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Biomedical subjects

F W Sharbrough

Publications and source records attributed to F W Sharbrough.

At least 127 records · Page 7Linked to original sources
PubMed1984

Electroencephalographic abnormalities in interferon encephalopathy: a preliminary report.

Although several studies have shown that interferon does not readily cross the blood-brain barrier, recent reports have described central nervous system effects in patients receiving interferon. At our institution, we encountered three patients who had symptoms of toxicity of the central nervous system (somnolence, confusion, and gait difficulties) in association with electroencephalographic abnormalities while receiving alpha 2-interferon therapy for multiple myeloma. The electroencephalogram showed diffuse slow-wave abnormalities in two of the patients and generalized sharp-wave discharges in the third patient. Because the use of interferon is increasing, physicians should be aware of the central nervous system complications and the electroencephalographic changes that can be associated with such therapy.

Aged↗
PubMed1984

EEG in cough syncope.

In 17 patients with cough syncope, electroencephalograms showed normal interictal recordings in 12 patients, minimally abnormal recordings in 4, and a moderately abnormal recording in 1. Fourteen episodes of cough syncope (six patients) were recorded, with the EEGs showing diffuse theta and delta slowing during the episodes. These findings were similar to those seen during other types of syncope. Although eight patients had rhythmic or clonic-like movements during the episodes, no epileptiform activity was seen. The exact mechanism of cough syncope is not known, but the vigorous coughing probably increases CSF pressure enough to impair intracranial circulation, causing syncope due to cerebral ischemia.

Adult↗
PubMed1983

Brainstem auditory evoked potentials in 20 patients with palatal myoclonus.

Brainstem auditory evoked potentials (BAEPs) were obtained in 20 patients with palatal myoclonus. The group included 14 men and six women whose ages ranged from 19 to 82 years. Six of the patients had abnormal BAEPs: two with severe head trauma and one each with a brainstem infarct, tumor, demyelination, and an indeterminate inflammatory process. The 14 patients with normal BAEPs had palatal myoclonus secondary to head trauma (five patients), brainstem infarcts (four patients), cerebellar tumors (two patients), degenerative processes (two patients), and an Arnold-Chiari malformation (one patient). Since the auditory pathways are separate from the structures associated with palatal myoclonus, it is possible to have discrete lesions producing palatal myoclonus with sparing of the auditory structures, whereas diffuse or multifocal lesions of the brainstem are more likely to be associated with abnormal BAEPs.

Adult↗
PubMed1983

Ictal tachycardia during temporal lobe seizures.

A seldom-recognized accompaniment of temporal lobe seizures is tachycardia. This phenomenon was observed in 12 consecutive patients in whom spontaneous seizures were recorded with simultaneous electroencephalographic, electrocardiographic, and videotape monitoring; this finding indicates with a 99% confidence level that this phenomenon may occur in at least 64% of temporal lobe seizures. The autonomic influences responsible for ictal tachycardia during temporal lobe seizures may be inconsequential in patients without cardiac disease but can have serious consequences in patients with cardiac disease.

Aged↗
PubMed1983

Oral glucose tolerance test compared with a mixed meal in the diagnosis of reactive hypoglycemia. A caveat on stimulation.

Reactive hypoglycemia is being diagnosed with increasing frequency. We compared plasma glucose, insulin, glucagon, epinephrine, and norepinephrine responses to an oral glucose tolerance test and to a mixed meal containing equivalent carbohydrate in 33 patients who had been referred to our institution with a presumed diagnosis of reactive hypoglycemia and in 2 patients who had insulinomas. In addition, a control group of 36 normal volunteers underwent the meal study. During the meal studies, electroencephalograms were obtained. Despite provocation of hypoglycemia by the oral glucose tolerance test, no consistent relationship between hypoglycemia and symptoms was observed. Despite similar symptoms, hypoglycemia did not develop after the meal test in the 33 patients without insulinomas. Both patients with insulinoma became hypoglycemic after ingestion of the meal. When a physiologic stimulus such as a meal is used to duplicate the daily dietary experience of patients, reactive hypoglycemia in the absence of a pancreatic pathologic lesion is an uncommon occurrence.

Adolescent↗
PubMed1982

Carotid occlusive disease. Effect of bright light on visual evoked response.

Four patients had severe carotid artery occlusive disease associated with ipsilateral visual blurring and exposure to bright light. Attenuation of the visual evoked response was noted after patients were exposed to an artificial source of light for 30 s. No significant abnormality of the visual evoked response was seen in the asymptomatic eyes or in the 16 eyes of eight control subjects, some of whom had carotid artery occlusive disease associated with ipsilateral venous stasis retinopathy. We concluded that ischemia of the macular region is necessary to produce these visual symptoms and that local retinal blood flow has been reduced to the flow threshold of electrical failure. These findings provide objective documentation of an abnormality that may be associated with an important symptom indicative of severe carotid artery occlusive disease.

