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PubMed1986

Corpus callosum and limbic system: neuroanatomic MR evaluation of developmental anomalies.

Agenesis of the corpus callosum is a complex malformation of the brain that has been associated with varying degrees of limbic system maldevelopment. We retrospectively reviewed the records of 11 patients with callosal agenesis (seven total, four partial) who underwent magnetic resonance (MR) imaging, with particular attention to the associated malformations of the limbic system. Comparison was made with selected images from MR examinations of healthy volunteers and with necropsy specimens from other patients with callosal agenesis. Ten of 11 patients demonstrated limbic anomalies (severe motion artifact precluded evaluation of these structures in one patient). MR depicted not only the abnormalities intrinsic to callosal agenesis but also the frequently associated malformations of the limbic system.

Agenesis of Corpus Callosum↗
PubMed1991

Abnormal corpus callosum: a sensitive and specific indicator of multiple sclerosis.

The authors investigated whether identification of corpus callosal (CC) involvement might increase the specificity of magnetic resonance (MR) imaging in differentiating multiple sclerosis (MS) from other periventricular white matter diseases (PWDs). They prospectively evaluated 42 patients with MS and 127 control patients with other PWDs. Ninety-three percent of the MS patients demonstrated confluent and/or focal lesions involving the callosal-septal interface (CSI). These lesions characteristically involved the inferior aspect of the callosum and radiated from the ventricular surface into the overlying callosum. CSI lesions were optimally demonstrated on sagittal long repetition time (TR)/short echo time (TE) images and frequently (45% of cases) went undetected on axial images. Only 2.4% of the control patients had lesions of the CC. The authors conclude that midsagittal long TR/short TE images are highly sensitive and specific for MS and that callosal involvement in MS is more common than previously reported.

Adult↗
PubMed1996

Agenesis of the corpus callosum: prenatal detection usually is not possible before 22 weeks of gestation.

PURPOSE: To determine whether agenesis of the corpus callosum can be diagnosed prenatally with standard ultrasonographic (US) evaluation before 22 weeks of gestation. MATERIALS AND METHODS: Initial scans obtained on or before 22 weeks and follow-up scans obtained in the third trimester were selected from all cases of agenesis of the corpus callosum diagnosed prenatally at the authors' laboratory. Follow-up was attained by means of review of the medical records and included imaging, karyotype, and clinical outcome. RESULTS: Among 15 fetuses with callosal agenesis confirmed by means of third-trimester scans, 10 had completely normal US scans at 16-22 weeks and five had other US abnormalities. Isolated callosal agenesis was identified in six children with normal development (except one with polydactyly). Among the others, four were developmentally delayed, three died, and two others had abnormal karyotype. CONCLUSION: Standard second-trimester US before 22 weeks of gestation may not show isolated callosal agenesis. Fetuses with this abnormality can have normal second-trimester scans and develop abnormal US findings in the third trimester.

Agenesis of Corpus Callosum↗
PubMed2003

The role of the corpus callosum in the coupling of bimanual isometric force pulses.

Two split-brain patients, a patient with callosal agenesis, and 6 age-matched control participants were tested on a bimanual force production task. The participants produced isometric responses with their index fingers, attempting to match the target force specified by a visual stimulus. On unimanual trials, the stimuli were presented in either the left or right visual field and the response was made with the ipsilateral hand. On bimanual trials, two stimuli were presented, one on each side, and the target forces could be either identical or different. Bimanual responses of the control subjects showed strong evidence of coupling. Forces produced by one hand were influenced by the forces produced by the other hand with positive correlations observed for all target force combinations. These assimilation effects and correlations were greatly attenuated in the acallosal group, with similar results observed for the split-brain patients and participant with callosal agenesis. Furthermore, the processes involved in selecting and planning the two responses occurred independently in the acallosal group; in contrast to the controls, the three acallosal participants exhibited no differences in reaction times or accuracy between bimanual trials in which the two target forces were the same or different. We also found a striking temporal desynchronization of the responses in the split-brain patients, indicating that in this context, temporal coupling is impaired after callosotomy. These results are congruent with the hypothesis that interference related to response selection and planning of bimanual force pulses arises from callosal interactions.

Analysis of Variance↗
PubMed1986

Interocular transfer of adaptation after effect in neurons of area 17 and 18 of split chiasm cats.

