Behcet's disease: presentation with sagittal sinus thrombosis diagnosed noninvasively.

The standard evaluation of patients with intracranial hypertension frequently does not reveal a discrete pathophysiologic process, leading in these cases to classification of the syndrome as "benign." We present a 35-year-old woman with a recent diagnosis of pseudotumor cerebri who presented with headache, emesis, and blurring of vision. Her symptoms were progressive despite two lumbar punctures that revealed normal cerebrospinal fluid under high pressure. Contrast and noncontrast CT scans were normal; both the cerebrospinal fluid and CT neuroimaging were thus consistent with benign intracranial hypertension. An MRI, however, supported the presence of sagittal sinus thrombosis, a finding which was confirmed by MR venography. Further workup for an underlying cause of sinus thrombosis disclosed symptoms and signs fulfilling the diagnostic criteria for Behcet's disease. Cerebral venous (or sinus) thrombosis should be considered in the differential diagnosis of intracranial hypertension. Behcet's disease, while extremely rare, should be considered as a potential cause of cerebral venous thrombosis. Magnetic resonance venography can serve as a useful diagnostic study in situations where confirmation or exclusion of sinus thrombosis is required.

Effect of stimulation in three subcortical sites on the thalamocortical augmenting response in the cat.

The thalamocortical augmenting response is a complex multineuronal response which can be elicited by repetitive stimulation of the ventrolateral thalamus. A major function of the ventrolateral thalamus is known to be a result of its participation in central nervous system activity related to motor behaviour. The significance of the thalamocortical augmenting response itself is not known. Since it would be reasonable to relate that response to motor behaviour, we evaluated the effect on the thalamocortical augmenting response of the stimulation of two other central nervous system structures which are also thought to participate in motor control, the cerebellum and the red nucleus. We conclude that at least part of the effect of red nucleus stimulation on the thalamocortical augmenting response is exerted through a rubro-olivo-cerebellar pathway. We then compared the effects of red nucleus and of cerebellar stimulation to the effect of stimulating a non-motor mesencephalic site, the periaqueductal gray. The changes induced in the thalamocortical augmenting response appear not to be fully explicable solely in terms of changes in motor behaviour.

Observations on the effect of morphine on thalamocortical excitability in the cat.

The acute effects of morphine on the thalamocortical augmenting response in the cat were evaluated. The thalamocortical augmenting response was elicited by delivering pairs of pulses to the ventrolateral thalamus and recording from ipsilateral sensorimotor cortex. A biphasic, dose-related, naloxone-attenuable effect on the augmenting response elicited by pulse pairs was observed. Although the clinical significance of those morphine-induced changes is currently uncertain, they can be correlated with the convulsant and anticonvulsant effects of different doses of morphine.

Preparation and stability of animal feed mixtures dosed with rotenone.

Studies at Midwest Research Institute for the National Toxicology Program show that rotenone/animal feed mixtures prepared by dry-mixing are more stable than mixtures produced by dosing the feed with alcoholic solutions of rotenone and then stripping the solvent. Also, recoveries of rotenone from the dry mix feeds are higher than those from feeds dosed by the solution method. A simplified analytical method from one previously reported for rotenone in feed is described.

Development of the thalamocortical augmenting response in the kitten.

Study of the developing central nervous system can lead to better understanding of the mature central nervous system. The thalamocortical augmenting response is a complex neurophysiological response considered to be related to the occurrence of some forms of epileptic activity. Using a paradigm previously developed in adult cats, we assessed the development of the thalamocortical augmenting response in kittens and found that the relative proportion of thalamocortical activity occurring at high frequencies of thalamic stimulation increased with increasing age. Anticonvulsants effective against petit mal seizures also increase the relative proportion of thalamocortical activity following high frequencies of thalamic stimulation. Developmental changes in the thalamocortical augmenting response can be related to the age-dependent decreases in the prevalence of petit mal seizures.

