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PubMed1982

[Effects of callosal bi-section on temporal cortical seizure and postictal refractory period in kindled cats].

Effects of midline bi-section including corpus callosum and hippocampal commissure on the kindled generalized convulsion and postictal refractory period (PRP) were examined in temporal cortical kindled cats. Time latency for re-appearance of generalized convulsion after the initial generalized convulsion was designated as a PRP arbitrarily in this experiment. Six repeated electrical stimulation at afterdischarge threshold intensity with one hour interval was performed, and EEG was recorded during PRP test session. Following results were obtained: 1) Kindled generalized convulsion in the split brain cats was characterized by asymmetrical or hemi-convulsion with lateralized afterdischarge in the stimulated hemisphere, 2) EEG silence and monorhythmic 2.5-3 cps high voltage slow activity in the split brain cats did not differ, rather prolonged than the control group in duration, but such postictal EEG changes were lateralized only in the stimulated hemisphere. Behavioral suppression was reduced markedly by midline bi-section, as compared with intact control, 3) In the PRP session of the split brain cats, the initially induced hemi-convulsion appeared with lateralized active afterdischarge lasting for 76.8 sec in the stimulated hemisphere. It was followed by the postictal EEG change as mentioned above in the stimulated hemisphere. In spite of such full-blown ictal events in the stimulated hemisphere, PRP was shorter (within 2 hrs) in the split brain cats than the control cats (more than 4 hrs). It is concluded that midline bi-section including corpus callosum and hippocampal commissure not only modify the pattern and duration of kindled generalized convulsion, but markedly reduce a seizure intensity reflected by shortening of postictal behavioral suppression and PRP.

Animals↗
PubMed1993

[A case of diagnostic dyspraxia without ideomotor apraxia by callosal lesion].

A case of diagnostic dyspraxia was reported. A 57-year-old right handed male had been suffering from the lack of cooperation between his right and left hands for six months. Except for decreased deep tendon reflexes in all extremities, there were no abnormal findings on neurological examination. On neuropsychological examination, he was attentive, well orientated and his spontaneous speech, comprehension, naming, repetition and reading were intact. There was peculiar dissociative behavior between his right and left hands. For instance, he put a cigarette or coin in the pocket with his right hand then his left hand took out and replaced them, and he buttoned his shirts with his right hand but then unbuttoned with his left hand. These left hand oppositional behavior to his right hand were triggered by voluntary activities of his right hand. Left unilateral agraphia was also revealed but ideomotor apraxia, compulsive manipulation of tools and grasp reflex were not demonstrated. T1-weighted MRI demonstrated irregular low signal intensity areas extending from the genu to the body of the corpus callosum. No definite lesion was detected in the medial aspect of the frontal lobe. Only small numbers of diagnostic dyspraxia have been reported and such cases without ideomotor apraxia or medial frontal lesion are even rare. MRI is very useful for detecting the lesion of the corpus callosum.

Apraxias↗
PubMed1997

[Letter-by-letter alexia after left hemispheral lesion without hemianopsia nor callosal involvement. 2 cases].

We describe two patients suffering from a letter-by-letter reading following an infarct in the left posterior cerebral artery's territory. Unlike most of the verbal alexics, this strategy was particularly fast and effective. Two other features distinguished these patients from verbal alexics: the absence of hemianopia and the sparing of the corpus callosum. A study of the reading of letters and words by each hemisphere was performed. In the first case, the left hemisphere was unable to identify any letter or word. The visual stimuli did not activate the visual word form, not the system which normally recognize letters. However, this latter could be activated by the information transmitted by the right hemisphere via the corpus callosum. In the second case, the left hemisphere could, as well as the right one, identify all the letters. On the other hand, identification of words was impaired, and did not improve when the duration of the visual presentation increased. The left hemisphere, unable to access to the visual word form, could not decipher letter-by-letter. One hypothesis is that the left visual working memory was reduced, and could not store more than one letter. The right hemisphere deciphered the words sequentially, and transmitted the information to the left systems which recognize the letter. These two observations confirm that letter-by-letter alexia could result exclusively from the destruction, of the inaccessibility of the visual word-form. A lesion of the left ventral occipito-temporal structures is sufficient, and a left hemianopia, or a splenial lesion is not absolutely necessary. The sparing of the corpus callosum allows a fast transmission to the left phonological processing, if the left systems recognizing letters are efficient.

Aged↗
PubMed1998

[A case of spastic paraparesis with mental deterioration and markedly thin corpus callosum--callosal dysfunction demonstrated by magnetic stimulation].

We have studied function of the corpus callosum in a patient with spastic paraparesis with mental deterioration and markedly thin corpus callosum using magnetic stimulation methods. In a 21-year-old woman with slowly progressive gait disturbance, neurological examination showed mental deterioration, euphoria, spastic paraparesis, bilateral Babinski's sign, and hyperesthesia caudal to the eighth thoracic level. No abnormalities were observed in electroencephalograms. Magnetic resonance imaging (MRI) studies of the brain showed cerebral cortical atrophy, markedly thin corpus callosum, and dilated cavum septum pellucidum and cavum Vergae, but spinal cord MRIs showed no abnormalities. The lysosomal enzyme activities, whose reduction was known to cause leukodystrophy, were all normal. Very long chain fatty acid was not increased in her blood, which is against adrenoleukodystrophy. She had no anti-HTLV-1 virus antibody. Based on these clinical features and the results of biochemical analyses, we diagnosed this patient as having spastic paraplegia associated with hypoplasia of the corpus callosum (Nojima and Iwabuchi). We performed three studies on the central motor pathways in this patient. The latencies of responses recorded from upper or lower limb muscles were all within the normal range, despite that the thresholds were slightly increased. This suggests that axonal degeneration occurs in the central motor pathways, which is consistent with the autopsy findings of a patient with hereditary spastic paraplegia associated with hypoplasia of the corpus callosum. Connection between the bilateral motor cortices was investigated by magnetic stimulation of both motor cortices. The suppression of the motor cortex evoked by stimulation of the contralateral motor cortex through the corpus callosum was absent in this patient. Intracortical inhibition within the motor cortex was demonstrated to be normal by a paired-magnetic stimulation technique. Based on the results of these results of these two experiments, we conclude that the function of the corpus callosum was disturbed in the present patient. This report first shows the functional abnormality of the extremely thin corpus callosum in a patient with hereditary spastic paraplegia associated with hypoplasia of the corpus callosum.

Adult↗