Brain Malformations
A 30-slide clinical learning module · Cortical development, migration disorders, midline anomalies, and posterior fossa
Slide 1 of 303% complete
Module Outline
🧭 Part 1
🧬 Part 2
🗺️ Part 3
🌀 Part 4
⚖️ Part 5
🧠 Part 6
📋 Part 7
Slide 1/30
🧭 Part 1: Approach & Development
When to Suspect a Brain Malformation
Start with the cortex: what does it look like?
- 1Suspect a brain malformation when a child presents with the triad of epilepsy, intellectual disability, and motor impairment — particularly when seizures are refractory, onset is neonatal or early infantile, and neurodevelopment is globally impaired from birth.
- 2Your first MRI question is always: "What does the cortex look like?" Classify by cortical appearance before reaching for gene panels: Is the cortex thick? Smooth? Bumpy? Does it have a cleft? Is it too folded? Each pattern points to a different developmental stage and gene class.
- 3The flowchart approach: cortical thickening with absent/reduced sulcation → lissencephaly or cobblestone; pseudothickening with increased folding → polymicrogyria; focal T2 blur at the gray-white junction → FCD; a cleft lined with gray matter → schizencephaly; normal-thickness cortex in abnormal locations → heterotopia.
- 4Always examine the extra-cortical structures: corpus callosum, cerebellum, brainstem, and ventricles. Many brain malformations are syndromic — a DWM variant plus ACC in the same child nearly always implies a genetic etiology. Association with other organ system anomalies (cardiac, renal, eye) expands your differential substantially.
- 5Order an MRI rather than a CT whenever possible. CT misses subtle gyral anomalies and exposes the brain to radiation. In a neonate with suspected brain malformation, plan the MRI after the first week when early myelination and edema have stabilized.
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Clinical Pearl
The single most useful question in approaching an MRI for brain malformation: "Is the cortex the right thickness?" Normal cortical thickness is 2–4 mm. Anything outside that range, or a cortex that fails to be smooth where it should be folded (or folded where it should be smooth), demands a systematic review of developmental stage.
Barkovich AJ et al., Brain 2012; Neuropathology: Brain Malformations & Pediatric Topics (Brock)