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369Discussion

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.

Our patient also experienced migraine with aura. Migraine, PFO, and their potential relation to ischemic stroke has been the subject of intensive research and is controversial. The prevalence of PFO was shown to be higher in cryptogenic stroke patients with migraine than in those without migraine (Mas et al 2001). In this study 267 out of 581 young stroke patients (45%) demonstrated a PFO with or without an ASA. Within the PFO group,

27.3% had migraines compared with 14% of patients in the group without a PFO. Migraine has also been related to PFO in several case–control studies and meta-analyses. In migraine patients with aura the prevalence of PFO was found to be 40–60% compared with 16% in patients without aura. The latter corresponds fairly well to the reported prevalence of 24% within a normal healthy population (Diener et al 2007, Lamy et al 2002, Schwedt et al 2008).

The association of migraine and PFO is even bidirectional. Individuals with a PFO have an ~5-fold increased risk of developing migraine (Brasselet and Duval 2011, Kurth and Diener 2012). On the other hand, there is also data available that argues against a correlation of PFO and migraine. The only available population-based study with a cross-sectional study design did not conﬁ rm any associ- ation of PFO and migraine with or without aura (Rundek et al 2008). Several hypotheses concerning the underlying pathophysiologic connection of PFO and migraine have been postulated. One of these is that vasoactive substances like prostaglandin, serotonin, and bradykinin are usually 85–95% ﬁ ltered by the lung. In right-to-left shunt they may bypass this ﬁ lter and this may lead to the induc- tion of migraine attacks (Nozari et al 2010). Several trials have been conducted on the basis of this hypothesis. Nonrandomized studies suggested positive results (Vigna et al 2009), but the only available randomized trial (MIST) could not conﬁ rm these ﬁ ndings (Dowson et al 2008). In addition, considering the periprocedural complications of PFO closure, an intervention for prophylactic treatment of migraine cannot be recommended (Berdat et al 2000).

Migraine with aura may not only mimic stroke but is itself associated with brain ischemia. Migraine in general, but specially migraine with aura, is related to ischemic stroke (Etminan et al 2005). The prevalence of migrainous infarctions in relation to all ischemic strokes derived from large clinical studies is 0.5–1.5%. The preferential brain location for migrainous infarctions is within the posterior circulation (Laurell et al 2011, Wolf et al 2011).

Three retrospective case–control studies found an increased relative risk of stroke ranging from 3.8% to 8.4% in women aged <45 years who had migraine with aura (Chang et al 1999, Donaghy et al 2002, Tzourio et al 1995). This risk is tripled if migraine and smoking are combined, and quadrupled if migraine and an oral contraceptive are combined. However, a comparative study that analyzed retrospective and prospective data found a twofold higher risk in the retrospective data than in the prospectively collected data, which indicated that retrospective studies overestimate the real risk of stroke (Stang et al 2005).

The association of both conditions is further supported by three available meta-analyses. In particular, migraine with aura seems to have the strongest relation to ischemic stroke (Etminan et al 2005, Schürks et al 2009, Spector et al 2010). Single studies in the latter group even report

a correlation of attack frequency (if >12–13 per year) and the patient’s stroke risk (Donaghy et al 2002, MacClellan et al 2007). The above ﬁ ndings are further supported by MRI studies, in which patients with migraine more frequently demonstrate clinically silent brain infarctions, especially within the posterior circulation. Furthermore, women with migraine seem to have a higher risk of developing so-called white matter lesions (Kruit et al 2010).

The increased rate of stroke is also in part explained by the fact that a variety of diseases such as ﬁ bromus- cular dysplasia, cervical artery dissection, arteriovenous malformations, and rare genetic conditions like CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) as well as MELAS (mitochondrial myopathy, encephalopathy, lactacidosis, and stroke) are related to migraine.

Overall, and in comparison with the classic risk factors of stroke, the migraine-related absolute risk of stroke is very low. In epidemiologic studies the estimated attributable risk ranges from 18 to 40 additional annual ischemic strokes per 100,000 women (Kurth et al 2005, Tzourio et al 1995).

In our patient, stroke appearance was not related to a migraine attack (which is only then deﬁ ned as migrain- ous stroke). According to the International Headache Society a migrainous stroke is deﬁ ned as one or more migrainous aura symptoms lasting more than 60 minutes associated with an ischemic brain lesion in appropriate territory demonstrated by neuroimaging (International Headache Society 2013). The underlying pathomechanism is still unclear. A possible hypothesis is a severe state of hypoperfusion during a migraine attack. However, most ischemic strokes in migraine patients occur within the headache-free interval (Bousser and Welch 2005). In our patient, migrainous stroke was unlikely as she denied headaches during stroke evolution. Other hypotheses postulate a severe hypoperfusion caused by cortical spreading depression alone or caused by microemboli (Nozari et al 2010). Also, a hypercoagulability (Cesar et al 1995) and transient vessel vasoconstriction have been hypothesized (Tsai et al 2010) indicating possible overlaps with other reversible vasoconstriction diseases (for reading on cerebral reversible vasoconstriction syndrome, see Case 36).

