Carotid Aneurysm

    • Ballooning of an unruptured segment of the intracranial internal carotid artery because of a vascular wall defect (“saccular aneurysm,” “berry aneurysm”)
    • Congenital defect in the vessel wall is worsened by arteriosclerosis, hypertension, smoking
    • Located at the internal carotid–ophthalmic artery junction or more distally on the supraclinoid internal carotid segment
    • Vision loss occurs by compression of the optic nerve or chiasm by an enlarging unruptured aneurysm
    • More distal aneurysm at the junction of the posterior communicating artery typically causes an ipsilateral third nerve palsy (See Third Nerve Palsy )
    • Core clinical features
      • Slowly progressive visual loss in one eye or both, although sudden enlargement of an aneurysm can produce acute vision loss
      • Visual acuity is normal or decreased
      • Nerve fiber bundle or hemianopic visual field defects
      • Afferent pupil defect
      • Normal-appearing or pale optic discs
    • Possible accompanying clinical features
      • Headache
      • Hypopituitarism
      • Ipsilateral third nerve palsy
    • Imaging features
      • Brain CT or MRI shows a mass in the middle fossa
      • CT or MR angiography confirms the diagnosis
      • Digital angiography defines the lesion
    • Other intracranial tumors
    • Optic neuritis
    • Neuromyelitis optica
    • Lymphocytic hypophysitis
    • Sarcoidosis
    • Metastatic cancer
    • Langerhans cell histiocytosis
    • Order brain CT or MRI in any patient with unexplained retrobulbar vision loss
    • Order brain CTA or MRA if you suspect aneurysm from CT or MRI
    • Refer to an interventionalist for clipping, coiling, stent-coiling, or a flow-diverting stent
    • Without intervention, rupture rates are based mostly on the cross-sectional diameter of the aneurysm
      • <7mm: negligible
      • ≥7mm but <13mm: 1/2% per year
      • ≥13mm to <25mm: 3% per year
      • ≥25mm (“giant aneurysm”): 8% per year
    • Intervention is usually reserved for aneurysms of greater than 7mm cross-sectional diameter
    • Coiling has the lowest morbidity, but coiling alone may not be safe in wide-necked aneurysms because of coil migration into the parent artery, in which case a stent may be added
    • Trap: coiling-induced aneurysm expansion or sac wall inflammation may exacerbate vision loss
    • Clipping has a low risk of aneurysm recurrence, but peri-operative morbidity is higher than with coiling
    • Flow diversion with a non-fenestrated stent may be sufficient to prevent aneurysm rupture
    • Choice and risks of intervention depend on the experience of the interventionalist, the features of the aneurysm, and the age and health of the patient

    Optic Nerve And Chiasm Disorders

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