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3 year-old male withseizures.

Hamartomatous overgrowth of hemisphere

Brain can be affected in isolation or can be associated with hemihypertrophy of part or all of the body

Macrocephaly at birth; seizures, hemiplegia, and severe developmental delay at very early age (usu before age 1).

Epidermal nevus syndrome

Proteus syndrome

Unilateral hypomelanosis of Ito

NF I

Tuberous sclerosis.

MR features

Enlarged cerebral hemisphere

Enlarged ipsilateral lateral ventricle (classic)

Cortical dysgenesis

FDG-PET features

Enlarged hemisphere

Diffuse hypermetabolism of affected hemisphere due to ongoing seizure activity.

Anatomic hemisherectomy

Must carefully screen contralateral side

Functional hemisherectomy

Hemidecortication

Intravascular hemisherectomy (no long term follow-up).