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PubMed2006

Extended, one-stage callosal section for treatment of refractory secondarily generalized epilepsy in patients with Lennox-Gastaut and Lennox-like syndromes.

PURPOSE: We report on the efficacy and safety of extended one-stage callosal section performed in a large and homogeneous series of patients. METHODS: Seventy-six patients with Lennox-Gastaut (n = 28) and Lennox-like (n = 48) syndrome were studied (42 male patients; mean age, 11.2 years). All patients had multiple seizure types per day, including atonic, tonic-clonic, atypical absence, myoclonic, and tonic seizures. All of them were developmentally impaired. The EEG showed intense secondary bilateral synchrony in all of them. All patients were submitted to an extended, one-stage, callosal section, leaving only the splenium intact. Mean follow-up time was 4.7 years. RESULTS: Worthwhile improvement (>50%) was noted in 69 of 76 patients; 52 patients had a > or =90% reduction in seizure frequency. Seven patients were seizure free after surgery. The seizure patterns most responsive to surgery were atonic (92%), atypical absence (82%), and tonic-clonic (57%) seizures. All patients had some degree of a transient acute postoperative disconnection syndrome. A consistent increase in attention level was observed postoperatively. CONCLUSIONS: We report one of the larger homogeneous series of patients submitted to callosotomy and are the first to report on the effectiveness and safety of performing extended callosal section in a single stage in this patient group. Extended callosal section should be considered a good palliative surgical option for suitable candidates. The increase in attention level was as useful as seizure control in improving quality of life of these patients.

Attention↗
PubMed2006

Relevance of callosal and periventricular MRI lesions to oligoclonal bands in multiple sclerosis.

OBJECTIVES: To evaluate the association between callosal or periventricular lesions, and the presence of oligoclonal IgG bands (OB) or the IgG index in Japanese patients with multiple sclerosis (MS). MATERIALS AND METHODS: Brain magnetic resonance imaging (MRI) was studied in 34 Japanese clinically definite MS cases. Sagittal 2-mm fast fluid-attenuated inversion-recovery (FLAIR) imaging was added to the routine MRI studies. RESULTS: Among the 34 patients, 20 (59%) were OB positive. Among the 20 patients with OB-positive MS, 17 (85%) had callosal lesions, although only two (14%) of 14 OB-negative MS patients had callosal lesions. The periventricular lesion area was significantly larger in the OB-positive patients compared with the OB-negative patients. CONCLUSIONS: The present study clearly demonstrated a strong association between the periventricular lesions and OB in Japanese MS. Certain OB-related immune mechanisms may contribute to the development of callosal and periventricular lesions in MS. OB may be an important factor to understand the pathomechanisms of MS lesions.

Adult↗
PubMed2001

The callosal dilemma: explaining diaschisis in the context of hemispheric rivalry via a neural network model.

It is often suggested that a major factor in diaschisis is the loss of transcallosal excitation to the intact hemisphere from the lesioned one. However, there is long-standing disagreement in the broader experimental literature about whether transcallosal interhemispheric influences in the human brain are primarily excitatory or inhibitory. Some experimental data are apparently better explained by assuming inhibitory callosal influences. Past neural network models attempting to explore this issue have encountered the same dilemma: in intact models, inhibitory callosal influences best explain strong cerebral lateralization like that occurring with language, but in lesioned models, excitatory callosal influences best explain experimentally observed hemispheric activation patterns following brain damage. We have now developed a single neural network model that can account for both types of data, i.e., both diaschisis and strong hemisphere specialization in the normal brain, by combining excitatory callosal influences with subcortical cross-midline inhibitory interactions. The results suggest that subcortical competitive processes may be a more important factor in cerebral specialization than is generally recognized.

Brain Injuries↗
PubMed2005

Investigating the functional role of callosal connections with dynamic causal models.

