WPF Header of the row-header column

Question

I need to add an Header on my Row-Header Column.

My DataGrid is a custom DataGrid.

This is my Row-Header:

<Datagrids:ImpDataGrid.RowHeaderStyle>
    <Style TargetType="DataGridRowHeader">
        <Setter Property="Content" Value="{Binding Linea}" />
    </Style>
</Datagrids:ImpDataGrid.RowHeaderStyle>

What should I do to add an Header to my RowHeader Column?