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 (eye moves inward) of the affected eye due to the unopposed action of the medial rectus muscle, innervated by the oculomotor nerve (CN III) [1]

Causes

Clinical Features

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

  • Excluding paresis of the other cranial nerves
  • Check ocular muscle movements
  • Check for papilledema
  • Test pupillary response
  • Test ocular motor nerves (CN III, IV, and VI)[3][4]
    • Trace a full H-pattern with 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

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]

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
  • Adults: Lenses can be fogged with clear tape, paint, or nail polish to decrease diplopia. Neurology can prescribe Fresnel prisms as an alternative.
  • 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