Yasuhiro Nishida

MRI measurements of normal extraocular muscles and other orbital structures.

Abstract Background: Studies of extraocular muscle (EOM) by magnetic resonance imaging (MRI) need to be extended to normal subjects of different ages to obtain data on the muscle thickness, cross-sectional area, and the volume of EOM and other orbital tissues. Methods: Forty-two orbits of 21 normal subjects in three age groups with an age range of 19–70 years were examined with surface-coil MRI. The transverse and sagittal images were used to measure the thickness of the four rectus muscles during fixation in different gaze positions. The coronal images with eyes in the primary position were used to calculate the cross-sectional areas. The volumes of all six EOM, orbital fatty tissue, the optic nerve and the eyeball were measured in the coronal plane and in either the transverse or the sagittal plane. Results: The horizontal muscles were thinner than vertical muscles. Muscle volume was larger in SR (superior rectus) than in IR (inferior rectus), larger in SO (superior oblique) than in IO (inferior oblique), and the same in LR (lateral rectus) as in MR (medial rectus). No significant differences were found in the values of the cross-sectional area in any image plane between the three age groups. There were no significant differences in muscle thickness and size and fatty tissue volume between age groups. The muscle thickness was linearly correlated to the angle of the eye deviation for all four rectus muscles, both in the ”on” and ”off” directions of the muscles. Conclusions: The study provides quantitative data, in normal subjects of different ages, on the thickness and size of EOM and the volume of other orbital tissues by MRI, to serve as a basis for further studies on the morphological changes of EOM in various orbital diseases.

Stereopsis-processing regions in the human parieto-occipital cortex.

We performed fMRI on the human parieto-occipital cortex in order to identify the neural processing regions of stereopsis. Visual stimulation for stereopsis was performed with a random-dot stereogram displayed in the image guides of a new binocular visual stimulation device that we developed. Interestingly, regions from the dorsal portion of the occipital lobe to the superior parietal lobule were activated by binocular disparity, while the inferior parietal lobule was not activated. Moreover, these regions were shown as dominant in the right hemisphere. Functional brain mapping revealed that the processing regions of stereopsis were dorsally located in parieto-occipital cortex, and that the superior parietal lobule is an important region for neural processing of human stereopsis.

Magnetic resonance imaging measurements of extraocular muscle path shift and posterior eyeball prolapse from the muscle cone in acquired esotropia with high myopia

PURPOSE To investigate extraocular muscle (EOM) path shift and prolapse of posterior eyeball from muscle cone in acquired esotropia with high myopia (AEHM), using magnetic resonance imaging. DESIGN A case-control study. METHODS There were 16 eyes with AEHM, 11 with high myopia (HM), 12 with moderate myopia (MM), and 11 control eyes. Extraocular muscle shift was evaluated by measuring angles formed by the line connecting orbital centroids and the line connecting each orbital centroid and each EOM centroid. The ratio of the prolapse in the posterior eyeball from the muscle cone was also measured. RESULTS Both inferior shift of lateral rectus (LR) and nasal shift of superior rectus (SR) muscle were observed in the AEHM group, compared with HM, MM, and control groups. Neither shifted significantly in the HM group compared with control group. The prolapse ratio in AEHM group was higher than in the HM, MM, and control groups. Greater EOM shifts and eyeball prolapse were observed when the AEHM was more severe, as in esotropia fixus. CONCLUSIONS In AEHM, a prolapsing eyeball shifts LR inferiorly and SR nasally; these findings were not observed in high myopia with neither ocular deviation nor restriction. These shifts reduce abduction and supraduction and increase infraduction and adduction in AEHM. The shifts would be predicted to create a hypoesodeviation, which is a common finding in AEHM. Both EOM shifts and superotemporal eyeball prolapse tend to be greater in esotropia fixus.

Novel missense mutations in red/green opsin genes in congenital color-vision deficiencies

The DNAs from 217 Japanese males with congenital red/green color-vision deficiencies were analyzed. Twenty-three subjects had the normal genotype of a single red gene, followed by a green gene. Four of the 23 were from the 69 protan subject group and 19 of the 23 were from the 148 deutan subject group. Three of the 23 subjects had missense mutations. The mutation Asn94Lys (AAC-->AAA) occurred in the single green gene of a deutan subject (A155). The Arg330Gln (CGA-->CAA) mutation was detected in both green genes of another deutan subject (A164). The Gly338Glu (GGG-->GAG) mutation occurred in the single red gene of a protan subject (A89). Both normal and mutant opsins were expressed in cultured COS-7 cells and visual pigments were regenerated with 11-cis-retinal. The normal red and green opsins showed absorbance spectra with lambda(max) of 560 and 530 nm, respectively, but the three mutant opsins had altered spectra. The mutations in Asn94Lys and Gly338Glu resulted in no absorbance and the Arg330Gln mutation gave a low absorbance spectrum with a lambda(max) of 530 nm. Therefore these three mutant opsins are likely to be affected in the folding process, resulting in a loss of function as a visual pigment.

An A−71C substitution in a green gene at the second position in the red/green visual-pigment gene array is associated with deutan color-vision deficiency

We studied 247 Japanese males with congenital deutan color-vision deficiency and found that 37 subjects (15.0%) had a normal genotype of a single red gene followed by a green gene(s). Two of them had missense mutations in the green gene(s), but the other 35 subjects had no mutations in either the exons or their flanking introns. However, 32 of the 35 subjects, including all 8 subjects with pigment-color defect, a special category of deuteranomaly, had a nucleotide substitution, A−71C, in the promoter of a green gene at the second position in the red/green visual-pigment gene array. Although the −71C substitution was also present in color-normal Japanese males at a frequency of 24.3%, it was never at the second position but always found further downstream. The substitution was found in 19.4% of Chinese males and 7.7% of Thai males but rarely in Caucasians or African Americans. These results suggest that the A−71C substitution in the green gene at the second position is closely associated with deutan color-vision deficiency. In Japanese and presumably other Asian populations further downstream genes with −71C comprise a reservoir of the visual-pigment genes that cause deutan color-vision deficiency by unequal crossing over between the intergenic regions.

