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309Follow-up Neurosonologic Findings (3 Months)

Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers All rights reserved. Usage subject to terms and conditions of license.

M1-MCA-L

Fig. B15.41 TCCS (trans temp oral ap proa ch), lef t-sid ed i nson ation , midbrain plane. Normalized ﬂ ow signal in the left M1-MCA after left ICA stenting (ﬂ ow velocity 74/26 cm/s).

C6-ICA-L

A1-ACA-L

Fig. B15.42 TCCS (trans temp oral ap proa ch), lef t-sid ed i nson ation , midbrain plane. Normalized ﬂ ow signal in the left A1-ACA segment after left ICA stenting (ﬂ ow velocity 95/46 cm/s).

OA-L

(TO)

Fig. B15.43 TCCS (trans temp oral ap proa ch), lef t-sid ed i nson ation , lower pontine plane. Normalized ﬂ ow in the left C6-ICA segment after left ICA stenting (ﬂ ow velocity 52/21 cm/s).

OA-L

(TT)

Fig. B15.45 TCCS (trans temp oral ap proa ch), lef t-sid ed i nson ation , upper pontine plane: Normalized antegrade left OA ﬂ ow using the transtemporal approach (ﬂ ow velocity 33/14 cm/s).

Fig. B15.44 TCCS (transorbital approach), left-sided insonation: Normalized antegrade ﬂ ow in the left OA (ﬂ ow velocity 55/18 cm/s).

P1-PCA-L

Fig. B15.46 TCCS (trans temp oral ap proa ch), lef t-sid ed i nson ation , midbrain plane. Normalized ﬂ ow signal in the left P1-PCA segment (ﬂ ow velocity 59/19 cm/s).

310 Case 15 Near-Occlusion of the Right and High-grade Stenosis of the Left Extracranial Internal Carotid Artery

P2-PCA-L

Fig. B15.47 TCCS (trans temp oral ap proa ch), lef t-sid ed i nson ation , midbrain plane. Normalized ﬂ ow signal in the left distal P2-PCA s e g m e n t ( ﬂ ow velocity 58/22 cm/s).

Conclusion

Normalization of ﬂ ow in all vessels after bilateral ICA stenting.

Final Diagnosis

MCA infarction on the right side caused by artery-to-artery embolism in near-occlusion of a severely atherosclerotic aﬀ ected right ICA. Success- ful treatment of the symptomatic right ICA and of an asymptomatic hemodynamically relevant contralateral ICA stenosis by stenting. Obvious amelioration of the patient’s neuropsychologic capacity after right-sided stent insertion.

Discussion

Clinical Aspects

Here we present a 58-year-old patient who experienced a territorial anterior right-sided MCA infarction, considered to be of embolic origin due to a transient occlusion of the anterior M2-MCA branch. The underlying cause was a near-occlusion of the right proximal ICA. The etiology of the stenosis was considered to be atherosclerotic, promoted by longstanding arterial hypertension and heavy smoking. Synonyms for a near-occlusion used in the literature are pseudo-occlusion, subocclusion, critical stenosis, preocclusive stenosis, and incomplete occlusion. A near-occlusion is radiographically deﬁ ned by a collapse of the poststenotic ICA with an ICA/CCA ratio of less than

0.42 (Rothwell and Warlow 2000).

The treatment options for symptomatic and asymptomatic ICA stenoses with carotid endarterectomy (CEA) and carotid stenting (CAS) are extensively discussed in Case 1. Here we focus on the treatment possibilities in near-occlusions of the ICA. The stroke risk in carotid stenosis increases with the grade of stenosis and it is now well accepted that patients with a symptomatic high-

grade stenosis of 70–99% (according to the NASCET criteria) distinctly beneﬁ t and those with a 50–69% stenosis moderately beneﬁ t from revascularization by CEA (Roth- well et al 2003a, 2003b). According to the above relation it was initially presumed that near-occlusions might carry the highest stroke risk. However, this hypothesis was not conﬁ rmed in the NASCET trial which demonstrated only a small beneﬁ t (Barnett et al 1998). The European Carotid Surgery Trial (ECST Collaborative Group 1998) even found no beneﬁ t at all. Finally, pooled data from both studies and the VA309 trial, including 6,092 patients, revealed a nonsigniﬁ cant trend in favor of CEA over medical treat- ment only at the 2-year follow-up. This trend even disappeared after 5 years (Rothwell et al 2003a). The perioperative risk in the CEA group was low but at the same time the stroke risk in the medically treated patients with near-occlusion was found to be similarly low (Morgenstern et al 1997). One reason for the low stroke risk may be that near-occlusions are far less likely to cause embolic events because of the poststenotic lumen reduction, the lower pressure, and the small residual proportion of blood ﬂ owing into the dependent hemisphere. The lat- ter can be seen in DSA, with a distinctly delayed contrast ﬁ lling of the aﬀ ected ICA and the presence of collateral pathways (Rothwell and Warlow 2000). A similar angiographic pattern was seen in our case, but here, despite the low ﬂ ow in the aﬀ ected ICA, a large embolic event had oc- curred. Considering the embolic source, an embolus from the near-occluded ICA seemed most likely. Alternative embolic pathways in our case could have been a proximal embolic source with an embolus running through the vertebrobasilar arteries via the right PCoA or through the right ECA via the retrograde OA into the MCA territory. However, as both pathways include functional narrowing (PCoA and OA), the passage of a large embolus through these vessels is less plausible. An impaired collateral ﬂ ow (in our case be cause of the presence of an additional contralateral high-grade ICA stenosis) might be another contributing explanation; as such a constellation increases the demand for a continuing antegrade ﬂ ow through the near-occluded vessel.