Responses to sinusoidal gratings for neurons in area 17 and 18 of split chiasm cats were recorded extracellularly, and the interocular transfer of the effect of adaptation to high-contrast gratings was studied. In area 17 all but one of the simple cells showed the phenomenon of adaptation and its interocular transfer; 60% of the complex cells showed the effect of adaptation, and of these cells 35% showed an interocular transfer of adaptation. The adaptation aftereffect was comparable both in strength and duration for the direct and the callosal pathway. The strength of the adaptation aftereffect through the callosal pathway was not related to the strength of the input from the contralateral eye. An interocular transfer of the adaptation aftereffect was found in several neurons with a very weak input from the contralateral eye and in five simple cells apparently responding only to the ipsilateral eye. Fifty-eight percent of the neurons in area 18 showed the effect of adaptation, and 55% of them showed interocular transfer. No interocular transfer of the adaptation aftereffect was found in those neurons where an input from the contralateral eye was undetectable. Interocular transfer of the adaptation was found in all the neurons recorded in area 17 of animals with section of the corpus callosum but intact chiasm. No interocular transfer was found in neurons recorded in area 17 of cats with both the optic chiasm and the corpus callosum sectioned. We conclude that callosal connections are sufficient for the transfer of the adaptation aftereffect, although they are not necessary.

Adaptation, Ocular↗
PubMed1999

Visual stimulus-dependent changes in interhemispheric EEG coherence in humans.

We analyzed the coherence of electroencephalographic (EEG) signals recorded symmetrically from the two hemispheres, while subjects (n = 9) were viewing visual stimuli. Considering the many common features of the callosal connectivity in mammals, we expected that, as in our animal studies, interhemispheric coherence (ICoh) would increase only with bilateral iso-oriented gratings located close to the vertical meridian of the visual field, or extending across it. Indeed, a single grating that extended across the vertical meridian significantly increased the EEG ICoh in normal adult subjects. These ICoh responses were obtained from occipital and parietal derivations and were restricted to the gamma frequency band. They were detectable with different EEG references and were robust across and within subjects. Other unilateral and bilateral stimuli, including identical gratings that were effective in anesthetized animals, did not affect ICoh in humans. This fact suggests the existence of regulatory influences, possibly of a top-down kind, on the pattern of callosal activation in conscious human subjects. In addition to establishing the validity of EEG coherence analysis for assaying cortico-cortical connectivity, this study extends to the human brain the finding that visual stimuli cause interhemispheric synchronization, particularly in frequencies of the gamma band. It also indicates that the synchronization is carried out by cortico-cortical connection and suggests similarities in the organization of visual callosal connections in animals and in man.

Adult↗
PubMed2000

Cross-species and intraspecies morphometric analysis of the corpus callosum.

A cross-species morphometric study of the corpus callosum was performed in the rat, rabbit, cat, dog, horse, cow and human. Across species, the results indicate a strong, although less than linear, dependency of callosal size on brain weight. This relation tends to lose significance within species. This is consistent with other morphometric studies indicating a tendency to decrease the correlations between morphometric variables in within-species analyses as compared to between-species analyses. There are species differences in the relative size of some callosal segments particularly in the posterior third, which is larger in frontally-looking species than in laterally-looking species. No sex differences in callosal size were detected in any of the species examined. These findings are discussed in the light of possible developmental and functional correlates of the variability observed.

Adult↗
PubMed1988

Disconnection syndrome in a right-handed patient with right hemispheric speech dominance.

The callosal disconnection syndrome is characterized by unilateral (left) tactile anomia, unilateral (left) agraphia and unilateral (left) ideomotor apraxia. We report on a right-handed patient, who developed a callosal disconnection syndrome due to the rupture of an anterior communicant aneurysm. As he had right hemisphere dominance for language and praxis, the signs described above were crossed. He also featured a left alien hand sign and motor aprosody. The authors believe this is the first case of callosal disconnection in a right-hander with crossed language and praxis functions.

Adult↗
PubMed1991

Aging of the human corpus callosum: magnetic resonance imaging in normal volunteers.

A brain magnetic resonance imaging (MRI) study of the corpus callosum in 36 normal volunteers, ages 26-79 years, revealed that age was positively correlated with the T1 spin-lattice relaxation time of the corpus callosum and was negatively correlated with the corpus callosum cross-sectional area. T1 relaxation times are sensitive to the content and macromolecular environment of tissue water, and variations in callosal T1 may reflect differences in the content or relaxation properties of callosal water. Such changes also potentially could occur secondary to alterations in the composition of callosal myelin. This study confirms and extends prior morphological studies that have reported age-related dimensional changes in the corpus callosum and, in addition, provides evidence of age-related biophysical tissue differences in the human corpus callosum.

Adult↗
PubMed2005

Clinical results of modified Mitchell's osteotomy for hallux valgus augmented with oblique lesser metatarsal osteotomy.

