Correspondence

Eye (2006) 20, 1416–1417. doi:10.1038/sj.eye.6702272; published online 17 February 2006

Recurrent isolated sixth nerve palsy secondary to an intracavernous carotid artery aneurysm

D Q Nguyen1, L Perera1 and G Kyle1

1Department of Ophthalmology, University Aintree Hospital, Rice Lane, Liverpool L9 1AE, UK

Correspondence: DQ Nguyen, St Paul's Eye Unit, Department of Ophthalmology, Royal Liverpool University Hospital, Prescot Street, Liverpool L7 8XP, UK. Tel: +44 7971 929 856; Fax: +44 151 706 5861; E-mail: danqbnguyen@hotmail.com

Sir,

We report the first case of a recurrent isolated painless sixth nerve palsy in a 60-year-old lady secondary to a large saccular aneurysm of the intracavernous carotid vasculature. This case demonstrates that recovery of an isolated sixth nerve palsy in a patient with presumed vasculopathic risk factors does not exclude a compressive lesion and may necessitate further investigation.

Top

Case report

A 60-year-old lady was initially referred with a 6-week history of horizontal diplopia, which had resolved spontaneously when seen in clinic. Her only significant past history of note was medically controlled hypertension. Ocular and neurological examinations were normal. Blood tests, other than an elevated cholesterol level of 6.0 mmol, were normal. The presumed diagnosis was a resolved sixth nerve palsy of microvascular origin. After 3 months, she re-represented with a painless right sixth nerve palsy, which again completely recovered spontaneously. After 18 months, she experienced a further episode of a painless, isolated right sixth nerve palsy (Figure 1). An MRI scan and subsequent angiography were performed which revealed a large right intracavernous carotid aneurysm (Figure 2). Neurosurgical opinion was to manage the aneurysm conservatively. Her sixth nerve palsy partially recovered before experiencing a further reoccurrence, whereby she subsequently received botulinum toxin injection into her right medial rectus muscle with a good result.

Figure 1.
Figure 1 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

(a and b) Right lateral rectus palsy.

Full figure and legend (195K)

Figure 2.
Figure 2 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

MRI showing large right intracavernous carotid artery aneurysm.

Full figure and legend (60K)

Top

Comment

The majority of sixth nerve palsies in older adults are attributed to presumed microvascular disease or are of unknown cause.1, 2 Up to 7% of sixth cranial nerve palsies are reportedly related to an intracerebral aneurysm1, 2, 3, 4 although the majority of these were accompanied by other cranial nerve palsies and additional neurological symptoms and signs. Recurrent isolated sixth nerve palsies of nonmicrovascular origin are rare. They have been associated with immunisation and viral illness in children,5 Rathke's pouch cyst3 and are known to occur in patients with skull base tumours.6 Hamilton and Lessell7 reported five cases of idiopathic recurrent isolated unilateral lateral rectus muscle palsy in adults.

Dolichoectasia of the ipsilateral cavernous carotid artery has been associated with a single episode of 8 and a persistent 9 sixth nerve paresis, and was also identified as the cause in a 59-year-old man who experienced multiple recurrent unilateral sixth nerve paresis.10 Dolichoectasia is a fusiform dilatation of an artery whereas an aneurysm is a focal dilatation of an artery with a neck. To the best of our knowledge, we report the first case of a recurrent isolated sixth nerve palsy secondary to a saccular aneurysm of the intracavernous carotid vasculature.

Mechanisms by which an aneurysm may cause abducens nerve dysfunction include direct compression due to the close proximity of the nerve to the carotid artery in the cavernous sinus and ischaemia secondary to intraluminal thrombus formation and blockade of the vasa nervora. Exactly what causes nerve dysfunction followed by spontaneous recovery despite the continued presence of the aneurysm is unknown, but similar mechanisms are described in cases of spontaneous aberrant regeneration of the oculomotor nerve11 in patients with untreated slow growing compressive lesions of the cavernous sinus. As the abducens nerve innervates only one muscle, regeneration may restore normal function.