In the NASCET study, collateral function was an important predictor of subsequent cerebral ischemia, in particular for the 85–99% stenoses. In contrast, however, in patients with near-occlusion the risk of stroke was nearly unrelated to the collateral vessel status and comparable to low-grade stenoses (Henderson et al 2000, Rothwell and Warlow 2000). Based on the currently available data, CEA cannot be generally recommended in symptomatic near-occlusion. In stable asymptomatic unilateral disease and well-established collaterals, no intervention may be the best option. In asymptomatic cases with diminished collateral pathways characterized by ultrasound with a severe poststenotic ﬂ ow pattern in the dependent vessels (mainly the MCA), and/or exhausted cerebrovascular reactivity, and/or contralateral severe ICA steno-occlusive pathology, revascularization may be indicated. In symptomatic stenoses with embolic stroke interventional treatment as in our case is recommended.

Successful CAS in near-occlusion of the ICA has been reported in small case series. In one study, 20 patients were treated, 17 of whom were symptomatic. The

311Discussion

mean grade of stenosis was reduced from 95% to 6.7%. No postinterventional ischemia was reported during an observational period of 25 months but one restenosis occurred, which was treated by repeated stenting (Terada et al 2006). Restenosis is an important problem and is more often observed after CAS compared with CEA. In a meta-analysis including 34 studies and 4,185 patients treated by percutaneous angioplasty (PTA) and CAS a restenosis was seen in 6% of cases after 1 year and

7.5% after 2 years when deﬁ ning a restenosis as a vessel narrowing ≥50% (Gröschel et al 2005). In a 10-year randomized trial of CEA versus CAS, the long-term protection against ipsilateral stroke provided by CAS and CEA did not diﬀ er. In this study, the ICA restenosis rate in the CAS group (assessed by ultrasound) was 3.3%. All of these patients remained asymptomatic (Brooks et al 2014).

One important clinical aspect in our patient refers to the improvement of his cognitive abilities after the ﬁ rst CAS on the right side. Without medical intention, he and his wife reported a huge improvement of the patients’ concentration and awareness. His wife mentioned that he had completely changed his behavior. Before stenting he suﬀ ered from severe fatigue, preventing him from fol- lowing his hobbies or visiting family and friends. After CAS this had changed completely. Cognitive dysfunction is increasingly recognized in cerebrovascular patients. Severe white matter lesions are a well-accepted cause of vascular dementia. Also, amyloid angiopathy was shown to be an associated factor for cognitive impairment in Alzheimer’s dementia. Chronic vascular impairment in extracranial large-vessel disease like the ICA is controversial, however. Starting from single case observations, larger studies have now been published that underline the role of steno-occlusive lesions of the ICA. In a systematic review of studies with symptomatic and asymptomatic ICA pathology 14 trials were identiﬁ ed that noted cogni- tive dysfunction prior to intervention (Bakker et al 2000). An “asymptomatic” ICA stenosis may predict future signiﬁ cant cognitive decline, as has been shown in a 5-year observational study in one-third of patients (Johnston et al 2004). Improvement after revascularization is now frequently reported. A mixed group of 35 symptomatic (>50% stenosis) and asymptomatic patients (>70% stenosis) of the ICA showed signiﬁ cant amelioration of working memory after CAS. The improvement was also related to increased regional CBF measured by single photon emission CT (SPECT) (He et al 2014). Of note, treatment side eﬀ ects like peri-interventional microembolism and silent infarctions may counterbalance the above beneﬁ ts. The history of our patient ﬁ ts well, as he and his wife reported convincingly about a marked decline of his cognitive abilities prior to stroke (for further reading on amnesia and stroke, see Case 44).

Angiologic and Anatomic Aspects

A near-occlusion is the term used for a partial collapse of a vessel due to a proximal high-grade stenosis. According to the Spencer’s curve, a progressing ICA stenosis initially demonstrates raised ﬂ ow velocities within the stenosis to maintain blood volume ﬂ ow. In a critical grade of stenosis (>75% diameter reduction or >90% area reduction), suﬃ -

cient blood ﬂ ow cannot be ensured and the volume ﬂ ow decreases. Initially systolic ﬂ ow velocities increase up to 500 cm/s, then quickly decrease ﬁ rst into the normal range and subsequently to a small residual ﬂ ow (for fur- ther reading on the Spencer’s curve see Chapter 5, “Stenoses and Occlusions” under “Arterial Pathology”). Even if the primary collateral pathways are activated, a residual ICA ﬂ ow may persist but may no longer contribute signif- icantly to the perfusion of the brain. If the stenosis continues to increase or the OA ﬂ ow becomes retrograde to contribute as a further collateral, perfusion pressure may become critically low. This was the case in our patient, who demonstrated a very small antegrade diastolic ﬂ ow through the right ICA. Furthermore, the internalized ECA ﬂ ow was suggestive of retrograde OA ﬂ ow, which was then conﬁ rmed during transorbital and also transtempo- ral insonation. The OA Doppler spectrum demonstrated a reduced pulsatility and increased ﬂ ow velocity, corre- sponding to a brain-supplying and not an eye-supplying ﬂ ow pattern.

