Functional magnetic resonance imaging of hearing-impaired children under sedation before cochlear implantation.

OBJECTIVE: To investigate functional magnetic resonance imaging (fMRI) in pediatric cochlear implantation candidates with residual hearing who are under sedation for evaluation of auditory function. DESIGN: During fMRI, subjects heard a random sequence of tones (250-4000 Hz) presented 10 dB above hearing thresholds. Tones were interleaved with silence in a block-periodic fMRI design with 30-second on-off intervals. Twenty-four axial sections (5 mm thick) covering most of the brain were obtained every 3 seconds for a total acquisition time of 5.5 minutes. SETTING: Single tertiary academic medical institution. PATIENTS: Severely to profoundly hearing-impaired children (n=10; mean age, 49.1 months). During fMRI, subjects were awake (n=2) or sedated with pentobarbital sodium if their weight was 10 kg or greater (n=4) or chloral hydrate if their weight was less than 10 kg (n=4). MAIN OUTCOME MEASURES: Detection of brain activation by fMRI in the primary auditory cortex (A1) in hearing-impaired patients under sedation, and correlation of A1 activation with hearing levels measured after cochlear implantation. RESULTS: In most subjects, fMRI detected significant levels of activation in the A1 region before cochlear implantation. The improvement in hearing threshold after cochlear implantation correlated strongly (linear regression coefficient, R=0.88) with the amount of activation in the A1 region detected by fMRI before cochlear implantation. CONCLUSIONS: Functional MRI can be considered a means of assessing residual function in the A1 region in sedated hearing-impaired toddlers. With improvements in acquisition, processing, and sedation methods, fMRI may be translated into a prognostic indicator for outcome after cochlear implantation in infants.

A longitudinal functional magnetic resonance imaging study of language development in children 5 to 11 years old.

OBJECTIVE: Language skills continue to develop rapidly in children during the school-age years, and the "snapshot" view of the neural substrates of language provided by current neuroimaging studies cannot capture the dynamic changes associated with brain development. The aim of this study was to conduct a 5-year longitudinal investigation of language development using functional magnetic resonance imaging in healthy children. METHODS: Thirty subjects enrolled at ages 5, 6, or 7 were examined annually for 5 years using a 3-Tesla magnetic resonance imaging scanner and a verb generation task. Data analysis was conducted based on a general linear model that was modified to investigate developmental changes whereas minimizing the potential for missing data. RESULTS: With increasing age, there is progressive participation in language processing by the inferior/middle frontal, middle temporal, and angular gyri of the left hemisphere and the lingual and inferior temporal gyri of the right hemisphere and regression of participation of the left posterior insula/extrastriate cortex, left superior frontal and right anterior cingulate gyri, and left thalamus. CONCLUSION: The age-related changes observed in this study provide evidence of increased neuroplasticity of language in this age group and may have implications for further investigations of normal and aberrant language development.

Cortical reorganization in children with unilateral sensorineural hearing loss.

Previous studies have shown evidence of cortical reorganization following unilateral sensorineural hearing loss (USNHL). In addition, study participants with right USNHL have shown greater deficits in academic and language performance compared with those with left USNHL. A preliminary functional magnetic resonance imaging investigation was performed on a small cohort of participants, four with left USNHL and four with right USNHL, using the paradigm of listening to random tones. While the participants with left USNHL displayed greater activation in the right superior temporal gyrus, those with right USNHL displayed greater activation in the left inferior frontal area immediately anterior to the superior temporal gyrus. The results provide preliminary evidence of disparate neural circuitry supporting auditory processing in participants with left and right USNHL.

Ventricular and periventricular structural volumes in first- versus multiple-episode bipolar disorder.

OBJECTIVE: Ventriculomegaly has been reported in bipolar disorder, although whether it occurs at illness onset or progresses during the course of the disorder is unknown. In addition, it is unknown whether ventriculomegaly in bipolar disorder reflects acquired volume loss or underdevelopment of periventricular structures. METHOD: Magnetic resonance imaging was used to measure the volumes of the lateral and third ventricles and periventricular structures (caudate, putamen, thalamus, hippocampus). Patients with DSM-IV bipolar disorder, 18 who were having a first episode and 17 with multiple episodes, were compared with 32 healthy subjects. RESULTS: The lateral ventricles were significantly larger in the patients with multiple-episode bipolar disorder than in the first-episode patients or the healthy subjects, even after periventricular and total cerebral volumes were taken into account. Having larger lateral ventricles was associated with a higher number of prior manic episodes. The multiple-episode patients had a smaller total cerebral volume than the healthy subjects but not the first-episode patients. The putamen was significantly larger in the first-episode patients (and nearly so in the multiple-episode patients) than in the healthy subjects, although there was no difference between patient groups. CONCLUSIONS: Lateral ventriculomegaly was greater in bipolar disorder patients who had had repeated manic episodes, but it does not appear to be secondary to small critical periventricular structures. A larger than normal striatum, which has been reported in previous studies, was observed in first-episode patients. These results support the importance of prospectively studying neuroanatomic changes in bipolar disorder.