Intracranial functional near-infrared spectroscopy: animal feasibility

• Intracranial fNIRS has been demonstrated as a potential hybrid modality for neural monitoring in an animal feasibility study.¹
• The approach is an early proof-of-concept for future BCI or neuroimaging applications.¹
• Reported in Frontiers; tier-2.^{1 1}

Weekly enrichment (2026-07-20)

• The underlying study, “Intracranial functional near-infrared spectroscopy: an animal feasibility study” (Heymann, Rein, Zurita et al.), was published in Frontiers in Medical Technology (7:1692573, 2025).²
• The intracranial fNIRS (ifNIRS) system uses depth optrodes (optode-electrodes) together with optical anchor bolts (OABs) seated in the skull to overcome scalp fNIRS limitations, namely shallow penetration (roughly 1.5–2 cm) and susceptibility to scalp hemodynamic noise.^{2 3}
• Feasibility was tested in a swine model of three animals, each implanted with three OABs, with depth optrodes inserted into two of the OABs; hemodynamic signals were recorded via OAB-to-OAB and depth-optrode-to-OAB channel configurations under fluoroscopy guidance and general anesthesia.^{2 3}
• Two interventions were used to drive hemodynamic change: rapid infusion of hypotonic saline to induce cerebral edema, and blood withdrawal (reported as roughly 2.15–2.5 L per animal via an arterial cannula).^{2 3}
• Measurements used near-infrared light at 785 nm (deoxyhemoglobin) and 830 nm (oxyhemoglobin), with total hemoglobin computed as their sum and concentration changes derived from the modified Beer-Lambert equation.^{3 2}
• Total hemoglobin decreased during blood withdrawal across all channel configurations that produced usable signals; hypotonic saline infusion produced variable patterns—two animals showed a steady tHb rise (greater HbO2, interpreted as venous collapse) and one showed variable tHb with a relative HbR increase (interpreted as arterial vasospasm).^{2 3}
• Postmortem examination found only minor extra-axial hemorrhages near the OABs, with no intracerebral bleeding or heat-related injuries, supporting preliminary safety.^{2 4}
• Earlier bench validation (phantom head model plus Monte Carlo simulation) reported that placing the emitter and detector inside the OAB yielded a signal more than 30 times higher than scalp-positioned fNIRS at a 3-cm separation and more than 6 times the detection limit in photon count at 5 cm, with greatly reduced scalp-noise sensitivity.⁵
• The stated clinical goal is to pair ifNIRS with stereo-EEG (SEEG) for patients with drug-resistant epilepsy, adding depth-resolved peri-ictal hemodynamic monitoring to help localize the seizure onset zone beyond SEEG’s “tunnel vision”.^{3 5}
• The work was funded by the Israeli Innovation Authority (grants 77084 and 77092); the authors emphasize that signal inconsistencies and further technical refinement remain before clinical translation.^{3 4}

Footnotes

1. https://news.google.com/rss/articles/CBMinAFBVV95cUxOV1hDM1E3Rld1emdmNDhJbnJfRk9WRXVsTnNZWUxQUG9vTTlfWWFYZF9CRjRIUHBfTW9RMXBPbTRnNGFlQWhqWEs1cWNidGxWclFUdzBnY0NFazBySGh4YTV0VzU4TkYtRzJWVlY0M2dTcE9IU1FiYi1hN3Q0Y2tsMGdzSlJubWVoZzl3d09UVThqWHNVRlNMdExkeW0?oc=5 ↩ ↩² ↩³ ↩⁴

2. https://www.frontiersin.org/journals/medical-technology/articles/10.3389/fmedt.2025.1692573/full ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

3. https://aesnet.org/abstractslisting/animal-study-of-intracranial-functional-near-infrared-spectroscopy-advancing-towards-combined-use-with-stereo-eeg ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

4. https://pmc.ncbi.nlm.nih.gov/articles/PMC12695811/ ↩ ↩²

5. https://doi.org/10.1109/jsen.2024.3493378 ↩ ↩²