Malignant Infarct of the Pons: Definition
A "malignant infarct" specifically refers to large territorial infarctions (primarily middle cerebral artery territory) that develop life-threatening brain swelling within 24-48 hours causing brain herniation—this term is NOT standardly applied to pontine infarctions. 1
Standard Definition of Malignant Infarction
The American Heart Association and American Stroke Association define "malignant infarction" as:
- A large territorial infarct that swells within 24 hours, causing brain herniation signs 2, 1
- Rapid and fulminant clinical course within 24-36 hours 1
- Mortality exceeding 80% with conventional medical treatment alone 1
- The term "malignant MCA infarction" is the most commonly used terminology in the literature and specifically applies to anterior circulation strokes, particularly MCA territory infarctions 1
Why This Term Does Not Apply to Pontine Infarcts
Anatomical and Clinical Distinctions
The term "malignant" was coined specifically for supratentorial anterior circulation strokes where:
- Mass effect manifests through compression of the frontal horn, shift of the septum pellucidum, and shift of the pineal gland 1
- Brain swelling typically occurs 4 days after MCA stem occlusion, but can develop within 24 hours in malignant cases 2
- The overall risk of brain swelling in anterior circulation ischemic stroke is 10-20% 2
Pontine Infarction Characteristics
Pontine infarctions have distinctly different clinical profiles:
- Pontine infarcts account for 10.2% of all first-ever ischemic strokes and present with pure motor hemiparesis/hemiplegia, cranial nerve dysfunctions, and eye movement disorders 3, 4
- Progressive neurological worsening in pontine stroke is associated with enlargement of the pontine lesion itself, not mass effect or herniation 5
- Pontine infarcts are characterized by penetrating branch artery disease affecting anteromedial and anterolateral territories 3
- Clinical features include higher frequency of diabetes mellitus (50%), nonvertiginous dizziness (58.3%), and progressive course (33.3%) 4
Posterior Fossa Considerations
Rapid deterioration from cerebellar infarcts with swelling is more common and may be associated with sudden apnea from brain stem compression, but this is distinct from the "malignant" terminology applied to supratentorial strokes 2. The incidence of brain swelling in posterior circulation stroke remains unknown. 2
Clinical Pitfall to Avoid
Do not use the term "malignant pontine infarct" as it conflates two distinct pathophysiological entities. If describing a large pontine infarction with progressive neurological deterioration, specify "progressive pontine infarction with neurological worsening" rather than borrowing terminology from supratentorial stroke syndromes. 5, 4