Angiologic and Anatomic Aspects

TEE is the current gold standard for PFO diagnosis but a higher sensitivity has been reported using the indirect TCD technique (Caputi et al 2009). Even transthoracic echocardiography may be used instead of TEE (Gonzáles-Alujas et al 2011). The combination of TCD and echocardiography yields a sensitivity and speciﬁ ci- ty of 100%, compared with autopsy ﬁ ndings (Schneider et al 1996) (for further general information about TCD, PFO and embolus detection, see Chapter 4, “Detection of Microemboli in Patent Foramen Ovale” under “Microembolic Signals”).

Intracranially, the anatomic peculiarity of our case is the early temporal M1-MCA branch, which led to an initial misinterpretation of the transcranial color-coded duplex sonography (TCCS) ﬁ ndings. Instead of the assumed M1-MCA segment, a marked temporal MCA

370 Case 22 Right Mid-part M1 Middle Cerebral Artery Occlusion with Prominent Early Temporal Branch and Patent Foramen Ovale

branch was visualized in a more basal upper pontine plane location. In view of the low ﬂ ow velocities but otherwise normal ﬂ ow proﬁ les, a distal occlusive pro- cess was suspected. According to the TIBI and COGIF classiﬁ cation, our ﬁ ndings correspond to a type 3 ﬂ ow pattern (see also Chapter 5, “Occlusions” under “Intracranial Pathology”). Our initial ultrasound report 1 day after thrombolysis was as follows: “successful M1-MCA recanalization after systemic thrombolysis with indirect signs of distal MCA branch occlusion.” In the TCCS control examination 10 days later a distinct MCA asymmetry was again apparent. The unaﬀ ected MCA followed a straight course whereas the aﬀ ected MCA was visu- alized only intermittently and far more basal. This, in combination with the knowledge that MCA vessel courses are usually symmetric in young subjects, led to the correction of our ultrasound report toward a persisting middle segment M1-MCA occlusion and visualization of an early temporal MCA branch. This signal had meanwhile become more prominent because of the persisting M1-MCA occlusion and the continuing demand for collateral ﬂ ow. This evaluation was conﬁ rmed by DSA, which demonstrated the linear MCA course on the left, the persisting M1-MCA occlusion on the right side, as well as the more basal course of its early temporal MCA branch (see Fig. B22.16 and Fig. B22.17). A careful ex- amination of the vessel sheaths in the B-mode images and consideration of the chosen insonation plane may help to avoid the above misinterpretation. In normal insonation conditions pulsations of the basal arteries can be observed. For ﬁ rst anatomic evaluation, the hypere- choic lateral ﬁ ssure is identiﬁ ed in which sometimes even the M1-MCA vessel sheath can be visualized as a hypoechoic pulsating structure. Color mode will then conﬁ rm the vessel location. A missing color signal in this insonation plane strongly hints at possible M1-MCA o c c l u s i o n . S t a r t i n g t h e T C C S i n s o n a t i o n o n t h e u n a ﬀ ect- ed side will provide a general idea of vessel course and ﬂ ow proﬁ les and subsequently help in interpretation of the pathologic ﬁ ndings. Equally important and helpful is the above-mentioned correct use of insonation planes. A basal temporal MCA branch is not visible if a clear midbrain plane insonation is performed but rather appears upon insonation within the upper pontine plane (for further reading, see Chapter 2, “Middle Cerebral Artery” under “Intracranial Arteries”).

Remarkably, the extracranial ICA ﬂ ow was not as signiﬁ cantly impaired as could have been expected in mid-part M1-MCA occlusion. This can be explained by a combination of the strong ipsilateral A1-ACA segment, the perfused early temporal MCA branch, and ﬁ nally the fetal-type anatomic PCA variant on the occlusion side, all draining blood from the ICA and functioning as collaterals (see also Case 17; Chapter 5, “MCA Occlusion” under “Intracranial Anterior Circulation;” and Fig. A5.98).

There are limited reports on the prevalence of early temporal MCA branches. The angiographic literature accounts for a prevalence of 6% (Huber 1982) whereas anatomic studies found early temporal MCA branches of highly diﬀ erent calibers in ≥90% (Gibo et al 1981, Tan- riover et al 2003). Using TCCS and preferably applying the anterior coronal insonation plane, an early temporal

branch has been detected in up to 26% of cases (Rogge et al 2015).

