Arterial dissection is an increasingly recognized but none the less rare cause of ischaemic stroke and TIAs. Sometimes there is a predisposing cause, particularly neck trauma, but often there is no explanation. Blood tracks along a split within the arterial wall and there may or may not be an intimal tear so that the false lumen is in communication with the true lumen. The artery may become occluded by the wall haematoma itself, thrombosis and embolism may complicate occlusive or non-occlusive dissections, and aneurysmal bulging of the weakened wall may occur (O'Connell et al. 1985). Arterial rupture is unusual.
Before, at the time of, and even without any stroke or TIA complications, internal carotid artery (ICA) dissection frequently causes ipsilateral pain (around the eye, face, and neck), sometimes an ipsilateral Horner's syndrome due to sympathetic nerve involvement in the lesion, and occasionally a cervical bruit which the patient may hear because the lesion can be much more distal than the usual proximal site of atheromatous ICA stenosis. Lower cranial nerve palsies, particularly hypoglossal, occasionally occur as a result of aneurysmal ICA dilatation at the base of the skull, or perhaps of periarterial inflammation and haematoma formation (Sturzenegger and Huber 1993; Silbert et al. 1995; Mokri et 1996).
As well as focal brainstem and cerebellar ischaemia, vertebral dissection often causes occipital pain over the site of the arterial lesion, usually at the level of the atlas and axis, and sometimes cervical root lesions due to compression from the distended arterial wall (Caplan and Tettenborn 1992a; Hetzel et al. 1996; de Bray et al. 1997).
On angiography there is usually a long, tapered, narrow or occluded segment, perhaps with an intimal flap, double lumen, or intraluminal thrombus, and sometimes an associated aneurysm. Intracranial arterial occlusion, presumably embolic, may be seen. Carotid dissection can often be strongly suspected on Duplex scanning (Sturzenegger et al. 1993, 1995), and both carotid and vertebral dissection even more strongly suspected by a combination of axial MRI through the lesion, to show the acute haematoma in the arterial wall, with MR angiography (Auer et al. 1998).
The radiological appearances of dissection normally resolve within days or weeks. Recurrent dissections in the same, or a different artery, are very infrequent unless the patient has a rare connective tissue abnormality such as the Ehlers–Danlos syndrome (Leys et al. 1995).
Intracranial arterial dissection is much rarer, may present with subarachnoid haemorrhage due to rupture of a pseudo-aneurysm, as well as with ischaemic stroke, and is less often diagnosed during life (Farrell et al. 1985; de Bray et al. 1997).
Aortic arch dissection causes profound hypotension with global, and sometimes boundary zone, cerebral ischaemia, or focal cerebral ischaemia if the dissection spreads up one of the neck arteries. Clues to this diagnosis are anterior chest or interscapular pain along with diminished, unequal, or absent arterial pulses in the arms or neck; a normal ECG, unlike acute myocardial infarction; acute aortic regurgitation; and pericardial effusion (Gerber et al. 1986; Carrel et al. 1991, Pretre and von Segesser 1997).