Although it is feasible that the repeated recurrence was simply a micropathic angiopathy with reportedly 31% of individuals with vasculopathic sixth nerve palsies experiencing recurrent palsies;12 or secondary to mechanisms involving interruption of the blood supply to the nerve unrelated to compression. We feel that the proximity of such a large lesion, makes it likely that it was the underlying cause.

General neuro-ophthalmic opinion advocates observation of a sixth nerve palsy in patients with vasculopathic risk factors. However, a recent paper suggests that systemic hypertension alone is not a significant independent risk factor for sixth nerve paresis.13 This case demonstrates that the recovery of a painless isolated sixth nerve palsy in a patient with presumed vasculopathic risk factors does not exclude a compressive lesion and necessitates further investigation.

Top

References

  1. Patel SV, Mutyala S, Leske DA, Hodge DO, Holmes JM. Incidence, associations, and evaluation of sixth nerve palsy using a population-based method. Ophthalmol 2004; 111: 369–375. | ISI |
  2. Tiffen PAC, MacEwen CJ, Craig EA, Clayton G. Acquired palsy of the oculomotor, trochlear and abducens nerves. Eye 1996; 10: 377–384. | PubMed |
  3. Richards BW, Jones Jr FR, Younger BR. Causes and prognosis in 4,278 cases of paralysis of the oculomotor, trochlear, and abducens cranial nerves [see comments]. Am J Ophthalmol 1992; 113: 489–496. | PubMed | ISI | ChemPort |
  4. Bendszus M, Beck A, Kolzenburg M, Vince GH, Brechtelsbauer D, Littan T et al. MRI in isolated sixth nerve palsies. Neuroradiology 2001; 43: 742–745. | Article | PubMed | ISI | ChemPort |
  5. Werner DB, Savino PJ, Schatz NJ. Benign recurrent sixth nerve palsies in childhood secondary to immunisation of viral illness. Arch Ophthalmol 1983; 101: 607–608. | PubMed | ISI | ChemPort |
  6. Volpe NJ, Lessell S. Remitting sixth nerve palsy in skull base tumours. Arch Ophthalmol 1993; 111: 1391–1395. | PubMed | ISI | ChemPort |
  7. Hamilton SR, Lessell S. Recurrent idiopathic lateral rectus muscle palsy in adults. Am J Ophthalmol 1991; 112: 540–542. | PubMed | ISI | ChemPort |
  8. Foroozan R. Spontaneous resolution of sixth nerve palsy with ipsilateral cavernous carotid dolichoectasia. B J Ophthalmol 2004; 88: 586–587. | Article | ISI | ChemPort |
  9. Neugebauer A, Kirsch A, Fricke J, Russmann W. New onset of crossed eyes in an adult. Surv Ophthalmol 2001; 45: 335–344. | Article | PubMed | ISI | ChemPort |
  10. Blumenthal EZ, Gomori JM, Dotan S. Recurrent abducens nerve palsy caused by dolichoectasia of the cavernous internal carotid artery. Am J Ophthalmol 1997; 124: 255–257. | PubMed | ISI | ChemPort |
  11. Cox TA, Wurster JB, Godfrey WA. Primary aberrant oculomotor regeneration due to intracranial aneurysm. Arch Neurol 1989; 36: 570–571.
  12. Sanders SK, Kawasaki A, Purvin VA. Long-term prognosis in patients with vasculopathic sixth nerve palsy. Am J Ophthalmol 2002; 134: 81–84. | Article | PubMed | ISI |
  13. Patel SV, Homes JM, Hodge DO, Burke JP. Diabetes and hypertension in isolated sixth nerve palsy. Ophthalmol 2005; 112: 760–763. | ISI |
Top

Acknowledgements

We have no financial, commercial, proprietary or competing interests related to the person described in this article and this has not been previously published or presented at any meeting. There has been no public or private support/funding of this submission.