Neurosurgery notes/Anatomy/Sensory/Visual/Ocular disease/Arteritic AION

Arteritic AION

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Ocular disease

General

  • Caused by inflammation of arteries supplying blood to the optic nerve.
  • The inflammation is due to a condition known as giant cell arteritis (GCA)

Numbers

  • Consist of 5-10% AION
  • M:F 3:1
  • >55 yrs

Mechanism

  • Inflammation and subsequent thrombosis of the short posterior ciliary arteries (SPCA’s), which originate from the ophthalmic artery, and results in optic nerve head infarction.

Clinical features

  • Visual symptoms
    • Painful
    • Sudden
    • Unilateral visual loss accompanied by decreased (either/or)
      • Visual acuity: typically severe: <20/200 in over 60% of the patients),
      • Visual field (altitudinal field defect is most common)
        • Altitudinal: involves the loss of visual sensation in the horizontal half of the visual field. Could be up or down
    • RAPD
    • Amaurosis fugax is an early sign that AAION may be present and that vision loss may be imminent.
  • Systemic symptoms of GCA
    • Headache (most common) and tenderness of the temporal arteries or scalp, jaw claudication (symptom most specific for the disorder), malaise, loss of appetite, anorexia and weight loss, fever, joint and muscle pain, and ear pain.
    • Choroidal ischemia may be associated with the optic neuropathy and produces peripapillary pallor and edema deep to the retina.
    • The disc of the fellow eye is of normal diameter in AAION, as is the physiologic cup.
    • Occult GCA
      • Without overt systemic symptoms
      • 20% of patients with AAlON.
      • Other presentations, however not reasonably common include hearing loss, vertigo, facial pain, lingual paralysis and carotid bruits.

Examination

  • Opthalmoscopy
    • Optic disc
        • A chalky-white pallor of the optic disc with edema, which may be severe, is the hallmark of AAION
        • Hyperemic swelling
         
        A close-up of a red blood vessels AI-generated content may be incorrect.
         
  • Diplopia, ptosis, nystagmus or pain or nodularity upon palpitation of the temporal artery

Laboratory Studies

  • ESR elevated (up to 70-120mm/min) and/or CRP
    • A 97% specificity for temporal arteritis both ESR and CRP were elevated in A-AION
    • Patients with NA-AION do not show these types of abnormalities
  • Platelet count
    • For possible thrombocytosis, leukocyte count, and hemoglobin levels.
    • Platelet count is often elevated acutely in cases of AAION

Biopsy

  • Superficial temporal artery biopsy
    • Positive biopsy findings (intimal thickening, internal limiting lamina fragmentation, and chronic inflammatory infiltrate with giant cells) is confirmatory for GCA.
  • A negative biopsy
    • Doesn’t rule out arteritis (both discontinuous arterial involvement (‘skip lesions’) and solely contralateral temporal artery inflammation may result in false-negative results)
    • Reports showing a 3-5% false-negative error rate.
    • If initial biopsy is found to be negative and suspicion for GCA is high, a biopsy of the contralateral temporal artery should be considered.

Imaging

  • Magnetic Resonance Imaging
    • Has recently provided evidence that it may be able to distinguish between A-AION and NA-AION.
    • The imaging scores identified the acute stage of giant cell arteritis-related anterior ischemic neuropathy with a statistically significant relationship between the side of the AION and the side of the “central bright spot” i.e. optic nerve head enhancement.
  • Ultrasound(US)
    • Characteristic dark wall swelling (halo) and acute occlusions
    • The temporal artery duplex ultrasound has demonstrated a sensitivity and specificity of 87% and 96% respectively with regard to clinical diagnosis.
    • It remains to be proven if ultrasound will one day be able to obviate the temporal artery biopsy which remains the current gold standard
  • Optic Coherence Tomography (OCT)
    • Useful in assessing sectoral disc edema, retinal nerve fiber layer thickness, as well as documenting the resolution to a normal or an atrophic optic disc.
  • Fluorescein Angiography (FA)
    • Delayed choroidal filling may be present and can serve as a diagnostic tool for AAION, given that the test is performed soon after the onset of vision loss

Differential Diagnosis

  • Non-arteritic anterior ischemic optic neuropathy,
  • Idiopathic optic neuritis,
  • Optic nerve inflammation related to syphilis or sarcoidosis, infiltrative optic neuropathies, anterior orbital lesions with optic nerve compression, and diabetic papillopathy.

Treatment

  • Steroids
    • High dose systemic corticosteroids are standard
    • Intravenous methylprednisolone at 1g/day for the first three days has been recommended for severe cases
    • Oral prednisone in the range of 60-100mg/day may be used initially and for follow up to intravenous pulse therapy.
    • Treatment is usually continued at a high dose for a several months before beginning taper, but may be required for several years in severe cases to avoid permanent vision loss.
  • Monoclonal Antibody
    • Tocilizumab
      • Binding to the alpha chain on IL-6 receptor → blocks signaling and downregulates the acute phase reactions
      • Very effective against corticosteroid resistant AAION, causing symptoms to halt immediately upon first dose.
        • However, more research into its ability to serve a protective role against bilateral blindness must be conducted to rule out any confounding variables.
  • Other Treatment Options
    • Methotrexate
      • Is one of the most widely studied “steroid sparing” agents
      • Significantly increase the probability of achieving a sustained discontinuation of using corticosteroids as well as decreasing the risks of relapses with the disease
      • Corticosteroid therapy while effective, can be very toxic leading to almost 60% of individuals getting major side effects such as diabetes or cataracts.
      • Indicated when want to reduce exposure to corticosteroids and their adverse effects.
      • The best therapeutic option may be conjunction therapy, in order to decrease exposure and possible relapse for those patients with AAION.

Course and Outcome

  • Without treatment, visual loss occurs in 54-95% of GCA patients typically within four months.
  • With corticosteroid therapy, the rate of such decline is reduced to an estimated 13%.
  • Visual recovery of the affected eye that has treatment is poor with a 15-34% improvement rate, which is higher with intravenous therapy.
  • Worsening visual acuity has been reported in 9-17% despite therapy.
  • Vision loss in both eyes is possible;
    • However, most cases have indicated it to be frequently when one patient is unaware of vision loss in the first eye.
    • Incidence of bilateral vision loss involves timing heavily as well as how aggressively corticosteroid therapy is utilized.
    • However, if left untreated, bilateral vision loss can proceed quickly from either optic nerve, retinal or choroidal ischemia in up to 50% of cases.