[Benign paralysis of the last 4 cranial nerves. Arguments in favor of an ischemic mechanism].

The last four cranial nerves are fed by the ascending pharyngeal artery, a branch of the external carotid artery. The fact that paralysis of these nerves may occur immediately after arteriography of the external carotid artery demonstrates that ischaemic truncular neuropathies do exist. The deficit is sudden and usually regressive. Ischaemia may account for regressive paralysis of these nerves reported in diabetes, herpes zoster and after some traumas. Apparently idiopathic and benign paralysis might be due to the same mechanism. All 4 nerves may be affected, or only the IXth, Xth and XIth nerves, or the XIth nerve may be spared, being fed by two arteries. Apart from the obvious case of arteriographic accident, the diagnosis of paralysis of ischaemic origin can only be made after other causes, notably compression, have been excluded, since direct evidence of arterial obstruction is exceptionally obtainable; regression at follow-up is a major argument in favour of ischaemia.