24 Dissection of the Right Extracranial Internal Carotid Artery and Left M1 Middle Cerebral Artery

Case 24


Dissection of the Right Extracranial Internal Carotid Artery and Left M1 Middle Cerebral Artery


Clinical Presentation


A 34-year-old woman presented with a 1-year history of severe headaches that were thought to be caused by repeated hypertensive episodes. She also reported a single episode of left-sided facial pain and ipsilateral conjunctival injection lasting for several hours ~1 year ago. After the initiation of antihypertensive treatment the headaches subsided. However, ambulatory examination of the optic fundi revealed retinal vessel narrowing. This finding prompted an ultrasound examination of the brain-supplying arteries. Transcranial Doppler (TCD) revealed a left M1 middle cerebral artery (MCA) stenosis. In addition to having hypertension, the patient was a smoker and used an oral contraceptive. An ambulatory cerebral CT scan had been unremarkable. She was now admitted to our department for elective catheter angiography to search for extended intracranial vascular pathology.


Initial Neuroradiologic Findings


Digital subtraction angiography (DSA) demonstrated mild bilateral extracranial internal carotid artery (ICA) elongations and wide carotid bulbs, but there was no evidence of stenosis or atherosclerosis. Intracranially a left long-segmented high-grade stenosis of the proximal M1-MCA segment could be confirmed. Distal to the stenosis, the residual M1 segment was mildly dilated. Also, a delayed contrast filling of the distal MCA segments in relation to the distal anterior cerebral artery (ACA) segments was seen indicating a high-grade stenosis of hemodynamic relevance. There were no signs of vasculitis (Fig. B24.1 and Fig. B24.2).


Suspected Diagnosis


Asymptomatic left high-grade M1-MCA stenosis. In the absence of atherosclerotic vessel changes, and the presence of a history of left-sided facial pain with associated conjunctival injection and headache 1 year previously, an MCA dissection was suspected.


Clinical Course (1)


Two weeks later, the patient was readmitted to our hospital for further evaluation. On admission she reported a continuing right-sided neck pain that started during the catheter angiography 2 weeks before and a sore throat on the day following it. The neurologic examination was normal; in particular, she did not have Horner’s syndrome.


MRI and MR Angiography (10:00 Hours)


No parenchymal lesions were seen on MRI. On T2-weighted axial MRI images, a distinctly reduced flow void could be seen in the distal ICA on axial and coronal images. 3D time-of-flight MR angiography (TOF-MRA) of the cerebral arterial circle (circle of Willis, CW) demonstrated the known left high-grade M1-MCA stenosis. A reduced signal was observed within the right terminal ICA. Cervical MRI and MRA of the extracranial vessels were not performed (Fig. B24.3 and Fig. B24.4).


Questions to Answer by Ultrasound Techniques



  • To confirm the left-sided MCA stenosis.
  • To assess collateral pathways if the stenosis was hemodynamically relevant.
  • To search for evidence of other vascular pathology, e.g., dissection of the right ICA.

Neurosonologic Findings (12:00 Hours)


Extracranial Duplex Sonography


There were no atherosclerotic vascular changes. The right ICA revealed a long-segmented lumen reduction that started 2 cm above the carotid bifurcation and continued over the whole visible distal vessel segment. There were no typical signs of a dissection. Flow velocity in the right ICA reached a systolic maximum of 200 cm/s. The right common carotid artery (CCA) showed a high-resistance flow signal with a reduced diastolic flow component. The left ICA, both external carotid arteries (ECAs), and the vertebral arteries (VAs) presented normal flow signals (all images not shown).


Transcranial Duplex Sonography


Within the left M1-MCA, transcranial color-coded sonography (TCCS) detected a turbulent stenotic flow (flow velocity 383/267 cm/s). A poststenotic flow pattern was observed in the left M2-MCA branches. The flow signal of the right M1-MCA segment appeared normal. The right A1-ACA segment showed reversed flow while the left-sided A1-ACA segment demonstrated increased flow velocities without turbulence (flow velocity 225/140 cm/s). Assessment of the posterior cerebral arteries, VAs, the basilar artery (BA), and the ophthalmic arteries (OAs) revealed overall normal antegrade flow signals without signs of leptomeningeal or ophthalmic collateral support. There was a positive oscillation effect in the right M1-MCA segment with slight submandibular tapping of the left ICA and the dominant left VA at the atlas loop. This indicated collateral flow through the anterior communicating artery (ACoA) and right posterior communicating artery (PCoA) (Fig. B24.5, Fig. B24.6, Fig. B24.7, Fig. B24.8, B24.9; see also Videos B24.1 and B24.2).






Conclusion


Hemodynamically relevant left high-grade M1-MCA stenosis. High-grade stenosis of the right extracranial ICA of hemodynamic relevance, suspicious for dissection, induced by the diagnostic DSA 2 weeks previously. Excellent collateral flow to the right MCA and ACA via the ACoA as well as the right PCoA.


Conventional Angiography (16:00 Hours)


DSA performed on the same day demonstrated a conical lumen reduction of the right ICA directly above the carotid bifurcation with a filiform stenosis up to the base of the skull which was suggestive of ICA dissection. Collateralization toward the right MCA and ACA territory was via the left ICA and ACoA. Selective VA angiography showed that the right MCA was also perfused by the ipsilateral PCoA. There was no evidence of ophthalmic collaterals. The known high-grade M1-MCA stenosis remained unchanged (Fig. B24.10, Fig. B24.11, Fig. B24.12). In addition, renal angiography was performed, which excluded signs of fibromuscular dysplasia.







Clinical Course (2)


The dissection of the right ICA was considered to be of iatrogenic origin caused by the catheter during the initial DSA. Intravenous heparin treatment was started, aiming for a twofold rise in partial thromboplastin time (PTT). The patient was then switched to oral anticoagulation with phenprocoumon for 6 months. The etiology of the left M1-MCA stenosis remained unclear. After exclusion of all other differential diagnoses, particularly vasculitis, a dissection was assumed to be most likely. After 6 months the patient was re-examined to evaluate the requirement for long-term secondary stroke prevention.


Jun 20, 2018 | Posted by in NEUROSURGERY | Comments Off on 24 Dissection of the Right Extracranial Internal Carotid Artery and Left M1 Middle Cerebral Artery
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