The anatomy of the corpus callosum has been described in considerable detail. Tracing studies in animals and human postmortem experiments are currently complemented by diffusion-weighted imaging, which enables noninvasive investigations of callosal connectivity to be conducted. In contrast to the wealth of anatomical data, little is known about the principles by which interhemispheric integration is mediated by callosal connections. Most importantly, we lack insights into the mechanisms that determine the functional role of callosal connections in a context-dependent fashion. These mechanisms can now be disclosed by models of effective connectivity that explain neuroimaging data from paradigms that manipulate interhemispheric interactions. In this article, we demonstrate that dynamic causal modeling (DCM), in conjunction with Bayesian model selection (BMS), is a powerful approach to disentangling the various factors that determine the functional role of callosal connections. We first review the theoretical foundations of DCM and BMS before demonstrating the application of these techniques to empirical data from a single subject.

Algorithms↗
PubMed1993

Callosal disconnection in multiple sclerosis.

A patient with MS demonstrated a striking callosal disconnection syndrome. MRI revealed callosal atrophy and extensive bilateral white matter changes. Of 15 comparison patients with clinically definite MS, only one had minimal callosal disconnection. Callosal disconnection in MS may be due to pathology of the corpus callosum as well as extensive white matter disease.

Adult↗
PubMed2004

Cingulotomy for psychiatric disease: microelectrode guidance, a callosal reference system for documenting lesion location, and clinical results.

OBJECTIVE: To evaluate magnetic resonance imaging (MRI)- and microelectrode recording-guided cingulotomy for patients with psychiatric disorders and to develop a new method of mapping lesion location in anterior cingulate cortex that takes into account the significant interindividual variability in callosal morphometry. METHODS: MRI and microelectrode recording were used to guide placement of radiofrequency lesions in patients with obsessive-compulsive disorder (n = 21) or affective disorders (n = 5). Postoperative improvement was evaluated with the Yale-Brown Obsessive-Compulsive Scale in 15 of the 21 obsessive-compulsive disorder patients studied. From the postoperative MRI scans, we developed a coordinate system for position in the anterior cingulate cortex. The callosal line passes from the most anterior point of the corpus callosum (c = 0) to the most posterior (c = 100). We reconstructed the lesions onto a sagittal map from the Talairach and Tournoux atlas using the distance along the callosal line and the distance above the upper surface of the corpus callosum. RESULTS: The location of neuronal activity distinguished gray and white matter and was useful in delineating the upper and lower cortical banks of the cingulate gyrus, the cingulate bundle, and the corpus callosum. This information was used to place the lesions. Lesions typically were 6 to 8 mm in diameter on T2-weighted MRI scans. The inferior margins were along the corpus callosum from c = 16 to c = 38. Four of 15 patients with obsessive-compulsive disorder had a documented decrease of more than 35% on the Yale-Brown Obsessive-Compulsive Scale, but only one patient had a sustained benefit for more than 1 year. CONCLUSION: Microelectrode recording is useful for lesion placement. Our system for reporting location in anterior cingulate cortex normalizes for differences in callosal morphometry. These techniques may aid future study.

Adult↗
PubMed2005

Laterality of motor control revisited: directionality of callosal traffic and its rehabilitative implications.

Based on evidence derived from personal data and a comprehensive review of the literature, this article provides a perspective of laterality of motor control in humans. The evidence supports existence of directionality in callosal traffic, codified in handedness. However, it is the neural handedness that definitively reveals the directionality of signal traffic between the executive and the minor hemisphere; the minor hemisphere is devoted to the affairs occurring on or toward the nondominant side of the body. Thus, moving the nondominant side of the body (and sensing from it) are bi-hemispherical events that require callosal participation. Time-resolved data are provided that indicate the absence of any ipsilateral corticospinal tract innervation in humans. The rehabilitative aspects of the new circuitry (i.e., one-way callosal traffic scheme) is reviewed, establishing that previously described plasticity or reorganization of cortical structure was a reflection of the newly described anatomy underpinning handedness. The distinction between neural and behavioral handedness is emphasized, suggesting simple and robust ways to establish a person's handedness without resorting to invasive and inconclusive tests currently in vogue. In the past, lack of knowledge of directionality in callosal traffic has resulted in surgical removal of healthy hemispheres (including the major hemisphere) in futile attempts to stop epilepsy in those with an intractable condition. Evidence is provided for lack of any motor communication from the minor to the major hemisphere, which makes the minor hemisphere incapable of initiating and propagating seizures.

