What vessels are involved in a pontine stroke?

Vessels Involved in Pontine Stroke

The primary vessels involved in pontine stroke are the basilar artery and its perforating branches, including paramedian, short circumflex, long circumflex, and median pontine arteries. 1, 2

Vascular Anatomy of the Pons

Basilar Artery

• The basilar artery is the main vessel supplying the pons
• Formed by the union of the two vertebral arteries
• Runs along the ventral surface of the pons
• Terminates by dividing into the posterior cerebral arteries

Pontine Perforating Arteries

Based on their origin, course, and distribution, pontine arteries can be classified into five types 2:

1. Paramedian branches - Supply the paramedian pons
2. Short circumflex branches - Supply lateral portions of the pons
3. Combined paramedian and short circumflex branches
4. Long circumflex branches - Supply posterolateral regions
5. Median branches - Penetrate along the basilar sulcus

Typical Distribution Pattern

The pontine arteries typically follow this pattern 2:

• First pontine artery below the Superior Cerebellar Artery (SCA): posterolateral pontine artery (type 4)
• Second: superolateral pontine artery (type 2)
• Middle three arteries: types 1,2, and 3 (supply most of ventral pontine surface)
• Sixth artery: anterolateral pontine artery (type 2)
• Seventh artery (below AICA): long circumflex arteries

Patterns of Pontine Infarction

Ventral Pontine Infarcts

• Most common type (58% of isolated pontine infarcts) 3
• Caused by occlusion of paramedian and short circumflex branches
• Clinical presentation varies from mild hemiparesis (ventrolateral syndrome) to severe hemiparesis with bilateral ataxia and dysarthria (ventromedial syndrome) 3

Tegmental Pontine Infarcts

• Represent approximately 31% of isolated pontine infarcts 3
• Present with eye movement disorders, cranial nerve palsies, and sensory disturbances
• Usually associated with milder motor deficits 3

Bilateral Ventrotegmental Pontine Infarcts

• Less common (11% of isolated pontine infarcts) 3
• Present with acute pseudobulbar palsy, bilateral motor deficits, and tegmental signs

Etiology of Pontine Stroke

Basilar Artery Branch Disease

• Most common cause (44% of cases) 3
• Associated with large ventral infarcts, severe symptoms, and progressive or fluctuating course
• Particularly common in patients with vascular risk factors 1

Small-Artery Disease

• Accounts for approximately 25% of cases 3
• Usually associated with small ventral or tegmental infarcts
• Typically presents with rapidly improving lacunar syndromes

Large-Artery Stenosis

• Less common (22% of cases) 3
• Often involves the basilar artery itself

Cardioembolic Events

• Least common mechanism (3% of cases) 3
• Associated with poorer prognosis, with mortality rates between 45-86% 1

Imaging Characteristics

Ischemic Changes

• Central pontine ischemic changes typically involve transverse pontine fibers
• These represent a vascular border zone supplied by penetrating arteries from the basilar and superior cerebellar arteries 4
• Multiple sclerosis lesions (differential diagnosis) are usually located at the periphery of the pons 4

Hemorrhagic Transformation

• Rare in brainstem infarction compared to supratentorial and cerebellar infarction
• Can occur as a complication of anticoagulant therapy 5

Clinical Pearls

1. Pontine Warning Syndrome: Characterized by recurrent stereotyped episodes of motor/sensory dysfunction, dysarthria, or ophthalmoplegia that signal imminent basilar artery branch infarction 6

2. Progressive Stroke: Extension of infarcted tissue to the pons surface has been indicated as a marker of basilar branch atheromatous disease and is associated with neurological worsening 7

3. NIHSS Limitations: The NIHSS may underestimate the severity of posterior circulation strokes as it focuses more on limb and speech impairments and less on cranial nerve lesions 4

4. Clinical Presentation: Symptoms can include loss of consciousness, headache, nausea, vomiting, dizziness, double vision, hearing loss, slurred speech, vertigo, imbalance, and unilateral extremity weakness 4

Understanding the vascular anatomy of the pons is crucial for accurate diagnosis, prognosis, and management of pontine strokes, as the specific vessel involved determines the clinical syndrome and potential outcome.