Internal Carotid Artery (ICA) - Intracranial Branches

Flowchart: ICA Intracranial Branches

INTERNAL CAROTID ARTERY (ICA)
│
├── 1. OPHTHALMIC ARTERY
│       │
│       ├── Central retinal artery → retina
│       ├── Lacrimal artery → lacrimal gland, eyelids
│       ├── Long & short posterior ciliary arteries → eyeball
│       ├── Muscular arteries → extrinsic eye muscles
│       ├── Supra-orbital artery → forehead, scalp
│       ├── Anterior ethmoidal artery → ethmoidal cells, nasal cavity, anterior meningeal branch
│       ├── Posterior ethmoidal artery → ethmoidal cells, nasal cavity
│       ├── Medial palpebral arteries → eyelids
│       ├── Dorsal nasal artery (terminal branch) → nose
│       └── Supratrochlear artery (terminal branch) → forehead
│
├── 2. POSTERIOR COMMUNICATING ARTERY (PComA)
│       └── Connects ICA to Posterior Cerebral Artery (PCA)
│           (forms part of Circle of Willis)
│
├── 3. ANTERIOR CHOROIDAL ARTERY
│       ├── Optic tract
│       ├── Posterior limb of internal capsule
│       ├── Anterior hippocampus
│       ├── Amygdala
│       ├── Globus pallidus (medial segment)
│       └── Enters brain at choroidal fissure
│
└── TERMINAL BIFURCATION
        │
        ├── 4. ANTERIOR CEREBRAL ARTERY (ACA)
        │       ├── Connected to contralateral ACA via Anterior Communicating A.
        │       ├── Segments: A1 (precommunicating), A2 (postcommunicating), A3 (distal)
        │       ├── Callosomarginal artery → follows cingulate sulcus
        │       ├── Pericallosal artery → adjacent to corpus callosum
        │       └── Supplies: medial frontal lobe, anterior parietal lobe, corpus callosum
        │
        └── 5. MIDDLE CEREBRAL ARTERY (MCA)
                ├── M1 segment → gives off lenticulostriate arteries
                │       └── Lenticulostriate arteries → striatum, putamen, internal capsule
                ├── Bifurcates (or trifurcates) in Sylvian fissure into:
                │       ├── Superior division → lateral frontal lobe, anterior parietal cortex
                │       └── Inferior division → temporal lobe, anterolateral parietal lobe
                └── Frontobasal (orbitofrontal) branch → orbital surface of frontal lobe

Detailed Supply of Each Branch

1. Ophthalmic Artery

• First branch of the ICA, given off just after ICA exits the cavernous sinus
• Passes through the optic canal with the optic nerve
• Key clinical point: occlusion of central retinal artery (a branch) → sudden blindness
• Branches listed above supply the entire orbit, eyeball, forehead, scalp, nasal cavity, and ethmoidal sinuses
• Gray's Anatomy for Students

2. Posterior Communicating Artery (PComA)

• Arises from the supraclinoid ICA
• Runs posteriorly to anastomose with the posterior cerebral artery (PCA)
• Forms the lateral limbs of the Circle of Willis
• Clinical: PComA aneurysm → CN III palsy (pupil-involving, painful ptosis)

3. Anterior Choroidal Artery

• Arises from the supraclinoid ICA distal to PComA
• Travels posteriorly over the medial optic tract
• Supplies: optic tract, posterior limb of internal capsule, anterior hippocampus, amygdala, tail of caudate, medial globus pallidus, lateral geniculate body
• Occlusion syndrome: contralateral hemiplegia + hemisensory loss + homonymous hemianopia (the triad)
• Goldman-Cecil Medicine; Adams and Victor's Neurology

4. Anterior Cerebral Artery (ACA)

• Two ACAs anastomose via Anterior Communicating Artery (AComA)
• ACA infarct → contralateral leg weakness (cortical homunculus: leg area is medial)