Brain Mapping↗
PubMed1992

[MR imaging of corpus callosal injuries].

The MR imaging and CT findings of corpus callosal injury were analyzed in 32 of 224 patients with acute head injuries. MR imaging was more sensitive than CT in the detection of callosal injuries. All 9 hemorrhagic lesions were visualized on both MR imaging and CT. Fifteen of 23 nonhemorrhagic lesions were not visualized on CT, although all nonhemorrhagic lesions were visualized on MR imaging. Twenty-four lesions of the corpus callosum were located in the splenium, but no lesion was located in the rostrum. Diffuse axonal shear injuries were visualized in 25 patients with callosal injury as associated traumatic lesions. Twenty-three patients with callosal injury had low initial Glasgow Coma Scale scores (less than 9), but 9 patients had high scores. Associated diffuse axonal shear injuries, especially in the brain stem could be a possible explanation for this difference. MR imaging is useful to detect traumatic lesions of the corpus callosum.

Accidents, Traffic↗
PubMed1990

[The ultrastructural characteristics of the pyramidal callosal neurons of layer III in the primary auditory area (A1) of the cat cortex].

An electron microscope study of retrogradely labelled pyramidal neurons in layer III of the primary auditory cortex (AI) after HRP injections into the contralateral AI has been carried out in cats. From 4 to 10 synapses were usually revealed on somatic profiles of these callosal neurons. Synapses occupied 20.0% of the somatic surface of these neurons. All of the revealed synapses on the somata of callosal neurons had symmetric contacts and were formed by axon terminals with small elongated synaptic vesicles. Average length of these synaptic contacts was 1.6 microns. In layer III anterogradely labelled terminals of callosal fibres were also revealed. The majority of them contained large round synaptic vesicles and formed asymmetric contacts on spines. Three labelled axon terminals with small elongated vesicles were found to form symmetric axo-somatic synapses on callosal neurons of layer III.

Animals↗
PubMed1991

[Ultrastructural characteristics of callosal neurons in deep layers of the primary auditory cortex (AI) in cat].

An electron microscope study of retrogradely labelled nonpyramidal neurons has been carried out in layers V-VI of the primary auditory cortex (AI) after HRP injections into the contralateral AI of cats. From 2 to 9 synapses were usually revealed on somatic profiles of these callosal neurons. Synapses occupied 15.8 +/- 1.7% (on the average) of the somatic surface of these neurons. All of the revealed synapses on the somata of these callosal neurons had symmetric contacts and were formed by axon terminals with small elongated synaptic vesicles. An average length of these synaptic contacts in sections was 1.6 +/- 0.1 mm. HRP-labelled axon terminals of callosal fibres in layers V-VI contained round synaptic vesicles and formed asymmetric synapses on spines and dendrites. Possible functional significance of axo-somatic synapses in formation of impulsation patterns of the callosal neurons is discussed.

Animals↗
PubMed1991

Absence of population cerebral asymmetries in mice with callosal defects induced by prenatal gamma irradiation.

The development of the corpus callosum of 19 male Swiss mice was disturbed by exposure to a 60Co gamma source on embryonic day 16 with a total dose of 2 Gy (dose rate of 56 to 59 rads/min). At adulthood the animals were perfused with saline followed by formaldehyde and the cerebral hemispheres were weighed and photographed in dorsal, lateral and medial views. Brain asymmetries were evaluated by measurements of hemisphere weight, as well as dorsal and lateral areas. From the measurements of the midsagittal callosal areas, performed on the medial views, 2 subgroups could be identified: one with a small callosal remnant (N = 9) and another with a non-measurable callosal area (N = 10). In spite of a pronounced individual asymmetry, the irradiated mice (N = 19) did not show a populational asymmetry toward any side. A slight tendency favoring the left hemisphere was found in the small remnant subgroup. These results are consistent with our previous data for a strain of mice in which some animals present callosal defects. We conclude that the present data support the hypothesis that the corpus callosum may play a role in directing morphological hemispheric asymmetries.