Effect of hyperthermia on a thalamocortical system in the kitten and the cat: a preliminary study.

Hyperthermia produces many changes in the ongoing electrical activity of the brain. One of the responses which fever can induce is seizure activity. The thalamocortical augmenting response, a complex neurophysiological response, has been related to seizure discharges. The changes in that complex neurophysiological response induced by experimental hyperthermia were assessed in adult cats and in kittens, using analytical methodology first developed in adult cats. The effect of two anticonvulsants (phenytoin and valproate) on those hyperthermia-induced changes in the thalamocortical augmenting response were compared in kittens. The differences between the effects of the two anticonvulsants on the thalamocortical augmenting response can be related to the reported clinical differences between the two anticonvulsants in patients with febrile seizures.

Offensive Lineman's Thumb.

In brief: An unusual blocking technique caused dislocation of the metacarpophalangeal joints of the thumbs of both a college and a high school football offensive lineman. They were attempting to use their thumbs for additional leverage in obtaining a better mechanical advantage over their opponents. As the rule stands this may be a legal technique, but the authors advise a rule change or clarification to discourage its use.

Cerebellar stimulation: regional effects on a thalamocortical system.

Regional effects of electrical stimulation of the cerebellar surface were quantitatively analyzed. Computer controlled stimulus sequences were delivered to ventrolateral thalamus and evoked responses recorded from ipsilateral sensorimotor cortex in the cat. Threshold and excitability profiles were produced with an on-line computer, and their modification by cerebellar stimulation was determined. The results of electrical stimulation of the cerebellar surface were: (1) depressed excitability from paramedian lobule and lobulus simplex; (2) uniquely elevated thresholds from paramedian lobule; and (3) a profound and long-lasting depression of excitability following termination of lobulus simplex stimulation. In comparison with our anticonvulsant drug studies, these data suggest that cerebellar surface stimulation has a far greater capacity to control excitability and threshold responsiveness of thalamocortical systems. Cerebellar electrode placement and temporal pattern of stimulation appear to be important factors in the production of antiepileptic effects.

Effects of valproate and ethosuximide on thalamocortical excitability.

Sodium valproate and ethosuximide are anticonvulsants employed in the treatment of petit mal epilepsy; both drugs are considered to be thalamically active. Valproate and ethosuximide both decreased the average evoked response following the second of two stimuli delivered to the ventrolateral thalamus at stimulus frequencies in the region of 3 Hz. Ethosuximide, but not valproate, enhanced the average evoked response at high stimulus frequencies an action shared with several convulsant treatments having different modes of action. The clinical effects of valproate and ethosuximide can be related to this differential modulation of thalamocortical excitability.

Cerebral complications of angiography for transient ischemia and stroke: prediction of risk.

We examined the records of 147 consecutive patients studied by femoral catheterization to identify factors contributing to angiographic risk in cerebrovascular disease. Cerebral complications occurred in 12.2 percent and were permanent in 5.2 percent. Computer-assisted multivariate analysis of 21 possible risk factors was done. Two of these risk factors correlated strongly with increased risk: number of previous transient ischemic attacks (TIAs) (p less than 0.001), and the presence of arterial stenosis of greater than 90 percent (p less than 0.03). Risk factors of marginal significance were: diabetes, female sex, and number of selective injections. A discriminant function for estimation of risk was derived: D = [8 X number of TIAs] + [6 x number of arteries catheterized] + [14 if diabetic, 0 if not] + [11 if female, 0 if male]. When D was greater than 55, 77 percent of patients had a complication. When D was less than 55, 98 percent of patients had no complication. Unfortunately, patients in whom the study is most indicated tend to be those at greatest risk.

Effects of antiepileptic drugs on thalamocortical excitability.

