Catheter versus non-catheter angiography in isolated third nerve palsy

Purpose: To discuss the controversies surrounding the indications for catheter angiography versus non-catheter and less invasive angiography techniques (e.g. magnetic resonance angiography (MRA) and computerized tomography angiography (CTA)) in the evaluation of patients with a third nerve palsy. Methods: Clinical opinion-perspective and literature review. Results: The patient with an isolated third nerve palsy might have a vasculopathic (and typically benign, self limited course) etiology or a life threatening intracranial posterior communicating artery aneurysm. Although it is clear that non-isolated third nerve palsies require imaging directed at the topographical localization of the clinical findings, the evaluation of the neurologically isolated third nerve palsy remains controversial. The completeness of the external (i.e. somatic) motor dysfunction and the presence or absence of internal (i.e. pupillary) dysfunction are generally used to guide the choice of initial neuroimaging. Advances in MRA and CTA technology have reduced but not eliminated our dependence upon catheter angiography in this setting. A properly performed and interpreted MRA or CTA probably will be able to detect greater than 95% of aneurysms producing a third nerve palsy. The issues surrounding the use of catheter angiography in third nerve palsy are reviewed. Conclusions: If the clinician is highly confident in the capability, availability, and reliability of the neuroradiologist and of their institutional experience and quality of less invasive non-catheter MRA and CTA and if the risk of aneurysm is low or if the risk of angiography is high (e.g. elderly, renal failure, iodinated contrast allergy, risk of stroke) then MRI and MRA (or CTA) may be a reasonable alternative to catheter angiography. Patients with a moderate or uncertain risk of aneurysm and a lower risk for catheter angiography or if there is a low confidence in the quality or the interpretation of the institutional MRA (or CTA) may still require catheter angiography in select circumstances. The lowest risk categories for aneurysm are the isolated dilated pupil without ptosis or motility deficit (generally not a third nerve palsy but more commonly the tonic pupil, pharmacologic dilation, or iris damage) and the isolated, pupil-spared but otherwise complete external dysfunction third nerve palsy in a vasculopathic patient. In these patients, the risks of catheter angiography is probably higher than the risks for aneurysm and CTA or MRA is probably sufficient to exclude aneurysm. Patients with high risk for aneurysm (e.g. acute painful pupil involved third nerve palsy) however probably still require strong consideration for catheter angiography but this decision must be individualized.