2025 American Academy of Neurology Abstract Website

Objective:

In this observational cohort study, we hypothesize that patients undergoing routine fluid shifts exhibit characteristic cranial accelerometry signatures at different fluid balances.

Background:

In patients with critical neurologic illness, close monitoring of fluid status is needed to identify patients at risk for secondary neurologic injury – especially during routine large-volume fluid shifts seen during diuresis and hemodialysis or in neurologic alterations of fluid homeostasis such as cerebral salt wasting. Recent studies have suggested that skull motion produced by pulsatile cerebral blood flow may a useful tool in vasospasm and cerebral edema; therefore, identification of a unique cranial accelerometry signal seen in systemic fluid shifts may be a valuable adjunct neuromonitoring tool.

Design/Methods:

Head pulse recordings were obtained prior to, during, and after hemodialysis using a device consisting of a headband-mounted triaxial accelerometer, circuit board, and electrocardiogram. This data was analyzed using MATLAB2022a, summed to generate a time-domain force signal, converted to the frequency domain using a Discrete Fourier Transform, normalized to the amplitude of the most prominent frequency band (5Hz), and weighted/averaged by volume removal.

Results:

Recordings were obtained in 14 subjects (9 inpatient, 5 outpatient). Average recording duration was 182min (+/-8.0min), average weight change was 2.2kg (+/-0.87kg), and average volume removed was 2172mL (+/-859.2mL). There was a significant 29% reduction in the 6Hz frequency band in pre-dialysis recordings compared to a 43% increase in dialysis recordings and a shift towards higher frequencies in all bands during dialysis. There were no observable changes in frequency throughout individual hemodialysis sessions.

Conclusions:

There was a significant increase in volume-corrected head pulse frequencies in dialysis recordings compared to pre-dialysis recordings. These unique cranial accelerometry signatures may be reflective of mildly increased brain volume or resistance. Further studies are needed to clarify this relationship and to evaluate the role of cranial accelerometry in patients with abnormal neurologic presentations.