From the Department of Radiology, Division of Neuroradiology, University of Pittsburgh Medical Center, 200 Lothrop St, PUH 2nd Floor, Suite 201 East Wing, Pittsburgh, PA 15213.
PURPOSE To determine the performance of Shannon entropy (SE) as a diagnostic tool in patients with mild traumatic brain injury (mTBI) with posttraumatic migraines (PTMs) and those without PTMs on the basis of analysis of fractional anisotropy (FA) maps.
MATERIALS AND METHODS The institutional review board approved this retrospective study, with waiver of informed consent. FA maps were obtained and neurocognitive testing was performed in 74 patients with mTBI (57 with PTM, 17 without PTM). FA maps were obtained in 22 healthy control subjects and in 20 control patients with migraine headaches. Mean FA and SE were extracted from total brain FA histograms and were compared between patients with mTBI and control subjects and between patients with and those without PTM. Mean FA and SE were correlated with clinical variables and were used to determine the areas under the receiver operating characteristic curve (AUCs) and likelihood ratios for mTBI and development of PTM.
RESULTS Patients with mTBI had significantly lower SE (P <.001) and trended toward lower mean FA (P =.07) compared with control subjects. SE inversely correlated with time to recovery (TTR) (r = -0.272, P =.02). Patients with mTBI with PTM had significantly lower SE (P <.001) but not mean FA (P =.15) than did other patients with mTBI. SE provided better discrimination between patients with mTBI and control subjects than mean FA (AUC = 0.92; P =.01), as well as better discrimination between patients with mTBI with PTM and those without PTM (AUC = 0.85; P <.001). SE of less than 0.751 resulted in a 16.1 increased likelihood of having experienced mTBI and a 3.2 increased likelihood of developing PTM.