Pontine Infarct Classification
This is a posterior circulation infarct (POCI), not a lacunar infarct (LACI), partial anterior circulation infarct (PACI), or total anterior circulation infarct (TACI). The hemipontinе location definitively places this in the posterior circulation territory, regardless of the clinical presentation.
Why This is POCI
The Oxfordshire Community Stroke Project (OCSP) classification divides ischemic strokes into four categories based on clinical syndromes and vascular territories 1:
- TACI: Large anterior circulation infarcts with cortical and subcortical involvement
- PACI: Restricted, predominantly cortical anterior circulation infarcts
- LACI: Infarcts confined to deep perforating artery territories
- POCI: Infarcts in the vertebrobasilar arterial territory
The pons is supplied by the basilar artery and its branches, making any pontine infarct by definition a posterior circulation stroke 2. Posterior circulation strokes account for approximately 20% of all strokes 2, 3, 4.
Important Clinical Nuances
Why the Confusion May Arise
Your patient's presentation with unilateral sensory symptoms (left upper limb and posterior neck numbness) might superficially resemble a lacunar syndrome. However:
- Pure sensory stroke CAN occur from pontine lacunar infarction affecting the medial lemniscus 5, 6
- These pontine sensory strokes are still classified as POCI, not LACI in the OCSP system
- The OCSP classification is based on vascular territory, not just clinical syndrome 1
Pontine Infarct Subtypes
Within pontine infarcts, there are morphological distinctions 7:
- Small deep infarcts (lacunar-type): 49% of pontine infarcts, well-circumscribed
- Paramedian wedge infarcts: 40%, from basilar branch atherosclerosis
- Both types remain POCI in the OCSP classification
The presence of headache in your patient is consistent with posterior circulation stroke, as headache is a common presenting symptom in this territory 2.
Clinical Implications
Posterior circulation strokes have distinct prognostic features 1:
- Better chance of good functional outcome compared to TACI
- Higher risk of recurrent stroke later in the first year
- Can present with subtle or atypical symptoms, including isolated sensory deficits 2
Critical Pitfall to Avoid
Do not dismiss posterior circulation stroke based on low NIHSS scores. The NIHSS is heavily weighted toward anterior circulation deficits and underestimates posterior circulation stroke severity 2. Patients with posterior circulation strokes can have NIHSS scores of 0 while still having significant symptoms like headache, vertigo, and sensory disturbances 2.
Bottom Line
Your patient has a POCI (posterior circulation infarct). The anatomical location in the pons supersedes the clinical presentation when applying the OCSP classification. The unilateral sensory symptoms represent a pontine lacunar syndrome within the posterior circulation territory, not an anterior circulation lacunar infarct.