Insonation of the petrosal C6-ICA conﬁ rmed the small residual ﬂ ow from the near-occluded ICA. At this level, no collateral vessels exist, thus permitting analysis of an unmodulated poststenotic ﬂ ow pattern. Flow patterns at the carotid siphon level may already be inﬂ uenced by activated PCoA or OA ﬂ ow.

Marked OA involvement, as in our case, implies an insuﬃ cient collateral ﬂ ow via the anterior communicating artery (ACoA) or PCoA. If either of the latter is present with a diameter corresponding to that of the basal cerebral arteries, an additional OA ﬂ ow or even leptomenin- geal collateral ﬂ ow is not needed. In our patient, collateral ﬂ ow via the ACoA toward the right anterior circulation was impeded by the hemodynamically relevant ICA stenosis of the left side. Subsequently, both anterior circulations were fed by prominent retrograde OAs. On the right side, an additional moderate ﬂ ow was present via the PCoA. On the left side, as no PCoA ﬂ ow was present, additional ﬂ ow was provided by leptomeningeal collater- als from the PCA. After right-sided ICA stenting the ﬂ ow to the right anterior circulation not only normalized, but high ﬂ ow velocities became evident in the C6-ICA and A1-ACA only. This pattern was considered to be a sign of new collateral ﬂ ow toward the left anterior circulation. As no cross-ﬂ ow was seen and the left A1-ACA remained antegrade, a leptomeningeal collateral ﬂ ow via the right A1-ACA and ACoA to the left A2-ACA was assumed. After right-sided CAS, ﬂ ow velocities in the right A1-ACA and C6-ICA regressed, indirectly con

tably, the left-sided intracranial ﬂ ow parameters nor-

rming our hypothesis.

ﬁ

malized after CAS of the left ICA. For further reading on ﬂ ow dynamics in extracranial ICA steno-occlusive disorders, see also Chapter 5, “Stenoses and Occlusions” and “Collateral Pathways.”

Angiographic determination of the grade of stenosis following the NASCET criteria in the case of near-occlusions is impaired as the distal vessel diameter cannot be determined because of the poststenotic vessel collapse. As the narrowest diameter within the stenosis is assessed in relation to the distal ICA diameter, near-occlusions will always result in an underestimation of the true grade of stenosis. An ICA/CCA ratio <0.42 has therefore been

312 Case 15 Near-Occlusion of the Right and High-grade Stenosis of the Left Extracranial Internal Carotid Artery

introduced to deﬁ ne ICA near-occlusion (Rothwell and Warlow 2000). Other criteria are based on delayed ﬁ ll- ing of the ICA and its branches as well as the presence of collateral pathways. Diﬀ erences in diameter between the ipsilateral and contralateral ICA as well as ipsilateral ICA and ECA are further indicators. If two or more of the above criteria are present, the sensitivity and speciﬁ c- ity of detection of a near-occlusion is 90.6% and 93.8%, respectively (Fox et al 2005).

DSA has been the method of choice in diﬀ erentiating

between occlusion and near-occlusion. Depending on the speciﬁ c technique used, ultrasound has comparable accuracy. Comparing ultrasound data with MRA in 20 patients, simple color-mode duplex sonography yielded a sensitivity and speciﬁ city of 70% and 92%, respectively. Using echo contrast agents, these values increased to 83% and 92%. If power-mode insonation was used alone or in combination with an echo contrast agent, the sensitivity and speciﬁ city was even higher (95% versus 94% and 92% versus 100%; Fürst et al 1999). However, these authors did not analyze the Doppler ﬂ ow pattern, which can be even more sensitive than the color-mode imaging in low ﬂ ow situations, so these results could probably be even further improved. Analysis of the Doppler spectrum is essential for any ultrasound investigation. With or without echo contrast agents the detection of minimal ﬂ ow beyond a severe stenosis assures a near-occlusion (Ohm et al 2005). In searching for residual ﬂ ow it is important to analyze not only the carotid bulb but also the distal accessible vessel segments. Even in physiologic states the bulb will show alternating ﬂ ow signals and low ﬂ ow velocities because of its physiologic widening. In case of a near-occlusion, an occlusion may wrongly be diagnosed if the bulb alone is examined.

A rare ultrasound ﬁ nding is the detection of an inspi- ration-dependent anterograde ﬂ ow within the stenosis, which turns into zero ﬂ ow during expiration. This phe- nomenon is detectable only by the ultrasound technique and is missed by other diagnostic modalities, which then usually diagnose an occlusion. However, a limiting factor may be a distinct calciﬁ cation with eﬀ acement of the u l t r a s o u n d b e a m i m p e d i n g a c l e a r e v a l u a t i o n . I n t h i s c o n dition additional administration of echo-contrast might facilitate the examination (Ohm et al 2005).

TOF-MRA should not be used for analysis of near-occlusion because of its low sensitivity of 47% in 3D MIP and 65% in 2D MIP (the speciﬁ city was 89% and 100%, respectively; Fürst et al 1999). Ce-MRA is commonly used for evaluation of extracranial occlusive ICA disease (Yang et al 2005). In small series analyzing the accuracy of ce-MRA compared with DSA, all extracranial near-occlusions of the ICA were detected, as in our case (Remonda et al 1998).

