Clinicopathologic Reports, Case Reports, and Small Case Series
May 2002

Primary Aberrant Oculomotor Nerve Regeneration From a Posterior Communicating Artery Aneurysm

Author Affiliations

Copyright 2002 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.2002

Arch Ophthalmol. 2002;120(5):663-665. doi:

Primary aberrant regeneration or oculomotor nerve synkinesis is a rare condition in which cranial nerve III regeneration occurs without a preceding, acute palsy. It has been typically associated with aneurysms or meningiomas in the cavernous sinus that do not warrant urgent imaging.1 We describe a patient with primary aberrant regeneration caused by an aneurysm located at the junction of the left posterior communicating (PCOM) and posterior cerebral arteries, indicating that imaging should not be delayed.

Report of a Case

A 65-year-old woman complained of right eyelid ptosis for 3 years. She denied diplopia. Her medical history was unremarkable. Her visual acuity was 20/25 OD and 20/20 OS. The eyelid margin to corneal reflex distance measured 2 mm OD and 4 mm OS. Her right pupil was 4 mm and reacted briskly to light. Her left pupil was 5 mm and did not react to light. No relative afferent pupillary defect was observed.

The patient assumed a chin-up position in primary gaze. The left eye had decreased elevation, adduction, and infraduction; motility was full in the right eye (Figure 1). With the right eye fixating at distance in primary position, she had 35–prism diopter (PD) hypotropia and 8 PD exotropia of the left eye. The hypotropia increased in upward gaze to 40 PD and the exotropia increased to 12 PD. The left upper eyelid retracted in downward gaze and adduction (pseudo–von Graefe sign). Slitlamp examination, tonometry, and ophthalmoscopic examination results were normal.

Figure 1.
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In primary position (center), there is a left hypotropia and left exotropia. A mild right ptosis is present. There is limited elevation, adduction, and infraduction in the left eye. Upper eyelid retraction is seen on adduction and infraduction in the left eye (lower left).

Since these findings suggested aberrant regeneration of the oculomotor nerve in her left eye, magnetic resonance imaging and magnetic resonance angiography of the brain were performed. The results revealed an enhancing lesion in the interpeduncular cistern, most likely impinging the left oculomotor nerve (Figure 2). Results of cerebral catheter angiography confirmed this to be a partially thrombosed aneurysm at the junction of the left PCOM and posterior cerebral arteries (Figure 3). After neurosurgical consultation, it was decided that the patient receive follow-up without surgery.

Figure 2.
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Axial T1-weighted pregadolinium (A) and gadolinium-enhanced (B) magnetic resonance image showing a 1-cm enhancing mass in the interpeduncular cistern region (arrows), consistent with a partially thrombosed aneurysm.

Figure 3.
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Frontal view of the cerebral angiogram of the posterior circulation following injection of the right vertebral artery. A focal outpouching is seen (arrow) at the P1-P2 junction of the left posterior cerebral and posterior communicating arteries, consistent with a partially thrombosed aneurysm.


Aberrant regeneration occurs after damage to the oculomotor nerve and is thought to be caused by misdirection of regenerating axons to anomalous connections.2 Clinically, the upper eyelid retracts on attempted downward gaze (pseudo–von Graefe sign) or adduction; there is minimal to no ptosis in primary position and there may be limited elevation, adduction, or infraduction. Also, the pupil, which does not react to light, may constrict on adduction and infraduction.

Primary aberrant regeneration occurs without a history of acute third cranial nerve palsy. This syndrome was originally thought to be pathognomonic of cavernous sinus meningiomas.1 Immediate imaging was not recommended since these masses are slow growing. Subsequently, other intracavernous mass lesions (aneurysms) were found to produce the syndrome.3

However, unruptured, extracavernous, intradural aneurysms may rarely cause primary aberrant regeneration.3,4 Our patient is the fourth in the literature, to our knowledge, in whom a PCOM aneurysm has caused primary aberrant regeneration.35 In 1952, Levin5 described a 68-year-old woman with primary aberrant regeneration who subsequently died of a ruptured aneurysm at the junction of the left internal carotid and PCOM arteries. Cox et al3 described a 76-year-old woman with primary aberrant oculomotor regeneration and chronic eye pain due to a large, partially thrombosed aneurysm at the junction of the right PCOM and internal carotid arteries. No surgery was performed. Varma and Miller4 described a 64-year-old woman with painless primary oculomotor nerve regeneration caused by an aneurysm at the junction of the right PCOM and internal carotid arteries. Their patient underwent successful aneurysm clipping.

Our patient had painless primary aberrant regeneration caused by a partially thrombosed aneurysm at the junction of the left PCOM and posterior cerebral arteries. This is the first reported instance of an aneurysm at this location causing primary oculomotor nerve synkinesis. Although primary aberrant regeneration is most likely associated with slow-growing cavernous sinus lesions, PCOM aneurysms rarely cause this syndrome. We believe that patients with primary aberrant oculomotor nerve regeneration should undergo immediate imaging to detect potentially treatable extracavernous, intradural aneurysms.

Corresponding author and reprints: Peter J. Savino, MD, Wills Eye Hospital, 900 Walnut St, Philadelphia, PA 19107.

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Cox  TAWurster  JBGodfery  WA Primary aberrant regeneration due to intracranial aneurysm. Arch Neurol. 1979;36570- 571. Article
Varma  RMiller  NR Primary oculomotor nerve synkinesis caused by an extracavernous intradural aneurysm. Am J Ophthalmol. 1994;11883- 87.
Levin  PM Intracranial aneurysms: clinicopathologic considerations of oculomotor-nerve regeneration and intracerebral hemorrhage. Arch Neurol Psych. 1952;67771- 786. Article