Table 3:

Possible distinguishing criteria between SDHy and cSDH in neuroimaging^{^a}

Criterion	SDHy	cSDH	Remarks
Neomembranes/septa/chamber formations	No	Yes	MRI more sensitive than CT
Neomembranes/septa/chamber formations	No	Yes	IV contrast may improve the detection of neomembranes
			First formation of neomembranes macroscopically visible after ∼10 days;⁷⁴ when using MR imaging contrast after ∼2–4 weeks²²
			Late (chronifying) SDHys may also have first thin neomembranes (transitional phase to cSDH, terminologic gray zone)
Structure/composition	Rather homogeneous (CSF-like)	Rather heterogeneous/complex (evidence for blood products and CSF)	Heterogeneity of different cSDH fluid areas by neomembrane-associated chamber formations
Coexisting brain edema	Possible	Unlikely	Brain edema = rather acute/subacute
Growth behavior	At first, often rapidly progredient in growth; subsequently, mostly regredient in growth or static	Rather static/only slowly progredient in growth	Requires serial neuroimaging
Density	Very CSF-like, between 3.5 and 11.5 HU⁶⁶	Slightly higher density than CSF due to admixture of blood components, between 6.4 and 24.6 HU⁶⁶	Requires standardized measurements of densities
			CSF = 5–10 HU
			SDHHys with low blood fraction and high dilution with CSF are likely to show HU values just above 10 HU as well; thus, differentiation between SDHy and SDHHy may be difficult

↵a According to Hedlund22 Wittschieber et al,27 Vezina,28 Zouros et al,29 Case,33 Bergström et al,66 and Walter et al.74