TLR4 and Ventriculomegaly: Furthermore, at physiological concentrations, intracerebroventricular delivery of metHgb activates TLR4 homodimers or TLR4/2 heterodimers, promoting nuclear translocation of NF‐κB as well as secretion of TNFα and IL‐1β [33, 34, 35], and is sufficient to cause ventriculomegaly [5, 34].