CTA has replaced DSA as the standard method for detection of ICA near-occlusions. Thus far, published results concerning near-occlusions are excellent. In a series of 20 patients, a comparison with DSA yielded a sensitivity and speciﬁ city of 100% (Chen et al 2004a). Other authors have reported sensitivity ranging from 90% to 97% and speciﬁ city ranging from 84% to 90% (Bartlett et al 2006). The results seem to depend on the postprocessing technique used. Evaluation of the source scans in axial view and additional evaluation of dots of the intraluminal contrast material may increase the d i a g n o s t i c s e n s i t i v i t y ( L e v e t a l 2 0 0 3 ) .

Because of the potential problems and pitfalls illustrated in this report, it is often advisable to combine diﬀ erent techniques in the evaluation of near-occlusions. However, therapeutic opportunities should be considered carefully.

Case 16

Giant Cell Arteritis with Bilateral Intracranial V4 Vertebral Artery Stenosis

313

Clinical Presentation

A 71-year-old man presented with recurrent episodes of vertigo, dizziness, double vision, and gait disorder, each lasting a few minutes, for 3 weeks prior to admission. The patient had a history of giant cell arteritis (GCA) that had been diagnosed 3 months before this presentation by temporal artery biopsy. At the time he had complained of right-sided temporal headache with jaw claudication, masseter pain, and abnormal fatigue. Laboratory ﬁ ndings revealed an increased erythrocyte sedimentation rate (ESR) (75 mm/h, Westergren) and an elevated C-reactive protein (CRP) of 57 mg/L (normal <5 mg/L). He had been treated with high-dose steroids for 3 weeks. This was subsequently reduced to a daily dose of 7.5 mg prednisolone. He had known vascular risk factors of arterial hypertension and a positive family history of stroke.

On admission, his neurologic examination was normal. He had no complaints suggestive of GCA, in particular any headaches or jaw claudication. The ESR was normal during treatment, but CRP levels were still slightly raised (19 mg/L).

Initial Neuroradiologic Findings

Cerebral CT on the day of admission was normal. There was no evidence of brain ischemia. CT angiogram (CTA) revealed bilateral ﬁ liform stenosis of the vertebral artery (VA) at the intradural entrance, more pronounced on the right side. Also, a calciﬁ ed plaque became visible in the distal right V4-VA segment (Fig. B16.1).

Initial Neurosonologic Findings (Day 1)

Extracranial Duplex Sonography

The carotid arteries showed mild atherosclerotic vascular changes with small hyperechoic plaques in both carotid bifurcations. The diameter in both V2-VA segments was within normal range (left 3.2 mm; right 3.6 mm). Doppler spectrum analysis demonstrated normal ﬂ ow signals in the left V2-VA segment. A high-resistance ﬂ ow signal with reduced ﬂ ow velocity (29/6 cm/s) was observed in the right V2-VA segment (Fig. B16.2 and Fig. B16.3).

Assessment of a branch of the right STeA showed reduced color ﬁ lling and a hypoechoic vessel wall thick- ening consistent with a dark halo sign (Fig. B16.4). No stenoses were seen in the main stem of the STeA and other branches of the ECA. The axillary and brachial arteries were not examined.

Transcranial Duplex Sonography

A poststenotic ﬂ ow pattern was detected in both the P1 and P2 segments of the posterior cerebral artery (PCA). The left VA at its V3–V4 junction revealed a turbulent ﬂ ow with increased ﬂ ow velocities reaching 230/121cm/s. At a similar site the right VA was also turbulent and the velocity was raised but no precise measurement was possible. The distal parts of both V4-VA segments as well as the basilar artery (BA) could not be clearly detected. The anterior circulation was normal (Fig. B16.5, Fig. B16.6, Fig. B16.7).

Suspected Diagnosis

Recurrent transient ischemic attacks (TIAs) in the vertebrobasilar territory due to bilateral VA stenosis at the V3–V4 junction of unknown origin.

Conclusion

Bilateral high-grade VA stenosis, accentuated on the right side, at the V3–V4 junction leading to a poststenotic ﬂ ow pattern in both PCAs. Sonographic conﬁ rmation of arteritis in the right STeA.

Questions to Answer by Ultrasound Techniques

• Were there signs of vasculitis or atherosclerosis in the brain-supplying arteries or in the external carotid artery (ECA), superior temporal artery (STeA), or STeA branches?

• What was the degree of the bilateral distal VA stenosis?

Clinical Course (1)

The neurologic symptoms of the patient were evaluated as recurrent vertebrobasilar TIAs probably of hemo dynamic origin and attributed to the bilateral distal VA stenoses. Their etiology was thought to be either of atherosclerotic origin or caused by the known GCA. The location of the

314 Case16 Giant Cell Arteritis with Bilateral Intracranial V4 Vertebral Artery Stenosis

V2-VA-L

Fig. B16.1 CTA, coronal oblique maximal intensity projection (MIP). Bilateral right-pronounced (arrows) severe VA stenoses at the entrance into the dura mater at the V3/V4 border. Note also small calciﬁ ed plaques in the distal right-sided V4-VA.

V2-VA-R

Fig. B16.3 Extracranial duplex, longitudinal plane. High-resistance flow signal with reduced flow velocity in the right V2-VA and increased pulsatility (flow velocity 29/6 cm/s, PI = 1.7, diameter 3.6 mm).

stenoses at the level of the dural passage and the symmetric pattern seemed atypical for a classic atherosclerosis. The ﬁ ndings were more suggestive of arteritis with the STeA insonation demonstrating the dark halo sign and with the raised CRP. The dose of prednisolone was therefore increased to 30 mg/day.

