I'm not sure if you meant that the CT scan showed active bleeding (as if the angioma had ruptured) or just 'blood' within the angioma - I presume it just showed blood within the angioma which is typical (without seeing the MRI it is difficult for me to comment acurately.
It may very well be an 'incidentaloma' - an incidental finding during a workup for a more benign condition such as a typical/noncomplicated headache. The question is then what do you do with it, and is it causally related to the headache - I suspect not if it is only 1cm in size. The location of the angioma from the info you provide is not that uncommon - they can occur anywhere. the spinal tap was probably done to look for evidence of bleeding/red blood cells.
An MRI can provide evidence that there was bleeding in the past by detecting blood degradtion products in the tissue around the angioma - usually only if a GRADIENT ECHO scan was included in the MRI.
The shaking of teh left hand could be a seizure, but would not typically result from a lesion in that spot (by teh ventricle) - a neurologist should be ablt to figure this out with an EEG.
Lack of reflexes ?all over, is relatively nonspecific and does not suggest anything else for now.
Discuss your concerns with your neurologist, but in all likliehood it should be left alone
Good luck