In the UK, you are legally required to notify the Driver and Vehicle Licensing Agency (DVLA) of any medical condition that may affect your driving. This includes subarachnoid haemorrhage, whatever the cause. You should not drive until you receive DVLA approval and your doctor has confirmed that you are fit to continue driving. This could be anything from a few weeks to a year or more. The procedure is explained in the following leaflet from the DVLA:
You should also tell your insurance company about your condition or future claims may be invalid. Driving against medical advice may also invalidate your insurance.
If you are in any doubt as to whether you should drive or not, you should contact the DVLA (see the links below) or ask your doctor.
This information applies to the UK only. The procedure in countries other than the UK may be different.