Diffuse cerebral hypoperfusion in epileptic patients observed from quantitative assessment with single photon emission computed tomography using N-isopropyl-(iodine-123)-p-iodoamphetamine

Regional brain perfusion in epileptic dogs evaluated by technetium-99m-ethyl cysteinate dimer SPECT

We evaluated the feasibility of interictal single photon emission computed tomography (SPECT) to detect alterations in regional cerebral blood flow and neuronal activity in dogs with idiopathic epilepsy. Twelve dogs with idiopathic epilepsy underwent interictal technetium-99m-ethyl cysteinate dimer SPECT of the brain. Different cortical regions of interest (ROIs), 1 ROI at the cerebellum and 1 ROI at the subcortical area were evaluated by semiquantitative analysis and compared with a control group (18 dogs). Significant hypoperfusion (P = 0.02) was present in the subcortical area of epileptic dogs. This hypoperfusion was not associated with seizure frequency, age at onset of seizures, duration of epilepsy, or time since the last seizure. Interictal SPECT did not reveal cortical or cerebellar perfusion alterations. The subcortical area may play an important role in the pathophysiology of canine idiopathic epilepsy.

Computed tomographic changes of the brain and clinical outcome of patients with seizures and epilepsy after an ischaemic hemispheric stroke

It is not well established whether seizures and epilepsy after an ischaemic stroke increase the disability of patients. Seventy-two patients with delayed seizures after a hemispheric infarct (37 with a single seizure and 35 with epilepsy) were included in the study. The modified Rankin scale was used to compare disability of the patients at 1 month after stroke and at 2 weeks after single or the last seizure, in case of epilepsy. The size of the X-ray hypoattenuation zone was compared on computed tomographic (CT) scans, performed in the weeks after the stroke and 1 week after single or repeated seizures. Lesion size was determined by superimposing the CT slices on digital cerebral vascular maps, on which the contours of the infarct area were delineated. The extent of the infarcts was expressed as the percentage fraction of the total surface area of the cerebral hemisphere. Groups with a single seizure and with epilepsy were mutually compared. Infarcts predominated in the parieto-temporal cortical regions. In the overall group the median Rankin score worsened significantly after seizures. The average size of the X-ray hypoattenuation zone was also significantly increased on the CT scans after the seizures, compared with those after stroke, without clear evidence of recent infarction. Mutual comparison of patients with a single seizure episode and of those with epilepsy showed only a trend of more severe disability and of increase in lesion size in the post-stroke epilepsy group. Delayed seizures and epilepsy after ischaemic stroke are accompanied by an increase in lesion size on CT and by worsening of the disability of the patients. This study does not allow to determine whether this is due to stroke recurrence or due to additional damage as a result of the seizures themselves.

Vascular cognitive impairment in patients with late-onset seizures after an ischemic stroke

BACKGROUND

Cognitive impairment and seizures are both common conditions in patients with cerebrovascular disease.

PURPOSE

The present study investigates whether the occurrence of late-onset seizures, following an ischemic stroke, contributes to vascular cognitive impairment.

PATIENTS AND METHODS

The mean Mini-Mental State Examination (MMSE) and the median modified Rankin (mR) scores were compared between 125 patients who developed late-onset seizures (66 with a single seizure and 59 with repeated seizures or epilepsy) following an ischemic stroke and 125 patients who did not during, at least, a 2-year follow-up.

RESULTS

There were no differences in age, gender, etiology and degree of neurological impairment on admission for their stroke between the groups with and without seizures. Although the mean MMSE score was similar between both groups the median mR score was significantly higher in the seizure patients. Comparing the patients with a single seizure to the non-seizure ones showed the same results. On the other hand, comparison of the patients with epilepsy to the non-seizure group revealed, in addition to the higher median mR score, a significantly lower mean MMSE score in the former group.

CONCLUSION

Repeated seizures following an ischemic stroke promote vascular cognitive impairment.

