Cranial Nerve VI Palsy

23 May

Submitted by Christina Brown, M.D.


  • Abducens nerve, CN VI
  • a somatic, efferent (motor) nerve that controls a single muscle; lateral rectus. 
  • sixth cranial nerve has the longest subarachnoid course of all the cranial nerves. 
  • sixth nerve nucleus is located in the pons, just ventral to the floor of the fourth ventricle and just lateral to the medial longitudinal fasciculus (MLF) [5].

RBO revisada JAN-FEV-13-en.pmd


study of 213 patients with unilateral isolated sixth nerve palsies, non-traumatic

  • 78% experienced spontaneous recovery of their palsy,
  • 37% recovering by 8 weeks
  • 74% by 24 weeks [3].
  • Only 16% failed to recover; of this group, however, almost 40 percent had serious underlying pathology accounting for their palsy.



  • primarily c/o horizontal diplopia (double vision producing a side-by-side image with both eyes open). 
  • Patients with idiopathic sixth nerve palsy often present with the sudden onset of horizontal diplopia that is better at near and worse at a distance.
  • Patients also may present with a head-turn to maintain binocularity and to minimize diplopia. [5].  
  • A sudden onset distinguishes idiopathic sixth cranial nerve palsies from tumor or myasthenia gravis [6]. 
  • Other things to pay particular attention to when dealing with sixth nerve palsies
    • fifth nerve (reduced facial sensation, often around the upper face and cornea) pointing to a lesion in the cavernous sinus
    • papilledema, suggesting a mass lesion causing raised intracranial pressure and displacement of the brainstem and thus stretching of one or both sixth nerves.


DDx – Giant cell arteritis, Mass Lesion, Myasthenia Gravis, Lyme disease, syphilis, cavernous sinus lesion, Medial Orbital Wall Fracture, Horner’s Syndrome, diabetes, meningitis [1,6]

Evaluation – For idiopathic CNVI palsy, spontaneous improvement over several weeks to months is expected, and failure to improve suggests more serious intracranial pathology.

  • 1st – Onset of presentation? A sudden onset distinguishes idiopathic sixth cranial nerve palsies from tumor or myasthenia gravis.
  • 2nd – Is a single nerve involved? Involvement of other nerves, even the opposite cranial nerve (eg, bilateral sixth nerve palsy), suggests a more serious underlying pathology.
  • 3rd – Is there a medical excuse for the problem? Diabetes, myasthenia gravis, etc.  As an example, one is more likely to work up a young person with a sixth nerve palsy than an older person in his seventies.
  • 4th – Headache? The presence of severe headache of sudden onset demands an urgent evaluation for cerebral aneurysm
  • 5th – Signs of improvement over time? Almost always point to a benign process. Isolated fourth or sixth never palsies can be observed for a few weeks. More extensive work-up should be done if the palsy does not resolve or if other symptoms appear. Persistent esotropia may require a surgical procedure.



  • Ophthalmology C/S if bilateral nerve involvement, CNV involvement, persistent esotropia.
  • Neuroimaging if high clinical suspicion for mass lesion, cerebral aneurysm.
  • If elevated ESR, CRP pointing toward temporal arteritis, start high dose steroids.



  2. Patel SV, Holmes JM, Hodge DO, Burke JP. Diabetes and hypertension in isolated sixth nerve palsy: a population-based study. Ophthalmology 2005; 112:760.
  3. King AJ, Stacey E, Stephenson G, Trimble RB. Spontaneous recovery rates for unilateral sixth nerve palsies. Eye (Lond) 1995; 9 ( Pt 4):476.
  4. Gutman I, Levartovski S, Goldhammer Y, et al. Sixth nerve palsy and unilateral Horner’s syndrome. Ophthalmology 1986; 93:913.
  6. Kline LB, Glaser JS. Bilateral abducens nerve palsies from clivus chordoma. Ann Ophthalmol 1981; 13:705.
  7. picture

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