ICG, but none at or below 322 µM ICG, even after 24 h of incubation. Behavioral tests and immunohistochemical analyses showed no differences between ICG-administered animals and controls. Intraventricular concentrations of ICG in collected human CSF ranged between 0.17 and 7.93 µM, with no adverse events associated with intravenous administration. With intraventricular microdosing of 100 µg ICG, maximal ICG concentrations in neonatal CSF range from 1.3 to 6 5 µM. CNS cell culture, rat safety studies, and surrogate measures in adults evidence the safety of microdosing ICG directly into the CSF.
Comparable studies
Other preclinical and animal studies on microdosing, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Psilocin and ketamine microdosing: effects of subchronic intermittent microdoses in the elevated plus-maze in male Wistar rats Wistar rats | 2018 | Experimental study | n = 40 |
| Repeated low doses of psilocybin increase resilience to stress, lower compulsive actions, and strengthen cortical connections to the paraventricular thalamic nucleus in rats. Rats | 2023 | Experimental study | |
| Repeated microdoses of LSD do not alter anxiety or boldness in zebrafish. Zebrafish (Danio rerio) | 2024 | Experimental study | |
| Application of microarray patches for the transdermal administration of psychedelic drugs in micro-doses. Excised neonatal porcine skin and rats | 2025 | Experimental study | |
| Toward Predicting Acute Myeloid Leukemia Patient Response to 7 + 3 Induction Chemotherapy via Diagnostic Microdosing Paired sensitive and resistant cancer cell lines, AML cell lines, and 10 viably... | 2018 | Preclinical cell line study with a pilot retrospective analysis of primary patient samples | n = 10 |