Postictal SPET in epilepsy

Typical and atypical perfusion patterns in periictal SPECT of patients with unilateral temporal lobe epilepsy

PURPOSE

To characterize perfusion patterns of periictal single-photon emission tomography (SPECT) in patients with unilateral temporal lobe epilepsy (TLE) and to determine their relationship to the epileptogenic zone (EZ).

METHODS

We studied periictal SPECT scans of 53 patients after anterior mesial temporal lobectomy who had good seizure outcome after surgery. Ictal SPECT scans were performed during video-EEG monitoring. Typical SPECT patterns consisted of ipsilateral ictal hyperperfusion or ipsilateral postictal hypoperfusion. Atypical ictal patterns included normal scans, bilateral temporal hyperperfusion, or contralateral patterns. These perfusion patterns were retrospectively analyzed searching for concordance rate with the EZ.

RESULTS

We obtained 51 ictal and two early postictal scans. In the typical group, 40 (75.4%) patients had ipsilateral ictal temporal lobe hyperperfusion, and one (1.9%) patient had ipsilateral postictal temporal lobe hypoperfusion. Twelve (22.7%) patients exhibited atypical perfusion patterns: seven (13.2%) patients had bitemporal ictal hyperperfusion (four cases showed asymmetric temporal lobe changes), four (7.6%) patients had contralateral hyperperfusion, and one (1.9%) patient had a normal SPECT scan. All four patients with bitemporal asymmetric hyperperfusions showed greater perfusion lateralized to the side of the EZ. Three of the four patients who had contralateral hyperperfusion also had a complex postictal-like pattern in the ipsilateral temporal lobe consisting of anteromesial hyperperfusion with adjacent lateral hypoperfusion.

CONCLUSIONS

This study analyzed typical and atypical perfusion patterns in unilateral TLE, and suggested that not only typical, but also some atypical perfusion patterns may contribute to the lateralization of EZ.

Cerebral blood flow abnormalities in symptomatic West syndrome: a single photon emission computed tomography study

BACKGROUND

Infantile spasm (IS) is an age-dependent epileptic encephalopathy of variable etiology. Although IS is well studied, its pathogenesis is unclear. Infantile spasm is usually considered a generalized epilepsy, but recent studies point to focal cerebral blood flow (CBF) abnormalities.

METHODS

In six symptomatic IS patients, single photon emission computed tomography (SPECT) with [99Tc]-HMPAO, electroencephalography (EEG), magnetic resonance imaging (MRI)/computed tomography (CT) and their correlation were evaluated.

RESULTS

Single photon emission computed tomography showed unifocal (regional) cerebral hypoperfusion in two infants, multifocal (diffuse) cerebral hypoperfusion in three infants and normal perfusion in the other infant. Electroencephalograms obtained in near-time of the SPECT studies showed diffuse abnormalities in five infants with hypoperfusion on SPECT. Cranial MRI/CT showed diffuse and/or localized cerebral lesions in all infants, all of whom had corresponding areas of hypoperfusion on SPECT. In one patient whose spasms were stopped with anticonvulsants, SPECT was normal, in two patients SPECT showed unifocal lesions, while in another three patients whose spasms were decreased but not stopped, SPECT showed multifocal hypoperfusion.

CONCLUSIONS

This pilot study may indicate that there are CBF anomalies in symptomatic IS. The degree of CBF may be a predictor of prognosis and multifocal hypoperfusion may be a poor prognostic criteria in IS.

Regional distribution of interictal 31P metabolic changes in patients with temporal lobe epilepsy

PURPOSE

We compared the 31P metabolites in different brain regions of patients with temporal lobe epilepsy (TLE) with those from controls.

METHODS

Ten control subjects and 11 patients with TLE were investigated with magnetic resonance imaging (MRI) and [31P]MR spectroscopic imaging (MRSI). [31P]MR spectra were selected from a variety of brain regions inside and outside the temporal lobe.

RESULTS

There were no asymmetries of inorganic phosphate (Pi), pH, or phosphomonoesters (PME) between regions in the left and right hemispheres of controls. In patients with TLE, Pi and pH were higher and PME was lower throughout the entire ipsilateral temporal lobe as compared with the contralateral side and there were no significant asymmetries outside the temporal lobe. The degree of ipsilateral/contralateral asymmetry for all three metabolites was substantially greater for the temporal lobe than for the frontal, occipital, and parietal lobes, and these asymmetries provided additional data for seizure localization. As compared with levels in controls, Pi and pH were increased and PME were decreased on the ipsilateral side in patients with TLE. There were changes in Pi, pH, and PME on the contralateral side in persons with epilepsy as compared with controls, contrary to changes on the ipsilateral side.

CONCLUSIONS

Our findings provide some insight into the metabolic changes that occur in TLE and may prove useful adjuncts for seizure focus lateralization or localization.

