Language after childhood hemispherectomy: A systematic review.

Abstract

To conduct a systematic review on language outcomes after left and right hemispherectomy in childhood, a surgical procedure that involves removing or disconnecting a cerebral hemisphere. We searched MEDLINE, Embase, and PsycInfo for articles published between January 1, 1988, and May 16, 2019. We included (1) all types of observational studies; (2) studies in which hemispherectomy was performed before age 18 years; and (3) studies with standardized scores measuring receptive vocabulary, expressive vocabulary, sentence comprehension, and/or sentence production. We calculated mean <i>z</i> scores after left and right hemispherectomy in the whole group and within etiology-specific subgroups. Our search identified 1,096 studies, of which 17 were eligible. The cohort added up to 205 individuals (62% left hemispherectomy) assessed 1 to 15 years after surgery. In the left surgery group, all language skills were impaired (<i>z</i> scores <-1.5) except sentence comprehension. In the right surgery group, language performance was in the borderline range (<i>z</i> scores ∼ -1.5). Children with cortical dysplasia showed the worst outcomes irrespective of surgery side (<i>z</i> scores <-2.5). Individuals with left vascular etiology and right-sided Rasmussen syndrome showed the best outcomes. Evidence based on the largest patient cohort to date (205 participants) suggests that the risk of language impairment after hemispherectomy is high, with few exceptions. Etiology plays a major role in postsurgical plasticity. We recommend specialist evaluation of language skills soon after surgery to identify intervention targets. Large-scale studies examining outcomes in consecutive cases are still needed.