20 Right Internal Carotid Artery Dissection with Fast Recanalization

Case 20


Right Internal Carotid Artery Dissection with Fast Recanalization


Clinical Presentation


A 56-year-old man presented with progressive paresis of his left arm. Three days prior to presentation, he had experienced some pain on the right side of his neck and headaches while exercising in a gym for the first time. The following day, he observed clumsiness of his left hand and drooping of his right eyelid. The left-sided paresis continued to progress, at which stage he presented to the hospital emergency department. The patient had no known vascular risk factors. The neurologic examination revealed a mild left-sided sensorimotor hemiparesis and Horner’s syndrome on the right side (National Institute of Health Stroke Scale [NIHSS] score: 3).


Initial Neuroradiologic Findings


Cranial CT on the day of admission revealed multiple hypodense areas in the right middle cerebral artery (MCA) territory. MRI confirmed multiple ischemic lesions within the internal border zone region of the right hemisphere. Axial images demonstrated a reduced flow void in the right carotid siphon. Time-of-flight MR angiography (TOF-MRA) depicted an absent signal of the right distal internal carotid artery (ICA) and a bilateral partial fetal-type posterior cerebral artery (FT-PCA) origin (Fig. B20.1 and Fig. B20.2).


Suspected Diagnosis


Right internal border zone infarction (BZI) caused by ICA dissection and secondary ICA occlusion.


Questions to Answer by Ultrasound Techniques



  • Was there evidence of dissection?
  • Was there a real occlusion or high-grade stenosis of the ICA?
  • If so, what were the intracranial collateral pathways?

Initial Neurosonologic Findings (Day 1)


Extracranial Duplex Sonography


B-mode imaging was normal. There were no atherosclerotic changes and no signs of proximal ICA dissection. Doppler spectrum analysis showed a high pulsatility in the right common carotid artery (CCA) and a high-resistance flow signal in the right ICA with a low and short systolic flow and completely absent diastolic flow component, indicative of either near-occlusion or occlusion of the ICA below of the origin of the ophthalmic artery (OA). External carotid artery (ECA) Doppler spectra were normal (Fig. B20.3, Fig. B20.4, Fig. B20.5, Fig. B20.6; see also Video Images B20.1).


Transcranial Duplex Sonography


The right M1-MCA segment presented a marked poststenotic flow pattern. The A1 segment of the anterior cerebral artery (A1-ACA) yielded a retrograde flow, also with severe poststenotic alterations. The anterior communicating artery (ACoA) was not visualized. Elevated flow velocities were seen in the right P1-PCA segment (125/69 cm/s), here with an obviously turbulent flow pattern, and in the left A1-ACA segment (150/75 cm/s), both indicative of collateral flow to the right anterior circulation via the ACoA and the posterior communicating artery (PCoA). The left MCA and PCA, in addition to the distal right P2-PCA segment, demonstrated normal flow. No flow was detected in the OA on the right side. The flow signal of the left OA was normal (Figs. B20.7B20.12; see also Video Images B20.1).


Evaluation of Collateral Function


Cerebrovascular Reactivity Testing


Intravenous administration of 1 g acetazolamide during continuous transcranial Doppler (TCD) monitoring of both M1-MCA segments revealed a 60.6% increase in flow velocity on the left side and a 1.6% increase in flow velocity on the right (Fig. B20.13) (see also Chapter 3, “Acetazolamide Infusion Test” under “Metabolic Coupling”).


Ultrasound Delay Testing


After intravenous administration of a 3-mL sonographic contrast bolus (Levovist, 300 mg/dL) and continuous monitoring of both M1-MCA Doppler spectra, a right-sided, 1-second delay of bolus arrival was observed (Fig. B20.14) (see also Chapter 3, “Ultrasound Delay Test” under “Metabolic Coupling”).






Conclusion


Suspected right distal ICA dissection with near-occlusion or occlusion proximal to the OA origin. Exhausted CVR and insufficient collateral pathways supplying the right MCA territory via the ACoA and the ipsilateral PCoA.


Conventional Angiography


Digital subtraction angiography (DSA) demonstrated a long segmental irregularity in the right ICA with a cone-shaped high-grade stenosis starting 5 cm above the carotid bifurcation and extending to the vertical segment of the petrous C6-ICA segment. Only residual and delayed contrast filling was seen in the distal ICA. Collateralization mainly occurred via the ACoA and partially via a hypoplastic right P1-PCA segment providing retrograde blood flow into the right MCA via the FT-PCA and antegrade blood flow into the distal PCA segments. Filling of the right MCA territory was delayed. These findings were consistent with a near-occlusion of the right ICA due to vessel wall dissection (Figs. B20.15B20.20).


Fig. B20.21 shows a schematic of the patient’s extra-and intracranial brain-supplying arteries.


Clinical Course (1)


Intravenous heparin, aiming for a twofold increase of partial thromboplastin time (PTT) was started. TOF-MRA 2 weeks later demonstrated a normalized right ICA signal.






Follow-up Neurosonologic Findings (Day 20)


Extracranial Duplex Sonography


A normalized flow pattern was seen in the right CCA and ICA compared with the contralateral side (Fig. B20.22, Fig. B20.23, Fig. B20.24, Fig. B20.25).


Transcranial Duplex Sonography


The right M1-MCA and A1-ACA as well as the PCA segments demonstrated normalized flow velocities and pulsatility. A flow within the hypoplastic right P1-PCA segment was no longer detectable (Fig. B20.26, Fig. B20.27, Fig. B20.28, Fig. B20.29, Fig. B20.30).


Conclusion


Flow normalization in all insonated vessels indicating a rapid resolution of the right ICA dissection.


Clinical Course (2)


The patient was switched to oral anticoagulation with phenprocoumon and was discharged with a mild left-sided hemiparesis. Anticoagulation was stopped 6 months later. Until that time no further clinical events had occurred and the left hemiparesis had completely resolved.


Jun 20, 2018 | Posted by in NEUROSURGERY | Comments Off on 20 Right Internal Carotid Artery Dissection with Fast Recanalization
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