PURPOSE: To evaluate postoperative results of modified Mitchell's osteotomy and its combination with oblique metatarsal osteotomy for the treatment of hallux valgus. METHODS: A total of 93 feet of 53 patients (2 men and 51 women) with hallux valgus underwent modified Mitchell's osteotomy and were followed up for at least 5 years. Patients' age ranged from 17 to 83 years, and the duration of follow-up ranged from 5 years one month to 18 years 4 months. Modified Mitchell's osteotomy was performed on 53 feet in 31 patients (group A), whereas modified Mitchell's osteotomy augmented with oblique lesser metatarsal osteotomy was performed to the remaining 40 feet in 22 patients (group B). Postoperative results were assessed using a clinical assessment system developed by the Tokyo Medical University based on 5 categories: pain in the first metatarsophalangeal, deformity of the metatarsophalangeal, plantar callosity and/or metatarsalgia of lesser metatarsals, the use of commercially available shoes, and local inflammatory symptoms. RESULTS: Mean total score improved from 3.8 to 7.9 on a 10-point scale. Scores for 2 categories--plantar callosity and/or metatarsalgia and the use commercially available shoes--were significantly higher in group B at postoperative 5 years. Before surgery, at postoperative 3 weeks, and at postoperative 5 years, respectively, the mean hallux valgus angles were 34.2, 12.0, and 17.1 degrees; mean M1-M2 angles were 16.7, 7.4, and 8.7 degrees; mean M1-M5 angles were 34.9, 25.8, and 26.6 degrees; and mean sesamoid bone shifts were 8.7 mm, 4.3 mm, and 5.9 mm. CONCLUSION: Modified Mitchell's osteotomy shortens the length of the first metatarsal bone and thus relieves tension in soft tissues such as the adductor hallucis. Nonetheless, the procedure can induce metatarsophalangeal joint malalignment and metatarsalgia, and plantar callosity may develop or persist after surgery. Combining oblique metatarsal osteotomy of the lesser metatarsal bones is useful in patients with uneven metatarsal bone lengths and metatarsophalangeal joint malalignment.

Adolescent↗
PubMed2000

Differential effects of aging on the functions of the corpus callosum.

Several structural imaging studies have revealed atrophy in regions of the corpus callosum due to normal aging. We examined the performance of young and senior adults on 2 behavioral measures of interhemispheric interactions to test for possible functional consequences of callosal decline. In a simple reaction time task, the efficiency of sensorimotor transfer was assessed by comparing response times from conditions that required interhemispheric transfer (e.g., the left hand responding to a right visual field light) to those from conditions that did not require transfer (e.g., the left hand responding to a left visual field light). Older adults were selectively slower when interhemispheric transfer was required. In the second task, participants matched letters presented within the same visual field or in opposite visual fields. This task is thought to index attentional functions of the corpus callosum, in particular, callosal contributions to resource allocation (Banich, 1998). For more difficult tasks, older participants showed a performance advantage on bilateral conditions requiring transfer compared to unilateral conditions that did not require transfer. This advantage equaled or exceeded that observed in younger adults. Together these results suggest that age does not have uniform effects on callosal function. Whereas sensorimotor functions show age-related decline, attentional functions of the corpus callosum may be relatively preserved and assume a more prominent role in the aging brain.

Adolescent↗
PubMed2003

MRI findings in Susac's syndrome.

BACKGROUND: Susac syndrome (SS) is a self-limited syndrome, presumably autoimmune, consisting of a clinical triad of encephalopathy, branch retinal artery occlusions, and hearing loss. All three elements of the triad may not be present or recognized, and MR imaging is often necessary to establish the diagnosis. OBJECTIVE: To determine the spectrum of abnormalities on MRI in SS. METHODS: The authors reviewed the MR images of 27 previously unreported patients with the clinical SS triad, and 51 patients from published articles in which the MR images were depicted or reported. RESULTS: All 27 patients had multifocal supratentorial white matter lesions including the corpus callosum. The deep gray nuclei (basal ganglia and thalamus) were involved in 19 (70%). Nineteen (70%) also had parenchymal enhancement and 9 (33%) had leptomeningeal enhancement. Of the 51 cases from the literature, at least 32 had callosal lesions. The authors could not determine the presence of callosal lesions in 18 of these patients, and only one was reported to have a normal MRI at the onset of encephalopathy. CONCLUSIONS: The MR scans in SS show a rather distinctive pattern of supratentorial white matter lesions that always involve the corpus callosum. There is often deep gray matter, posterior fossa involvement, and frequent parenchymal with occasional leptomeningeal enhancement. The central callosal lesions differ from those in demyelinating disease, and should support the diagnosis of SS in patients with at least two of the three features of the clinical triad.

