Table 2.

Differential diagnosis between primary angiitis of the central nervous system (PACNS) and reversible cerebral vasoconstriction syndrome (RCVS) (adapted from Calabrese et al. 2007 [31])

	RCVS	PCNSV
Feature	Recurrent thunderclap headache	Insidious, chronic headache
Infarct pattern	‘Watershed’	Small, scattered
Lobar haemorrhage	Common	Very rare
Cortical SAH	Common	Very rare
Reversible oedema	Common	Possible
Angiography	‘Sausage on a strine’ sign	Irregular, notched, ectasia

SAH: subarachnoid haemorrhage.