Erik Ryding

Motor imagery activates the cerebellum regionally. A SPECT rCBF study with 99mTc-HMPAO.

Our earlier findings of a cerebellar activation during motor imagery (Brain Res., 535 (1990) 313-317) were made with a technique with low regional resolution. Therefore we could not elucidate the distribution of the cerebellar activation. In the present study the cerebellar regional cerebral blood flow (rCBF) changes during motor imagery (MI) was measured with a single photon emission computed tomography (SPECT) rCBF method (99mTc-HMPAO) with higher regional resolution during (1) silent counting, and (2) MI (which included silent counting) in 17 normal subjects. Comparing the SPECT results from the two tasks revealed the regional activations during MI. We confirmed that the most pronounced regional activations during MI were found in the cerebellum, especially in its infero-lateral parts on both sides.

Disturbances of speech prosody following right hemisphere infarcts.

ABSTRACT The ability to perceive and express emotional, as well as number of linguistic prosodic qualities of speech was tested in 20 Swedish‐speaking patients with right‐sided cortical, as well as purely subcortical brain infarcts, and in 18 normal controls. The infarcts were assessed by clinical neurological examination, and by CT, EEG, and measurements of regional cerebral blod flow (rCBF). In the patients the identification of emotional messages was disturbed, as well as the identification and production of several linguistic prosodic qualities. The study supports the claim that prosodic impairment could be linguistic in nature, and not secondary to affective disorder. The total degree of anatomical and functional disturbance of the right hemisphere played a role for both the ability to identify emotional messages and for identification of two of the linguistic prosodic qualities tested. However, it was not possible to find support for the hypothesis that the organization of prosody in the right hemisphere mirrors that of propositional speech on the left side.

Effects of Iso- and Hypervolemic Hemodilution on Regional Cerebral Blood Flow and Oxygen Delivery for Patients with Vasospasm after Aneurysmal Subarachnoid Hemorrhage

Summary.Summary. Background: Arterial vasospasm after subarachnoid hemorrhage may cause cerebral ischemia. Treatment with hemodilution, reducing blood viscosity, and hypervolemia, increasing cardiac performance and distending the vasospastic artery, are clinically established methods to improve blood flow through the vasospastic arterial bed. Method: Eight patients with transcranial Doppler verified vasospasm after subarachnoid hemorrhage were investigated with global (two-dimensional 133Xenon) and regional (three-dimensional 99 mTc-HMPAO) cerebral blood flow (CBF) measurements, before and after 1/iso- and 2/hypervolemic hemodilution. Hematocrit was reduced to 0.28 from 0.36. Hypervolemia was achieved by increasing blood volume by 1100 ml. Findings: Isovolemic hemodilution increased global cerebral blood flow from 52.25±10.12 to 58.56±11.73 ml * 100 g−1 * min−1 (p<0.05), but after hypervolemic hemodilution CBF returned to 51.38±11.34 ml * 100 g−1 * min−1. Global cerebral delivery rate of oxygen (CDRO2) decreased from 7.94±1.92 to 6.98±1.66 ml * 100 g−1 * min−1 (p<0.001) during isovolemic hemodilution and remained reduced, 6.77±1.60 ml * 100 g−1 * min−1 (p<0.001), after the hypervolemic hemodilution. As a test of the hemodilution effect on regional CDRO2 an ischemic threshold was defined as the maximal amount of oxygen transported by a CBF of 10 ml * 100 g−1 * min−1 at a Hb 140 g/l which corresponds to a CDRO2 of 1.83 ml * 100 g−1 * min−1. The brain volume with a CDRO2 exceeding the ichemic threshold was 1300±236 ml before intervention. After isovolemic hemodilution the non-ischemic brain volume was reduced to 1206±341 (p<0,003). After hypervolemic hemodilution the non-ischemic brain volume remained reduced at 1228±347 ml (p<0.05). Interpretation: The present study of controlled isovolemic hemodilution demonstrated increased global CBF, but there was a pronounced reduction in oxygen delivery capacity. Both CBF and CDRO2 remained decreased during further hypervolemic hemodilution. We conclude that hemodilution to hematocrit 0.28 is not beneficial for patients with cerebral vasospasm after SAH.

Associations between cerebral blood-flow measured by single photon emission computed tomography (SPECT), electro-encephalogram (EEG), behaviour symptoms, cognition and neurological soft signs in children with attention-deficit hyperactivity disorder (ADHD).

