Static balance function in children with cochlear implants.

OBJECTIVE: This study aimed to assess the static balance function in deaf adolescents with cochlear implants. METHODS: We included 24 adolescents who had received unilateral cochlear implantation for at least 5 years. Each subject underwent stabilometry testing under 4 different conditions: (A) firm surface with eyes open; (B) firm surface with eyes closed; (C) foam pad with eyes open; and (D) foam pad with eyes closed. All of them received tests with their cochlear implant turned on and off. Another 24 age- and sex-matched adolescents with normal hearing were tested in the same way for comparison. Sway velocity and circular area were measured and analyzed. RESULTS: The mean sway velocity of the cochlear implant group under conditions A-D was 1.68, 1.98, 2.36, and 5.25 cm/s, respectively, and the mean circular area of the cochlear implant group under conditions A-D was 7.39, 6.68, 12.21, and 34.27 cm(2), respectively. Both of the parameters showed statistical significance between the cochlear implant group and the normal hearing group for conditions A, C and D (p<0.05). Furthermore, there was no significant balance function change among cochlear implant group with their implant "on" and "off". CONCLUSIONS: This study showed that the static balance function in adolescents with long-term use of cochlear implants was worse than those of normal hearing peers. The difference between the cochlear implant group and normal hearing group was the highest when both visual and somatosensory inputs were disrupted. The postural stability was similar whether or not the cochlear implant was activated.

Assessing the development of balance function in children using stabilometry.

OBJECTIVE: This study assessed the development of balance function in children using platform stabilometry. METHODS: A total of 251 healthy children aged from 3 to 12 years were enrolled in this study. Each subject underwent stabilometry under four various conditions (A: firm surface with eyes open; B: firm surface with eyes closed; C: foam pad with eyes open; and D: foam pad with eyes closed). Another 23 healthy adults were also tested with the same protocol for comparison. Sway magnitudes such as sway velocity and circular area were calculated and compared. RESULTS: Since the age was positively correlated with body height and body weight, age factor was used to correlate with the sway magnitude. The sway velocity under conditions A through D reached adult level when the child grew up to 7, 7, 8 and 12 years, respectively. In contrast, the circular area under conditions A through D reached adult level when the child was at the age of 5, 6, 8 and 7 years, respectively. Thus, balance function can be up to adult levels by age 12 years. CONCLUSIONS: Compared to adults, higher sway velocity and larger circular area in children indicate incomplete development of vestibular and central nervous systems integration. Our results suggest that age factor serves the most reliable index to estimate the functional development of balance system, and a child at the age of 12 years is supposed to reach balance level of an adult.

Myelination progression in language-correlated regions in brain of normal children determined by quantitative MRI assessment.

OBJECTIVE: To investigate the myelination progression course in language-correlated regions of children with normal brain development by quantitative magnetic resonance imaging (MRI) analysis compared with histological studies. METHODS: The subjects were 241 neurologically intact neonates, infants and young children (128 boys and 113 girls) who underwent MRI between 2001 and 2007 at the University of Tokyo Hospital, ranging in age from 0 to 429 weeks corrected by postnatal age. To compare their data with adult values, 25 adolescents and adults (14 men and 11 women, aged from 14 to 83 years) were examined as controls. Axial T2-weighted images were obtained using spin-echo sequences at 1.5 T. Subjects with a history of prematurity, birth asphyxia, low Apgar score, seizures, active systemic disease, congenital anomaly, delayed development, infarcts, hemorrhages, brain lesions, or central nervous system malformation were excluded from the analysis. Seven regions of interest in language-correlated areas, namely Broca's area, Wernicke's area, the arcuate fasciculus, and the angular gyrus, as well as their right hemisphere homologous regions, and the auditory cortex, the motor cortex, and the visual cortex were examined. Signal intensity obtained by a region-of-interest methodology progresses from hyper- to hypointensity during myelination. We chose the inferior cerebellar peduncle as the internal standard of maturation. RESULTS: Myelination in all these seven language-correlated regions examined in this study shared the same curve pattern: no myelination was observed at birth, it reached maturation at about 1.5 years of age, and it continued to progress slowly thereafter into adult life. On the basis of scatter plot results, we put these areas into three groups: Group A, which included the motor cortex, the auditory cortex, and the visual cortex, myelinated faster than Group B, which included Broca's area, Wernicke's area, and the angular gyrus before 1.5 years old; Group C, consisting of the arcuate fasciculus, has similar degree of myelination as Group B before 1.5 years but then myelinated more slowly after 3 years of age. No gender or left-right differences between homologous regions were found. CONCLUSIONS: In this study, we determined the sequence of myelination of language-correlated regions in infants and children by quantitative MRI assessment. The higher cortical areas matured later than the primary cortical areas, and the arcuate fasciculus matured last. The observation that myelination reaches maturity after 18 months suggests that myelination may be a reason for the acceleration in vocabulary acquisition observed in children from that age. The slow pace of myelination also suggested the possibility of language development's continuation into early adult life. Myelination assessed by MRI was at least 1 month behind that assessed by histological staining. No gender or left-right hemisphere differences in myelination were noted.