Adult↗
PubMed1992

Two alien hand syndromes.

Review of the clinical characteristics and neuroanatomy of 20 reported cases of alien hand syndrome (AHS) and a patient of our own confirm that AHS is actually two distinct syndromes. Frontal AHS occurs in the dominant hand; is associated with reflexive grasping, groping, and compulsive manipulation of tools; and results from damage to the supplementary motor area, anterior cingulate gyrus, and medial prefrontal cortex of the dominant hemisphere and anterior corpus callosum. Callosal AHS is characterized primarily by intermanual conflict and requires only an anterior callosal lesion. the occurrence of frontal AHS in the dominant limb can be explained by an increased tendency for dominant limb exploratory reflexes coupled with release from an asymmetrically distributed, predominant nondominant-hemisphere inhibition. Callosal AHS is best explained by hemispheric disconnection manifested during behaviors requiring dominant-hemisphere control.

Aged↗
PubMed1998

Brain size, head size, and intelligence quotient in monozygotic twins.

Many studies of monozygotic (MZ) twins have revealed evidence of genetic influences on intellectual functions and their derangement in certain neurologic and psychiatric diseases afflicting the forebrain. Relatively little is known about genetic influences on the size and shape of the human forebrain and its gross morphologic subdivisions. Using MRI and quantitative image analysis techniques, we examined neuroanatomic similarities in MZ twins and their relationship to head size and intelligence quotient (IQ). ANOVA were carried out using each measure as the dependent variable and genotype, birth order, and sex, separately, as between-subject factors. Pairwise correlations between measures were also computed. We found significant effects of genotype but not birth order for the following neuroanatomic measures: forebrain volume (raw, p < or = 0.0001; normalized by body weight, p = 0.0003); cortical surface area (raw, p = 0.002; normalized, p = 0.001); and callosal area (raw, p < or = 0.0001; normalized by forebrain volume, p = 0.02). We also found significant effects of genotype but not birth order for head circumference (raw, p = 0.0002; normalized, p < or = 0.0001) and full-scale IQ (p = 0.001). There were no significant sex effects except for raw head circumference (p = 0.03). Significant correlations were observed among forebrain volume, cortical surface area, and callosal area and between each brain measure and head circumference. There was no significant correlation between IQ and any brain measure or head circumference. These results indicate that: 1) forebrain volume, cortical surface area, and callosal area are similar in MZ twins; and 2) these brain measures are tightly correlated with one another and with head circumference but not with IQ in young, healthy adults.

Adult↗
PubMed2000

Long-term changes of hemodynamics and metabolism after carotid artery occlusion.

OBJECTIVE: To investigate whether in selected patients with internal carotid artery (ICA) occlusion and initially normal oxygen extraction fraction (OEF) measured with PET, subsequent changes of cerebral hemodynamics and metabolism occur during long-term follow-up and, if so, whether the changes are associated with atrophy of the corpus callosum or subsequent ischemic strokes. BACKGROUND: The course of the changes in cerebral hemodynamics and metabolism after ICA occlusion remain unclear. After ICA occlusion, an increase in OEF may increase the risk of cerebral ischemia, and an increase in cortical ischemia would cause progression of callosal atrophy. METHODS: The authors used PET and MRI to examine twice seven medically treated patients with unilateral ICA occlusion and initially normal OEF at intervals ranging from 24 to 64 (mean +/- SD, 42 +/- 17) months. No intervening ischemic attacks occurred between the two examinations. RESULTS: In the hemisphere with ICA occlusion, OEF increased and blood flow decreased during follow-up. At the follow-up evaluation, abnormally increased OEF values were found in three patients, in whom ipsilateral ischemic strokes occurred during subsequent follow-up (18 +/- 6 months). A decrease in oxygen metabolism also occurred and was significantly correlated with the decrease of callosal size. CONCLUSIONS: These preliminary findings in a small, selected patient sample suggest that in patients with ICA occlusion and initially normal OEF, deteriorations of cerebral hemodynamics and metabolism during long-term follow-up may be associated with callosal atrophy or subsequent ischemic strokes.

Aged↗
PubMed1995

Transcallosal removal of lesions affecting the third ventricle: an anatomic and clinical study.