Clinical predictors of late-onset seizures and epilepsy in patients with cerebrovascular disease

BACKGROUND

Seizures and epilepsy are harmful and worsen the disability of stroke patients. There are currently no good clinical predictors of late-onset seizures and epilepsy in patients with cerebrovascular disease (CVD).

PATIENTS AND METHODS

110 patients with delayed seizures after an ischaemic or a haemorrhagic stroke, a transient ischaemic attack or a subarachnoid haemorrhage (60 with a single seizure and 50 with epilepsy) and 366 without seizures were included in this retrospective study. The clinical syndrome, the stroke aetiology and the vascular risk factors were compared. The groups with a single seizure and with epilepsy were also analysed separately.

RESULTS

There were no differences in age, gender, aetiology and vascular risk factors between the groups with and without seizures. When comparing the incidence of the clinical syndromes, ischaemic partial anterior circulation syndrome (PACS) was significantly more and transient ischaemic attack less frequent in the group with seizures compared to the control group. The severity of the neurological impairment on admission and the degree of disability on discharge after a PACS was similar in those who developed late-onset seizures compared with those who did not. Also on the Cox proportional hazards analysis, PACS appeared to be the only clinical risk factor for development of seizures and epilepsy in patients with CVD. No differences were observed in clinical predictors between patients with a single seizure and those with epilepsy.

CONCLUSION

PACS is the only independent predictor for the occurrence of late-onset seizures in patients with CVD.

A case of temporal lobe epilepsy with improvement of clinical symptoms and single photon emission computed tomography findings after treatment with clonazepam

A 26-year-old female presented psychomotor seizures, deja vu and amnestic syndrome after meningitis at the age of 14 years. Repeated electroencephalograms (EEG) demonstrated occasional spikes localized in the right temporal region in addition to a considerable amount of theta waves mainly in the right fronto-temporal region. Single photon emission computed tomography (SPECT) showed a marked hypoperfusion corresponding to the region in which the EEG showed abnormal findings, although magnetic resonance imaging (MRI) demonstrated no abnormal findings associated with the clinical features. Treatment with clonazepam in addition to sodium valproate resulted in a remarkable improvement of clinical symptoms (i.e. psychomotor seizures and deja vu), as well as of the EEG and SPECT findings. The present study suggests that SPECT is a useful method not only to determine the localization of regions associated with temporal lobe epilepsy but also to evaluate the effect of treatment in temporal lobe epilepsy.

Developmental changes of cortical and cerebellar motor control: a clinical positron emission tomography study with children and adults

Functional neuroimaging data regarding the development of motor organization in normal children and adolescents are virtually unavailable because of ethical concerns. As an alternative approach, we studied child and adult lesion patients, focusing on movement of the hand ipsilateral to the lesion and on brain activations in the contralesional hemisphere. [15O]-water positron emission tomography was performed during rest and sequential finger-thumb tapping in 10 children (aged 6 to 14 years) and 15 adults (aged 18 to 74 years) with unilateral lesion. We expected more distinct activation/deactivation patterns during movement in adults than in children. While there were no group differences in activation of primary and secondary motor cortices, deactivations in nonmotor cortex were significantly more pronounced in adults than in children. This indirectly supports our hypothesis of developmental focalization of cerebral motor control. Activations in the cerebellum and vermis were significantly stronger in the adults than in the children, possibly reflecting normal developmental patterns.