Anatomically, the early temporal branch is most frequently the temporopolar artery which originates directly below the lenticulostriate arteries from the M1-MCA segment. From there it runs, as seen in our patient’s DSA, on the unaﬀ ected side in a lateral and more basal direction (see Fig. B22.16). Reported diameters of the early temporal branch vary. Gibo and coworkers (1981) found diameters ≤1.5 mm, measuring between 1 mm and

1.5 mm, in 38% of cases only. In contrast, the other cortical MCA branches exceeded 1.5 mm in 50–90% of cases. Tanriover and coworkers (2003) found a mean diameter of 1.4 mm (for further reading, see Chapter 2, “Middle Cerebral Artery” under “Special Arterial Anatomy and Ultrasound Anatomy”). It is important to note that, in cases of M1-MCA occlusion, the early temporal branch becomes more prominent because of its additional collateral function and will subsequently be more easily visualized. If present, a middle or distal M1-MCA occlusion may be overlooked even if TCCS is used, and special attention must be paid. Diﬀ erentiation by TCD is probably impossible. Patients with a temporal branch have a better prognosis, if this is functioning as collateral in MCA occlusion. In a conventional angiography study of 98 patients, 45% showed a temporal branch, which was signiﬁ cantly correlated with a better outcome (D. Liu et al 2014).

Considering MCA anatomic variants, the early temporal branch needs to be diﬀ erentiated from a medial M1-MCA (i.e., an early M1-bifurcation), which might occur within the ﬁ rst centimeter of the MCA main stem. However, the latter is rare, being reported in up to 3% of patients studied angiographically (Huber 1982) and up to 2% of patients studied by TCCS (Rogge et al 2015).

The observed MCA main-stem occlusion persisted over at least 11 days and permitted a comparison of MRA,

, and DSA, which were performed within this period.

C The initial CTA ﬁ ndings were interpreted as a proximal M1-MCA main-stem occlusion. The readily visible insular branches were thought to be perfused retrograde. Only after comparing CTA and DSA was the early temporal MCA branch recognized in the CTA. This underlines that the general sensitivity of the CTA technique is high. However, the examiner needs to focus attention not only on the primary vessel disease (i.e., the proximal M1-MCA occlusion) but also on potential collateral pathways. In comparison, TOF-MRA visualized neither the temporal MCA branch nor the insular branches. The latter may have been inﬂ uenced by the severe hemorrhagic trans- formation of the infarcted parenchyma. In our case, DSA remained the most convincing radiologic method to gather all of the above hemodynamic information (for further discussion on angiologic aspects of intracranial occlusion, see Case 10).

Finally, the persisting MCA occlusion over >11 days needs to be discussed. The main acute treatment goal to minimize the infarct size is of course to achieve an early vessel recanalization, either by intravenous thrombolysis or by intra-arterial thrombectomy. A large number of studies analyzing recanalization rates before the introduction of local thrombectomy are available. In a series of 31 patients with M1-MCA occlusion (50% treated by

371Discussion

systemic thrombolysis), 26% reopened within 24 hours and 65% after 3 days (Ringelstein et al 1992). A further study of 16 patients with MCA occlusion not receiving thrombolysis reported a similar recanalization rate of

62.5% after several weeks (Kaps et al 1992b). In an exclusively observational TCD study of 50 patients with M1-MCA occlusion, reopening was observed in 86% of patients within 2 weeks (Alexandrov et al 1994). In patients receiving intravenous thrombolysis, MCA mainstem recanalization was seen in four of eight cases within the ﬁ rst 2 hours and in 75% after 24 hours (Gerriets et al

2000). A signiﬁ cantly higher 1- and 6-hour recanalization rate after systemic thrombolysis was observed in cardiac embolism (59% and 76%) compared with artery-to-artery embolic occlusions (8 and 33%, respectively), indicating that cardioembolic clots seem to respond faster and better to thrombolysis (Molina et al 2004).

From the above data it can be assumed that most

i n t r a c r a n i a l e m b o l i c l a r g e v e s s e l o c c l u s i o n s r e c a n a l i z e d .

This often occurs spontaneously and may take time (up to several weeks). Cardioembolic occlusions seemed to recanalize faster than artery-to-artery embolism. A permanent occlusion, however, rather favors primary severe atherosclerotic vessel pathology as the underlying course. However, a permanent occlusion caused by embolism cannot completely be excluded: For example, an embolus composed mainly of calciﬁ ed material may rather cause persisting occlusion. The observation of the so-called “spot sign” in central retinal artery occlusion, thought to present a persisting calciﬁ ed embolic clot, gives some indication that the above considerations are correct and may also be applicable to brain vessel occlusions (for further reading on central artery occlusion, see Case 38). To date, meticulous data on time course of vessel recanalization in determined and undetermined stroke is not available. It is notable that in our patient the MCA occlusion remained for at least 11 days despite intravenous thrombolysis and a suspected cardiac embolism.