Follow-up Neurosonologic Findings (6 Weeks)

Fig. B16.2 Extracranial duplex, longitudinal plane. Normal ﬂ ow sig-

nal in the left V2-VA (ﬂ ow velocity 40/17 cm/s, PI = 0.9, diameter

3.2 mm).

STeA-R

Fig. B16.4 Extracranial duplex (linear transducer 11 MHz). A branch of the right STeA shows reduced color ﬁ lling and a vessel wall thickening in form of a dark halo sign (arrows).

inferior cerebellar artery (PICA) origin (Fig. B16.8 and Fig. B16.9). No dark halo sign was seen in either of the STeA.

Transcranial Duplex Sonography

Flow velocity in the left V3–V4 transition now reached 355/255 cm/s. No ﬂ ow signal was detected in projection of the corresponding contralateral side. BA identiﬁ cation again was not possible (Fig. B16.10). Both PCAs further on presented poststenotic ﬂ ow patterns.

Extracranial Duplex Sonography

The left V2-VA segment showed unchanged normal ﬂ ow signals. The right V2-VA segment, however, now demonstrated an even more pronounced high-resistance ﬂ ow signal with a small and short systolic ﬂ ow and complete- ly absent diastolic ﬂ ow component indicative of distal VA occlusion of the right side proximal of the posterior

Conclusion

Secondary occlusion of the right VA at the V3–V4 junction with compensatory ﬂ ow increase in the pre-existing corresponding left VA stenosis. Further progression of the left VA stenosis was, however, a possible alternate diagnosis.

315Discussion

P2-PCA-L

Fig. B16.5 TCCS (tr anst emporal appro ach) , left -sided insonati on, thalamic plane. Reduced ﬂ ow velocity and poststenotic ﬂ ow pat- tern in the left distal P2-PCA (ﬂ ow velocity 21/12 cm/s).

V4-VA-R

V4-VA-L

Fig. B16.6 TCC S (t rans foram inal a pproach ). I ncrease d ﬂ ow ve- locity in the left V4-VA suggestive of stenosis (ﬂ ow velocity 230/ 121 cm/s).

V2-VA-L

Fig. B16.7 TCCS (tra nsfor amin al ap proa ch). Se vere turb ulence and raised ﬂ ow velocity in the right V4-VA hindering a clear ﬂ ow velocity measurement.

Clinical Course (2)

During the ultrasound examination the patient again developed vertigo and diplopia lasting for a few minutes. CTA conﬁ rmed the neurosonologic ﬁ ndings of right VA occlusion starting at the V3–V4 junction and ending before the origin of the PICA. The left VA stenosis appeared unchanged (Fig. B16.11). Because of the new ischemic event and the progression of the occlusive disease, the steroid dose was i n c r e a s e d t o 5 0 m g / d a y p r e d n i s o l o n e . T h e C R P w a s s t i l l s l i g h t ly elevated (6.8 mg/L). Based on CRP monitoring, the steroid dosage was gradually reduced over the ensuing months until below Cushing levels. The 2-year follow-up revealed no further clinical events and showed unchanged neurosonologic ﬁ ndings with low-dose prednisolone (2 mg/day).

Final Diagnosis

Recurrent vertebrobasilar TIAs of hemodynamic origin caused by bilateral VA stenosis starting at the V3–V4 junction with extension to the proximal V4 segment and

Fig. B16.8 Extracranial duplex, longitudinal plane. Follow-up after 6 weeks: Unchanged normal ﬂ ow in the left V2-VA (ﬂ ow velocity 45/23 cm/s).

secondary occlusion of the right V4-VA below the PICA origin. GCA seemed to be the most likely etiology.

Discussion

Clinical Aspects

Here we discuss a patient with recurrent TIAs in the posterior circulation. This evaluation was based on the type and temporal pattern of symptoms lasting for minutes only. The combination of transient vertigo, diplopia, and gait disturbances was rather suggestive of impaired brainstem perfusion of hemodynamic origin. This assumption was conﬁ rmed by the radiologic ﬁ ndings of bilateral VA stenoses starting at the level of the V3–V4 junction with extension to the proximal V4 segments.

Three months prior to the reported neurologic symptoms, GCA was diagnosed and histologically conﬁ rmed in one temporal artery. GCA is an autoimmune vasculitis of unknown origin that typically occurs in medium and large arteries with well-developed wall layers and adventitial vasa vasorum (Weyand and Goronzy 2003).

316 Case16 Giant Cell Arteritis with Bilateral Intracranial V4 Vertebral Artery Stenosis

V2-VA-R

Fig. B16.9 Extracranial duplex longitudinal plane. Follow-up after 6 weeks: High-resistance ﬂ ow signal in the right V2-VA reveals a small and short systolic ﬂ ow and absent diastolic ﬂ ow indicative of distal vessel occlusion proximal of the PICA origin (ﬂ ow velocity 19/0 cm/s).