Comparative effects of anticonvulsant drugs on the thalamocortical system were analyzed quantitatively. Paired stimuli were delivered to the ventrolateral thalamus with evoked responses recorded from the ipsilateral sensorimotor cortex in the cat. Threshold and excitability profiles were developed with an on-line computer. Effects of phenytoin and diazepam were generally similar, with depression of excitability and slight elevation of thresholds. Ethosuximide produced a pronounced pair-interval dependent effect of unchanged or increased excitability and lowered threshold at shorter intervals, with depressed excitability and raised threshold at longer intervals. These data demonstrate a marked difference in effect of the petit mal and grand mal agents tested and suggest a basis for the effectiveness of ethosuximide in controlling 3-per-second repetitive activity.

Ethosuximide and bicuculline inhibition in petit mal epilepsy.

The mechanisms of petit mal epilepsy remain a mystery despite successful therapy. Previous workers have proposed that paroxysmal activity of cortical inhibitory systems plays a role in absence seizures. In this study, we have compared the effects of bicuculline, a potent convulsive agent and GABA antagonist, with ethosuximide, a drug used to treat petit mal epilepsy, on the thalamocortical motor system of the cat. Under chloralose anesthesia, sequential pairs of pulses were delivered to ventrolateral thalamus (VL) varying either pulse amplitude or interval. The evoked responses were recorded from sensorimotor cortex, analyzed on-line by computer, and plotted as an excitability curve (mean response amplitude as a function of pulse interval), or a family of threshold curves (mean response amplitude as a function of stimulus amplitude at various fixed intervals). Administration of each drug resulted in increased thalamocortical excitability and decreased threshold to stimulation for short pulse-pair intervals, with diminished duration of the excitability curve. Increased alertness was produced by both drugs. Studies with grand mal anticonvulsants demonstrated entirely different effects. Because GABA is thought to be the primary inhibitory transmitter in VL and cerebral cortex, bicuculline would be expected to result in disinhibition. The similarity of the data for ethosuximide suggests that ethosuximide also suppresses inhibition in the thalamocortical motor system and adds further to the accumulating evidence of the role of inhibitory system in petit mal epilepsy.

Stabilization of the thalamocortical motor system by cerebellar stimulation.

Epilepsy typifies instability in a complex control system. We have previously identified parameters of the thalamocortical motor system of the cat which correlate with epileptiform activity and are controlled by common anticonvulsants. This study is concerned with the control of such parameters by cerebellar stimulation, potencially promoting stability within the motor system. Under computer control, stimuli were delivered to both ventrolateral thalamus and cerebellar cortex, with multichannel recording of evoked responses obtained from sensorimotor cortex. Cortical evoked responses were plotted as an excitability curve (mean response amplitude as a function of pulse interval) or a family of threshold curves (mean response amplitude as a function of stimulus amplitude at various fixed intervals). The present study reveals that cerebellar epidural stimulation can reduce both the height and duration of the excitability curve, as well as increase the response threshold and reduce the saturation level of the threshold curve. The degree and direction of these parameter changes are dependent on the frequency, polarity, and amplitude of cerebellar stimulation, with the amount of parameter change exceeding that achieved by monotoxic doses of anticonvulsants. These data suggest that control of parameters related to excitability and threshold in the thalamocortical motor system may be the means by which cerebellar stimulation accomplishes control of clinical seizures.

Associated systemic factors in cerebrovascular ischemia.

Systemic disorders (eg, cardiac, hematologic) are commonly recognized as predisposing and sometimes actual precipitating events in cerebral ischemia. From available studies, the incidence of precipitation is not clear. To determine this, we undertook a comprehensive investigation of all patients with ischemic brain disease for a one-year period. Results reveal that brain ischemia is more commonly precipitated by systemic illness than usually supposed, particularly transient ischemic attacks of the vertebrobasilar circulation and completed infarcts in the carotid distribution. Cardiac disorders outnumber all other precipitating events. As they are more amenable to therapy than atherosclerosis, a diligent search for such precipitating events is warranted in patients with ischemic symptoms.