What are the clinical features and management of named pontine stroke syndromes?

Named Pontine Stroke Syndromes and Their Features

Pontine strokes present with characteristic combinations of motor deficits, cranial nerve palsies (particularly nerves V-VIII), and horizontal gaze abnormalities that vary based on whether the infarct involves the basal (ventral), tegmental (dorsal), or combined regions of the pons. 1

Anatomical Classification and Clinical Features

Basal (Ventral) Pontine Infarcts

• Dysarthria is nearly universal (present in 100% of cases in one series) 2
• Faciobrachial-predominant hemiparesis with upper extremity weakness greater than lower extremity involvement 2
• Isolated brachial monoparesis occurs in approximately 15% of cases 2
• Pathological laughing or emotional lability may occur 2
• Motor deficits result from corticospinal tract involvement without cranial nerve or gaze abnormalities 2

Tegmental (Dorsal) Pontine Infarcts

• Horizontal gaze abnormalities are the hallmark feature, including 1, 2:
  • Internuclear ophthalmoplegia (INO)
  • Horizontal gaze palsy
  • One-and-a-half syndrome (combination of INO and horizontal gaze palsy)
  • Isolated abducens nerve palsy
• Sensory disturbances affecting superficial or proprioceptive sensation 2
• Truncal ataxia is common and frequently missed on bedside examination 1
• Motor weakness is typically absent or minimal 2

Basal-Tegmental (Combined) Infarcts

• Combination of hemiparesis with horizontal gaze abnormalities 2
• Sensory dysfunction in approximately 50% of cases 2
• More severe initial presentation than isolated basal or tegmental infarcts 2

Named Syndromes and Special Presentations

Locked-In Syndrome

• Results from bilateral pontine infarcts, typically from proximal basilar artery occlusion 1, 3
• Quadriplegia with preserved vertical eye movements and blinking 1
• Can present with fluctuating symptoms in the acute phase 3

Pontine Warning Syndrome

• Characterized by recurrent stereotyped episodes of motor weakness, dysarthria, or horizontal gaze palsy lasting minutes, indicating imminent basilar artery branch infarction 4, 5
• Episodes fluctuate with blood pressure changes, suggesting hypoperfusion mechanism 5
• High risk for permanent deficit if not recognized and treated 4
• Analogous to capsular warning syndrome but in the posterior circulation 4

Diagnostic Pitfalls

NIHSS Limitations

• The NIHSS significantly underestimates posterior circulation stroke severity because it emphasizes limb weakness and speech over cranial nerve deficits 1
• Patients with pontine stroke can have an NIHSS score of 0 despite significant disability 1
• Truncal ataxia is the most common finding in NIHSS 0, DWI-positive patients 1

Timing of Symptoms

• Posterior circulation strokes frequently present with non-specific symptoms that delay diagnosis, including headache, nausea, vomiting, dizziness, vertigo, double vision, hearing loss, and imbalance 1
• Neurological deterioration typically occurs within 72-96 hours with peak swelling at several days 1
• Some patients deteriorate at 4-10 days due to delayed swelling and hemorrhagic transformation 1

Etiological Considerations

Basilar Artery Branch Disease (BABD)

• Most frequent cause of isolated pontine infarction (43% of cases) 6
• Associated with pontine warning syndrome presentation 4, 5
• Lowest 5-year recurrence rate (2.3%) among pontine stroke etiologies 6

Small-Artery Disease (SAD)

• Second most common cause (34% of cases) 6
• Hypertension present in 94% of cases 6
• Highest 5-year recurrence rate (29.4%) 6

Large-Artery Occlusive Disease (LAOD)

• Accounts for 21% of isolated pontine infarcts 6
• Most severe neurological impairment on admission 6
• Highest 1-month mortality (14.3%) and disability (61.1%) 6

Prognostic Factors

• Upper pontine lesions have significantly better outcomes than lower pontine lesions at both admission and 60 days 2
• Overall 5-year mortality ranges from 14-24% depending on etiology 6
• Long-term survival is generally good, with initial differences in short-term outcome resolving over time 6

Management Considerations for Pontine Warning Syndrome

• Avoid hypotension and promote permissive hypertension to maintain adequate perfusion 5
• Standard thrombolysis may be considered if no contraindications exist 4
• Blood pressure fluctuations directly correlate with neurological worsening and improvement 5
• Goal is asymptomatic normotension to permissive hypertension during acute phase 5