Feasibility of Microneurography to Measure Sympathetic Nerve Activity Following Severe Traumatic Brain Injury During Inpatient Rehabilitation

Research Objectives: To demonstrate the feasibility of using microneurography to objectively measure muscle sympathetic nervous system activity (MSNA) in a patient admitted to inpatient rehabilitation (IPR) following traumatic brain injury (TBI). To date, objective measures of sympathetic nervous system (SNS) activity with MSNA have not been completed in persons with moderate to severe TBI nor done in a hospital environment.

Design: This study included a single subject to demonstrate the feasibility of obtaining MSNA, which is the criterion standard to measure SNS activity, during IPR admission following TBI.

Setting: IPR at a county hospital.

Participants: A 29-year-old previously healthy male who suffered severe TBI (GCS 3 at scene) due to motor vehicle accident 27 days prior to testing. Our previously published “normative” data from 10 healthy males with mean age 29 years (SD 6) was used as a comparison.

Interventions: N/A

Main Outcome Measures: MSNA burst frequency and incidence were measured using microneurography via a sterile tungsten microelectrode inserted into the left radial nerve, adjusted until pulse-synchronous bursts appeared in response to breath holding.

Results: Resting heart rate in the patient with TBI was 101 beats per minute. MSNA burst frequency was 37 bursts/minute and burst incidence was 35 bursts per 100 heartbeats. These findings suggest elevated SNS activity in this patient with severe TBI when compared with “normative” data from 10 healthy men with mean resting heart rate 61 beats per minute (SD 11) that had mean MSNA burst frequency of 17 bursts/minute (SD 8) and burst incidence of 29 bursts per 100 heartbeats (SD 14).

Conclusions: This study highlights the feasibility of making direct recordings of MSNA in a patient with severe TBI while admitted to IPR. This information is crucial to better understand the impact of TBI on SNS function short-term after injury.

Author(s) Disclosures: This project was funded by National Institute of Neurological Disorders and Stroke (NINDS) 1R01NS133245-01, PI: Shanti Pinto, MD