372

Case 23

Takayasu’s Arteritis with Right-sided Subclavian Steal

Clinical Presentation

A 32-year-old man of Turkish origin was admitted with an episode of unconsciousness that lasted for ~2 minutes, and was then followed by nausea and vomiting. He complained about worsening of his visual acuity in the preceding 3 days. Several years earlier he had sustained a similar episode of unconsciousness that at the time was considered to be due to orthostatic dysregulation. At that time, no neurologic examination or cerebral imaging had been performed. The patient had no vascular risk factors and no relevant past medical history. On neurologic examination, he had left complete and right partial homonymous hemianopia (National Institute of Health Stroke Scale [NIHSS] score: 3). In addition, asymmetric radial pulses were noted.

Initial Neuroradiologic Findings

MRI showed bilateral subacute occipital ischemic brain lesions in the posterior cerebral artery (PCA) territory (Fig. B23.1). MR angiography (MRA) was not performed.

Suspected Diagnosis

Tra nsi ent “top of the b asila r” sy ndrom e wit h in compl ete cortical blindness caused by bilateral infarction in the PCA territory.

Questions to Answer by Ultrasound Techniques

246 cm/s peak systolic ﬂ ow velocity was detected. The left subclavian artery (SA) was not visualized. Doppler spectrum analysis of the right V2-VA segment revealed alternating, mostly retrograde ﬂ ow. Muscular activity of the right arm led to an increase of the retrograde ﬂ ow component. The right SA was not detectable (Fig. B23.2, Fig. B23.3, Fig. B23.4, Fig. B23.5; see also Video A normal triphasic ﬂ ow signal was seen in the left brachi- al artery. The right brachial artery revealed a poststenotic ﬂ ow pattern with a monophasic ﬂ ow signal and reduced pulsatility (not shown).

B23.1).

Transcranial Duplex Sonography

Normal ﬁ ndings were seen in both anterior and middle cerebral arteries. Both PCAs were visible but presented a marked poststenotic ﬂ ow pattern in all segments with a band-like nonpulsatile ﬂ ow and reduced ﬂ ow velocities. Transforaminal insonation revealed a mildly poststenotic ﬂ ow pattern in the left V4-VA segment and alternat- ing ﬂ ow in the right V4-VA segment. The basilar artery (BA) was not visualized (Fig. B23.6, Fig. B23.7, Fig. B23.8,

Fig. B23.9; see also Video

B23.2).

Conclusion

Proximal high-grade stenosis of the left VA and rightsided incomplete subclavian steal syndrome (grade 2) i n d i c a t i n g h i g h - g r a d e s t e n o s i s o r o c c l u s i o n o f t h e proximal right SA. In addition, marked hemodynamically compromised ﬂ ow in both PCAs indicating no relevant collateralization from the anterior circulation via the posterior communicating artery (PCoA).

• Was there evidence of pathologic change in the vertebrobasilar system?

• If so, was it of atherosclerotic or vasculitic origin?

Initial Neurosonologic Findings

Extracranial Duplex Sonography

There was no evidence of atherosclerotic or vasculitic changes in the carotid arteries. The caliber of both vertebral arteries (VAs) was normal (left 4.5 mm; right 3.9 mm). The left VA presented a poststenotic ﬂ ow pattern with de- layed systolic ﬂ ow increase and reduced ﬂ ow velocity in its V2 segment. At its origin an increased ﬂ ow reaching

Conventional Angiography

Emergency digital subtraction angiography (DSA) was performed shortly after ultrasound examination and demonstrated a proximal short high-grade stenosis of the right SA proximal to the origin of the VA. The right VA was not visualized, but a high-grade stenosis was observed at the origin of the left VA, with collateral vessels in its vicinity. No further obstacle was seen in the left intracranial VA an d in t he BA . Th e ﬂ ow in both PCAs appeared dimin- ished, without signs of obstruction. Both carotid arteries were regular but no collateral ﬂ ow was detectable via one or both PCoAs. Both renal arteries and the aorta were normal (Fig. B23.10, Fig. B23.11, Fig. B23.12).

V2-VA-L

373Neurosonologic Findings (6 Months)

Fig. B23.1 MR FLAIR image, axial plane. Bilateral occipital hyperin-

tense areas (arrowheads) with right-sided accentuation considered to be subacute territorial PCA infarctions. Additional small left c e r e b e l l a r l e s i o n e v a l u a t e d a s s m a l l l e f t s u p e r i o r c e r e b e l l a r i n f a r c t i o n .

V1-VA-L

Fig. B23.3 Extracranial duplex, longitudinal plane. Increased ﬂ ow in the proximal left V1-VA segment (angle-corrected ﬂ ow velocity 246/106 cm/s).