A series of 54 patients with lesions affecting the third ventricle with a wide range of pathology were operated on by the transcallosal approach. Hydrocephalus was present in 68.5% of all patients, and preoperative shunting was performed in 73.0% of them. Before the partial callosotomy, 16 patients were studied by the use of a cognitive, affective, and behavioral battery, which was repeated 10 and 100 days after the operation. No physiological consequences were ever observed after the partial commissurotomy. The postoperative callosal defect was verified by magnetic resonance imaging. Furthermore, 40 formalin-fixed brains were sectioned to study the variations of the anterior cerebral arteries. On the other hand, magnetic resonance imaging measurements of the corpus callosum in 40 normal subjects were performed to establish a classification system for the corpus callosal area. The results showed a wide variability of the cross-sectional area of the corpus callosum. The differences in the thickness of the truncus were responsible for this variability; the length of the corpus callosum was uniform. This may suggest that subjects with a large corpus callosum may have more interhemispheric connections with higher specialization of each hemisphere and that a smaller number of callosal connections may correlate with more ipsilateral pathways and more independent hemispheres. The results and the clinical as well as anatomical material indicate that the anterior transcallosal route is a safe and feasible alternative in the management of a wide spectrum of pathological lesions within the third ventricle and deserves preference over the transcortical technique.

Adult↗
PubMed2006

Diffusion tensor imaging of frontal white matter and executive functioning in cocaine-exposed children.

BACKGROUND: Although animal studies have demonstrated frontal white matter and behavioral changes resulting from prenatal cocaine exposure, no human studies have associated neuropsychological deficits in attention and inhibition with brain structure. We used diffusion tensor imaging to investigate frontal white matter integrity and executive functioning in cocaine-exposed children. METHODS: Six direction diffusion tensor images were acquired using a Siemens 3T scanner with a spin-echo echo-planar imaging pulse sequence on right-handed cocaine-exposed (n = 28) and sociodemographically similar non-exposed children (n = 25; mean age: 10.6 years) drawn from a prospective, longitudinal study. Average diffusion and fractional anisotropy were measured in the left and right frontal callosal and frontal projection fibers. Executive functioning was assessed using two well-validated neuropsychological tests (Stroop color-word test and Trail Making Test). RESULTS: Cocaine-exposed children showed significantly higher average diffusion in the left frontal callosal and right frontal projection fibers. Cocaine-exposed children were also significantly slower on a visual-motor set-shifting task with a trend toward lower scores on a verbal inhibition task. Controlling for gender and intelligence, average diffusion in the left frontal callosal fibers was related to prenatal exposure to alcohol and marijuana and an interaction between cocaine and marijuana exposure. Performance on the visual-motor set-shifting task was related to prenatal cocaine exposure and an interaction between cocaine and tobacco exposure. Significant correlations were found between test performance and fractional anisotropy in areas of the frontal white matter. CONCLUSIONS: Prenatal cocaine exposure, alone and in combination with exposure to other drugs, is associated with slightly poorer executive functioning and subtle microstructural changes suggesting less mature development of frontal white matter pathways. The relative contribution of postnatal environmental factors, including characteristics of the caregiving environment and stressors associated with poverty and out-of-home placement, on brain development and behavioral functioning in polydrug-exposed children awaits further research.

Child↗
PubMed1997

Evaluation of the impact of podiatrist care in the primary prevention of foot problems in diabetic subjects.

OBJECTIVE: To evaluate the influence of podiatrist activities on the outpatient care of diabetic patients in terms of knowledge of diabetic foot care, self-care, and minor foot problems. RESEARCH DESIGN AND METHODS: There were 733 patients, aged 10-79 years, identified from the national diabetes register. Patients without recent visits to a podiatrist and without an obvious need for foot care were randomized into a podiatric care group (education and primary prevention measures, n = 267) and a control group (written instructions only, n = 263). The patients were examined by an independent study podiatrist at baseline and after 1 year. RESULTS: Patients in the podiatrist group had greater improvement in knowledge of diabetic foot care (P = 0.004) and self-care (P < 0.001) scores compared with control subjects. The prevalence of callosities in regions other than the calcaneal region decreased more (P = 0.009) in the podiatrist group (from 54.5 to 39.5%) than in the control group (from 51.3 to 48.2%), and the size of the callosities decreased more (P < 0.001) in the podiatrist group than in the control group. Reduction in the prevalence of callosities was associated with younger age (< 50 years). CONCLUSIONS: Education and primary preventive measures provided individually by a podiatrist result in significant improvements in knowledge and foot self-care scores and in improvements in the prevalence of some minor foot problems. Long-term studies are needed to evaluate whether the intervention of podiatrists starting at an early phase would lead to a reduction in major foot problems.

Adolescent↗