The disease occurs almost exclusively in individuals older than 50 years, with peak incidence at the age of 70–80 years (Gonzalez-Gay et al 2009). The age-adjusted incidence is 24.2/100,000 for women and 8.2/100,000 for men among white northern European populations (Salvarani et al 1995). The incidence is lower in southern European populations and markedly lower in American populations of Asian or African descent. Based on large autopsy studies, the prevalence of GCA is estimated at ~1% (Östberg 1971). The typical histopathologic picture is an inﬂ ammatory inﬁ ltrate in all three tunicae of the arterial wall with giant cells forming granulomas in the media. Fragmentation of the internal elastic lamina is characteristic, and medial vascular smooth muscle cells are destroyed. Vasculitis leads to luminal occlusion due to intimal hyperplasia and therefore to ischemic complications such as ischemic optic neuropathy. Giant cells are commonly present, and are consequently detected in 60–70% of samples (Lie 1990, Liozon and Catanzano

1982). In up to 100% of cases the STeA, the VA, the OA, the central and posterior ciliary arteries, or a combination of these vessels are aﬀ ected (Wilkinson and Russell 1972). Vessel wall changes might also be found in other arteries such as external carotid branches (e.g., occipital and facial), subclavian, axillary, brachial, ulnar, radial, femoral, popliteal, posterior tibial, dorsal pedal arteries, and the thoracic aorta (W.A. Schmidt et al 2002a, Weyand et al 2012). Intracranial involvement may also occur but is rare. A small study reported on nine patients with histologically proven temporal arteritis and intracranial vasculitis shown by angiography and/or histology (Salvarani et al 2006). Involvement of the intracranial ICA with symptomatic stenosis and subsequent ischemic events is more frequent, but the intracranial VAs are seldom aﬀ ected. These reports of intracranial vessel involvement might, however, be falsely low because the options to conﬁ - dently diagnose intracranial involvement are currently limited. A recent MRI study, using 3-T imaging for the identiﬁ cation of intramural vessel wall changes, detect- ed intradural ICA aﬀ ection in 10 out of 20 patients with

V4-VA-L

Fig. B16.10 TCCS (tra nsforamin al a pproach ). Fo llow -up a fter 6 weeks: Turbulence and increased ﬂ ow in the left V4-VA sugges- tive of progressive stenosis or partly collateral ﬂ ow (ﬂ ow velocity 355/249 cm/s).

Fig. B16.11 CTA, coronal oblique MIP (following bone removal). Follow-up after 6 weeks: Occlusion of the right VA beginning at the V3–V4 junction (arrows). Unchanged pre-existing left-sided VA stenosis (arrow). Note the calciﬁ ed plaque in the distal right V4-VA (ar- rowhead), which appears exaggerated in comparison to Fig. B16.1 because the selected display window is smaller.

GCA (Siemonsen et al 2015). The typical predominantly extracranial vascular involvement is in part explained by the inﬂ ammation being conﬁ ned to elastic ﬁ bers. As intracranial arteries have less elastic ﬁ ber in the media, lack an external membrane, and have a rather small internal membrane, they are less frequently involved. Inﬂ am- mation of the extracranial VA ceases abruptly no more than a few millimeters after it perforates the dura mater. If present, a symmetric involvement of the VA is common in GCA (Crompton 1959, Wilkinson and Russell 1972).

317Discussion

The main clinical symptoms are headaches, visual disturbances, muscle pains, jaw claudication, and fever. Neurologic manifestations are mainly cranial or peripheral neuropathies and neuro-otologic and neuropsychiatric syndromes. The spectrum of symptoms in the event of VA involvement comprises headaches and neck pains but also TIAs and stroke. A retrospective study reported cerebral ischemia in 7% of patients with GCA, in whom about one-third occurred in the posterior circulation (Caselli et al 1988). TIAs in GCA are reported to be 2.5 times more common than in patients with atherosclerotic vessel wall changes (Lipton et al 1987).

A deﬁ nitive diagnosis is made following the criteria of the American College of Rheumatology (ACR) which includes, besides the collection of demographic, clinical, and paraclinical parameters, a biopsy and histologic evaluation of the STeA (Hunder et al 1990). Elevated ESR and CRP levels are common in GCA, but in a study of 764 patients with suspected GCA, with the diagnosis conﬁ rmed in 177 patients, the sensitivity of an elevated ESR was 86% and that of an elevated CRP was 86% with speciﬁ city 30% (Kermani et al 2012). Biopsy of the STeA remains the diagnostic standard with highest accuracy as it identiﬁ es CGA in up to 85–95% of cases (Kermani et al 2013). However, as the disease may show only segmental involvement of the above arteries, a negative biopsy result has been reported in 9–44% of patients with otherwise positive clinical signs of GCA (Karassa et al 2005). Ultrasound has therefore become more important in diagnosing GCA (see “Angiologic and Anatomic Aspects” below).

Treatment consists of the immediate administration of initially high-dose corticosteroids, especially if visual disturbances are reported. In addition to a review of the clinical symptoms, CRP and ESR are suitable parameters for treatment monitoring, but elevated levels of these markers should not be the only indication for immunosuppressive therapy. However, no speciﬁ c biomarkers for GCA have been validated. Secondary agents used included inﬂ iximab, methotrexate, cyclophosphamide, azathioprine, and antimalarial agents, but no validated data exist (Kötter et al 2012). In addition, a meta-analysis with 638 patients reported that the use of the above-mentioned agents in addition to steroids did not improve therapeutic eﬃ cacy as compared with steroids alone (Yates et al 2014).

