'Side locked' migraine and trigeminal autonomic cephalgias: evidence for clinical overlap.

This paper will discuss evidence which supports a link between 'side locked' migraine (SLM) and the trigeminal autonomic cephalgias (TACs). Recent papers brought strictly unilateral primary headaches into focus, proposing new classification and discussing pathophysiological mechanisms. We reviewed those proposals and present evidence that SLM falls in between the well-defined TACs and side shifting migraine (SSM). It is difficult to differentiate SLM from the recently proposed headache subtype called hemicrania generis incerti (i.e. hemicrania continua unresponsive to indomethacin). We also present cases that may exemplify the considerations made in the paper.