How may porencephaly be said to occur rarely?

Answer:
A 1984 study of 18,000 patients with seizure disorder or retarded neural development that 11 had porencephaly, a rate of 1:1650 in that abnormal population.
First answer by Gale Ency of Neuro Dis. Last edit by Gale Ency of Neuro Dis. Contributor trust: 14 [recommend contributor recommended]. Question popularity: 1 [recommend question].