Twenty‐eight children with attention‐deficit hyperactivity disorder (ADHD) were examined with SPECT (single photon emission computed tomography). Seven of the children had abnormal distribution of the regional cerebral blood‐flow (rCBF) on visual evaluation and 10 had abnormal EEG findings. The only clinical finding that differentiated the group with normal from abnormal rCBF was behaviour symptom load. A factor analysis of the rCBF in different regions of interest yielded one factor with low rCBF in the temporal and cerebellar regions and high rCBF in the subcortical and thalamic regions, which was significantly associated with the degree of motor impairment and results on a cognitive test (WISC). Another factor consisting of high rCBF in frontal and parietal regions had a significant negative correlation with the degree of behaviour symptoms. There was a negative correlation between the rCBF in the right frontal regions and the degree of behaviour symptoms. The number of minor physical anomalies (MPA) was negatively correlated to the rCBF in the frontal lobes bilaterally.

Simultaneous intracranial and extracranial recording of interictal epileptiform activity in patients with drug resistant partial epilepsy: patterns of conduction and results from dipole reconstructions

Ten patients with complex partial epileptic seizures undergoing invasive video/EEG-monitoring were recorded with a combination of 10 subdural strip electrode contacts (subtemporal + lateral temporal), and 22 extracranial recording sites. In each patient several spikes with different intracranial distributions were identified, and spikes with similar distributions were averaged together with their extracranial activity. Dipole analysis of the extracranial activity was performed with the BESA program (Scherg, Garching Instrumente, München). In the horizontal plane subtemporal spikes gave oblique posterior, and lateral temporal spikes straight lateral or oblique anterior dipole orientations. In the coronal plane all spikes had an elevated orientation, most pronounced for medial subtemporal spikes. Dipole locations did not separate as well as dipole orientations. In our opinion our results would be difficult to explain without postulating a substantial degree of volume conduction from deep temporal areas to the surface. We conclude that dipole analysis of the interictal epileptiform activity does provide substantial information about which parts of the temporal lobe are involved in the epileptogenic process, making the method a useful tool in the preoperative investigation of patients with drug resistant partial epilepsy.

Regional cerebral blood flow in normal man during insulin-induced hypoglycemia and in the recovery period following glucose infusion

The effect of moderate hypoglycemia (p-glucose, 2.0 +/- 0.3 mmol/L; mean +/- SD) on regional cerebral blood flow (rCBF) was studied in a group of 10 healthy, right-handed men (aged 23 to 28 years) using an intravenous xenon 133 single photon emission computed tomography technique (SPECT). After 10 minutes of hypoglycemia, global CBF had increased to 46.3 +/- 9.6 mL/100 g/min compared with the initial normoglycemic flow of 38.6 +/- 6.8 mL/100 g/min (P less than .01). The relative distribution of the rCBF changed significantly (P less than .05, ANOVA) from before to during hypoglycemia. Of the 10 regions analyzed, the highest increments in rCBF during hypoglycemia were found in the frontal (21.5% +/- 15.2%) and parietal (20.6% +/- 14.2%) lobes, and the lowest (10.7% +/- 9.4%) were found in the pons/brainstem regions. The increase in rCBF persisted for 15 minutes after normalization of blood glucose. The persisting high flow after hypoglycemia affected all regions, but a further 10.1% +/- 7.2% increase was observed in the pons/brainstem area (P less than .05). The CBF was significantly higher in the right compared with the left hemisphere (2.8%, 1.2%, and 3.9%, respectively; P less than .05) in all measurements. A decrease in brain volume was found at the final examination, compared with the hypoglycemic state (2.6%; P less than .05). It is concluded that moderate hypoglycemia leads to a marked increase in CBF and in the relative distribution of rCBF, which persists in the immediate period after normalization of the blood glucose level.

The role of dopamine and serotonin in suicidal behaviour and aggression

Serotonin and dopamine are two monoamines which are known to interact with each other. Their role for suicidal behaviour, aggression and mood are reviewed in this chapter. We found a substantial amount of evidence for the relevance of a serotonin and dopamine model of aggression, and for aggression as a major risk factor for suicide. Evidence was found that serotonin and dopamine also may be involved in depressed mood, and possibly the individuals ability to cope with imminent suicidality.

