14 Isolated Left Carotid Siphon Stenosis

Case 14


Isolated Left Carotid Siphon Stenosis


Clinical Presentation


A 17-year-old Caucasian woman presented with recurrent transient episodes of right-sided sensorimotor deficits and speech disturbance, each lasting up to 60 minutes. The symptoms had first occurred 3 years before presentation with a transient numbness of the fingers of her right hand. One week before admission to a district general hospital, she developed brachiofacial hemiparesis and Broca-type aphasia. These symptoms gradually resolved after 15 minutes. She had no vascular risk factors and no history of migraine or stroke in her family. She had never used illicit drugs. Clinical examination yielded no focal neurologic deficit. She was started on a combination of aspirin and clopidogrel and was then referred to our department for further evaluation following MR angiography (MRA) and digital subtraction angiography (DSA), which showed contradictory findings.


Initial Neuroradiologic Findings


Cerebral MRI revealed no ischemic parenchymal lesions. Time-of-flight (TOF)-MRA demonstrated a severe left carotid siphon stenosis. Also a fetal-type left posterior cerebral artery (FT-PCA) was noted (Fig. B14.1 and Fig. B14.2). In contrast to the MRA findings, conventional DSA 1 day later demonstrated only a mild stenosis in the left distal carotid siphon despite the use of different oblique projections (Fig. B14.3, Fig. B14.4, Fig. B14.5, Fig. B14.6, Fig. B14.7).


Suspected Diagnosis


Recurrent transient ischemic attacks (TIAs) in the territory of the left middle cerebral artery (MCA) caused by a carotid siphon stenosis of undetermined origin and unknown degree.


Questions to Answer by Ultrasound Techniques



  • Were there pathologic vascular changes in the extracranial vessels?
  • What was the conformation and grading of the stenosis in the left carotid siphon?
  • Was there evidence of any further intracranial stenotic process, overrated by MRA or underrated by DSA?

Initial Neurosonologic Findings


Extracranial Duplex Sonography


B-mode and color-mode imaging revealed no atherosclerosis or other vascular pathology. Doppler spectrum analysis showed normal and symmetric flow signals.


Transcranial Duplex Sonography


Increased flow velocities with turbulence were found in the left proximal M1-MCA segment using the midbrain plane (flow velocity 141/61 cm/s). No poststenotic flow pattern was detected in the distal M1-MCA segment and M2-MCA branches. Tilting the probe to the upper pontine plane, the carotid siphon presented flow velocities reaching peak systolic values of 300 cm/s. Both anterior cerebral arteries (ACAs) and PCAs, and the right MCA, showed normal flow signals. A positive oscillation effect was observed in the left P2-PCA segment upon ipsilateral extracranial internal carotid artery (ICA) artery tapping (Fig. B14.8, Fig. B14.9, Fig. B14.10; see also Video images B14.1).


Conclusion


High-grade but not hemodynamically relevant stenosis of the left carotid siphon with turbulent flow in the proximal M1-MCA segment. Left fetal-type PCA.


Clinical Course


The patient’s recurrent TIAs were interpreted as embolic events in the left MCA territory, caused by the high-grade carotid siphon stenosis. The etiology of the stenosis remained unclear. Blood pressure measurements were normal. Other causes, such as vasculitis or chronic inflammatory disease, were considered unlikely because of the clinical presentation, normal blood tests, and normal cerebrospinal fluid (CSF) studies. Differential diagnoses such as early moyamoya syndrome or fibromuscular dysplasia (FMD) could not be confirmed at the stage of disease at which she presented. We changed the secondary stroke prevention to monotherapy with clopidogrel and recommended follow-up ultrasound examination after 1 year. Unfortunately, the patient was lost to follow-up.







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Jun 20, 2018 | Posted by in NEUROSURGERY | Comments Off on 14 Isolated Left Carotid Siphon Stenosis

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