Hemodynamic Oscillations in Mild TBI During Postural Change: An fNIRS Pilot Study

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Imaging

Background:

• Mild traumatic brain injury (mTBI) can lead to subtle, long-term neurological deficits.
• Cerebral autoregulation, the brain's ability to maintain stable blood flow, may be impaired after mTBI.
• Non-invasive methods to assess cerebral hemodynamics are crucial for early diagnosis and management of mTBI.

Purpose of the Study:

• To investigate whether low-frequency oscillations (LFOs) in cerebral hemodynamics differ between individuals with mTBI and healthy controls.
• To explore the potential of LFOs measured by frequency-domain functional near-infrared spectroscopy (FD-fNIRS) as biomarkers for mTBI-related cerebral autoregulatory dysfunction.

Main Methods:

• A pilot study involving 2 mTBI patients and 13 healthy controls.
• Utilized frequency-domain functional near-infrared spectroscopy (FD-fNIRS) to measure cerebral hemodynamic oscillations.
• Analyzed total hemoglobin concentration (THC), oxyhemoglobin (HbO), and deoxyhemoglobin (Hb) dynamics during head-of-bed positional changes using spectral and time-frequency analyses, including continuous wavelet transform (CWT).

Main Results:

• mTBI subjects showed significantly larger changes in total hemoglobin concentration (THC) during postural changes compared to controls (9.49 µM vs. 1.03 µM).
• Elevated LFO power was consistently observed in mTBI across slow frequency bands (0.01-0.2 Hz), especially in the Slow-5 band (0.01-0.027 Hz).
• CWT analysis confirmed persistent amplification of LFOs in mTBI during and after postural transitions, indicating dysregulated cerebral vasomotion.

Conclusions:

• Low-frequency oscillations in cerebral hemodynamics, particularly those derived from total hemoglobin concentration, are altered in individuals with mTBI.
• These LFO measures show promise as early, non-invasive biomarkers for detecting impaired cerebral autoregulation following mTBI.
• FD-fNIRS offers a potential tool for objective assessment of hemodynamic dysregulation in mTBI.