Aged↗
PubMed1981

Correlation of brain blood flow, intracellular pH and metabolism in hypoglycemic cats under halothane and barbiturate anesthesia.

The neurophysiological alterations associated with transient insulin-induced hypoglycemia were compared in 14 cats anesthetized with halothane and 14 cats anesthetized with pentobarbital fasted for 18 h prior to the study. Each anesthetic group was further divided into acute and chronic preparations which in turn were prepared and studied in an identical manner except for the anesthetic agent employed. In the chronic animals there was no difference in survival between the two groups following a 2-h period of hypoglycemia. In these preparations there were no significant differences in: blood glucose levels, mean arterial blood pressure (MABP); arterial carbon dioxide tension (paCO2), arterial oxygen tensions (paO2), arterial pH (pHa), or acid-base balance during the period of hypoglycemia. Differences in the electroencephalograms were commensurate with the anesthetic used. In the acute preparations cerebral blood flow (CBF), xenon-133 clearance technique; brain pH, pH sensitive fluorescent indicator method; and cerebral metabolic rates of oxygen (CMRO2) and glucose consumption were determined at 15-min intervals in addition to the measurements recorded in the chronic group. During a 3-h period of regular insulin administration at a rate of 30 units/kg/h there were no significant differences in any of the systemic or brain measurements recorded except for CBF (halothane greater than barbiturate). EEGs in the acute group of animals paralleled the chronic group and improved but did not return to normal following glucose resuscitation at the end of the period of hypoglycemia. All the acute animals had a normal paCO2-CBF response curve prior to the insulin administration. CBF and brain pH remained constant during the period of hypoglycemia in both groups. However, following the administration of glucose there was a significant brain acidosis and EEG change without a change in CBF. We conclude that: the protective effects of barbiturates in states of hypoxemia or ischemia do not extend to hypoglycemia, brain pH and blood flow are not altered by moderate (as opposed to severe) hypoglycemia, and brain pH may not be the prime regulator in the CBF-metabolic blood flow couple.

Acid-Base Equilibrium↗
PubMed1981

Canine cerebral metabolic tolerance during 24 hours deep pentobarbital anesthesia.

The impact of tolerance on cerebral metabolism during prolonged pentobarbital-induced anesthesia was evaluated in 16 dogs. Cerebral metabolic rate for oxygen was calculated from direct measurements of venous blood flow rate and the difference in blood oxygen content between arterial and venous blood during four periods of continuous and unvarying deep pentobarbital anesthesia-0-3 hours, 3-6 hours, 12-15 hours, and 21-24 hours. During 0-3 h, the metabolic rate was 1.8-2.0 ml 02.100 g brain-1.min-1. This increased to 2.3-2.6 ml.100 g-1.min-1 during 3-6, 12-15, and 21-24 h. In all studies, the electroencephalogram indicated a constant deep burst-suppression level at 2-6 bursts/min, and blood pentobarbital levels were unchanged at 4.9-5.9 mg/dl throughout the entire period of anesthesia. The sustained increase in cerebral metabolism that occurred after 3 h and continued through 24 h of pentobarbital anesthesia is presumably due to tolerance. This was a phenomenon in which metabolism increased during steady deep anesthesia with unchanged blood levels of pentobarbital, rather than one in which greater blood levels were necessary to maintain the same level of anesthesia.

Animals↗
PubMed1981

Hypothermia plus thiopental: prolonged electroencephalographic suppression.

Duration of EEG suppression was compared to three groups of patients undergoing hypothermic cardiopulmonary bypass (CPB) at 25-30 degrees C under halothane-nitrous oxide anesthesia. Group I (n = 8) received three doses of thiopental (8 mg/kg i.v.): 1) for induction of anesthesia, 2) immediately after the institution of CPB, and 3) just after emergence from CPB. Group II (n = 5) received no thiopental. Group III (n = 4) received thiopental, 8 mg/kg administered intravenously, during CPB only. An unexpectedly prolonged duration of EEG suppression (26.1 min) was noticed in Group I patients with thiopental and hypothermia in combination, as compared with 4.8 min of suppression in Group II patients during hypothermic CPB without thiopental. To rule out a possible cumulative effect of thiopental administration, Group III patients were studied. With only a single dose of thiopental, administered during CPB, 29.3 min of EEG suppression was noticed. Mild cardiovascular depression occurred with thiopental administration during induction of anesthesia, whereas mild-to-moderate depression was associated with thiopental administration following emergence from CPB. It appears that thiopental and hypothermia, when administered in combination in modest doses during CPB, result in profound depression of cerebral electrical activity and presumably cerebral metabolism.