Interictal cerebral metabolic levels in Wistar rats sensitive to audiogenic seizures

In the present study, we compared interictal local cerebral metabolic rates for glucose (LCMRglcs) in a strain of audiogenic rats (Wistar AS) selected in our laboratory to interictal LCMRglcs in a strain of control non-epileptic (NE) rats. Two groups of Wistar AS were studied, one group exposed to a single audiogenic seizure and one group of kindled rats exposed to 40 daily repetitive seizures. Control NE animals were exposed to a single sound exposure which did not induce any behavioral disturbance. Interictal LCMRglcs were measured by the quantitative autoradiographic [14C]2-deoxyglucose technique 5 days after the last sound exposure. LCMRglcs were similar in the three groups of rats in 80% of the structures. Compared to the control NE strain, interictal metabolic levels were mainly decreased in auditory structures of Wistar AS, either naive or kindled, thus confirming auditory impairment in audiogenic animals. LCMRglcs were increased over control levels in both groups of Wistar AS in cerebellar regions. This increase of cerebellar functional activity in Wistar AS compared to control NE rats might reflect an increased cerebellar input which, together with auditory impairment, may facilitate the induction of seizure activity in Wistar AS. Finally, there was no difference between the interictal cerebral metabolic level of naive and kindled Wistar AS, except in the cerebellar dentate nucleus where LCMRglc was significantly higher in kindled than in naive animals.

Cerebellar and subcortical blood flow abnormalities in children with partial epilepsy

Cerebellar and cerebral subcortical blood flow in 41 children with partial epilepsy and 6 normal controls was investigated during the interictal state using single photon emission computed tomography with technetium-99m hexamethylpropyleneamineoxime. Seventeen of 41 patients had been treated with antiepileptic drugs (AEDs) for 4.65 +/- 3.80 years (range 0.2-12) and 24 patients were drug-free. Unilateral hypoperfusion of cerebellum and cerebral subcortical gray matter was demonstrated in 11 (28%) and 16 (40%) patients, respectively. Most of them also had focal cerebral cortical perfusion abnormalities, ipsilateral or contralateral to the cerebellar and cerebral subcortical hypoperfusion. The mean asymmetry indices of cerebellar blood flow in the medicated and the unmedicated patients were significantly higher than in the control cases (P < 0.02 and P < 0.04), whereas the differences in the asymmetry indices in cerebral subcortical areas were insignificant. AED therapy did not affect the perfusion of cerebellum and cerebral subcortical regions (P > 0.05 and P > 0.05). Our results suggest that functional alterations on anatomically connected remote areas in patients with partial epilepsy are not related to the drug effect and probably due to primary epileptogenic activity.

Positron emission tomographic study of late-onset cryptogenic symptomatic seizures

Ten patients with epilepsy of unknown origin, starting after the age of 50 years, and without clear evidence of cognitive decline were studied with positron emission tomography, using the steady state technique with 15O. Cerebral blood flow and oxygen metabolism were significantly decreased in all cortical areas. No focal areas of hypometabolism were detected. Treatment with phenytoin did not influence the results. It is suggested that late-onset seizures could be the premonitory signs of a progressive encephalopathy of unknown origin.

Epilepsy and SPECT

SPECT studies for rCBF imaging in clinical epilepsy are reviewed divided into interictal, ictal and postictal SPECT studies in partial and generalized epilepsies, as compared with the corresponding PET studies, and at times referring to SPECT studies in experimental models of epilepsy. All of the interictal, ictal and postictal SPECT scans in partial epilepsy are useful for the regional determination of epileptic foci, in view of the high appearance rates of focal abnormalities on these SPECT scans and good correlation with epileptic EEG foci. Mechanisms underlying the focal abnormality on interictal SPECT scans (i.e., focal hypoperfusion) image are complicative, and therefore, studies concerning the underlying mechanisms are reviewed with regard to correlations of the SPECT abnormality with the following various clinical factors: focal organic lesions on X-ray CT or MRI scans, frequencies of clinical seizures or interictal seizure discharges on EEGs, background EEG activity, propagation of epileptic activity, antiepileptic drugs, and cognitive functions. Further, new neurochemical SPECT studies using 123I-Iomazenil for benzodiazepine receptor imaging in clinical epilepsy are reviewed and compared with earlier SPECT studies for rCBF imaging with regard to their utility in regional determination of epileptic foci. In addition, the few SPECT or PET studies available on epileptic psychosis are reviewed.