Clinical Course (1)

An artery-to-artery embolic event from the proximal left VA s te no si s w as t ho ug ht to b e t he c au se o f t he c er eb ra l ischemia. An atherosclerotic etiology was considered unlikely because of the angiographic and ultrasound ﬁ ndings, the young age of the patient, and the lack of vascular risk factors. Infectious diseases were ruled out by laboratory tests and analysis of the cerebrospinal ﬂ uid (CSF). Howev- er, mild anemia, an increased erythrocyte sedimentation rate (ESR) of 47 mm/h, a C-reactive protein (CRP) level of 10 mg/L (normal <5 mg/L), and the involvement of the proximal vessel segments were suggestive of Takayasu’s arteritis. Long-term therapy with oral steroids (75 mg/day prednisolone) and antiplatelet therapy with aspirin was commenced. Six months later the patient was admitted for follow-up examination and ultrasound imaging.

Fig. B23.2 Extracranial duplex, longitudinal plane. Reduced ﬂ ow velocity and pulsatility, suggesting a poststenotic ﬂ ow pattern in the left V2-VA, which shows a normal diameter of 4.5 mm (ﬂ ow velocity 36/16 cm/s).

V2-VA-R

Fig. B23.4 Extracranial duplex, longitudinal plane. Alternating, but almost retrograde ﬂ ow in the right V2-VA with a normal diameter of 3.9 mm (ﬂ ow velocity 40/0 cm/s).

Question to Answer by Ultrasound Techniques (6 Months)

• Was there evidence of stenosis regression after the steroid treatment?

Neurosonologic Findings (6 Months)

Extracranial Duplex Sonography

Identical ﬂ ow patterns were seen in the left V1- and V2-VA segments (not shown). The right V2-VA segment now presented a completely retrograde ﬂ ow pattern (Fig. B23.13). Assessment of the SA was again not p o s s i b l e .

374 Case 23 Takayasu’s Arteritis with Right-sided Subclavian Steal

V2-VA-R

Fig. B23.5 Extracranial duplex, longitudinal plane. Complete retrograde ﬂ ow in the right V2-VA after muscular activity of the right arm (ﬂ ow velocity 60/20 cm/s).

V4-VA-R

V4-VA-L

Fig. B23.6 TCCS ( transfo raminal approa ch). Mi ldly po stst enotic

ﬂ ow pattern in the left V4-VA (30/10 cm/s).

P1-PCA-L

Fig. B23.7 TCCS (t rans foram inal approach ). Alte rnat ing ﬂ ow in the right V4-VA (ﬂ ow velocity −10/15 cm/s).

P2-PCA-R

Fig. B23.9 TCCS (t rans tempo ral approach) , right -sid ed in sona tion, midbrain plane. A similar severe poststenotic ﬂ ow pattern was pres- ent in the right proximal P2-PCA (ﬂ ow velocity 34/20 cm/s).

Fig. B23.8 TCCS (tr anst emporal appro ach) , left -sided insonati on, midbrain plane. Severe poststenotic ﬂ ow pattern with a band-like ﬂ ow in the left P1-PCA (ﬂ ow velocity 30/25 cm/s).

Transcranial Duplex Sonography

Unchanged prominent poststenotic ﬂ ow patterns were seen in both PCAs. On transforaminal insonation, the left V4-VA segment also appeared almost unchanged, but the right V4-VA segment now demonstrated a continuous retrograde ﬂ ow. The BA was not visualized (not shown).

Conclusion

Unchanged long-segmented stenosis at the origin of the left VA . Wo rs en in g r ig ht -s id ed s ub cl av ia n s tea l ( gr ad e 3 ), p ro b ably due to progressive stenosis or occlusion of the right SA.

Clinical Course (2)

With long-term treatment with oral steroids, the ESR normalized and no further ischemic events occurred.

375Clinical Course (2)

Fig. B23.10 DSA, selective right brachiocephalic injection, posteroanterior view. Proximal short high-grade stenosis of the right SA (arrow) proximal to the origin of the VA. Note, that there is no contrast ﬁ lling of the right VA due to alternating, mostly retrograde VA ﬂ ow, and this must not be confused with VA occlusion.

Fig. B23.11 DSA, selective left SA injection, posteroanterior view. Long-segmented left proximal irregular high-grade VA stenosis (arrows). Note the collateral vessels in the vicinity.

V2-VA-R

Fig. B23.13 Extracranial duplex, longitudinal plane. Six months follow-up: Worsening of ﬂ ow in the right V2-VA—completely retro- grade ﬂ ow pattern (ﬂ ow velocity 37/12 cm/s).

Fig. B23.12 DSA, selective left VA injection, posteroanterior view. Fai nt v esse l co ntr ast wi thi n bo th PC A t erri tor ies (a rrowh eads ) in otherwise normal intracranial vertebrobasilar vessels.

