1. Control #: 633 Poster #: EP-82 Duy LAN, Badeeb AO, Coffin P, Martin D, Small JE

2. No Disclosures

3. Purpose: Background  The most valuable literature about the natural history of a subdural hematoma (SDH) is several decades old.  Nonspecific density terms without objective measurements are seen in the literature

4. Purpose: Background continued  Previous descriptions have lead to the notion that hyperacute or even acute SDH may be entirely hypodense  The literature is unclear if even a small hyperdense component is absent.  Case reports of homogenously hypodense acute SDH exist, and one possible explanation in the literature is anemia

5. Purpose  The purpose of this study is to determine if acute SDH always contain a hyperdense component (HU>40)  In addition, we sought to demonstrate if anemia correlated with hypodense acute SDH.

6. Materials and Methods  Inclusion criteria: Patients that had more than 2 head CTs in 48 hours. Scans took place between January and June 2013 Patients had a subdural collection on the first scan.

7. Materials and Methods  Exclusion criteria: Patients could not have a SDH before initial presentation if prior imaging was available. Post-surgical collections were excluded. Patients had to be able to provide a history of a single event compatible with development of a SDH.

8. Materials and Methods  A total of 49 patients with SDH were included in the study.  All subsequent follow-up examinations until surgical intervention, CT documented resolution, or loss to follow- up were included in the analysis  A total of 200 studies were analyzed.

9. Materials and Methods  The degree of SDH heterogeneity was classified into homogenous, simple layering, or heterogeneous.  The Houndsfield units (HU) of the densest portion of the SDH were recorded.  The patient’s hematocrit on the day of the first scan was recorded.

10. Subdural classification Homogeneous Simple layeringHeterogeneous

11. Green arrow shows the portion of the SDH measured for density. Red arrow shows areas not measured for density.

12. Materials and Methods  Two tailed heteroscedastic student T- test was used to derive statistical significance.

13. Results All acute SDH had a hyperdense component (>40 HU) (<7 days, or less than 168 hours). (P<0.05)

14. Results: Natural history of SDH Density over time (days) A hyperdense component (>40 HU) was present in all SDH during the first week

15. Results (continued) 100% of our anemic patients (N=9; 13 scans; hematocrit ≤33 Range: 15.6 – 33) had hyperdense (>40 HU) component to their acute (<7 days) SDH.

16. Conclusion  All SDH in our study had a hyperdense (>40 HU) component in the acute phase (<7 days)  Even in anemic patients with hematocrits as low as 15.6 a hyperdense SDH component was evident.  Our findings suggests that anemia alone does not correlate with an acute isodense to hypodense SDH.

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