Hearing loss and intellectual outcome in children treated for embryonal brain tumors: Implications for young children treated with radiation sparing approaches.

PURPOSE: We investigate the impact of severe sensorineural hearing loss (SNHL) and for the first time evaluate the effect of unilateral versus bilateral SNHL on intellectual outcome in a cohort of children with embryonal brain tumors treated with and without radiation. METHODS: Data were from 94 childhood survivors of posterior fossa (PF) embryonal brain tumors who were treated with either: (1) chemotherapy alone (n = 16, 7.11 [3.41] years, 11M/5F), (2) standard-dose craniospinal irradiation (CSI) and/or large boost volumes (n = 44, 13.05 [3.26] years, 29M/15F), or (3) reduced-dose CSI with a boost restricted to the tumor bed (n = 34, 11.07 [3.80] years, 19M/15F). We compared intellectual outcome between children who: (1) did and did not develop SNHL and (2) developed unilateral versus bilateral SNHL. A Chang grade of ≥2b that required the use of a hearing aid was considered severe SNHL. Comparisons were made overall and within each treatment group separately. RESULTS: Patients who developed SNHL had lower full scale IQ (p = 0.007), verbal comprehension (p = 0.003), and working memory (p = 0.02) than patients without SNHL. No differences were observed between patients who had unilateral versus bilateral SNHL (all p > 0.05). Patients treated with chemotherapy alone who developed SNHL had lower mean working memory (p = 0.03) than patients who did not develop SNHL. Among patients treated with CSI, no IQ indices differed between those with and without SNHL (all p > 0.05). CONCLUSIONS: Children treated for embryonal brain tumors who develop severe SNHL have lower intellectual outcome than patients with preserved hearing: this association is especially profound in young children treated with radiation sparing approaches. We also demonstrate that intellectual outcome is similarly impaired in patients who develop unilateral versus bilateral SNHL. These findings suggest that early intervention to preserve hearing is critical.

Early Cognitive Outcomes Following Proton Radiation in Pediatric Patients With Brain and Central Nervous System Tumors.

PURPOSE: To report, from a longitudinal study, cognitive outcome in pediatric patients treated with proton radiation therapy (PRT) for central nervous system (CNS) tumors. METHODS AND MATERIALS: Sixty patients receiving PRT for medulloblastoma (38.3%), gliomas (18.3%), craniopharyngioma (15.0%), ependymoma (11.7%), and other CNS tumors (16.7%) were administered age-appropriate measures of cognitive abilities at or near PRT initiation (baseline) and afterward (follow-up). Patients were aged ≥ 6 years at baseline to ensure consistency in neurocognitive measures. RESULTS: Mean age was 12.3 years at baseline; mean follow-up interval was 2.5 years. Treatment included prior surgical resection (76.7%) and chemotherapy (61.7%). Proton radiation therapy included craniospinal irradiation (46.7%) and partial brain radiation (53.3%). At baseline, mean Wechsler Full Scale IQ was 104.6; means of all 4 Index scores were also in the average range. At follow-up, no significant change was observed in mean Wechsler Full Scale IQ, Verbal Comprehension, Perceptual Reasoning/Organization, or Working Memory. However, Processing Speed scores declined significantly (mean 5.2 points), with a significantly greater decline for subjects aged <12 years at baseline and those with the highest baseline scores. Cognitive outcome was not significantly related to gender, extent of radiation, radiation dose, tumor location, histology, socioeconomic status, chemotherapy, or history of surgical resection. CONCLUSIONS: Early cognitive outcomes after PRT for pediatric CNS tumors are encouraging, compared with published outcomes from photon radiation therapy.

Left lateralizing transcranial direct current stimulation improves reading efficiency.

BACKGROUND: Poor reading efficiency is the most persistent problem for adults with developmental dyslexia. Previous research has demonstrated a relationship between left posterior temporal cortex (pTC) function and reading ability, regardless of dyslexia status. OBJECTIVE/HYPOTHESIS: In this study, we tested whether enhancing left lateralization of pTC using transcranial direct current stimulation (tDCS) improves reading efficiency in adults without dyslexia. METHOD: Twenty-five right-handed adults with no history of learning disorder participated. Real and sham "Left lateralizing" tDCS were applied to the pTC in separate sessions. Standardized word and nonword reading tests were given immediately after stimulation. RESULTS: Modeling of the induced electrical field confirmed that tDCS was likely to increase left pTC excitability and reduce right pTC excitability as intended. Relative to sham, real tDCS induced improvements in word reading efficiency in below average readers. CONCLUSIONS: Enhancing left lateralization of the pTC using tDCS improves word reading efficiency in below-average readers. This demonstrates that left lateralization of the pTC plays a role in reading ability, and provides stimulation parameters that could be used for a trial of tDCS in adults with developmental dyslexia. Such short-term gains could amplify the effect of appropriate reading interventions when performed in conjunction with them.

Evidence for a basal temporal visual language center: cortical stimulation producing pure alexia.

BACKGROUND: Dejerine and Benson and Geschwind postulated disconnection of the dominant angular gyrus from both visual association cortices as the basis for pure alexia, emphasizing disruption of white matter tracts in the dominant temporooccipital region. Recently functional imaging studies provide evidence for direct participation of basal temporal and occipital cortices in the cognitive process of reading. The exact location and function of these areas remain a matter of debate. OBJECTIVE: To confirm the participation of the basal temporal region in reading. METHOD: Extraoperative electrical stimulation of the dominant hemisphere was performed in three subjects using subdural electrodes, as part of presurgical evaluation for refractory epilepsy. RESULTS: Pure alexia was reproduced during cortical stimulation of the dominant posterior fusiform and inferior temporal gyri in all three patients. Stimulation resulted in selective reading difficulty with intact auditory comprehension and writing. Reading difficulty involved sentences and words with intact letter by letter reading. Picture naming difficulties were also noted at some electrodes. This region is located posterior to and contiguous with the basal temporal language area (BTLA) where stimulation resulted in global language dysfunction in visual and auditory realms. The location corresponded with the visual word form area described on functional MRI. CONCLUSION: These observations support the existence of a visual language area in the dominant fusiform and occipitotemporal gyri, contiguous with basal temporal language area. A portion of visual language area was exclusively involved in lexical processing while the other part of this region processed both lexical and nonlexical symbols.