8B

Acute Pupil Involved Third Nerve Palsy

CASE NO. 8B

A 52-year-old woman presented in the ER complaining of a sudden severe headache followed by emesis and photophobia. While she was being driven to the ER, she felt her left eyelid starting to close.

In the ER, her visual acuity was 20/20 OD and 20/30 OS. The left pupil was dilated and unreactive to light. There was limitation in adduction, elevation and depression of the left eye and complete ptosis OS (Figs. 8B.1 and 8B.2). The remainder of the eye exam was normal.

Dr. Lee. The clinical presentation of severe headache, nausea, vomiting, photophobia and signs of a third nerve palsy should be considered to be a ruptured aneurysm until proven otherwise. Although a complete exam is important in all patients in this setting, getting to a diagnosis quickly and then performing an imaging study might be life-saving. The motility findings are consistent with a third nerve palsy (Fig. 8B.2) and the pupil involvement should invoke the “rule of the pupil.” The rule simply stated is that a pupil-involved third nerve palsy is an aneurysm of the posterior communicating arteryinternal carotid artery junction until proven otherwise. Typically in this setting I would recommend starting with a noncontrast CT of the head to exclude hemorrhage (e.g. parenchymal, intraventricular, or subarachnoid bleed) and a contrast CT angiogram for aneurysm. If the noncontrast head CT shows subarachnoid hemorrhage or if the clinical exam is still highly suggestive of aneurysm, then catheter

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Emergencies in Neuro-Ophthalmology: A Case Based Approach

Fig. 8B.1. External photograph at presentation shows the complete left ptosis.

Fig. 8B.2. External photographs demonstrating a left third nerve palsy. Note normal abduction OS and there was intact intorsion on downgaze consistent with an intact fourth nerve function OS.

angiography might still be necessary even with a negative CTA. The use of CTA alone in this setting is highly dependent upon the skill of the interpreting neuroradiologist and the quality of the institution’s CTA technology and the individual CTA images. In a patient with a third nerve palsy and no clinical or radiographic evidence for subarachnoid hemorrhage, then an MRI (MRA) is useful to exclude non-aneurysmal causes for third nerve palsy. Although in most centers

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Acute Pupil Involved Third Nerve Palsy

a CTA is superior to an MRA for the detection of aneurysm. The MRI is superior to the CT scan for following the course of the third nerve for alternative etiologies other than aneurysm. The order of testing: CTA followed by MRI (MRA), or vice versa, is an individual institution’s decision, especially as both techniques (CTA and MRA) continue to improve and have proponents on both sides.

Dr. Brazis. Acute third nerve palsy is a neuro-ophthalmogic emergency requiring immediate CT and CTA. Immediate evaluation by a neurosurgeon or endovascular aneurysm specialit is required. I agree with Dr. Lee’s comments about the use of CTA vs MRA.

Course. The noncontrast CT scan showed intraventricular hemorrhage (Fig. 8B.3). The CT angiogram showed a left posterior communicating artery aneurysm (PCOM) and another asymptomatic right MCA aneurysm (Figs. 8B.4A, 8B.4B, and 8B.4C). The patient underwent diagnostic and therapeutic catheter angiography with endovascular coiling and obliteration of the aneurysm via interventional radiology.

Fig. 8B.3. Noncontrast CT head shows hyperdensity consistent with blood in the ventricles (arrow).

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Emergencies in Neuro-Ophthalmology: A Case Based Approach

Fig. 8B.4. (A, B, C). A CT angiogram showing a left posterior communicating artery aneurysm (PCOM), labeled with yellow arrow and a right MCA aneurysm.

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Acute Pupil Involved Third Nerve Palsy

Fig. 8B.4. (Continued )

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Emergencies in Neuro-Ophthalmology: A Case Based Approach

Fig. 8B.4. (Continued )

She was discharged from the hospital two weeks later. The third nerve palsy improved slowly over the next four months but did not resolve completely (Figs. 8B.5 and 8B.6). A follow-up diagnostic CTA showed complete obliteration of the aneurysm without recurrence. The second asymptomatic MCA aneurysm was treated one year later.

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Acute Pupil Involved Third Nerve Palsy

Fig. 8B.5. External photograph post endovascular coiling shows improving ptosis.

Fig. 8B.6. External photograph post coiling showing improved ophthalmoplegia.

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