Language after childhood hemispherectomy: A systematic review

OBJECTIVE: 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. METHODS: 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 where hemispherectomy was carried out before age 18 and; (3) studies with standardised scores measuring receptive vocabulary, expressive vocabulary, sentence comprehension, and/or sentence production. We calculated mean z-scores after left and right hemispherectomy in the whole group and within aetiology-specific subgroups. RESULTS: 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 (z scores <-1.5) except sentence comprehension. In the right surgery group, language performance was in the borderline range (z scores ∼ -1.5). Children with cortical dysplasia showed the worst outcomes irrespective of surgery side (z scores <-2.5). Individuals with left vascular aetiology and right-sided Rasmussen Syndrome showed the best outcomes. CONCLUSION: 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. Aetiology plays a major role in post-surgical 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