# Add a break between theorem head and theorem body if theorem note (the #3 arg) exists

I'm using the amsthm package for theorem style setting. I want the style like:

Theorem 1 A triangle ...

Theorem 2 (someone)

A square ...

that is, when the theorem includes a note, the body should begin with a new line after the theorem head.

\documentclass{article}
\usepackage{ntheorem}
\usepackage{marginnote}
\makeatletter
\newtheoremstyle{optbreak}%
{\item[\hskip\labelsep \theorem@headerfont ##1\ ##2\theorem@separator]}% from plain style