30 Multilocular Extra- and Intracranial Stenoses and Occlusions

Case 30


Multilocular Extra- and Intracranial Stenoses and Occlusions


Clinical Presentation


A 41-year old woman presented to a district general hospital because of transient episodes of numbness in the left face and hand as well as left-sided blurred vision. There she underwent cerebral MRI and MR angiography (MRA). She was subsequently commenced on aspirin and 3 weeks later referred to our department for further clinical evaluation. No ultrasound examination was performed. The medical history revealed migraine, smoking, and alcohol misuse. There was no known arterial hypertension and she did not take any medication. On admission, her neurologic examination was normal.


Initial Neuroradiologic Findings (Day 1)


Cerebral MRI on admission to the district general hospital showed multiple signal abnormalities in the right hemisphere, consistent with internal border zone infarction (BZI). Contrast-enhanced extracranial MRA revealed vessel wall irregularities in the carotid arteries and occlusion of the left external carotid artery (ECA). Intracranially, time-of-flight (TOF) MRA demonstrated a patent flow signal in the left distal internal carotid artery (ICA) and absent flow signals in the right M1 middle cerebral artery (MCA), and A1 anterior cerebral artery (ACA) segments. On T2-weighted images, however, a signal void of the right M1-MCA segment was clearly visible indicating patency of the MCA (Fig. B30.1, Fig. B30.2, Fig. B30.3, Fig. B30.4).


Suspected Diagnosis


Recurrent left-sided sensory transient ischemic attacks (TIAs) presumed to be of hemodynamic origin because of suspected pathology of the right MCA. Unresolved vessel status of the left distal ICA.


Questions to Answer by Ultrasound Techniques



  • Were there real occlusions of the right M1-MCA and A1-ACA segments?
  • Was there evidence of a distal occlusion of the asymptomatic left intracranial ICA?
  • Were there signs of atherosclerosis or vasculitis?

Initial Neurosonologic Findings (Day 20)


Extracranial Duplex Sonography


B-mode sonography revealed left-accentuated severe atherosclerotic vascular changes with iso- to hyperechoic plaques, especially in the carotid bulbs. No flow signal was seen in the left ECA. Color-mode image of the left proximal ICA demonstrated a lumen reduction of ~40–50% caused by hypoechoic material. The flow signal in this area was regular (flow velocity 115/58 cm/s). A markedly reduced flow velocity was seen in the right ICA (flow velocity 24/11 cm/s). Assessment of the vertebral arteries (VAs) and right ECA revealed normal findings (Fig. B30.5, Fig. B30.6, Fig. B30.7).


Transcranial Duplex Sonography


Raised flow velocities were found in the left-sided carotid siphon (flow velocity 228/94 cm/s) and proximal M1-MCA segment (flow velocity 221/131 cm/s). The distal MCA segments on the left side revealed a mild poststenotic flow pattern. A marked, slightly turbulent, and poststenotic flow pattern was seen in the left A1-ACA segment which seemed to supply both A2 segments (flow velocity 132/69 cm/s). The anterior communicating artery (ACoA) could not be detected. The left posterior cerebral artery (PCA) was almost normal with only slightly increased velocities. The right proximal M1-MCA segment demonstrated a turbulent flow with increased velocity (flow velocity 161/74 cm/s). The M2 branches revealed a distinct poststenotic flow pattern. No right A1-ACA segment was detected. Raised flow velocities were found in the right P1- and P2-PCA segments indicating leptomeningeal collateralization (flow velocity 159/88 cm/s). No flow signal was seen in the left ophthalmic artery (OA) while the right OA flow was antegrade. Unsuspicious Doppler spectra were seen within the VAs and the basilar artery (BA) (Figs. B30.8B30.15; see also Videos images B30.1 and B30.2).


Conclusion


Severe atherosclerosis in the extracranial segments of the brain-supplying arteries with a left-sided proximal ICA stenosis of ~40–50% (low grade) and left ECA occlusion. Intracranially, left-sided high-grade tandem stenosis of the ICA siphon and proximal M1-MCA, together reaching hemodynamic relevance. On the right side, a hemo-dynamically relevant proximal M1-MCA stenosis and A1-ACA occlusion or aplasia was assumed. Blood supply to the right MCA territory via the ipsilateral ICA and leptomeningeal PCA anastomoses. Supply of the right ACA territory assumed to be via cross-flow from the contralateral A1-ACA segment.


Conventional Angiography (Day 22)


Digital subtraction angiography (DSA) was performed to further analyze flow pathways and to consider therapeutic options. It confirmed a left-sided moderate extracranial ICA stenosis and occlusion of the ECA as well as a left-sided intracranial ICA siphon and M1-MCA stenosis. Blood supply of both ACA territories was provided via the left A1-ACA segment. On the right side the A1-ACA and M1-MCA segments seemed to be occluded. During the late arterial sequences of the right ICA projection, however, a distinct temporal branch and a prominent insular M2 branch became visible. Abnormal dilated lenticulostriate vessels corresponding to a vascular collateral network were seen adjacent to the affected main vessels. Left VA injection revealed a marked collateral flow to the right MCA territory via leptomeningeal collaterals from the right PCA. In summary, the right-sided intracranial vessel status was evaluated as a near-occlusion of the right M1-MCA segment with collateralization of the MCA territory via the right PCA and right A1-ACA occlusion with collateralization via the contralateral ACA (Figs. B30.16B30.21).