5. Middle Cerebral Artery (MCA)

• Largest branch of ICA; supplies the largest territory
• Lenticulostriate arteries (from M1) = "arteries of cerebral hemorrhage" - supply internal capsule and basal ganglia; end arteries with no collaterals
• MCA infarct → contralateral face + arm weakness (lateral hemisphere) + aphasia (dominant side) + neglect (non-dominant side)

Summary Table

• [Gray's Anatomy for Students](ISBN 9780323934237), pp. 1019, 1307
• [Goldman-Cecil Medicine](ISBN 9780323930345) - Anterior Choroidal and ICA sections
• [Adams and Victor's Principles of Neurology, 12th Ed.](ISBN 9781264264520) - Anterior Choroidal Artery Stroke Syndrome

Vertebral Artery - Complete Anatomy, Branches & Supply

Origin & Course

Flowchart: Vertebral Artery Branches

SUBCLAVIAN ARTERY
│
└── VERTEBRAL ARTERY (V1–V3: neck branches — muscular + spinal)
        │
        └── V4 (INTRACRANIAL) — enters foramen magnum
                │
                ├── 1. MENINGEAL BRANCH (small)
                │       └── Supplies dura of posterior cranial fossa
                │
                ├── 2. POSTERIOR INFERIOR CEREBELLAR ARTERY (PICA)
                │       ├── Lateral medulla (dorsolateral)
                │       ├── Inferior half of cerebellar hemispheres
                │       ├── Inferior vermis
                │       └── Choroid plexus of 4th ventricle
                │
                ├── 3. POSTERIOR SPINAL ARTERY
                │       └── Descends on posterior surface of spinal cord
                │           (posterior columns, posterior horns)
                │           [Note: more commonly arises from PICA]
                │
                └── 4. ANTERIOR SPINAL ARTERY (contribution)
                        └── Both VAs join to form 1 anterior spinal artery
                            → descends in anterior median fissure
                            → anterior 2/3 of spinal cord
                            (anterior horns, anterolateral white matter)
                │
                ↓
        ════════════════════════════════
        BASILAR ARTERY (formed by union
        of both vertebral arteries at
        pontomedullary junction)
        ════════════════════════════════
                │
                ├── 5. ANTERIOR INFERIOR CEREBELLAR ARTERY (AICA)
                │       ├── Lateral caudal pons
                │       ├── Inferior surface of cerebellar hemispheres (anterior part)
                │       └── Labyrinthine (internal auditory) artery (often from AICA)
                │
                ├── 6. PONTINE BRANCHES (paramedian + circumferential)
                │       ├── Paramedian → medial pons (corticospinal fibers, MLF)
                │       └── Circumferential → lateral pons
                │
                ├── 7. SUPERIOR CEREBELLAR ARTERY (SCA)
                │       ├── Superior cerebellar peduncles
                │       ├── Superior vermis + superior cerebellar hemispheres
                │       └── Dorsal midbrain (caudal)
                │
                └── TERMINAL BIFURCATION
                        │
                        └── 8. POSTERIOR CEREBRAL ARTERY (PCA) × 2
                                ├── P1 segment → midbrain perforators (thalamic)
                                ├── P2 → posterior thalamus, medial temporal lobe
                                ├── Calcarine artery → primary visual cortex (V1)
                                ├── Posterior temporal artery → inferior temporal lobe
                                └── Connected to ICA via Posterior Communicating A.

Detailed Supply of Each Branch

1. PICA (Posterior Inferior Cerebellar Artery)

• Largest branch of the intracranial VA
• Supplies the dorsolateral medulla (most clinically important - site of Wallenberg syndrome)
• Supplies inferior half of cerebellum + inferior vermis
• Supplies choroid plexus of 4th ventricle

Wallenberg Syndrome (Lateral Medullary Syndrome) - most often due to ipsilateral VA occlusion (not PICA itself):

• Ipsilateral: Horner syndrome, loss of pain/temp on face, ataxia, dysphagia, hoarseness
• Contralateral: loss of pain/temp on body
• Spared: motor power (corticospinal tract medial = supplied by VA perforators)

