**2.1 Ultrasonography (US) of the large cervical and cervico-brachial vessels**

In 2012, during the Chapel Hill Consensus Conference [19, 28], large vascular vasculitis (LVV) was well-defined as a vasculitis involving the aorta and its major branches, although any size of artery may be affected. This definition does not state that LVV mainly affects large vessels because in many patients, the number of medium and small arteries affected is greater than the number of large arteries involvement. For example, in GCA, only few branches of the ECAs may be affected when there is involvement of numerous small branches extending into the eye and orbit (e.g., central retinal artery, posterior ciliary arteries) [29, 30]. Less frequently, the CCA and the ICA are also affected (**Figures 3** and **4**) [9].

As Sturzenegger pointed up, angiography is not able to illustrate the vessel wall, so as to diagnose the inflammation of the large cervical and cervico-brachial vessels (aorta and its supra-aortic branches), the US can be very useful, since it can define alterations of the vessel wall with the use of B-mode imaging, while Doppler spectral flow velocity evaluation can help identify the stenosis or occlusion of the vessel [19].

Color Doppler Duplex sonography (CDDS) is an excellent device used in screening the large vessels involvement. Agreeing with different authors, including Sturzenegger, there are two ultra-sonographic hallmarks of large vessels GCA:


**Figure 3.** *Large vessels GCA; CT-angiography- occlusion of the left CCA, ECA, and ICA [9].*

#### **Figure 4.**

*Large vessels GCA, color Doppler ultrasound in transverse view of the right CCA. Hypoechoic wall swelling with right CCA occlusion [9].*

#### **Figure 5.**

*Large vessel GCA, color Doppler ultrasound in longitudinal view of the right CCA with hypoechoic wall swelling [4].*

Remarkably in some cases [9], the common carotid and the internal carotid arteries are also involved (large-vessel GCA) (**Figures 3**–**5**).

### **2.2 Ultrasonography (US) of the temporal arteries (TAs)**

Extracranial Duplex sonography investigates almost completely the whole length of the common superficial TAs, including the frontal and parietal branches, and founds that inflammation is segmental (intermittent arterial involvement) [19–27]. The common superficial TA derives from the ECA. It divides into the frontal and parietal ramus in front of the ear. The distal common superficial TA and the rami are localized between the two layers of the temporal fascia, which is like a bright band at ultrasound examination [19–27].

#### *2.2.1 Technical requirements*

High-resolution color Doppler US can illustrate the vessel wall and the lumen of the TAs. One should use linear probes with a minimum gray scale frequency of 8 Mhz. Color frequency should be about 10 Mhz [19–27].

*An Integrated Approach to the Role of Neurosonology in the Diagnosis of Giant Cell Arteritis DOI: http://dx.doi.org/10.5772/intechopen.96379*

#### *2.2.2 Machine adjustments*

The pulse repetition frequency (PRF) should be about 2.5 kHz as maximum systolic velocities are rather high (20-100 cm/s). Steering of the color box and the Doppler beam should be maximal as the rami are parallel to the probe. It is important that the color covers the artery lumen exactly [19–27].

#### *2.2.3 Sonographer training*

The sonographer should perform at least 50 Duplex ultrasound of the TAs of subjects without GCA to be sure about the appearance of normal TAs before starting to evaluate patients with GCA [19–27].

#### *2.2.4 Sequence of the ultrasound examination*

The investigation should begin with the TA, using the longitudinal scan. The probe should then be moved along the course of the TA to the parietal ramus. On the way back one should delineate the TA in transverse scans. Using the transverse scan, one can find the frontal ramus, which should then be delineated in both scans (longitudinal and transverse). If the color signal indicates localized aliasing and diastolic flow, one should use the pw-Doppler mode to confirm the presence of stenosis [19–27].

In 1997 Schmidt et al. proved that the most specific (almost 100% specificity) and sensitive (73% sensitivity) sign for GCA was a concentric hypo-echogenic mural thickening, dubbed "halo", which the authors interpreted as "vessel wall edema" [24].

Other positive findings for GCA are the presence of occlusion and stenosis [19–27].

In conclusion, there are three important items in the ultrasound diagnosis of temporal arteritis:


Related ultrasound patterns can be found in other arteries: the facial, the internal maxillary, the lingual, the occipital, the distal subclavian and the axillary arteries.

The best time to perform ultrasound investigation is before initiating the corticosteroid treatment, or in the first 7 days of treatment, since with corticosteroid therapy the" halo" revealed by TAs ultrasound disappears within 2-3 weeks. The wall inflammation, stenosis, or occlusions of the larger arteries (CCA, ICA) remain for months, despite corticosteroid treatment. However, the diagnosis process should not postpone the initiation of therapy. Ultrasound may also detect inflamed

#### **Figure 6.**

*Color Doppler ultrasonography (CDUS) of the right TA shows a hypoechoic halo around the lumen in transverse view (arrow). The "halo sign" corresponds to edema of the artery wall [11].*

#### **Figure 7.**

*Longitudinal view of the right TA by color Doppler ultrasonography (CDUS) shows a hypoechoic halo of the TA and the presence of turbulent and weak flow, suggesting the presence of stenosis. The PSV is 1 m/s, that is double compared to the segment without stenosis [11].*

TAs in patients with clinically normal TAs. Some patients with the clinical image of polymyalgia rheumatica, but with hidden TAs may be diagnosed using ultrasonography [9–16, 19–27].

In 2010, Arida et al. [26] evaluated a number of studies that examined the sensitivity and specificity of the "halo" sign confirmed by TA ultrasound (US) for GCA diagnosis versus the American College of Rheumatology (ACR) 1990 criteria for the classification of this vasculitis (used as a reference standard). Only 8 studies involving 575 patients, 204 of whom received the final diagnosis of GCA, achieved the technical quality criteria for US. This meta-analysis disclosed a sensitivity of 68% and a specificity of 91% for the unilateral "halo" sign, as well as 43% and 100%, respectively, for the bilateral "halo" sign in TA US for GCA diagnosis when the 1990 ACR criteria are used as the reference standard. The authors established that the halo sign in US is of great utility in diagnosing GCA [19–27].

In the case of consistent clinical and sonographic results, temporal arteries biopsy (TAB) does not appear to be useful and justified [19, 27].

Sturzenegger affirmed that differential diagnosis with arteriosclerosis is important in patients over 50 years, taking into consideration that GCA with large vessels disease disturbs almost exclusively this category of patients. There are some characteristic features of the arteriosclerotic wall: the thickening usually appears less homogeneous; there are calcified arteriosclerotic plaques ulcers; stenosis extends over shorter segments, they are not concentric, not tapering, and location of lesions differs (e.g., mainly bifurcations) [19].

Besides, agreeing to Sturzenegger, differential diagnosis with the other LVV, especially Takayasu arteritis, has to be reflected:

