\newtheoremstyle{changebreak}%
  {\item[\rlap{\vbox{\hbox{\hskip\labelsep \theorem@headerfont
          ##2\ ##1\theorem@separator}\hbox{\strut}}}]}%
  {\item[\rlap{\vbox{\hbox{\hskip\labelsep \theorem@headerfont
          ##2\ ##1\ (##3)\theorem@separator}\hbox{\strut}}}]}

\usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc} %Symbol- und Zeichensatz
\usepackage[left=4cm,right=3.5cm,top=2cm,bottom=3cm, includeheadfoot]{geometry}  %Seitenränder
\usepackage{scrpage2}
\pagestyle{scrheadings}
\clearscrheadfoot
\cfoot{\pagemark}
\usepackage{graphicx,textcomp,booktabs}
\usepackage{calc}
\usepackage{mathptmx,courier}
\usepackage[dvips]{color}
\usepackage[scaled]{helvet}
\usepackage[ngerman]{babel}
\usepackage{ae}              %Umlaute
\usepackage{amssymb,amsfonts,amsmath}
\usepackage[thmmarks,hyperref]{ntheorem}

\makeatletter
\newtheoremstyle{changebreak}%
  ...
\makeatother