Verbal and Nonverbal Cognitive Parameters of Children with Perinatal Unilateral Infarctions – No Crowding Hypothesis in Children without Cognitive Impairment?

Background: Patients with left-sided perinatal infarctions have often been reported to show intact verbal functions, because language is reorganized into the healthy right hemisphere. Cognitive processes originally located in the right hemisphere (e.g. visuospatial functions) thus show deficits – the “crowding hypothesis”. Patients with right-sided perinatal infarctions show no such reorganization into the intact left hemisphere. Hence, a predominance of verbal over nonverbal functions is anticipated, regardless of the side of the lesion. Previous research has, however, mainly focused on patients with impaired cognitive abilities, often due to refractory epilepsies.

Aims: To investigate the crowding hypothesis in a sample of patients with perinatal unilateral infarctions without refractory epilepsies and without severe cognitive impairment; to validate the hypothesis on cognitively impaired patients with refractory epilepsies.

Method: Prospectively, we examined 12 patients (7 f, aged 8 - 28 years) with perinatal infarctions (10 l, 2 r) and 28 healthy controls (13 f, aged 8 - 29 years). They completed neuropsychological tests of verbal (P-IPTA) and nonverbal intelligence (TONI-4), fMRI for language lateralization and MRI (evaluation is in progress). Retrospectively, pre-epilepsy-surgical IQ-data (HAWIK-III, WIE) from 11 hemiparetic children (7 f, aged between 8 – 21 years) with perinatal infarctions (4 l, 7 r) and refractory epilepsies were analyzed.

Results: Children with infarctions without severe cognitive impairment tended to show better non-verbal than verbal performance, healthy controls better verbal than non-verbal performance. Patients with refractory epilepsies (IQ 46–79) showed below-average verbal and nonverbal performance, verbal IQ was always superior to performance IQ.

Interpretation: As predicted by the crowding hypothesis, cognitively impaired children with infarctions and refractory epilepsies showed disadvantages of nonverbal compared with verbal cognitive performance. Surprisingly, this difference could not be shown for patients with unilateral infarctions without severe cognitive impairment. Here, in contrast to healthy controls, non-verbal performance tended to be even better than verbal performance.

Conclusion: In children with unilateral infarctions without severe cognitive impairment, we found no evidence for relative deficits in non-verbal performance, and thus no evidence for the crowding hypothesis. The ongoing evaluation of the fMRI and MRI data will clarify the influence of language reorganization and lesion size.