Temporal arteritis overview

# Overview
Temporal arteritis 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).

# Historical Perspective
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. In 1957, Birkhead first described the use of steroids to prevent progression to blindness.

# Classification
There is no established system for the classification of temporal arteritis.

# Pathophysiology
Temporal arteritis is caused by transmural inflammation of elastic arteries. It is understood that temporal arteritis is the result of cell mediated immunity which arises as a response to endothelial injury and is antigen-driven disease with T-cell and macrophage activation in the elastic tissue in the arterial walls. The adventitia of the vessel is the initial site of immunologic injury. The activation of dendritic cells in the adventitia causes a production of chemokines that recruit CD4+ T helper cells. The CD4+ T helper cell convert in to Th17 cells which produce interleukin 17 and Th1 cells which produce interferon gamma. Giant cell are one of many inflammatory cells that are recruited and produce growth factor which narrows and obstructs the vessels. The concentric inflammation occurs in segments. Macrophages in the adventitia produce interleukin 6. While in the intima and media of the vessel, macrophages produce vascular endothelial growth factor (VEGF) and metalloproteinases which destroy the internal elastic lamina. An increased activated platelets express P-selectin which may cause vessel inflammation and thromboembolic events. Temporal arteritis arises from giant cells, which are fused monocytes cells that are normally involved in the body immune response. 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.

# Causes
The cause of temporal arteritis has not been identified.

# Differentiating Temporal Arteritis from Other Diseases
The differential of temporal arteritis include Takayasu arteritis, neurofibromatosis 1 and 2, fibromuscular dysplasia, Ehlers-Danlos syndrome, polymyalgia rheumatica (PMR), amyloidosis, and cerebral aneurysm.

# Epidemiology and Demographics
Incidence of temporal arteritis ranges from approximately 0.5 to 27 cases per 100,000 people aged 50 years or older. The incidence of temporal arteritis increases with age; the median age at diagnosis is 76.7 years. Temporal arteritis commonly affects individuals older than 70 years of age. Temporal arteritis usually affects individuals of the white race. Black, Asians, and Hispanic individuals are less likely to develop temporal arteritis. Women are more commonly affected by temporal arteritis than men. The female to male ratio is approximately 3 to 1. The highest incidence of temporal arteritis is reported in Scandanavian countries at 32.7 per 100,000 people for people over 50 years of age.

# Risk Factors
Common risk factors in the development of temporal arteritis may be environmental, genetic, and viral. Common risk factors in the development of temporal arteritis include age, hypertension, and thrombocytosis. Less common risk factors in the development of temporal arteritis include allele HLA-DRB1*04 genetic polymorphisms, varicella zoster virus infection, and smoking.

# Natural History, Complications and Prognosis
The symptoms of temporal arteritis usually develop in the fifth decade of life, and start with symptoms such as headache, fatigue, jaw claudication, and vision problems. Common complications of temporal arteritis include blindness, aortic aneurysm, stroke, death, and side effects from steroid or immune-suppressing medications. Depending on the extent of the vessels involved in temporal arteritis at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as poor. If left untreated, 2% of patients with temporal arteritis may lead to death by MI or stroke.

# Diagnosis

## History and Symptoms
The hallmark of temporal arteritis is a headache. The most common symptoms of temporal arteritis include headache, jaw claudication, and fatigue. Common symptoms of temporal arteritis include visual symptoms, jaw claudication, headache, fatigue, and neck, shoulder, pelvic girdle pain. Less common symptoms of temporal arteritis include limb claudication, TIA, stroke, facial pain, bleeding gums, mouth sores, and joint pains.

## Physical Examination
Patients with temporal arteritis usually appear in pain or normal. The presence of temporal tenderness on physical examination is highly suggestive of temporal arteritis. Ophthalmoscopic exam may be abnormal with findings of sludging of blood in retinal arterioles, optic disc may show chalky white pallor and edema, with or without splinter hemorrhages, posterior ischemic (retrobulbar) optic neuropathy, central retinal artery occlusion, branch of retinal artery occlusion, and choroidal ischemia. Tenderness upon palpation of the temporal region including erythema, nodularity, and thickening on affected side. Other findings include facial tenderness, diplopia, ptosis, nystagmus, internuclear ophthalmoplegia (INO), and pupillary abnormalities.

## Laboratory Findings
The sedimentation rate is very high in most of the patients, but may be normal in approximately 20% of the cases. An elevated concentration of blood erythrocyte sedimentation rate (ESR) is suggestive of temporal arteritis. Laboratory findings consistent with the diagnosis of temporal arteritis include normochromic anemia, deceased albumin level, elevated alkaline phosphatase, and elevated C-reactive protein. Some patients with temporal arteritis may have elevated concentration of interleukin-6, which is usually suggestive of progression.

## CT
Contrast enhanced brain CT is generally negative in this disorder.

## MRI
A contrast enhanced brain MRI is generally negative in this disorder.

## Ultrasound
A radiological examination of the temporal artery with ultrasound yields a halo sign. Ultrasound of the temporal artery may be helpful in the diagnosis of temporal arteritis. Findings on an ultrasound suggestive of temporal arteritis include hypoechoic halo around the lumen of the temporal artery. The halo is suggestive of edema in the temporal artery wall.

## Other Diagnostic Studies
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. Findings diagnostic of temporal arteritis include skip lesions and normal intervening segments, intimal thickening, with prominent cellular infiltration, lymphocytes in the internal or external elastic lamina or adventitia, areas of necrosis may be present in the arterial wall, granulomas containing multinucleated histiocytic and foreign body giant cells, helper T-cell lymphocytes, plasma cells, and fibroblasts. Risks of temporal artery biopsy are temporary or permanent damage to the temporal branch of the facial nerve, infection, bleeding, hematoma, and dehiscence.

# Treatment

## Medical Therapy
The mainstay of treatment for temporal arteritis is corticosteroids. Damage may be irreversible if treatment is delayed beyond 48 hours. Oral prednisone 40-60 mg/day should be started, with a temporal artery biopsy performed within 1 week. Prednisone doses of 80-100 mg/day have been suggested for patients with visual or neurologic symptoms of temporal arteritis and follow-up care within 72 hours after starting therapy should be arranged. Patients with acute visual changes from temporal arteritis can be started on intravenous (IV) methylprednisolone at a dose of 1,000 mg daily for 3 days. Initial high-dose IV corticosteroid, methylprednisolone, treatment 15 mg/kg of ideal body weight/day may reduce remission rates. Use of low-dose aspirin (81 mg) for prevention of visual loss and stroke is recommended in temporal arteritis. Improvement of systemic symptoms occurs within 72 hours after initiation of therapy. The elevation in erythrocyte sedimentation rate and ischemic symptoms such as headache and jaw claudication improve over several days. High-dose steroid therapy should be maintained long enough for symptoms to resolve and then be tapered slowly to the lowest dose required to suppress symptoms. Long-term corticosteroid therapy complications include diabetes mellitus, vertebral compression fractures, steroid myopathy, steroid psychosis, and immunosuppression related infections. Tocilizumab has been approved for use in rheumatoid arthritis and is now approved for use in temporal arteritis.

## Surgery
Surgical intervention is not recommended for the management of temporal arteritis.

## Primary Prevention
There is no known prevention for temporal arteritis.