Adult↗
PubMed1981

A clinical and electrophysiological evaluation of myoclonus.

The records of 23 consecutive patients with myoclonus who were seen during a 16-month period were analyzed prospectively. The patients were divided into two groups: epileptic and nonepileptic. The epileptic patients had focal and stimulus-elicitable myoclonus with enlarged somatosensory evoked potentials and enhanced long-loop reflexes, and they responded well to anticonvulsants, especially clonazepam and valproic acid. The nonepileptic group had massive and spontaneous jerks with normal-sized somatosensory evoked potentials and long-loop reflexes, and they responded poorly to anticonvulsants. Evaluation of these clinical and electrophysiologic characteristics can help in the classification of obscure movement disorders and in predicting responses to therapy.

Adolescent↗
PubMed1980

Correlation of intracellular redox states and pH with blood flow in primary and secondary seizure foci.

Epileptogenic foci were created by topical application of penicillin to the cerebral cortex in 40 paralyzed and artificially ventilated cats receiving halothane anesthesia. The animals were divided into two equal groups to compare primary and secondary foci. The following variables were recorded at normocapnia, hypocapnia, and hypercapnia prior to and during seizure activity: cerebral blood flow (CBF), determined by clearance of xenon 133; cortical redox states, measured by the fluorescence of reduced pyridine nucleotides (PN); brain pH, measured using a lipid-soluble, pH-sensitive fluorescent indicator; and electroencephalograms (EEG). Mean arterial blood pressure, arterial pH, arterial carbon dioxide tension (PaCO2), and arterial oxygen tension (PaO2) were monitored in each animal. All animals had a normal PaCO2-CBF response prior to the creation of a seizure focus, assuring the presence of autoregulation and normal metabolic function. CBF increased equally with seizures in the primary and secondary hemispheres. The relative increase was related to the PaCO2 but approximated 68% at normocapnia. There was an alteration in the PaCO2-CBF response with seizures, but the ability of the cerebral vasculature to constrict and dilate with hypocapnia and hypercapnia was retained. There was no significant difference in the reduced PN signal with variations in PaCO2 prior to seizures, but there was an apparent 10 to 15% fall with seizures. The "equivalent" intracellular pH fell to 6.94 at normocapnia in the primary focus but remained essentially unchanged from the control value of 7.10 in the secondary focus. These differences in pH were consistent with the greater degree of seizure activity observed in the primary focus. We conclude that a nonhypoxic acidosis existed in the primary focus and that changes in CBF were not related to it because the CBF changed equally in both hemispheres.

Animals↗
PubMed1979

Stimulus-induced EEG complexes and motor spasms in subacute sclerosing panencephalitis.

Patients with subacute sclerosing panencephalitis (SSPE) typically present with spontaneous periodic, stereotyped electroencephalographic (EEG) complexes and motor spasms, which are not usually affected by sensory stimuli. This report describes two patients with SSPE in whom the EEG complexes and the motor movements occurred mainly in response to afferent stimuli. Various forms of stimuli were effective in precipitating the movements and EEG complexes, particularly when the stimulus was unexpected or startled the patient. During sleep, the EEG complexes spontaneously occurred in a more periodic fashion, typical of SSPE, but afferent stimuli were still effective in evoking the EEG complexes and associated motor spasms.

Adolescent↗
PubMed1978

Effects of hypothermia on the human brainstem auditory response.

Latency measurements between three potentials (waves I, III, and IV/V) of the human brainstem auditory response can allow early detection of certain posterior fossa lesions. The diagnostic use of these interwave latencies requires knowledge of what factors may prolong them in the absence of disease. Hypothermia appears to be one such factor--in 5 neurologically and audiometrically normal patients, mean esophageal temperatures as high as 34.5 degrees C resulted in prolongations of central auditory conduction time. Interwave latency prolongations that were abnormal relative to an age-matched normal population were seen at 32.1 degrees +/- 0.3 degrees C in patients with both spontaneous and induced hypothermia, and these abnormalities disappeared after rewarming to normothermia. Hypothermia often accompanies intoxication and coma and should therefore be considered when brainstem auditory response abnormalities are being interpreted in these two clinical conditions.

Adult↗
PubMed1978

Movement-activated central fast rhythms: an EEG finding in action myoclonus.

Five patients with relatively mild but disabling action myoclonus displayed a subtle and heretofore unemphasized electroencephalographic manifestation of action myoclonus consisting of low-voltage, central fast activity somatotopically related to the extremity being used. The importance of recognizing this rhythm lies in its association with milder forms of action myoclonus which resemble other types of movement disorders, the difficulty in recognizing this rhythm unless special tests are carried out, and the beneficial response of anticonvulsant therapy if the nature of the movement is realized.

Adolescent↗