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Basic Science
Anatomy
13 notes available
1 Last Minute Review 2 Embryology & Developmental Anatomy 3 Vascular Anatomy 4 Cerebral Cortex 5 Subcortical Nuclei (BG, Thalamus, Hypothalamus) 6 Limbic System 7 Cerebellum 8 Brainstem 9 Cranial Nerves 10 Spinal Cord 11 Motor System 12 Sensory System 13 Peripheral Nerves and Muscles
Basic Science › Anatomy

Vascular Anatomy

Vascular Anatomy

What You'll Learn

  • ICA segments (C1–C7) — Bouthillier classification, key branches at each level, distinction between extradural and intradural segments
  • MCA anatomy & stroke syndromes — M1–M4 segments, lenticulostriate arteries, superior vs. inferior division syndromes, dominant vs. non-dominant hemispheric deficits
  • ACA anatomy & stroke syndromes — A1–A2 segments, ACom, recurrent artery of Heubner, classic ACA syndrome (leg weakness, abulia, alien limb)
  • Anterior choroidal artery — origin, territory, classic AChA triad (hemiplegia, hemianopia, hemisensory loss)
  • Circle of Willis — complete anatomy, common variants (fetal PCA, absent A1, absent PCom), aneurysm sites and frequencies
  • Vertebrobasilar system — vertebral artery segments (V1–V4), PICA, anterior spinal artery, basilar branches (AICA, SCA, pontine perforators)
  • PCA anatomy & stroke syndromes — P1–P4 segments, thalamogeniculate and thalamoperforating arteries, artery of Percheron, PCA cortical syndromes
  • Classic brainstem stroke syndromes — Wallenberg, medial medullary, lateral pontine (AICA), locked-in, Weber, Benedikt, Claude, top of the basilar
  • Cerebral venous system — superficial veins, deep veins, dural sinuses, cavernous sinus contents, cerebral venous sinus thrombosis
  • Spinal cord vascular supply — anterior spinal artery, posterior spinal arteries, artery of Adamkiewicz, watershed zones, anterior spinal artery syndrome
HighYield Pearls
  • ICA segments (Bouthillier C1–C7): cervical → petrous → lacerum → cavernous → clinoid → ophthalmic → communicating; ophthalmic artery is the first major intradural/supraclinoid branch → central retinal artery occlusion = painless monocular vision loss / amaurosis fugax.
  • MCA stroke: contralateral face/arm > leg weakness, gaze deviation TOWARD the lesion, homonymous hemianopia, aphasia (dominant) or neglect (non-dominant); superior division = Broca + face/arm motor; inferior division = Wernicke + superior quadrantanopia (“pie in the sky”).
  • Lenticulostriate perforators (off M1): supply basal ganglia + internal capsule → classic pure motor lacunar stroke; HTN is the dominant risk factor.
  • Recurrent artery of Heubner (A1/A2 junction): head of caudate + anterior limb IC + putamen → classically contralateral face/arm-predominant weakness + abulic/behavioral features (leg weakness suggests ACA cortical/A2 territory or broader injury) — classic ACA aneurysm clipping complication.
  • ACA stroke: contralateral leg > arm weakness + abulia + urinary incontinence + frontal release signs + alien limb (callosal).
  • Anterior choroidal artery TRIAD: contralateral hemiplegia + hemisensory loss + homonymous hemianopia (optic tract / LGN / posterior limb IC).
  • Circle of Willis variants: fetal PCA (P1 hypoplastic, PCom dominant) in 10–20% — PCA stroke from ICA disease, NOT posterior circulation; hypoplastic/absent A1 → bilateral ACA infarct from one-sided occlusion.
  • Top-of-the-basilar: bilateral thalami + bilateral occipital → cortical blindness + amnesia + agitated delirium + oculomotor palsies; artery of Percheron = bilateral paramedian thalamic infarct from a single perforator.
  • Wallenberg (lateral medullary, PICA/vertebral): ipsilateral Horner + facial pain/temp loss + ataxia + dysphagia + hoarseness + nystagmus & contralateral body pain/temp loss; face and body on opposite sides.
  • AICA syndrome: lateral pons + anterior-inferior cerebellum + MCP/flocculus + labyrinthine artery → ipsilateral deafness + vertigo + facial weakness + Horner; the classic and highest-yield stroke localization for acute ipsilateral hearing loss with vertigo and facial weakness.
  • PCA stroke: contralateral homonymous hemianopia with macular sparing (collateral MCA supply to occipital pole); dominant-side → alexia without agraphia (splenium + left occipital); thalamic involvement → Déjerine–Roussy thalamic pain.
  • Watershed infarcts: ACA–MCA cortical → “man in a barrel” (proximal arm > distal); bilateral MCA–PCA parieto-occipital border-zone → Balint syndrome (simultanagnosia + optic ataxia + ocular apraxia); deep internal watershed = chronic carotid stenosis / hypoperfusion.
  • Cavernous sinus contents: ICA + CN III, IV, V1, V2, VI; CN VI is the most vulnerable (free within the sinus, not on the wall) — isolated abducens palsy is the earliest sign of cavernous pathology.