Fig B30-22 shows a schematic of the patient’s extra-and intracranial brain-supplying arteries at this stage.


Clinical Course (1)


The multilocular extracranial and intracranial pathology was attributed to atherosclerosis on the basis of the known heavy smoking and alcohol misuse and newly diagnosed hypercholesterolemia and hyperhomocysteinemia.


During the first few days in the hospital the patient had further mild clinical events with sensory disturbances of the left hand while her blood pressure was slightly elevated. Several days later she developed new recurrent contralateral symptoms—a severe right-sided brachiofacial paresis and global aphasia—each lasting 20–30 minutes. She was then referred to the stroke unit for further monitoring and blood pressure control. Despite a systolic blood pressure of 200 mm Hg achieved by dopamine infusion she finally developed severe akinetic mutism. Follow-up MRI 1 day later revealed a new left-sided internal BZI, larger than on the right side. Extracranial ce-MRA and intracranial TOF-MRA showed no signal in the left common carotid artery (CCA), ICA, ECA, and ACA and a weak signal in both MCAs (Fig. B30.23, Fig. B30.24, Fig. B30.25).


Questions to Answer by Ultrasound Techniques



  • Was there a real complete occlusion of the left carotid arteries?
  • What is the vessel status of the right side?
  • Was there permanent near-occlusion of the right M1-MCA segment?

Follow-up Neurosonologic Findings (Day 29)


Extracranial Duplex Sonography


The lumen of the left ICA and CCA was still visible. The flow pattern of the left ICA had changed, revealing now a high-resistance flow signal with a low and short systolic flow and completely absent diastolic flow, suggestive of distal ICA occlusion below the OA origin (Fig. B30.26). The left ECA signal remained absent. Flow signals in the right carotid arteries remained unchanged. Flow velocities in the VAs were increased.


Transcranial Duplex Sonography


No flow signal was detected in the left distal ICA. The turbulent flow pattern of the left MCA remained unchanged, but flow velocities had decreased (flow velocity 81/46 cm/s). Also the flow velocity of the left A1-ACA segment was found to be lower than before and the poststenotic flow pattern had become more prominent if compared with the first ultrasound examination (flow velocity 53/33 cm/s). Raised flow velocities were now found for the first time in the left P1-PCA segment (flow velocity 190/99 cm/s). Distinct turbulences could be detected in the left posterior communicating artery (PCoA) indicating collateral function and blood supply toward the anterior circulation. Correspondingly, a raised flow velocity but no turbulent flow was now found in the BA (flow velocity 208/106 cm/s) (Fig. B30.27, Fig. B30.28, Fig. B30.29, Fig. B30.30, Fig. B30.31; see also Video images B30.3). Unchanged flow patterns were seen in the right MCA and OA.


Conclusion


Progressive vessel pathology with distal occlusion of the left ICA and inadequate collateralization via the left PCoA. Unchanged right-sided vessel status with near-occlusion of the M1-MCA segment.


Clinical Course (2)


Considering the dynamic vascular process, intravenous heparin was started, aiming for a doubling of the partial thromboplastin time (PTT). The new left-sided distal ICA occlusion was finally considered to be of atherothrombotic origin. Iatrogenic dissection of the ICA after conventional catheter angiography was discussed, although the latency between DSA and onset of symptoms was 4 days. Cervical MRI, however, revealed no mural hematoma on cross-sectional images. Biopsy of one branch of the superficial temporal artery (STeA) revealed no signs of large-vessel arteritis.


The akinetic mutism improved slowly during the following days. Treatment was changed from heparin to antiplatelet therapy with clopidogrel. After clinical stabilization, the patient was discharged for rehabilitation with mild right-sided hemiparesis and motor aphasia. Follow-up after 2 months revealed no further clinical events but further regression of paresis and aphasia. CT scan ruled out further infarction. CT angiography (CTA) findings were compatible with left M1-MCA stenosis and right M1-MCA near-occlusion (Fig. B30.32).


Follow-up Neurosonologic Findings (3 Months)


Extracranial Duplex Sonography


B-mode sonography showed hyperechoic material occluding the left ICA, ECA, and distal CCA. Color-mode imaging revealed absent color signal. Doppler spectrum analysis showed a stump signal in the proximal CCA (Fig. B30.33).


Transcranial Duplex Sonography


The results were unchanged from the preceding examination (not shown).


Conclusion


Distal occlusion of the left-sided CCA due to retrograde thrombosis. Blood supply of the left MCA territory and both ACA territories from the posterior circulation via the left PCoA. Unchanged near-occlusion of the right M1-MCA segment with blood supply from the ipsilateral ICA and via leptomeningeal collaterals from the PCA.


Fig B30-34 shows a schematic of the patient’s extra-and intracranial brain-supplying arteries.


Final Diagnosis


Marked atherosclerosis with right near-occlusion of the M1-MCA and left M1-MCA stenosis. Secondary left intracranial ICA occlusion and subsequent ipsilateral retrograde CCA thrombosis. Unfavorable collateralization via the cerebral arterial circle (circle of Willis) leading to bilateral internal BZIs.




Jun 20, 2018 | Posted by in NEUROSURGERY | Comments Off on 30 Multilocular Extra- and Intracranial Stenoses and Occlusions
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