However, ultrasound suggested further progression of the right-sided SA disease. High-dose intravenous cortisone therapy was administered for 5 days, but this did not improve the vascular status. Considering the progression of vascular pathology and because of the absent PCoA on both sides, it was decided to perform a right carotid–subclavian bypass connecting the common ca-

rotid artery (CCA) with the SA distal to the SA stenosis but proximal to the origin of the VA to improve the posterior circulation. The surgery proceeded uneventfully and medication for long-term stroke prevention was subsequently continued with aspirin. No interventional treatment was considered for the left-sided proximal VA stenosis, which remained stable. Afterwards, the patient

376 Case 23 Takayasu’s Arteritis with Right-sided Subclavian Steal

V2-VA-R

Fig. B23.14 Extracranial duplex, longitudinal plane. Eight months follow-up: Normalized and antegrade ﬂ ow in the right V2-VA after right-sided carotid–subclavian bypass (ﬂ ow velocity 70/33 cm/s).

clinically remained in remission without laboratory evidence of inﬂ ammatory activity. Therefore, corticosteroid treatment was discontinued. The patient was reviewed 2 months postoperatively.

Questions to Answer by Ultrasound Techniques (8 Months)

V4-VA-R

Fig. B23.15 TCCS (t ransfor aminal app roach). Ei ght months fo llow-up: Normalized antegrade ﬂ ow signal in the right V4-VA (ﬂ ow velocity 30/15 cm/s).

Final Diagnosis

Bilateral PCA infarcts caused by artery-to-artery embolism from a left V0/V1-VA stenosis in Takayasu’s arteritis. Right subclavian steal syndrome (grade 3) with markedly compromised posterior circulation in bilateral hypofunctional PCoA. Improved perfusion of the vertebrobasilar circulation after right-sided carotid–subclavian bypass.

• Was the bypass patent?

• If so, was there antegrade blood ﬂ ow in the right VA?

• Had the blood ﬂ ow in the BA and both PCAs normalized?

• Were there any hemodynamic changes in the left VA?

Neurosonologic Findings (8 Months)

Extracranial Duplex Sonography

Flow in the left VA remained unchanged. The bypass was not visualized, but normal and antegrade ﬂ ow signals were found in the right V2-VA segment (Fig. B23.14).

Transcranial Duplex Sonography

Both PCAs presented normalized ﬂ ow signals (not shown) while the left V4-VA segment was unchanged. The right V4-VA segment now revealed an almost normalized antegrade ﬂ ow (Fig. B23.15; see also Video

Conclusion

Complete normalization of ﬂ ow in the right VA with no signs of the subclavian steal following carotid–subclavian bypass. Unchanged ﬂ ow pattern in the left VA origin, indi- cating stable proximal high-grade VA stenosis.

Fig. B23.16 and Fig. B23.17 show schematics of the patient’s extra- and intracranial brain-supplying arteries before and after right CCA—SA bypass.

B23.3).

Discussion

Clinical Aspects

Here we report on a 32-year-old man of Turkish origin with bilateral PCA infarctions. The underlying cause was a complex pathology within the vertebrobasilar vascular system. A high-grade proximal SA stenosis on the right side initially resulted in an incomplete subclavian steal (grade 2) that over time progressed to a complete steal grade 3 (for further discussion on subclavian steal, see also Chapter 5, “SA Proximal Stenosis and Occlusion” under “Extracranial Pathology,” and Case 28). An additional left-sided high-grade stenosis at the VA origin led not only to bilateral posterior infarction but also to a distinct impairment of the posterior circulation. The etiology of a bilateral occlusive disorder of the proximal posterior circulation is mostly atherosclerotic, but other causes such as traumatic injury, emboli, or inﬂ ammatory disease such as Takayasu’s arteritis (TA) might also lead to proximal SA obstruction and subsequent subclavian steal. The young age of our patient, the absent atherosclerotic vessel wall changes, and the involvement of the proximal arteries close to the aortic arch, in combination with the raised ESR and CRP, were suggestive of TA.

TA is a chronic large-vessel vasculitis of unknown eti-

ology that predominantly aﬀ ects the aorta and its main branches, segmentally or the entire vessel. It is a rare condition with three cases per million population per year in Europe and North America (Arend et al 1990). It

377Discussion

Fig. B23.16 Schematic of the patient’s extra- and intracranial brain-supplying arteries: Initial ﬁ ndings. High-grade right SA and left V0/V1-VA stenosis with subclavian steal and a vertebro-vertebral overﬂ ow from left to right (circles).

most frequently occurs in young Asians 10–40 years old and women are aﬀ ected in 80–90% of cases, although it can aﬀ ect individuals from other racial backgrounds and age groups. Infectious, autoimmune, and hereditary factors have been discussed (Noris 2001). The disease starts u s u a l l y a t t h e m i d o r p r o x i m a l p a r t o f t h e l e f t S A . I n u p t o 85% of cases, the SA (bilateral in 47%) is involved. The vertebral and the renal arteries are also frequently aﬀ ected, the latter in up to 75%, followed by the descending aorta in 58%, the carotid arteries (mainly the CCA) in 44% and bilateral in 19%, the mesenteric arteries in up to 43%, the ascending aorta in 30%, and the abdominal aorta in 20% (Procter and Hollier 1992, Watts et al 2009).