Early myelination patterns in the central auditory pathway of the higher brain: MRI evaluation study.

OBJECTIVE: The purpose of this study was to use magnetic resonance imaging (MRI) to investigate the early myelination patterns of the central auditory pathway and then compare the data with past histological research. We observe the MRI signal intensity of the central auditory pathway and clarify the time course difference between MRI and previous histological research studies. METHODS: A total of 192 infants ranging in age from -4 to 224 corrected postnatal weeks were included in the study. Images were obtained using a 1.5 T MR unit. We chose three sites (medial geniculate body, auditory radiation, and splenium of the corpus callosum) of the central auditory pathway for analysis. Three cross sections were obtained perpendicular to the long axis of the brain and used to analyze the signal changes of the T1- and T2-weighted MRI by employing a region-of-interest (ROI) methodology that was corrected for postnatal age. RESULTS: At 10 corrected postnatal weeks, the medial geniculate body showed myelinated intensity changes on T2-weighted images. Auditory radiation showed myelinated intensity changes at 19 corrected postnatal weeks on the T1-weighted images and at 24 corrected postnatal weeks on the T2-weighted images. The splenium of the corpus callosum showed myelinated intensity changes at 16 corrected postnatal weeks on T1-weighted images and at 24 corrected postnatal weeks on T2-weighted images. CONCLUSIONS: As compared to the histological literature, the MRI documented signal intensity changes caused by myelination occurred approximately 3 weeks later for the medial geniculate body, 7-24 weeks later for the auditory radiation and 7-15 weeks later for the splenium of the corpus callosum. Since myelination is a process that occurs gradually, substantial changes of the myelin sheath makeup, a loss of water and the addition of lipids are more required in order to be detectable by MRI than myelin staining of histological study.

Hearing profile and MRI myelination of auditory pathway in Pelizaeus-Merzbacher disease.

CONCLUSIONS: This study showed that delayed auditory pathway myelination is common in Pelizaeus-Merzbacher disease (PMD), but this delay does not necessarily indicate poor hearing function. OBJECTIVE: PMD is a rare recessively inherited X-linked leukodystrophy characterized by defective central nervous system myelination owing to a mutation in the proteolipid protein gene (PLP). The aims of this study were to evaluate the hearing function and auditory brain response (ABR) findings of patients with PMD and relate these findings to MRI-assessed myelination in the central auditory pathway. PATIENTS AND METHODS: We retrospectively studied eight male pediatric patients with PMD. Serial auditory examinations included audiometry, behavior audiometry, distortion product otoacoustic emission (DPOAE), and ABR. MRI-assessed myelination in the auditory pathway was evaluated in the PMD patients and in 23 normal young children as a control group. RESULTS: Audiometry showed normal to moderate hearing impairment and the hearing threshold improved with age and became almost normal over time. DPOAEs positivity and only ABR wave I or waves I and II were found in all the patients. MRI showed delayed myelination in all the patients and the auditory pathway was myelinated up to the inferior colliculus in four cases and up to the medial geniculate body in four cases. Serial MRIs showed no progression in myelination. No clear relation was found between hearing threshold and MRI-assessed myelination in the auditory pathway.