Abnormalities, Radiation-Induced↗
PubMed1982

[Associative and callosal stellate neurons in the parietal area of the cat cerebral cortex].

After horseradish peroxidase has been injected into the cat parietal area, in the ipsilateral visual and limbic cortical areas, as well as in the contralateral parietal area long axonal associative and callosal stellate neural cells are revealed. Their bodies are round or oval, 18-25 mcm in size. In the associative neurons--they are always labelled better than the callosal ones--radial arrangement with nearly an equal distance between each other is specific for the dendrites, while in the callosal neurons they are grouped polarly. The associative stellate cells are situated in the layer II and in the upper part of the layer III of the visual and limbic cortex at the side where the enzyme is injected, and the callosal ones--in the lower part of the layer III and in the layer IV of the homotypical portions of the contralateral parietal cortex area. The main difference between the neurons detected is a various length of the axon. In the cortico-cortical ipsilateral neurons the axons are nearly 3--4 times shorter than those in the commissural stellate cells. Hence, the neuronal category described is present not only in the projection cortical zones, as it has been stated previously, but in the associative areas, as well.

Animals↗
PubMed1980

[Lipoma of corpus callosum with callosal agenesis (author's transl)].

Intracranial lipoma is rare. The case reported here was a woman aged 60. She came to our hospital with complaint of headache. Neurological examination was negative. Plain craniogram showed abnormal calcification in the callosal region. A-P view of right carotid angiogram revealed winding sinous course of bilateral anterior cerebral arteries around the calcific deposit. Lateral view showed vertical stretching of ascending portion of the anterior cerebral artery. In the frontal projection of the pneumogram, the lateral ventricles were separated and concave medially with hornlike superior angles. The third ventricle extended upward between the lateral ventricles. The plain CT scan revealed an abnormal low density area (Hounsfield's number-90- -50) in the callosal region. The calcific deposit was seen within a low density area. At operation, the callosal tumor was partially removed. Histologically, lipomatous tissue was demonstrated. In reference to literature, we discussed the roentgenographic findings, especially computed tomography of callosal lipoma.

Agenesis of Corpus Callosum↗
PubMed1995

Holoprosencephaly: an analysis of callosal formation and its relation to development of the interhemispheric fissure.

PURPOSE: To correlate the degree of hemispheric fusion in holoprosencephaly with degree of callosal formation, with degree of thalamic and basal ganglia fusion, and with presence or absence of dorsal cyst. METHODS: MR, CT, and ultrasonography from 19 patients with holoprosencephaly was retrospectively reviewed. The imaging studies were graded according to extent of the hemispheric fusion, thalamic fusion, corpus striatum fusion, callosal formation, and the presence or absence of a dorsal cyst. These factors were statistically correlated with each other using Kendall rank correlation coefficient. RESULTS: There were significant correlations between hemispheric fusion and failure of corpus callosum formation, presence of dorsal cyst and failure of corpus callosum formation, and hemispheric fusion and presence of dorsal cyst. Additional correlations were noted between thalamic fusion and corpus striatum fusion. CONCLUSIONS: Our results suggest that the presence of an interhemispheric fissure is necessary for callosal formation, and the presence of a dorsal cyst may interfere with callosal formation in holoprosencephaly.

Agenesis of Corpus Callosum↗
PubMed1995

Tumours of the callosal area: problems and surgical strategies.