  • CVST patterns: superior sagittal → bilateral parasagittal venous infarcts ± hemorrhage; vein of Galen / deep system → bilateral thalamic edema; cavernous sinus → proptosis + chemosis + painful ophthalmoplegia.
  • Artery of Adamkiewicz: dominant lower thoracic radicular feeder (T9–T12, usually LEFT); aortic surgery / dissection / aortic cross-clamp → anterior spinal artery syndrome (paraplegia + bilateral pain/temp loss, preserved proprioception/vibration).
  • Central cord syndrome: cervical hyperextension (often older patients with cervical stenosis) → disproportionate upper-extremity and hand weakness, variable sensory loss, possible bladder dysfunction — most common incomplete cord syndrome.
🔍 Quick ReferenceArterial territories · Perforators / variants · Venous / spinal
Arterial territories
  • Contralateral face/arm > leg + aphasia or neglect + gaze deviation TOWARD lesion → MCA stroke (M1)
  • Contralateral leg > arm + abulia + incontinence + alien limb → ACA stroke
  • Homonymous hemianopia with macular sparing ± alexia without agraphia → PCA cortical stroke (dominant occipital + splenium)
  • Cortical blindness + amnesia + agitated delirium + oculomotor palsies → top-of-the-basilar syndrome
  • Ipsilateral Horner + facial pain/temp loss + dysphagia + hoarseness + crossed body pain/temp → Wallenberg / lateral medullary (PICA or vertebral)
  • Ipsilateral deafness + vertigo + facial palsy + Horner + ataxia → AICA / lateral pontine syndrome (labyrinthine artery)
  • “Pie in the sky” superior quadrantanopia + Wernicke aphasia → MCA inferior division (Meyer’s loop / temporal optic radiations)
  • Contralateral hemiplegia + hemisensory loss + homonymous hemianopia (TRIAD) → anterior choroidal artery (posterior limb IC + optic tract + LGN)
  • Painless monocular vision loss / amaurosis fugax → ophthalmic artery / central retinal artery (first major intradural/supraclinoid ICA branch)
Perforators / variants
  • Lenticulostriate arteries (M1) → basal ganglia + internal capsule (pure motor lacunar stroke, HTN)
  • Recurrent artery of Heubner (A1/A2 junction) → head of caudate + anterior limb IC (contralateral face/arm-predominant weakness + behavioral/abulic features; leg weakness suggests ACA cortical/A2 territory or broader injury)
  • P1 paramedian thalamoperforating arteries → medial thalamus ± rostral midbrain (Percheron variant if a single perforator supplies both sides); P2 thalamogeniculate/inferolateral arteries → ventrolateral/posterolateral thalamus (classic Déjerine–Roussy territory)
  • Artery of Percheron → bilateral paramedian thalami (single perforator variant; bilateral thalamic infarct + altered consciousness)
  • Pontine paramedian perforators (basilar) → ventral pons (locked-in syndrome, pure motor hemiparesis)
  • Fetal PCA (P1 hypoplastic, dominant PCom) → PCA fed by ICA (PCA stroke from carotid disease; 10–20% of population)
  • Absent/hypoplastic A1 → contralateral A1 may dominantly supply both ACA territories across the ACom, so dominant A1/ICA compromise can affect both ACAs. Azygos ACA is a separate variant (single unpaired A2 trunk supplies bilateral distal ACAs); occlusion can cause bilateral ACA infarction.
  • Persistent trigeminal artery → fetal carotid–basilar anastomosis (most common persistent carotid–vertebrobasilar connection)
Venous / spinal / pearls
  • Cavernous sinus → ICA + CN III, IV, V1, V2, VI (CN VI most vulnerable — runs free within the sinus)
  • Vein of Trolard → superior anastomotic vein (superficial Sylvian → superior sagittal sinus)
  • Vein of Labbé → inferior anastomotic vein (superficial Sylvian → transverse sinus); thrombosis → temporal lobe venous infarct
  • Internal cerebral veins → vein of Galen → straight sinus → torcular Herophili → deep venous drainage (deep CVST → bilateral thalamic edema)
  • Superior sagittal sinus thrombosis → bilateral parasagittal hemorrhagic venous infarcts (“empty delta” sign on contrast CT)
  • Artery of Adamkiewicz (T9–T12, usually left) → thoracolumbar anterior cord (aortic surgery / dissection → paraplegia)
  • Anterior spinal artery syndrome → paraplegia + bilateral pain/temp loss + preserved proprioception/vibration (dorsal columns spared)
  • “Man in a barrel” → ACA–MCA cortical watershed (proximal arm > distal weakness from hypoperfusion)
  • Balint syndrome → bilateral parieto-occipital/dorsal-stream lesions, classically bilateral MCA–PCA border-zone infarcts (simultanagnosia + optic ataxia + ocular apraxia)
  • Central cord syndrome → cervical hyperextension (often older patients with cervical stenosis) → disproportionate upper-extremity and hand weakness, variable sensory loss, possible bladder dysfunction
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