In contrast to giant cell arteritis, involvement of the intracranial arteries in TA has been considered extremely rare in the past (Nasu 1975). When intracranial arteries were studied with TCCS and MRA, however, intracranial stenoses without alternative explanation were reported in 3 out of 10 well-documented cases (Ringleb et al 2005) and have been also shown by catheter angiography (Klos et al 2003). Sometimes the pulmonar y and coronary arteries are also involved. Within these vessels, the disease might progress to stenoses, occlusions, or to the development of aneurysms. The clinical manifestation depends on the location and extent of the aﬀ ected vessels as well as the activity of the inﬂ ammation.

In the early stages of the disease, vascular symptoms may be completely absent. Patients often complain of fatigue, weight loss, subfebrile temperatures, and myalgia. Laboratory analysis often reveals anemia as a sign of chronic disease as well as pathologically altered values of nonspeciﬁ c markers of inﬂ ammation (raised ESR, CRP, α2-globulin, and hypoalbuminemia). The leukocyte count is usually normal (Kerr 1995). Later on, stenosis, occlusion, or dilatation of aﬀ ected vessel segments might lead to a variety of clinical symptoms. Visual disturbance such as blurred vision, diplopia, and amaurosis fugax are found in up to one-third of cases, mainly

Fig. B23.17 Schematic of the patient’s extra- and intracranial brain-supplying arteries after carotid–subclavian bypass surgery. Unchanged left V0/V1-VA stenosis. After surgery there is now antegrade ﬂ ow in the right VA (circles).

caused by a hemodynamically critical circulation, and ischemic stroke (embolic or hemodynamically) is observed in 5–14% of patients (Procter and Hollier 1992). For further reading in visual disturbances in stroke, see Case 38 and Case 42.

Diagnosis is based on the American College of Rheumatology (ACR) criteria. Three of the following six criteria must be present (Arend et al 1990):

• Age at onset ≤40 years.

• Claudication of an extremity.

• Decreased brachial artery pulse.

• Diﬀ erence in systolic blood pressure between the right

and left arms >10 mm Hg.

• A bruit over the subclavian arteries or the aorta.

• Angiographic evidence of narrowing or occlusion of the

entire aorta, its primary branches, or large arteries in the proximal upper or lower extremities.

Applying the above criteria, sensitivity and speciﬁ city are

90.5% and 97.8%, respectively. Laboratory ﬁ ndings may further support the diagnosis. Because the large proximal arteries are predominantly involved, a conﬁ rmatory bi- opsy, as would usually be done in giant cell arteritis, is generally not possible.

Treatment of TA consists of administration of corticosteroids. Early drug treatment results in an improvement of systemic symptoms, normalization of laboratory parameters, and a complete halt of the inﬂ ammatory process. About 50% of patients do not suﬃ - ciently respond to treatment with steroids alone (Kerr

1995). Other immunosuppressive agents such as methotrexate, azathioprine, mycophenolate, tocilizumab, or leﬂ unomide may then be used. Cyclophosphamide should be reserved for those who have continued disease activity despite those medications. There are no data allowing a clear recommendation of one of these supplemental drugs over others. Treatment should start with one familiar drug for at least 4–6 months and

378 Case 23 Takayasu’s Arteritis with Right-sided Subclavian Steal

then switch to a diﬀ erent one if the results are unsatis- factory. Anti-TNF agents may be useful as an alternative to cyclophosphamide, but evidence is needed to assess the eﬃ cacy and safety of inﬂ iximab or etanercept in this setting (Seko 2007).

In cases with stenosis or occlusion, additional endovascular or surgical interventions might become necessary; however, these should only be considered if the vascular changes are symptomatic. Depending on the aﬀ ected vas- cular segments, surgical intervention with insertion of a bypass demonstrates good success rates. Compared with bypass operations for atherosclerosis, however, bypass stenoses are more frequently observed (Giordano et al

1991). An analysis of the patency of carotid–subclavian bypasses inserted for subclavian steal syndrome in an unspeciﬁ ed patient group showed good technical and clinical results. Ten years after insertion, the primary and secondary patency was 92% and 95%, respectively. The 30-day morbidity was 6%. There were no perioperative strokes or deaths (AbuRahma et al 2000). An important alternative to the surgical approach is intravascular balloon dilatation and placement of endovascular stents. There are no systematic reports on the interventional management of TA. Percutaneous transluminal angioplasty is less likely to be successful when stenoses or occlusions aﬀ ect lengthy portions of an artery or when the artery is heavily scarred. In noninﬂ ammatory vessel diseases single case reports suggest good technical results. In patients with atherosclerosis, a primary technical success rate of 84% and a secondary cumulative patency rate of 72% after 100 months were reported (Körner et al 1999). With regard to the rates of restenosis, the stent placement method seems to be superior only to balloon dilatation (Rodriguez-Lopez et al