Tumours of the callosal area are quite common. However, those primarily located in this region which remain confined within the corpus callosum area not frequent. The introduction of intraoperative location devices, coupled with preoperative MR, CT and angiography, has further enhanced the operability of lesions of the deep area around the callosal body. On the basis of their site of origin, three groups of tumours can be identified: tumours originating from the corpus callosum (defined as properly callosal); tumours secondarily invading the corpus callosum; tumours affecting the corpus callosum because of their surgical approach. Various routes have been developed to reach the callosal area, the site and direction of growth of the tumour providing indications for the preferred approach. The commonest routes are the following: interhemispheric approach; transcerebral approach; transcallosal approach; the transcallosal approach to the ventricles offers a valuable corridor in the management of intraventricular tumours. It provides a rapid and safe access, without the attendant epilepsy that often follows the transcortical approach. The neuro-psychological effect of callosotomy are minimal and not affecting the daily activities of patients. Thus it is possible to reach remote regions through a narrow entry with very low neuro-psychological impact.

Brain Neoplasms↗
PubMed2000

Preliminary investigation of debridement of plantar callosities in rheumatoid arthritis.

OBJECTIVE: To determine the effect of expert debridement of foot callosities on forefoot pain and plantar pressure distribution in rheumatoid arthritis (RA). METHODS: Plantar callosities on 14 feet of eight RA patients were debrided by a single podiatrist. Measurements of subjective pain severity in the forefoot and global arthritis pain were undertaken using a visual analogue scale, repeated at 7-day intervals to the next treatment (28 days). Plantar pressures were recorded at the lesion sites using an in-shoe flexible transducer insole before and after lesion debridement. RESULTS: Following debridement, all patients reported symptomatic relief with an average change in pain score of 48% (P = 0.01) but the treatment effect was lost by 7 days. Immediately following scalpel debridement, peak pressures were elevated in 10 of 14 feet, whilst contact time was reduced and peak force increased. None, however, reached statistical significance. CONCLUSION: Scalpel debridement of forefoot plantar callosities reduces forefoot pain for about 7 days, but pressure distribution is not significantly altered.

Aged↗
PubMed1998

Chevron osteotomy of lesser metatarsals for intractable plantar callosities.

We performed distal chevron osteotomy of the second, third, or fourth metatarsal for painful plantar callosities in 19 non-rheumatoid patients (16 women, 3 men; 21 feet); their mean age was 59 years (32 to 85). The mean follow-up was four years (2 to 7). The overall results were good in 16 feet, fair in two, and poor in three, with four patients still having painful plantar callosities. There was union in all feet, but transfer metatarsalgia developed in three and three required an orthosis. Distal chevron osteotomy for intractable plantar callosities was successful both clinically and radiologically in most patients.

Activities of Daily Living↗
PubMed2003

Callosal neglect.

BACKGROUND: According to the interhemispheric inhibition model of neglect, the uninjured hemisphere inhibits (via the corpus callosum) the injured hemisphere but the injured hemisphere can no longer inhibit the opposite hemisphere, which becomes hyperactive and produces an ipsilesional attentional bias. Alternatively, according to the compensation hypothesis, the uninjured hemisphere helps compensate for the damaged hemisphere, which is impaired in directing attention to contralateral stimuli. If the inhibition model of neglect is correct, callosal disconnection should reduce neglect. If the compensation model is correct, however, it may increase or induce neglect. PATIENT: A 32-year-old woman, at age 14 years, developed a right frontal astrocytoma and was treated with surgery and radiation but had a cardiopulmonary arrest secondary to aspiration. Subsequent imaging studies revealed damage to the frontal, parietal, and occipital regions of the right hemisphere and damage to the temporal region of the left hemisphere. After discharge, she was able to return to school and drive a car, without any evidence of neglect. About 10 years later, she developed complex partial and atonic seizures that were multifocal and medically intractable. She underwent a complete section of her corpus callosum at age 31 years. RESULTS: One year after the callosal section, she demonstrated (1) diminished spontaneous saccades to the left, hypometric leftward saccades, and left gaze impersistence; (2) left arm hemispatial limb akinesia; (3) unilateral spatial neglect; and (4) motor and cognitive impersistence. CONCLUSION: In patients with right hemisphere injury, callosal section may induce or enhance motor-intentional deficits and hemispatial neglect.

Adult↗