Prediction and Prevention of Delayed Ischemic Dysfunction after Aneurysmal Subarachnoid Hemorrhage and Early Operation

Mean hemispheric cerebral blood flow (CBF) was studied after the intravenous administration of xenon-133 in 20 anesthetized patients with aneurysmal subarachnoid hemorrhage. Before early aneurysm operation, repeated CBF measurements were made to evaluate the cerebral vascular reactivity to controlled hyperventilation. Thirteen individuals received intravenous treatment with the calcium channel blocker nimodipine, whereas the other seven patients did not receive such specific antiischemic treatment. Five of the latter patients had an impaired CO2 response, and three showed delayed ischemic deterioration (DID), whereas none of the seven nimodipine-treated patients with impaired CO2 response showed DID. One nimodipine-treated patient with a preserved CO2 response, in whom operation was complicated, developed DID. The observed findings indicate that DID after uncomplicated early aneurysm operation may be associated with an early disturbance of cerebral vasoreactivity. Treatment with nimodipine may counteract the development of DID in patients with an impaired CBF CO2 response.

Impulsivity related to brain serotonin transporter binding capacity in suicide attempters.

Altered monoaminergic activity has earlier been associated with violent suicidal behaviour. In this study whole brain binding potential of the serotonin transporter (5HTT) and dopamine transporter (DAT) was measured by single photon emission computerised tomography (SPECT) in 12 patients after a serious suicide attempt and in 12 age, sex and season matched healthy controls. Clinical and temperamental assessments were analysed for possible associations with 5HTT and DAT. We found no significant 5HTT or DAT differences between patients and controls. In patients, but not in controls, there was a significant correlation between whole brain 5HTT and DAT. Impulsiveness according to the Marke Nyman Temperament (MNT) was significantly correlated to 5HTT in suicide attempters, but not in controls. Neither of the transporters could be regarded as a marker for serious suicidal behaviour. A previously discussed connection between serotonin and dopamine was replicated in this study. In suicide attempters, low 5HTT was associated with impulsivity and to some extent with depressive disorder-key factors for suicidal behaviour.

Effects of nitrous oxide on human regional cerebral blood flow and isolated pial arteries.

BackgroundResults from previous studies on the effect of nitrous oxide (N2O) on the cerebral circulation are conflicting. Early reports claim N2O to have no effect whereas recent findings demonstrate a cerebral cortical vasodilatation during N2O inhalation, but the regional cerebral blood flow (CBF) in the subcortical structures is unknown. MethodsRegional CBF was measured three-dimensionally with single photon emission computer-aided tomography after injection of xenon 133 in 8 spontaneously breathing men (mean age 29.6 yr) during normocapnia and hypocapnia with and without inhalation of 50% N2O. 8 isolated human pial arterial segments were mounted in organ baths. The segments were contracted with prostaglandin F2α and subjected to 30% oxygen and 5.6% carbon dioxide in nitrogen or N2O. ResultsNormocapnic young men had a global CBF of 55 ± 4 ml · 100 g−1. min−1. Decreasing end-tidal CO2 tension by 1.3 kPa (9.3 mmHg) reduced CBF uniformly, with a decrease in global CBF to 45 ± 2 ml · 100 g−1. min−1 (P < 0.0001). During normocapnia, inhalation of 50% N2O increased mean CBF to 67 ± 7 ml · 100 g−1. min−1 (P < 0.0001). Inhalation of 50% N2O during hypocapnia increased mean CBF to 63 ± 5 ml · 100 g−1. min−1 (P < 0.0001). During N2O inhalation there was no significant difference in mean CBF between normo- and hypocapnia. However, during hypocapnia, but not during normocapnia, N2O inhalation significantly changed the distribution of regional CBF (P < 0.0001). Compared with hypocapnia without N2O, flow increased through the frontal (143%), parietal (140%) and temporal (133%) regions as well as through insula (151%), basal ganglia (145%) and thalamus (133%). In isolated human pial arteries, addition of N2O changed neither basal tension, nor the contraction elicited by prostaglandin F2α. ConclusionsInhalation of 50% N2O increased global CBF mainly by augmenting flow in frontal brain structures. In contrast, changes in carbon dioxide without N2O affected CBF uniformly in the brain. The uneven change in distribution of the CBF when N2O was added during hypocapnia, the reduced carbon dioxide response, and the lack of effect of N2O on isolated human pial arteries suggest that N2O may increase metabolism in selected brain areas.