Posterior Circulation Pathophysiology
Vessels that constitute the posterior circulation (8).
What are the vertebral arteries, basilar artery, posterior cerebral arteries (PCA), posterior communicating arteries (PCom), posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA), superior cerebellar artery (SCA), and anterior spinal artery (ASA)
Main branches (5) supplied by the internal carotid artery.
What are the ophthalmic artery (pre-terminal), posterior communicating artery (pre-terminal), anterior choroidal artery (pre-terminal), anterior cerebral artery, and middle cerebral artery?
A patient develops sudden-onset right face and arm weakness, nonfluent aphasia, right gaze preference, and left-sided neglect. Sensation is preserved and there is no visual field deficit. Imaging shows an infarct sparing the temporal and parietal lobes. Which segment of the affected vessel is most likely occluded?
What is the superior division (M2 segment) of the left middle cerebral artery?
Clinical features distinguishing vertebrobasilar TIA from anterior circulation TIA.
What are vertigo, diplopia, dysarthria, ataxia, and bilateral limb symptoms (vertebrobasilar) versus unilateral weakness, aphasia, or monocular visual loss (anterior circulation)?
Occlusion of this artery causes vertigo, ataxia, and dysphagia without hemiparesis, due to infarction of brainstem and cerebellar structures.
What is the posterior inferior cerebellar artery (PICA)?
Pathophysiological consequence of ACA infarction
Contralateral leg weakness, abulia, urinary incontinence, primitive reflexes, and cognitive or language deficits due to medial frontal and parietal lobe involvement.
This rare neurobehavioral syndrome results from bilateral parieto-occipital damage and is characterized by the inability to perceive multiple objects simultaneously, impaired visually guided hand movements, and difficulty with voluntary eye movements, despite intact visual acuity and alertness.
What is Balint syndrome?
A 78-year-old man with a history of atrial fibrillation and prior transient ischemic attacks suddenly develops right-sided hemiplegia and expressive aphasia upon awakening. Non-contrast head CT is negative for hemorrhage, and CT angiogram reveals an abrupt cutoff in the left M1 segment of the middle cerebral artery with no significant atherosclerotic disease visible. Which is the most likely underlying mechanism for his large vessel occlusion?
What is cardioembolic stroke?
A patient suddenly develops quadriplegia, loss of horizontal eye movements, preserved vertical gaze, and is unable to speak but remains fully conscious. Physical exam also reveals facial weakness, hearing loss, and dysphagia. Which major artery is most likely occluded?
What is the basilar artery?
Clinical features distinguishing ACA infarction from MCA infarction
What is predominant contralateral lower limb weakness and sensory loss with abulia, urinary incontinence, and frontal lobe signs in ACA stroke, versus contralateral face and upper limb weakness, sensory loss, aphasia (dominant hemisphere), neglect (non-dominant), and gaze preference toward the side of the lesion in MCA stroke?
A patient with bilateral occipital infarctions insists she can see, even though she is functionally blind. She confabulates descriptions of her surroundings and denies any deficit. This paradoxical unawareness of visual loss is the hallmark of this rare syndrome.
What is Anton syndrome?
A 41-year-old man experiences acute-onset vertigo, neck pain, and right-sided limb ataxia after chiropractic neck manipulation. Imaging shows an occlusion of the right vertebral artery just proximal to the posterior inferior cerebellar artery (PICA). What is the most likely mechanism for this large vessel occlusion?
What is arterial dissection?
A 62-year-old man presents with sudden right-sided hearing loss, vertigo, left-beating nystagmus, right-sided facial weakness, and right-sided ataxia. Examination also reveals decreased pain and temperature sensation on the left side of his body. MRI shows a lateral caudal pontine infarct. Which artery is likely occluded, and what are the key anatomical structures involved?
What is the right anterior inferior cerebellar artery (AICA); involved structures include the facial nerve/nucleus (facial weakness), cochlear and vestibular nuclei (hearing loss, vertigo, nystagmus), middle cerebellar peduncle (ataxia), and spinothalamic tract (contralateral body sensory loss).
What are leptomeningeal anastomoses between ACA and MCA cortical branches, deep perforator overlap, and support via the anterior communicating artery?
A 70-year-old woman with atrial fibrillation develops sudden onset "crossed" neurological deficits: right facial paralysis and left hemiplegia. She also has dysarthria, loss of taste on the anterior two-thirds of her tongue, and decreased lacrimation. Imaging shows a large infarct in the ventral pons. Which classic brainstem stroke syndrome does this presentation most closely represent, and which artery is typically involved?
What is Millard-Gubler syndrome, due to occlusion of perforating branches of the basilar artery?
A 55-year-old woman with metastatic colon cancer develops sudden left-sided hemiplegia and hemisensory loss. She has no known vascular risk factors, and imaging shows an occlusion of the right proximal middle cerebral artery with no evidence of atherosclerosis or dissection. Laboratory workup reveals markedly elevated D-dimer and evidence of disseminated intravascular coagulation. What is the most likely mechanism of her large vessel occlusion?
What is a hypercoagulable (prothrombotic) state due to malignancy (Trousseau syndrome)?
A 60-year-old woman is brought in with acute-onset right homonymous hemianopia, alexia without agraphia, and visual hallucinations. She has no motor or sensory deficits. MRI reveals a left occipital and medial temporal lobe infarct. Which artery is occluded, and what is the underlying pathophysiology of her visual and language findings?
What is occlusion of the left posterior cerebral artery (PCA); pathophysiology involves infarction of the left occipital cortex (causing homonymous hemianopia), and splenium of the corpus callosum (disconnecting visual input from language areas, producing alexia without agraphia).
Clinical implications of anterior choroidal artery occlusion.
What are contralateral hemiplegia, hemianesthesia, and homonymous hemianopia due to involvement of internal capsule, thalamus, and optic tract?
A 68-year-old man with a history of hypertension presents with sudden-onset left-sided hemiparesis and left sensory loss. On examination, he has right eye ptosis, a dilated right pupil that is unreactive to light, and the right eye is deviated “down and out.” He also displays tremor and involuntary movements of the left extremities. MRI reveals an infarct involving the right midbrain, sparing the pons and medulla. What is the name of this clinical syndrome, and which artery is most commonly involved?
What is Weber syndrome (alternating oculomotor hemiplegia), due to occlusion of a branch of the posterior cerebral artery (PCA) (paramedian branches supplying the midbrain)?
A 29-year-old triathlete with no cardiovascular risk factors collapses with sudden right-sided weakness and aphasia while swimming. She has no personal or family history of arrhythmias or clotting disorders. On arrival, she is afebrile with a regular heart rate and no murmurs. Head CT is negative for hemorrhage; CT angiogram shows a left M1 MCA occlusion without arterial dissection or atherosclerosis. She recalls mild right calf soreness after a recent transatlantic flight but denies chest pain or shortness of breath. Laboratory studies are normal, EKG is unremarkable, and TTE with agitated saline performed after Valsalva maneuver reveals microbubbles in the left atrium within three cardiac cycles. Lower extremity duplex ultrasound confirms a distal right femoral vein thrombus. What is the most likely underlying stroke mechanism?
What is paradoxical embolism through a patent foramen ovale (PFO)?