Incidence: Giant cell arteritis is more common than Takayasu's and PACNS.

Age: older adults (usually over 55 y/o). Involvement of the opthalmic artery may lead to blindless.

Association: Frequently associated with polymyalgia rheumatica and the patients will have elevated ESR and is also quite responsive to steroid treatment.

Negative biopsy: involvement is usually focal and a negative biopsy cannot rule out GCA.

Vessels affected: mostly extracranial arteries of the head with the intracranial arteries often spared. Temporal artery and opthalmic artery are frequently involved. Medium to small size arteries are most affected. Involvment is focal.

Histology:

3 general patterns:

Granulomatous lesions replete with giant cells (foreign body or Langhan's type) most frequently seen in the inner media associated with the irregular fragments of the frqyed internal elastic membrane. Epitheliod type histiocytes in the adventitia.
Nonspecific white cell infiltration fibrosis with no morphologically apparent disruption of the internal elastic membrane.
Giant cells are seen in 2/3 of cases. The artery is changed into an obliterative fibrous cord in the healed stage.

Additional histologic features:

The involvement seems to fade as the vessel penetrate the dura.
Aneurysm resulted from weakening of the wall is rarely seen.

NeuroLearn NeuroHelp Vascular For Comment: KarMing-Fung@ouhsc.edu