2. Posterior Spinal Artery

• Usually arises from PICA (not directly from VA)
• Descends on posterior surface of spinal cord
• Supplies: posterior columns (fine touch, proprioception, vibration) and posterior horns

3. Anterior Spinal Artery

• Single midline artery formed by union of contributions from BOTH VAs
• Descends in anterior median fissure
• Supplies: anterior 2/3 of spinal cord - anterior horns (motor), lateral corticospinal and spinothalamic tracts
• Occlusion → loss of motor + pain/temp below lesion; posterior columns spared (dissociated sensory loss)

4. AICA (Anterior Inferior Cerebellar Artery) - basilar branch

• Supplies lateral caudal pons + anterior inferior cerebellum
• Gives off labyrinthine artery (to inner ear) - occlusion causes vertigo + ipsilateral deafness
• AICA syndrome: ipsilateral facial palsy, deafness, vertigo, Horner + contralateral body pain/temp loss

5. Pontine Branches (basilar)

• Paramedian arteries: corticospinal tract, corticobulbar tract, MLF (medial longitudinal fasciculus)
• Short circumferential: lateral pons structures

6. SCA (Superior Cerebellar Artery) - basilar branch, just before bifurcation

• Superior cerebellar peduncle, superior vermis, superior cerebellum
• Caudal dorsal midbrain
• SCA syndrome: ipsilateral ataxia, contralateral pain/temp loss, CN IV palsy

7. PCA (Posterior Cerebral Artery) - terminal basilar branches

• Perforates: midbrain, thalamus
• Cortical: occipital lobe (visual cortex), inferior + medial temporal lobe
• PCA infarct → contralateral homonymous hemianopia (macular sparing common)

Summary Table

Medullary Branches - Blood Supply to the Medulla Oblongata

Flowchart: Medullary Blood Supply

VERTEBRAL ARTERY (intracranial)
│
├─── 1. PARAMEDIAN (ANTEROMEDIAL) BRANCHES
│         │
│         ├── Direct small perforators from Vertebral Artery
│         └── Anterior Spinal Artery branches
│              → Supply: MEDIAL MEDULLA
│                 • Pyramid (corticospinal tract)
│                 • Medial lemniscus
│                 • Hypoglossal nucleus & CN XII fascicles
│
├─── 2. LATERAL (SHORT CIRCUMFERENTIAL) BRANCHES
│         │
│         └── PICA (Posterior Inferior Cerebellar Artery)
│              → Supply: LATERAL MEDULLA (dorsolateral)
│                 • Inferior cerebellar peduncle
│                 • Vestibular nuclei
│                 • Spinal trigeminal nucleus & tract (CN V)
│                 • Spinothalamic tract
│                 • Descending sympathetic fibers
│                 • Nucleus ambiguus (CN IX, X)
│                 • Nucleus solitarius (taste)
│                 • Dorsal motor nucleus of vagus
│
└─── 3. POSTERIOR BRANCHES
          │
          └── Posterior Spinal Artery (from PICA)
               → Supply: POSTERIOR MEDULLA
                  • Gracile nucleus (lower limb proprioception)
                  • Cuneate nucleus (upper limb proprioception)
                  • Posterior column nuclei

The Three Vascular Zones of the Medulla

Clinical Syndromes (Key Exam Topics)

1. Medial Medullary Syndrome (Dejerine Syndrome)

Memory: Medial = Motor (pyramid) + proprioception (lemniscus) + CN XII The classic triad: contralateral hemiplegia + contralateral position/vibration loss + ipsilateral tongue weakness

2. Lateral Medullary Syndrome (Wallenberg Syndrome)

Key: Motor power is PRESERVED (pyramids are medial, not affected) Crossed sensory loss = hallmark: ipsilateral face + contralateral body

3. Hemimedullary Syndrome (Babinski-Nageotte Syndrome)

• Combination of medial + lateral medullary infarction
• Caused by occlusion of the ipsilateral VA proximal to PICA and its anterior spinal artery branches
• Features: all findings of both syndromes above combined

Summary Diagram

Quick Comparison: Medial vs Lateral Medullary