Abducens nerve palsy

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Background

  • Also called 6th cranial nerve (CN VI).
  • Most common ocular nerve palsy
  • Innervates the ipsilateral lateral rectus muscle controlling eye abduction
  • Esotropia of the affected eye due to the unopposed action of the medial rectus muscle, innervated by the oculomotor nerve (CN III). [1]

History

Patient with abducens nerve palsy may complain of:[1][2]

  • Frequently present with diplopia upon attempting lateral gaze and esotropia at rest
  • May have a head turn to help correct their diplopia
  • Vision loss
  • Hearing loss
  • Symptoms of vasculitis, most commonly giant cell arteritis (headache, tenderness of the scalp, jaw claudication, reduced visual acutity, tinnitus, fever
  • Ask about history of diabetes, hypertension, stroke, fever, and headache.

Examination

  • A typical workup of the abducens nerve involves: excluding paresis of the other cranial nerves, checking the ocular muscle movements, for papilledema, and testing pupillary response.
  • To test the ocular motor nerves (CN III, IV, and VI), one can trace a full H-pattern with their finger and have the patient follow the finger only with their eyes. Patients with abducens nerve palsy are unable to move the affected eye laterally. In order to avoid diplopia, patients will turn their heads away from the lesion so that both eyes are looking sideways. Check deep tendon reflexes and strength to exclude corticospinal tract involvement. [3][4]

Differential Diagnosis

  • Increased intracranial pressure (ICP): Because of its position and intracranial length, increased ICP from any cause can lead to injury and dysfunction
  • Vascular: Aneurysm, central venous thrombosis
  • Inflammatory: Post-viral, demyelinating, sarcoid, giant cell arteritis, Miller-Fisher Syndrome variant of Guillian-Barre Syndrome
  • Neoplastic: Lesions in the cerebellopontine angle. In children – pontine glioma
  • Degenerative/deficiency: Vitamin B deficiency, Wernicke-Korsakoff syndrom
  • Idiopathic: Post-lumbar puncture, status-post surgery involving head
  • Infection: Meningitis, lyme disease, syphilis
  • Congenital: Rare to find true congenital sixth nerve palsy
  • Autoimmune: Myasthenia Gravis
  • Trauma: Especially if a torsional head motion or medial wall orbital fracture(with entrapment of the medial rectus muscle
  • Endocrine: Diabetic cranial mononeuropathy - the incidence of palsy in the 3rd, 6th, and 7th cranial nerves is significantly higher in patients with diabetes. [1][2] [3][4][5][6][7]


Diagnostic Evaluation

Evaluation

Work-up

  • POC glucose
  • CBC
  • BMP
  • ESR
  • Lyme Titer
  • RPR (If suspect syphilis)
  • Lumbar puncture with cerebrospinal fluid analysis indicated to exclude meningitis
  • Antinuclear antibody test
  • CT head: before LP to exclude acute bleed or mass
  • MRI: indicated for brainstem findings on the exam and to exclude pontine glioma in children and in adults where the abducens nerve palsy does not improve. [3][4]


Management

Disposition

  • Dispo appropriate to etiology, consult either Neuro or Ophtho.
  • True isolated cases: often benign; can be followed up by neurologist for serial exams.
  • Children: Can be treated with alternating patching to decrease probability of developing amblyopia in the affected eye
  • Adults: Lenses can be fogged with clear tape, paint, or nail polish to decrease diplopia. Neurology can prescribe Fresnel prisms as an alternative.
  • Giant cell arteritis: TX with prednisone or intravenous methylprednisolone.
  • Surgery: If patient does not improve within 6 months after treatment and serial check-ups, surgery may be required

[3][4]

See Also

External Links

References

  1. 1.0 1.1 1.2 Tintinalli JE, Kelen GD, Stapczynski JS, Ma, OJ, Cline DM, editors. Tintinalli’s Emergency Medicine. 7th ed. New York: McGraw-Hill; 2011. 763, 1037, 1546
  2. 2.0 2.1 Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. Philadelphia, PA: Mosby/Elsevier; 2013
  3. 3.0 3.1 3.2 3.3 Yanoff M, Duker JS. Opthalmology. Mosby International Ltd; 2013
  4. 4.0 4.1 4.2 4.3 Gerstenblith AT. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease. Lippincott Williams and Wilkins
  5. http://www.ncbi.nlm.nih.gov/pubmed/26314216
  6. http://www.ncbi.nlm.nih.gov/pubmed/17157701
  7. http://www.ncbi.nlm.nih.gov/pubmed/11555800