[Diagnostic approach for acquired and isolated third cranial nerve palsy: 18 case reports].

Purpose: The aim of this work was to establish a clinical diagnostic flow chart for third nerve palsy.

Material And Methods: [corrected] We report a series of 18 patients with third nerve palsy seen at the department of ophthalmology in the Marseille North Hospital between 1997 and 1999. All patients had a complete clinical examination and were classified into four clinic types. An etiological diagnosis was given in all cases after a systematic approach, including first intention MRI.

Result: Three patients presented abnormal pupil reflex secondary to an aneurysm diagnosed by carotid angiography; the MRI was pathological in two cases. The 15 other patients had pupil sparing. Among them, eight patients had a total external involvement secondary to diabetes mellitus; the MRI suggested an ischelic origin in four cases (50%) showing nuclear infarctus. In seven cases the external involvement was incomplete secondary to multiple etiologies: demyelinating illness, traumatic lesions, orbital tumor, metastasis or myasthenia gravis. The MRI contributed to diagnosing four cases.

Conclusion: The MRI must be systematically used in all the patients with isolated third nerve palsy, except for patients with pupil sparing associated with total external involvement. Ischemic etiology was the rule: simple clinical surveillance is proposed, total spontaneous regression being the norm.