The most important diﬀ erential diagnosis is athero- sclerosis, which is the most frequent cause of occlusive VA disease. Intracranial VA atherosclerosis occurs as frequently as in the proximal V0/V1 segments, and bilateral involvement is also common (Caplan et al 2004) (see also Case 8). As our patient showed atherosclerotic vascular changes in all brain-supplying arteries and especially calciﬁ ed plaques in the distal right V4-VA segment, an ather- osclerotic etiology had also to be considered, particularly in view of his age and vascular risk proﬁ le. Furthermore, our patient did not complain of pain, which typically occurs in acute GCA. Neck pain is a major ﬁ nding in VA arte- ritis and was present in all eight patients in the literature so far. Also, in seven of these eight patients, stroke was a clinical feature and mortality was distinctly higher than in patients with atherosclerosis (Rüegg et al 2003). In favor of GCA was the previous histologic conﬁ rmation, the

sonographic dark halo sign in the STeA, the extracranial location at the dural entrance, and the clinical stabilization under steroid medication. Even the secondary right VA occlusion, despite the intensiﬁ ed steroid medication, could be compatible with arteritis as several patients with rapidly progressing stenoses despite immunosuppressive therapy have already been reported in the literature (Rüegg et al 2003). A ﬁ nal conclusive diagnosis was, however, not possible in our case.

In the presence of an acute amaurosis a central retinal artery occlusion has to be considered which might be treated by thrombolysis (for further reading on central retinal artery occlusion, see Case 38).

Angiologic and Anatomic Aspects

Duplex ultrasound can relevantly contribute to the diagnosis of GCA, particularly by visualization of the inﬂ ammatory vessel wall which appears as a hypoechoic mostly concentric mural thickening, known as the “dark halo sign” (de Bray et al 1997, Pfadenhauer and Weber 2003, Schmidt et al 1997). A hypoechoic vessel wall may also occur in intramural hematoma (i.e., dissection), but is then, in contrast to the arteritis, eccentric in location. In positive STeA ﬁ ndings this is irrelevant, as dissections hardly ever occur. The mural thickening in GCA may also result in stenoses or occlusions of the aﬀ ected vessel seg- ments. A single-center study of 751 patients revealed an 88% diagnostic sensitivity for ultrasound in relation to the clinical diagnosis and a 95% diagnostic sensitivity in relation to a positive histologic ﬁ nding. For the clini- cal diagnosis, a positive dark halo sign had a speciﬁ city of 99.5% and stenoses or occlusions had a speciﬁ city of 96% (Schmidt and Gromnica-Ihle 2003). A meta-analysis of 23 studies including a total of 2,036 patients, however, demonstrated lower values reﬂ ecting the heterogeneity of investigators and instruments used. The sensitivity and speciﬁ city of the halo sign were 55% and 94%, respec- tively, compared with clinical diagnostic ACR criteria and 69% and 82%, respectively, compared with biopsy (Karassa et al 2005). Another meta-analysis published in 2010 including 998 patients, conﬁ rmed the above results. The sensitivity of the halo sign in patients with biopsy-proven GCA was 75% and the speciﬁ city was 83% (Ball et al 2010). The speciﬁ city can be as high as 100% if a bilateral halo sign is detected, but this reduces the sensitivity to 43% (Ar ida et al 2010 ). So me au tho rs re com men d in clu ding duplex ultrasound in the routine diagnostic criteria for GCA and reserving temporal artery biopsy for patients with negative ultrasound ﬁ ndings (Ball et al 2010).

In clinical routine, ultrasound of the temporal artery is well accepted and in some centers it is considered to be just as valuable as biopsy for treatment decisions (Alberts and Mosen 2007). At what point in the course of the disease and at which stage of the inﬂ ammatory process the halo sign becomes detectable is not clearly known. Schmidt and Gromnica-Ihle (2003) reported that four of eight patients with a false-negative ultrasound ﬁ nding showed only little inﬂ ammatory inﬁ ltration in the histo- logic analysis, aﬀ ecting one vessel layer or the vasa va- sorum only. They assumed that these might be ﬁ ndings of an early phase of the disease. This view has been

318 Case16 Giant Cell Arteritis with Bilateral Intracranial V4 Vertebral Artery Stenosis

c h a l l e n g e d b y M u r a t o r e a n d c o w o r k e r s , w h o c o n s i d e r e d a “periadventitial small vessel vasculitis” (SVV) and/or a “vasa vasorum vasculitis” (VVV) as subgroups of GCA. If not treated, these patients have the same risk of suﬀ er- ing ischemic events as those with a typical GCA. In 30 biopsy-proven patients with a SVV and/or VVV, the authors found a sensitivity of 20% and speciﬁ city of 80.6% for the halo sign, which diﬀ ered from the analysis of 63 patients with a classical GCA (82.5% and 80.6%, respectively) (Muratore et al 2013).

Valid data exist concerning the time period from onset of the immunosuppressive treatment during which the halo sign is detectable. It usually disappears 2–3 weeks (mean 16 days) after treatment initiation. This observation corresponds well with data derived from biopsies taken after commencement of the immunosuppressant therapy. However, the possible range is larger in i n d i v i d u a l c a s e s : t h e h a l o s i g n m a y d i s a p p e a r a s e a r l y a s 1–2 days after treatment initiation or may remain detectable for up to 2 months (Santoro et al 2013, Schmidt et al 1995, 1997). A recent study reported that the ultrasound sensitivity for detection of biopsy-proven GCA may drop from 92% on treatment day 1 to 80% on day 2 to 50% from day 4 onwards. The corresponding speciﬁ cities were 57%, 83%, and 25%, respectively (Hauenstein et al 2012).