Magnetic resonance spectroscopic determination of a neuronal and axonal marker in white matter predicts reversibility of deficits in secondary normal pressure hydrocephalus

Background: Normal pressure hydrocephalus (NPH) is considered to be a treatable form of dementia, because cerebrospinal fluid (CSF) shunting can lessen symptoms. However, neuroimaging has failed to predict when shunting will be effective. Objective: To investigate whether 1H (proton) magnetic resonance (MR) spectroscopy could predict functional outcome in patients after shunting. Methods: Neurological state including Hasegawa’s dementia scale, gait, continence, and the modified Rankin scale were evaluated in 21 patients with secondary NPH who underwent ventriculo-peritoneal shunting. Outcomes were measured postoperatively at one and 12 months and were classified as excellent, fair, or poor. MR spectra were obtained from left hemispheric white matter. Results: Significant preoperative differences in N-acetyl aspartate (NAA)/creatine (Cr) and NAA/choline (Cho) were noted between patients with excellent and poor outcome at one month (p = 0.0014 and 0.0036, respectively). Multiple regression analysis linked higher preoperative NAA/Cr ratio, gait score, and modified Rankin scale to better one month outcome. Predictive value, sensitivity, and specificity for excellent outcome following shunting were 95.2%, 100%, and 87.5%. Multiple regression analysis indicated that NAA/Cho had the best predictive value for one year outcome (p = 0.0032); predictive value, sensitivity, and specificity were 89.5%, 90.0%, and 88.9%. Conclusions: MR spectroscopy predicted long term post-shunting outcomes in patients with secondary NPH, and it would be a useful assessment tool before lumbar drainage.

Cortical representation of hearing restoration in patients with sudden deafness

To characterize brain activity in response to auditory stimuli during recovery from acute hearing loss, fMRI was performed at two time points in 11 patients with sudden deafness in the right ear, and 10 subjects with normal hearing. In the acute phase, right-ear auditory stimulation induced only a small response in the auditory cortex, limited to the left hemisphere. In the recovery phase, the auditory response was more extensive than in the acute phase. Stimulation of the left ear induced a more extensive response in the left than right hemisphere in both acute and recovery phases, which differed from the pattern in normal subjects. The changes in cortical activation patterns were seen within 1 week of sudden deafness. Thus, alteration of cortical response in deafness occurs earlier than suggested by previous reports.

A Muscle Transposition Procedure for Abducens Palsy, in Which the Halves of the Vertical Rectus Muscle Bellies Are Sutured Onto the Sclera

PURPOSE To review the results of a muscle transposition procedure in which the halves of the vertical rectus muscle bellies are sutured onto the sclera, without tenotomy of vertical recti as in Hummelsheims procedure or surgical treatment of the lateral rectus (LR) as in Jensens procedure. METHODS Ten patients with abducens palsy received the procedure. We measured the ocular deviation and the field of single binocular vision, and observed the LR using magnetic resonance imaging (MRI). RESULTS Preoperative or postoperative deviation was distributed from +27 to +58 prism diopters (PD) or orthophoria to +12 PD, respectively, in 7 patients with unilateral paresis, and +75 to +120 PD or +2 to +37 PD in 3 patients with bilateral paresis. The average correction was 42.4 PD per eye. Seven patients were able to regain the field of single binocular vision at least in the primary position. No postoperative complications were observed. MRI showed that the LR was atrophic and floppy, lacking muscle tension. CONCLUSIONS Our procedure enabled the patients to obtain satisfactory postoperative results without treatment of the LR or tenotomy of the transposed muscles. This procedure can reduce operative damage to the eye more than Hummelsheims or Jensens procedure.

A case of extraocular muscle swelling due to IgG4-related sclerosing disease.

A novel clinicopathological entity of IgG4-related sclerosing disease has recently been proposed that is characterized by infiltration of IgG4-positive plasma cells and T lymphocytes with fibrosis into various organs [1]. Mikulicz disease, characterized by symmetric bilateral swelling of the lacrimal and salivary glands, is considered a subtype of IgG4-related sclerosing disease [2]. We report a case of concurrent extraocular muscle swelling and Mikulicz disease.

Common neural processing regions for dynamic and static stereopsis in human parieto-occipital cortices.

We performed functional magnetic resonance imaging to identify the neural processing regions in the parieto-occipital cortices for human dynamic and static stereopsis. The subjects were ten ophthalmologists professionally trained to do microscopic surgery. Visual stimuli for dynamic or static stereopsis were performed with solid stereograms displayed in the image guides of a binocular visual stimulation device that we developed. The dorsal occipital portion and the superior parietal lobule (i.e. dorsal parieto-occipital portion) were activated not only in static stereopsis, but also in dynamic stereopsis. The activation showed a right hemispherical dominancy. On the other hand, the temporo-occipital junction (i.e. human MT (middle temporal area) / MST (medial superior temporal area) complex) was activated in dynamic stereopsis. This demonstrates that the dorsal parieto-occipital portion is a common neural processing region for dynamic and static stereopsis.