Clinical Features of Pontine Stroke Syndrome
Pontine stroke syndromes present with characteristic combinations of motor deficits, cranial nerve palsies (particularly CN V-VIII), and sensory disturbances that vary based on the specific anatomical location of the infarct within the pons. 1
Core Clinical Presentations by Anatomical Location
Anteromedial (Basal) Pontine Infarcts (Most Common - 58%)
- Motor deficits with upper extremity predominance or faciobrachial distribution 2, 3
- Dysarthria (present in nearly all cases) 2, 3
- Ataxia 3
- Pathological laughing (less common) 2
- Brachial monoparesis may occur 2
- Tegmental signs present in approximately one-third of patients 3
Anterolateral Pontine Infarcts (17%)
- Combined motor AND sensory deficits (present in 50% of cases) 3
- Tegmental signs more frequent (56% of cases) compared to anteromedial infarcts 3
- More severe clinical presentation than pure basal infarcts 3
Tegmental (Dorsal) Pontine Infarcts (10%)
- Horizontal gaze abnormalities are the hallmark feature 1, 2, 3
- Sensory disturbances (superficial or proprioceptive) 2, 3
- Vestibular symptoms including vertigo, dizziness 3
- Motor deficits typically mild 3
Bilateral Pontine Infarcts (11%)
- Transient loss of consciousness 3
- Tetraparesis 3
- Acute pseudobulbar palsy 3
- Locked-in syndrome with proximal basilar occlusions 1
- Worst prognosis of all pontine stroke subtypes 3
Specific Named Pontine Syndromes
Mid-Basilar Occlusion Syndromes
- Millard-Gubler syndrome, Foville syndrome, locked-in syndrome, and facial colliculus syndrome result from variable involvement of CN V-VIII with additional neurologic deficits 1
Top of Basilar Syndrome
- Somnolence 1
- Peduncular hallucinosis 1
- Convergence nystagmus, skew deviation, oscillatory eye movements 1
- Retraction and elevation of eyelids 1
- Vertical gaze paralysis 1
Non-Specific Presenting Symptoms (Common Pitfalls)
Posterior circulation strokes frequently present with non-specific symptoms that delay diagnosis: 1
- Headache, nausea, vomiting 1
- Dizziness and vertigo 1
- Double vision 1
- Hearing loss 1
- Slurred speech 1
- Imbalance 1
Physical examination findings include: 1
- Ataxia (particularly truncal ataxia, which is commonly missed on bedside examination) 1
- Nystagmus 1
- Visual field defects 1
Critical Diagnostic Considerations
Pontine Warning Syndrome
This represents crescendo transient ischemic attacks with stereotyped, fluctuating neurological deficits due to basilar artery branch disease: 4, 5
- Recurrent episodes of motor weakness, sensory dysfunction, dysarthria, or ophthalmoplegia 5
- Symptoms fluctuate with blood pressure changes 4
- High risk for imminent permanent pontine infarction 5
- Episodes may include complete bilateral horizontal conjugate gaze palsy lasting minutes 5
- NIHSS scores may fluctuate dramatically (3-15) over hours 5
NIHSS Limitations in Pontine Stroke
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 NIHSS score of 0 despite significant disability 1
- Truncal ataxia is the most common neurological sign in NIHSS 0, DWI-positive patients 1
- Baseline NIHSS cutoff for favorable outcome is significantly lower in posterior versus anterior circulation stroke 1
Timing and Evolution
Acute Phase
- Neurological deterioration typically occurs within 72-96 hours in patients with significant mass effect 1
- Some patients deteriorate at 4-10 days due to delayed swelling and hemorrhagic transformation 1
- Peak swelling occurs several days after onset 1
Prognostic Indicators
Upper pontine lesions have significantly better outcomes than lower pontine lesions (p<0.01) 2
- Basal-tegmental infarcts in upper pons have better prognosis than those in lower pons (p<0.02) 2
- Bilateral pontine lesions have the worst prognosis 3
- Overall outcome is generally excellent except in bilateral cases 3
Key Clinical Pitfalls
Maintain high clinical suspicion even with subtle symptoms: 1