[Paralysis of the 3d cranial nerves in diabetes and common oculomotor vascularization]

The purpose of this paper is to present explanations for various patterns of IIIrd cranial nerve involvement in diabetes mellitsus, based on its vascularisation. Three clinical cases of diabetes with numerous attacks of IIIrd nerve paralysis are reported. The following patterns were observed: (1) isolated; (2) associated with Vth nerve involvement and; (3) associated with invovlement of the Vth, IVth, VIth, and occasionally IInd and VIIth nerves. An anatomical study of IIIrd nerve vascularisation demonstrates three territories which could correspond to the 3 patterns of clinical expression. The arterial branches to the IIIrd nerve give off no collaterals in the posterior region of the circle of Willis. In the supra-cavernous region, vascularisation of the IIIrd nerve may be associated with that of the IVth. Eventually, vascularisation of the IIIrd nerve in the intracavernous region is associated with that of the Vth, IVth, VIth, and occasionally IInd and VIIth cranial nerves. Thus, a painless paralysis of the IIIrd nerve (isolated or associated only with an involvement of the IVth) would predictably be related to a vascular disturbance limited to the first or second portion of this nerve, whereas a painful paralysis of the IIIrd nerve, without or with associated involvement of other cranial nerves, would relate to a vascular distrubance in the intra-cavernous region. The anatomo-clinical relationships that have been presented: (1) support the vascular basis of IIIrd nerve paralysis in diabetes; (2) explain the various clinical patterns of IIIrd nerve involvement in that disorder and; (3) act as a model which can be applied to the study of ischemic pathology in other cranial nerves and other etiologies.