A 9-month-old boy presents with a first prolonged focal motor seizure (right arm and right face clonic jerking, 35 minutes duration) requiring IV lorazepam and phenytoin. On examination, there is a large port-wine stain on the left forehead, upper eyelid, and cheek in the V1 distribution, present since birth. MRI shows leptomeningeal angiomatosis over the left parieto-occipital cortex with cortical atrophy and gyriform calcifications. The EEG demonstrates the finding marked **A** in the diagram. Which of the following best explains the pathophysiological basis of this EEG abnormality in Sturge-Weber syndrome?
A. Focal cortical dysplasia with abnormal neuronal migration in the distribution of the trigeminal nerve
B. Demyelination of subcortical white matter tracts secondary to chronic inflammation
C. Chronic cerebral hypoxia and venous stasis from abnormal cortical venous drainage leading to progressive cortical ischemia and gliosis
D. Acute hemorrhage into the leptomeningeal angioma causing mass effect and transient focal depression
Explanation
Why chronic cerebral hypoxia and venous stasis from abnormal cortical venous drainage leading to progressive cortical ischemia and gliosis is right
The focal slowing and background attenuation marked A over the hemisphere ipsilateral to the port-wine stain reflects the underlying pathophysiology of Sturge-Weber syndrome: abnormal cortical venous drainage due to leptomeningeal angiomatosis causes chronic venous stasis, progressive cortical ischemia, and gliosis. This leads to loss of normal cortical electrical activity (attenuation) and replacement by slower frequencies (delta and theta activity). The Nelson Textbook of Pediatrics emphasizes that the EEG abnormality directly correlates with the degree of cortical hypoxia and metabolic dysfunction from impaired venous return, not acute hemorrhage or structural malformation alone.
Why each distractor is wrong
Acute hemorrhage into the leptomeningeal angioma causing mass effect and transient focal depression: While hemorrhage can occur in Sturge-Weber syndrome, the EEG finding marked A represents a chronic, persistent pattern of focal slowing and attenuation, not an acute transient depression. Acute hemorrhage would produce more dramatic focal suppression or seizure activity rather than the characteristic chronic background slowing.
Focal cortical dysplasia with abnormal neuronal migration in the distribution of the trigeminal nerve: Sturge-Weber syndrome is not a primary cortical malformation or neuronal migration disorder. The cortical abnormality is secondary to the leptomeningeal angiomatosis and resulting ischemia, not primary dysplasia. The EEG pattern reflects ischemic injury, not dysplastic cortex.
Demyelination of subcortical white matter tracts secondary to chronic inflammation: Although chronic inflammation may contribute to tissue injury in Sturge-Weber, the focal slowing and attenuation marked A primarily reflects cortical gray matter dysfunction from ischemia, not white matter demyelination. The EEG pattern is cortical in origin, not subcortical.
High-YieldNEET PG
In Sturge-Weber syndrome, the EEG shows focal slowing and attenuation ipsilateral to the leptomeningeal angioma due to chronic venous stasis and cortical ischemia, not primary cortical dysplasia or acute hemorrhage.
Nelson Textbook of Pediatrics, 21st ed., Chapter 614: Neurocutaneous Syndromes — Sturge-Weber
Practice similar questions
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.
