Dominant hemisphere's vulnerability may explain chronic fatigue after mild traumatic brain injury (mTBI)

Objectives Patients with mild traumatic brain injury (mTBI) may present with impaired neuropsychological function. The study objective was to investigate its correlation with resting rCBF.

Methods Fifteen right-handed mTBI patients (12 F, 3 M, 45±11 years) with chronic fatigue underwent Tc-99m ECD brain perfusion SPECT at rest and also the PASAT (Paced Auditory Serial Addition Task) consisting of 4 sessions. Patients with reproducible low scores were considered as impaired neuropsychological function. SPECT images were analyzed using 3D-SSP. Comparison with normal database of 15 age- and sex-matched volunteers provided individual z-score maps allowing visualization of regional perfusion abnormality. The results were summarized in 10 cortical regions and were statistically investigated.

Results Total scores of 4 PASAT sessions for the normal controls were 147 ± 24, while patients with mTBI were 158 ± 12 (p = n.s) for preserved (9/15), and 74 ± 38 (p < 0.0001) for impaired (6/15) neuropsychological function. Z-score maps and statistical analyses observed laterality towards hypoperfusion (higher z-score values) in the left hemisphere, particularly in patients with preserved neuropsychological function (1.32 ± 0.35 vs. 1.59 ± 0.26, p < 0.05).

Conclusions Patients with mTBI showed hypoperfusion particularly in the dominant (left) hemisphere, which may explain fatigue symptoms even without abnormal neuropsychological test. Patients with impaired function did not demonstrate laterality, probably due to globally reduced rCBF.