1999). However, no long-term follow-up studies or controlled trials have been conducted, especially no studies using drug-eluting stenting or balloon angioplasty which are supposed to counteract neointimal proliferation and restenosis (Speck et al 2014)

In our case, a right high-grade SA stenosis led to an ipsilateral subclavian steal syndrome and the left-sided high-grade VA stenosis to bilateral PCA infarction. This, in combination with the insuﬃ cient collateral blood ﬂ ow via bilateral hypoplastic PCoAs, led to distinct hemodynamic impairment in the posterior circulation. Revascularization to improve this constellation seemed to be the best therapeutic approach, and a carotid–subclavian bypass was performed. After intervention, ﬂ ow proﬁ les in the posterior circulation markedly improved and the inﬂ ammatory activity declined. The symptomat- ic left-sided VA stenosis was treated medically by antiplatelet agent.

The long-term prognosis in patients after surgical revascularization has been reported to be good. In a Japanese study of 106 patients with a mean follow-up of

19.8 years overall survival at 20 years was 73.5% (Miyata et al 2003).

Angiologic and Anatomic Aspects

Besides the above-mentioned clinical signs, the main diagnostic criterion of TA is the typical angiographic topography of the vascular lesions. Conventional angiogra-

phy as well as MRA and CT angiography (CTA), however, cannot visualize the vessel wall and therefore vessel wall thickening may be overlooked if it does not lead to obvious vascular lumen reduction in early phases of the disease (W.A. Schmidt et al 2002b).

In contrast, extracranial ultrasound is an excellent technique to visualize even discrete vessel wall alterations and follow-up. The typical ﬁ nding in TA is a ho- mogeneous, circumferential mid-echogenic vessel wall thickening often associated with stenosis or occlusion (see also Chapter 5, “Vasculitis” under “Vessel Wall Pathology”). In progressive vessel disease concentric thickening, rather than longitudinal spreading, was reported (Sun et al 1996). Although similar to the ﬁ ndings in giant cell arteritis, the vessel wall changes in TA are slightly clearer and therefore called a “macaroni phenomenon” (Schmidt 2004). Assessment of inﬂ ammatory vessel wall pathology in SA and VA is more diﬃ cult than in the CCA. In our patient, the CCA was not aﬀ ected, which explains the absence of the typical ultrasound ﬁ ndings. Although atherosclerotic vessel wall changes appear distinctly diﬀ erent from vasculitic changes, the two may coexist. Several authors have indicated that chronic vessel wall inﬂ ammation might lead to premature atherosclerosis (Bacon et al 2002, Manzi 2000, van Doornum et al 2002). Coexistence of atherosclerotic and inﬂ ammatory changes has also been reported in TA (Filer et al 2001, Numano et al 2000a, Numano et al 2000b). In a series of 30 female patients with TA, atherosclerotic plaques were found in 27%, but only in 2% of an age- and sex-matched healthy population. Furthermore, the thickness of the intima media was also signiﬁ cantly increased in the patients with arteritis (0.95 ± 0.31 mm versus 0.59 ± 0.08 mm) (Seyahi et al 2006).

Inﬂ ammatory vessel wall changes can also be visual- ized using MRI. A delayed enhancement after contrast administration was observed in seven patients within 20 minutes (Desai et al 2005). Signiﬁ cant diﬀ erences in vessel wall thickness and wall signal intensities following contrast administration in MRI have also been shown in other studies (Jiang et al 2012, Li et al 2011).

In a series including 55 consecutive patients CTA was not only able to detect continuous and segmented vessel involvement but also to diﬀ erentiate between active and inactive inﬂ ammation (J.W. Chung et al 2007). Posi- tron emission tomography (PET scanning) utilizing radioactively labeled ﬂ uorodeoxyglucose has been also used to image the aorta and great vessels. Areas of increased uptake of the tracer indicate aﬀ ected arterial segments seen by MRI. PET seems to be more sensitive than MRI in detecting segmental arterial inﬂ ammation and distin- guishing vessel thickening due to active inﬂ ammation from scar formation, which may be of help in therapeutic decision-making (Alibaz-Oner et al 2015).

Our case demonstrates a particularly unfavorable hemodynamic constellation of the posterior circulation. A grade 3 subclavian steal was present on the right side (for further reading on ultrasound assessment of subclavian steal, see also Case 28) so that the left VA provided the blood supply to the posterior circulation as well as to the right arm via the right VA but was itself hemodynamically impaired by the high-grade stenosis at its

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