Temporal arteritis (giant cell arteritis) is an inflammatory vasculopathy that affects medium and large-sized arteries, which are usually branches of the carotid artery. While the superficial temporal branch is highly susceptible, other arteries may be affected as well. Temporal arteritis is a granulomatous panarteritis with mononuclear cell infiltrates and giant cell formation within the vessel wall. This histologic characteristic confirms the diagnosis of temporal arteritis in biopsy specimens of the temporal artery.[1][2][3][4]

Understanding the anatomy of the superficial temporal fascia, superficial temporal artery, superficial temporal nerve, and the safe and danger zones these structures create is crucial to perform a temporal artery biopsy safely.

Superficial Temporal Artery (Fig 1 & 2)

The superficial temporal artery, which is one of the terminal branches of the external carotid artery, arises in the parotid gland and courses superiorly in front of the tragus, immediately giving off an anterior branch, the middle temporal artery. The anterior auricular branch is posterior and just at the superior root of the helix. It then divides into the frontal branch and the parietal branch, both of which have multiple secondary branches. The division into the frontal branch and the parietal branch is high in 73%, intermediate (just below the helix apex) in 20% and low (just above the tragus in 7%. This is important to note because the risk of injury to the temporal branch of the facial nerve is higher in patients with the low division because the safety zone is smaller. 

Relationship of the superficial temporal artery to the temporal facial nerve (Fig 3)

The superficial temporal fascia lies deep in the subcutaneous adipose tissue of the skin. It is contiguous with the superficial musculoaponeurotic system (SMAS) of the face inferiorly and the frontalis-galea complex superiorly. Within the superficial temporal fascia, the superficial temporal artery travels cephalad within the preauricular cheek and then bifurcates into a frontal and parietal branch roughly 3 cm superior to the zygoma in 73% of patients. The temporal branch of the facial nerve exits the parotid gland at a depth of 0.9 cm but then travels superficially over the middle third of the zygoma underneath the surface of the superficial temporal fascia in the temple region to reach the frontalis and orbicularis oculi muscles which it innervates. The distal rami of the temporal branch of the facial nerve always travel deep to the muscles they innervate. The temporal artery is within the superficial temporal fascia (also called the temporoparietal fascia) superficially in the loose areolar tissue, whilst the temporal facial nerve is just a little deeper but also within this tissue.

Safe Zone (Video 1)

The anterior temporal hairline lies lateral to the frontalis muscle, so dissecting superior or posterior to the anterior hairline during a temporal artery biopsy is not likely to produce injury to the temporal branch of the facial nerve. However, because there are no muscles of facial expression but rather only the thin superficial temporal fascia in the temple region, the temporal branch of the facial nerve is particularly susceptible to injury over the zygoma and within the temple region. One group of authors defines the temporal danger zone for the temporal branch of the facial nerve by outlining a region bounded by an inferior line from the earlobe to the lateral eyebrow and a superior line from the intertragic notch or earlobe to the lateral edge of the highest forehead crease. Additionally, one group defined the area 1.5 cm posterior to the lateral orbital rim and 1cm anterior to the attachment of the helix along with the level of the zygoma as safe zones to avoid nerve injury.[5][6][7][8] It is wise to learn to mark the safe zone as we have shown in the video, based upon cadaver studies by Shin et al. [9] 

Anatomical site of biopsy:

Some authors recommend obtaining the biopsy from the trunk of the superficial temporal artery, before the division into the frontal and parietal branches. [10] This sacrifices an unacceptably large arterial zone. Branches of the superficial temporal artery are useful for craniofacial reconstruction with vascularized flaps and when performing free flaps to repair large facial defects. It behoves the surgeon to only sacrifice a part of the anterior branch of the superficial temporal artery.

Other surgeons have suggested obtaining a biopsy from the parietal branch of the superficial temporal artery to avoid injury to the temporal branch of the facial nerve. [11] The parietal branch travels subperiosteally from the division of the superficial temporal artery. The sensitivity and specificity of specimens from the parietal branch is not known. The parietal branch of the temporal artery is also known to provide collateral circulation to the brain and should be preserved.

Patients with temporal arteritis (giant cell arteritis) may present with visual disturbances, including temporary or permanent blindness, which necessitates an efficient diagnosis. While a number of clinical changes such as head or neck pain, jaw claudication, polymyalgia, temple tenderness on palpation, and lab alterations such as elevated C-reactive proteins or erythrocyte sedimentation rate may suggest the diagnosis, unfortunately, no one cluster of these signs or symptoms demonstrates a sensitivity or specificity which approaches temporal artery biopsy (TAB). Given its greater than 90% positive predictive value, TAB is the gold standard test for diagnosing temporal arteritis and should be performed in anyone in which temporal arteritis is suspected. It is important to note that treatment with systemic corticosteroids should not be delayed until after TAB as up to 10 days of such therapy does not significantly affect sensitivity, and early steroid therapy reduces morbidity.

There should be a high suspicion for temporal arteritis with the presence of the following in an individual greater than 50 years of age and elevated laboratory inflammatory markers:

• A new or atypical headache
• New visual changes
• Jaw claudication

Biopsy contraindications include:

• Patients who have had prolonged treatment with glucocorticoids. Diagnostic yield decreases significantly after 30 days of corticosteroid therapy. In contrast, TAB will remain abnormal for up to 2 weeks after initiation of steroids 
• A relative contraindication is a negative result of a properly performed biopsy. The rate of a positive contralateral biopsy is approximately 1%.

Equipment includes the following:

• Nonsterile preparation stand
• Water-based lubricating jelly
• Marking pen
• 4 x 4 gauze
• Liposomal lidocaine cream 4%
• Lidocaine 1% with 1:200,000 epinephrine
• Bupivacaine 0.5% with 1:200,000 epinephrine
• Needle, 18-gauge
• Needle, 27-gauge (1-1/4 inch)
• A syringe with 3-ring control, 10 mL Doppler ultrasound
• Electric hair shaver
• Specimen container with formalin
• Benzalkonium chloride
• Sterile Mayo stand
• Scalpel, No. 15 blade
• Single skin hook
• Adson-Browns forceps
• Bishop-Harmon forceps
• Tenotomy scissors
• Metzenbaum scissors
• Suture scissors
• Frazier suction, No. 10
• Hemostat clamps
• Castro-Viejo needle holder
• Webster needle holder
• Small Weitlaner self-retractors
• Ruler
• Towel clamps
• Mono or bipolar cautery
• 4.0 or 5.0 Polyglactin 910 suture
• 5-0 Monocryl on RB-1
• 5-0 Fast-absorbing gut on PC-1 needle
• 3-0 Silk-free ties
• Dressing
• Aquaphor ointment
• One-inch tape
• Kerlix