Thanks for writing in.
SHM is defined as migraine attacks associated with some degree of motor weakness or hemiparesis during the aura phase and where no first degree relative has identical attacks. These patients are at an increased risk of getting typical migraine attacks. Verapamil has been found to be effective in treating some of these attacks. These patients rarely have gene mutations as compared to Familial hemiplegic migraine.
It is a rare disorder and is diagnosed with great difficulty after ruling out other serious neurological possibilities.
Hope this helps!