Temporal arteritis

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Synonyms: GCA, temporal arteritis, cranial arteritis, Horton's disease, Horton disease, Horton's arteritis, Horton syndrome, Horton's syndrome, granulomatous arteritis, polymyalgia arteritica, anterior ischemic optic neuropathy, AION

Overview
Temporal arteritis, also called giant cell arteritis (GCA) is an inflammatory disease of blood vessels (most commonly large and medium arteries of the head). It is therefore a form of vasculitis. The name comes from the most frequently involved vessel (temporal artery which branches from the external carotid artery of the neck). The alternative name (giant cell arteritis) reflects the type of inflammatory cell that is involved (as seen on biopsy).

The disorder may coexist (in one quarter of cases) with polymyalgia rheumatica (PMR), which is characterized by sudden onset of pain and stiffness in muscles (pelvis, shoulder) of the body and seen in the elderly. Other diseases related with temporal arteritis are systemic lupus erythematosus, rheumatoid arthritis and severe infections.

This diagnosis should be considered in any patient over the age of 50 with the new onset of headache, particularly is the erythrocyte sedimentation rate is elevated.

Prompt treatment with steroids is a medical emergency to reduce the risk of blindness.

History
The disease was first described in 1890 by Hutchinson. The histopathology of the disorder was first described in 1932 by Horton. Visual loss was first reported by Jennings in 1938. Birkhead first described the use of steroids to prevent progression to blindness.

Epidemiology and Demographics
It is more common in females than males by a ratio of 3.7:1. The mean age of onset is about 70 years and is rare at less than 50 years of age. It is more prevalent in caucasians.

Most likely as a result of increase clinical recognition of the syndrome, the incidence of temporal arteritis increased between 1950 and 1975 from 5.1 to 17.4 incident cases per 100,000 population per year in persons aged 50 years and older in Olmsted County, Minnesota. More recently in this population, the prevalence was even higher at 133 cases per 100,000 in persons aged 50 years and older.

Because temporal arteritis is a disease of the elderly, the prevalence of the disease is very dependent upon the age of the population. As a result, there is a lower prevalence in countries with a shorter or reduced life expectancy.

There is little data regarding the prevalence of disease outside the US, but given the variation in life expectancy and demographics, the prevalence is thought to vary significantly. The highest reported rates of disease outside the US are in Scandinavia, where the prevalence is 23.3-33.6 per 100,000 people older than 50 years.

Pathophysiology
The damage to the vasuclature is mediated by an attack on the internal elastica lamina by activated CD4+ T helper cells. This occurs in repsonse to the presentation of an antigen by macrophages. The inciting antigen has not been identified.

Because the disease involves only arteries with internal elastic lamina, the aortic arch and its branches are often involved. Intracranial arteries do not have internal elastic lamina and are not involved. The distribution of involved arteries are as follows:

Commonly involved sites:
Cervicocephalic arteries: carotid artery and vertebral artery. The vertebral artery is involved as frequently as the temporal artery in fatal cases. Involvement of the basilar artery is rare.

Intraorbital branches: Posterior ciliary artery and ophthalmic artery.

External common, external, and internal carotid artery involvement: It is less common for proximal intracranial arteries to be involved.

External vertebral arteritis: It is less common though for the disease to extend more than 5 mm beyond the dural penetration.

Subclavian, axially and proximal brachial artery: There can be typical vasculitic lesions with long, smooth, lesions with tapered occlusions.

Coronary arteries: for a full discussion of the involvement of the heart in this disorder see the chapter on The Heart in Temporal Arteritis / Giant Cell Arteritis

Less commonly involved sites:
Descending aorta: Mesenteric, iliac, femoral and renal arteries are less often involved. In these cases there can be mesenteric ischemia, renal infarction, and ischemic mononeuropathy can occur.

Pulmonary artery

Differential Diagnosis of Disorders that Temporal Arteritis Should be Distinguished From
Cluster Headache

Migraine Headache

Multi-infarct Dementia

Persistent Idiopathic Facial Pain

Polyarteritis Nodosa

Postherpetic Neuralgia

Sinusitis

Trigeminal Neuralgia

Stroke

Wegener granulomatosis

Symptoms
Patients present with:
 * fever
 * headache
 * tenderness and sensitivity on the scalp
 * jaw claudication (pain in jaw when chewing)
 * reduced visual acuity (blurred vision)
 * acute visual loss (sudden blindness)

The inflammation may affect blood supply to the eye and blurred vision or sudden blindness may occur. In 76% of cases involving the eye, the ophthalmic artery is involved causing anterior ischemic optic neuropathy. Loss of vision in both eyes may occur very abruptly and this disease is therefore a medical emergency.

Physical exam
Palpation of the head reveals sensitive and thick arteries with or without pulsation.

Laboratory tests
Sedimentation rate is very high in most of the patients, but may be normal in approximately 20% of cases.

Biopsy
The gold standard for diagnosing temporal arteritis is biopsy, which involves removing of a small part of the vessel and examining it microscopically for giant cells infiltrating the tissue. Since the blood vessels are involved in a patchy pattern, there may be unaffected areas on the vessel and the biopsy might have been taken from these parts. So, a negative result does not definitely rule out the diagnosis.

Radiology
Radiological examination of the temporal artery with ultrasound yields a halo sign. Contrast enhanced brain MRI and CT is generally negative in this disorder.

Treatment
Corticosteroids must be started as soon as the diagnosis is suspected (even before the diagnosis is confirmed by biopsy). Steroids do not prevent the diagnosis later being confirmed by biopsy, although certain changes in the histology may be observed towards the end of the first week of treatment and are more difficult to identify after a couple of months.

A 3 day course of pulse steroids with 250 mg of IV solumedrol BID is critical in reducing the risk of permanent visual loss. If there is progression of visual loss on steroids, IV heparin can be administered to reduce the risk of thrombotic occlusion.

Treatment should not be deferred while waiting on the results of a temporal artery biopsy.

Additional Resources

 * Polymyalgia Rheumatica

Arteriitis cranialis Arteritis de células gigantes Maladie de Horton 側頭動脈炎 Dev hücreli arterit