Xanthogranulomas of the third ventricle.

Two patients with xanthogranuloma of the 3rd ventricle are described. In each instance the tumor obstructed the interventricular foramina and caused dilatation of the lateral ventricles and signs of increased intracranial pressure; computerized tomography demonstrated the dense, nonenhancing lesion in the anterior 3rd ventricle. The pathogenesis of these rare tumors is discussed. These cases affirm the need to consider xanthogranuloma in the differential diagnosis of anterior 3rd ventricle tumors in adults.

Corpus callosum and propagation of afterdischarge to contralateral cortex and thalamus.

The patterns of seizure spread were investigated in cats with experimental seizure foci in the motor cortex. Recordings were made with tungsten microelectrodes. When convulsive activity developed at the focus, there was activation of the ipsilateral thalamus before there was propagation of afterdischarge to the opposite hemisphere. Section of the corpus callosum did not prevent propagation of afterdischarge to the contralateral thalamus, and prolonged the circulation of abnormal activity between the cortex and ipsilateral and contralateral thalamus.

Cryptococcal infection of the central nervous system.

Two patients with cryptococcal infection of the central nervous system are described. The first presented with signs of an intracranial mass and was subsequently shown to have two lesions within the brain which were later identified as cryptococcal granulomata. Antifungal therapy did not eradicate the lesions; following their excision and continued therapy, the CSF became sterile however. The other patient had signs of a fulminant meningoencephalitis which initially were thought to represent the pathophysiological expression of an expanding brain tumor. These reports are used as a basis to review the various aspects of central nervous system cryptococcosis, particularly as they may relate to the neurosurgeon and the therapy of the disease.

Paroxysmal atrial tachycardia and frontal lobe tumor.

We describe a patient who experienced repeated episodes of paroxysmal atrial tachycardia. He was found to have an epileptogenic focus within the right frontal lobe adjacent to a frontal lobe glioma. Subsequent to excision of the tumor, no further attacks have occurred.

Malignant hyperthermia.

The authors report the case of an infant with noncommunicating hydrocephalus, Arnold-Chiari malformation, and a lumbar myelomeningocele, in whom malignant hyperthermia occurred. The genetics and presumed etiology of this unusual problem are reviewed. The management is directed toward establishing effective cooling measures, reversing tissue hypoxia, and correcting respiratory and metabolic acidosis.

Driving of slow oscillations in the human somatosensory system.

Potentials evoked by brief electrical pulses applied to the median nerve, were recorded from the frontal, central and vertex regions of human subjects. Averaging and spectral analysis showed that the responses contained time-locked components ranging in frequency from 0.75 to 4 c/sec and extending over periods as long as 3500 msec after the stimulus. There was no significant difference between evoked potentials induced by stimuli which were accompanied by a twitch in the muscles innervated by the median nerve and evoked potentials induced by stimuli which caused no muscular response. Stimulation by pulses separated by random intervals caused an increase in the amplitude of the late components over a broad frequency spectrum while periodic stimulation caused an increase in amplitude in much narrower ranges. When the frequency of stimulation was progressively increased from 0.25 to 5 pulses/sec it was found that the late oscillations could be "driven" at specific frequencies which caused an increase in the amplitudes of specific frequency components, harmonically related to each other and to the frequency of the stimulus. In a few instances in which a series of 125 individual evoked potentials was studied, it was found that the average computed from the last 50 potentials contained late components of considerably lower amplitudes than the average computed from the first 50 potentials. The administration of barbiturates caused a selective decrease in the amplitude of the late components and a redistribution of energy in the frequency spectrum. The essential characteristics of these late components: their wide distribution over the frontal, central and vertex regions, their occurrence over long periods after the stimulus, the decrease in their amplitude with repeated stimulation, indicating the possibility of "habituation", and their enhancement at specific frequencies of stimulation, suggest that they may be related to the activities of the nonspecific systems of the brain.

Aqueductal occlusion by midline arteriovenous malformation.

An adult presented with signs of chronic obstructive hydrocephalus. Angiography showed an arteriovenous malformation in the region of the posterior diencephalon and mesencephalon with venous drainage into the vein of Galen. Pneumoencephalography demonstrated obstruction of the aqueduct. This case affirms the need to consider the presence of an arteriovenous malformation in adults who present with signs of aqueductal stenosis.

Intraventricular craniopharyngioma.

An unusual case of an adult with a craniopharyngioma within the third ventricle is reported. The patient complained of headaches, had a history suggestive of diabetes insipidus, and presented with a severe dementia. A brain scan revealed the suprasellar midline lesion, and a pneumoencephalogram confirmed its location within the third ventricle. Therapy included partial surgical excision, followed by a ventriculoatrial shunt and radiation.