Potential pitfalls for ultrasound are an atherosclerotic STeA stenosis or false-positive halo signs that may be present in infectious or malignant diseases (Karassa et al

2005). The diagnostic validity of ultrasound also depends on the experience of the sonographer. A lack of experience might lead to artifacts. An incorrectly adjusted color gain (too high or too low) may mask or falsely simulate a vessel wall thickening, interpreted as a halo sign. Aschwanden and coworkers tried to introduce a new ultrasound test for GCA. They prospectively performed a bilateral ultrasound analysis in 80 patients with suspected GCA searching for a halo sign and in addition performing a compression test. A test result was deﬁ ned as positive if the temporal artery remained visible in B-mode sonography during a compression of the artery, performed with the ultrasound transducer. Afterwards, the patients were split into two groups of 43 GCA-positive and 37 GCA-negative patients, according to the ACR criteria. In 34 of the GCA-positive group the halo sign and compression test were positive, while all GCA-negative patients showed negative ultrasound ﬁ ndings. The resulting sen- sitivity and speciﬁ city were 79% and 100%. The authors concluded that the halo sign and compression test were of equal value. The missing positive compression test in the remaining 9 GCA-positive patients was presumed to be due to less extensive inﬂ ammation in these patients (Aschwanden et al 2013).

Ultrasound diagnosis in vessels other than the STeA is more diﬃ cult and positive ﬁ ndings are less frequent. For example, in the VA, a positive dark halo sign was reported in only 2.2% of cases with known GCA (Pfadenhauer et al 2005). However, if a concentric hypoechoic mural thickening is present, the halo sign is highly speciﬁ c for the diagnosis of GCA (García-García et al 2011). The low identiﬁ cation rate is probably caused by the limited B-mode insonation conditions within the distal V2- and the V3-VA segments, caused by the vessel course and its

close relation to the spinal column. In this location, alterations of vessel wall echogenicity are diﬃ cult to assess. Correspondingly, in our patient the typical dark halo sign was found only in the STeA and not in the VA.

Besides the cervical arteries, other large extracervical

vessels may also be aﬀ ected. Involvement of the proximal arm arteries, especially of the axillary arteries, is particularly frequent (Czihal et al 2012). Compared with the classical cervical artery GCA, these patients are younger and often do not fulﬁ ll the ACR criteria, leading to longer time periods from disease onset to diagnosis. Axillary artery insonation is therefore recommended for all patients with clinical signs of GCA, pyrexia of unknown origin, or claudication symptoms of the arms (Blockmans et al 2009, Brack et al 1999, Schmidt et al 2008).

High-resolution MRI has demonstrated its usefulness

in the imaging of GCA. In single cases, a mildly hyperintense signal of the aﬀ ected vessel walls has been reported in T2-weighted MRI (Reinhard et al 2003). Better results are achieved if T1-weighted contrast-enhanced (ce)-MRI is used which allows direct imaging of the mural thickening and mural enhancement. In a study of 64 consecutive patients, a sensitivity of 80.6% and a speciﬁ city of 100% were reported when compared with clinical criteria including temporal artery biopsy (Bley et al 2007). More recently, sensitivity and speciﬁ city numbers of 88.7% and

90.4% have been reported (depending on the subcohort addressed) for ce-MRI in GCA patients. Interestingly, diagnostic accuracy of ce-MRI also remained high in patients undergoing steroid treatment until day 5 of steroid intake (Klink et al 2014). MRI sensitivity may increase further if 3-T MRI systems are used. In one recent study an enhancement even of the intradural ICA was reported in 10 out of 20 patients with clinical or biopsy-proved GCA, whereas superﬁ cial extracranial arteries revealed vessel wall enhancement in 16 out of 20 patients (Siemonsen et al 2015). Even using ce-MRI, the diagnostic sensitivity decreases after initiation of cortisone therapy, but not to the same extent as in ultrasound. The reported sensitivity for diagnosis of biopsy-proven GCA dropped from 90% on day 1 to 78% on day 2 and 80% from day 4 onwards. The corresponding speciﬁ city was 77%, 71%, and 75%, which is also higher than reported values for the ultrasound technique (Hauenstein et al 2012).

CT and CTA do not show active vessel wall inﬂ amma- tion, but rather reveal stenoses or occlusions in GCA patients as well as the presence and extent of hard plaques which might be of importance in diﬀ erential diagnosis (for further discussion on sonographic and radiologic ﬁ ndings in distal VA stenosis, see also Case 8).

Ultrasound diagnosis of secondary proximal V4-VA occlusion in our reported case was based on the remaining systolic ﬂ ow being only small and diastolic ﬂ ow being completely absent, suggestive of a distal VA occlusion prior to the origin of the PICA.

A special feature of the reported case is the secondary ﬂ ow velocity increase in the stenosed left VA and the concurrent right occlusion. As only ﬂ ow velocities were measured, a diﬀ erentiation between a worsen- ing of stenosis or a ﬂ ow rise due to an increased col- lateral ﬂ slight incr

ow by ultrasound was not possible. The only

ease of ﬂ ow velocity in the left V2-VA from

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