Temporal bone pathological study on maxillary sinus carcinoma with bilateral temporal bone metastasis.

We report a case in which metastasis occurred from a left-side maxillary carcinoma to bilateral temporal bones through different routes, manifested by rapidly progressing left-side mixed hearing loss, left-side vestibular dysfunction, and serous otitis media. Later the left-side hearing threshold became severely elevated, suggesting profound sensory hearing loss. Histopathology of the temporal bones revealed that the side with the lesion was severely damaged by tumor through direct and hematogenous metastasis. On the contralateral side, it showed four findings: (i) sparse and separate tumor invasion of the petrous bone, the mastoid cavity, and the facial canal (hematogenous spread); (ii) tumor involvement in the lower part of the cochlear aqueduct without invasion of the internal acoustic canal or cochlea, implying early meningeal carcinomatosis; (iii) vascular stria atrophy, spiral ganglion diminution, and well preserved hair cells; and (iv) diffuse effusion in the middle ear and mastoid cavity. Our observations revealed that tumor cells dispersed to the same side through different routes, whereas early metastasis to the contralateral side was mainly through hematogenous and subarachnoid spread.

Early myelination patterns in the brainstem auditory nuclei and pathway: MRI evaluation study.

OBJECTIVE: The purpose of this study is to investigate the early myelination patterns of brainstem auditory nuclei and pathway on magnetic resonance imaging compared with past histological research. We aimed to identify the time course difference in myelination of the brainstem auditory nuclei and pathway between magnetic resonance imaging and histological research results. METHODS: Subjects were 192 infants ranging in age from -4 to 224 corrected postnatal weeks. Images were obtained using a 1.5 T magnetic resonance unit. In four sites (cochlear nucleus, superior olivary nucleus, lateral lemniscus, inferior colliculus) of the brainstem auditory nuclei and pathway on four cross-sections obtained perpendicular to the long axis of the brainstem, signal changes of T1- and T2-weighted magnetic resonance images were analyzed using a region-of-interest methodology according to corrected postnatal age. RESULTS: The cochlear nucleus and superior olivary nucleus showed myelinated intensity change from -3 to 13 corrected postnatal weeks on T2-weighted images. The lateral lemniscus showed myelinated intensity change from -3 to 8 corrected postnatal weeks on T1-weighted images and from -1 to 13 corrected postnatal weeks on T2-weighted images. The inferior colliculus showed myelinated intensity change from -2 to 39 corrected postnatal weeks on T2-weighted images. CONCLUSIONS: Magnetic resonance imaging revealed the signal intensity change by myelination 11-18 weeks later than those reported in the histological literature. This time lag suggests that apart from histological research, the necessity for the milestones of auditory pathway maturation using MRI is suggested to evaluate the development of brainstem auditory pathway using MRI. This result suggests that myelination does not take place suddenly but happens gradually, so definite myelination, namely the complete change of myelin sheath ingredients, loss of water, and gain of lipids, is needed to be detected by magnetic resonance imaging.

Tuberculous meningitis-induced unilateral sensorineural hearing loss: a temporal bone study.

The relationship between meningitis and sensorineural hearing loss (SNHL) has long been studied. Many histopathological studies of animal models and human temporal bones with respect to bacterial meningitis have been carried out. However, the relationship between SNHL and tuberculous meningitis was seldom addressed and the pathophysiology remains unclear. We carried out temporal bone studies on material from a 22-year-old patient who developed a right unilateral SNHL before dying from tuberculous meningitis. The histopathological findings for the right temporal bone were as follows: (1) inflammation mainly appeared in the internal auditory canal, modiolus and Rosenthal's canal and extended to the osseous spiral ligament, whereas the perilymphatic spaces were less involved; (2) the organ of Corti, cochlear nerve fibres and spiral ganglion cells were severely degenerated, particularly in the basal and middle turns; (3) the contralateral side (for which the patient had no complaints) showed an inner space free from inflammation, but some granulomatous formations were observed in the middle ear cavity. We conclude that the modiolus and cochlear aqueduct are the main routes for the spread of infection from the meninges to the inner ear. The progression of hearing loss resembles that of bacterial meningitis and shares attributes of retrocochlear SNHL.