Ictal and interictal SPECT in a newborn infant with intractable seizure

Neonatal seizures can be difficult to classify according to partial vs generalized onset based on clinical appearance, electroencephalogram (EEG) or other adjunctive imaging techniques. Single-photon emission computed tomography (SPECT) has proven to be useful in adults; however, its use is limited in the paediatric age group, particularly in neonates. A case of a 12-d-old infant with intractable seizures is reported, on whom an interictal Tc-99m HMPAO SPECT showed an area of hypoperfusion in the left temporal cortex, whereas the ictal SPECT revealed prominent hyperperfusion in the same area. The EEG of the infant demonstrated generalized epileptiform activity, while computed tomography and magnetic resonance (MR) imaging findings were normal. This case indicates that the use of SPECT may provide valuable data in evaluation of neonatal seizures, particularly with poorly localized EEG changes and normal MRI scans.

Ictal regional cerebral blood flow in frontal lobe seizures

99mTC (single photon emission computed tomography) (HMPAO SPECT) was carried out during 16 frontal-lobe seizures in 15 patients. Focal changes in regional cerebral blood flow were seen during all seizures. In 9 of 16 seizures SPECT showed hyperperfusion localized to one frontal lobe. In 1 of 16 seizures ictal hypoperfusion was seen in one frontal lobe. In 2 of 16 seizures there was hyperperfusion in both frontal lobes, and in 4 of 16 seizures hyperperfusion involved the frontal lobe or lobes plus other lobes of the brain. These changes were accompanied by hyperperfusion of subcortical structures in 13 seizures. SPECT thus localized to one frontal lobe in 10 of 16 seizures, and localized to the frontal lobes without lateralizing in two further seizures. No seizure showed a pattern of perfusion similar to that reported in mesial-temporal-lobe seizures. We conclude that ictal SPECT may provide useful localizing information in frontal-lobe seizures.

Ictal single photon emission computed tomography in occipital lobe seizures

PURPOSE

Ictal single photon emission computed tomography (SPECT) has been evaluated as an adjunctive localizing technique in temporal lobe epilepsies and, to a lesser degree, in some extratemporal epilepsies. The purpose of this study was to determine whether occipital lobe seizures are associated with distinctive ictal cerebral blood perfusion (rCP) patterns.

METHODS

SPECT was used with the tracer 99mTc HMPAO to image ictal rCP in 6 patients in whom clinical, EEG, and imaging data indicated occipital lobe seizures.

RESULTS

Two patterns of rCP were seen. Four patients had hyperperfusion that was restricted to the occipital lobe, and two patients had hyperperfusion of the occipital lobe and the ipsilateral mesial temporal lobe, with hypoperfusion of the lateral temporal lobe. The latter 2 patients had clinical and surface EEG evidence of temporal lobe involvement in the seizure discharge.

CONCLUSIONS

Ictal rCP patterns in occipital lobe seizures are distinct from those in temporal lobe seizures and may vary according to whether or not ipsilateral temporal lobe structures are involved in the ictal discharge.

Clinical brain radionuclide imaging studies

A recent survey of the knowledge and practice of both positron-emission tomography (PET) and single-photon emission computed tomography (SPECT) of the brain among referring physicians in Europe (neurologists and psychiatrists) showed a disquieting lack of knowledge of the potential of these methodologies in the investigation and management of patients of their own specialities. The need to bring the knowledge of the potential of these techniques to the practicing physicians is paramount. It is imperative that the methodologies and concepts that preside over the application of these techniques in neurology and psychiatry must become more uniform if an impact is to be felt at a clinical level. There is clear improvement in the instrumentation available with the new state-of-the-art tomographic devices and with the development of new technetium-based radiopharmaceuticals for the study of cerebral perfusion. The constant progress made with ligands that permit the study of neurotransmission, tumor metabolism, and turnover do expand our capability to improve the knowledge concerning neurophysiology, neuropathology, and neuropharmacology of a variety of disease states. PET and SPECT will be progressively included in protocols aimed at stratifying patients with dementia, monitoring therapeutic trials, and improving our ability to determine outcome. Clinical usefulness of PET and SPECT begin to emerge in cerebral vascular disease, in the identification of cerebral death, in epilepsy, in cerebral trauma, in the investigation of HIV-positive patients with cerebral involvement, and in the monitoring of tumor recurrence and postirradiation damage. This review article outlines a current perspective of SPECT and PET as practiced in Europe, its potential, and its limitations.

MRI and brain spect findings in patients with unilateral temporal lobe epilepsy and normal CT scan

26 patients with temporal lobe epilepsy clinically documented by several abnormal interictal surface EEGs with typical unitemporal epileptiform activity and a normal CT scan were studied. Interictal 99mTC HMPAO brain SPECT and MRI were performed in all subjects. Abnormalities were shown in 61.5% of MRI (n = 16) and 65.4% of SPECT (n = 17). Hippocampal atrophy associated to a high signal on T2-weighted MRI slices suggesting mesial temporal sclerosis was the main finding (n = 12; 75% of abnormal MRI). MRI correlated well to surface EEG in 50% (n = 13). There was also a good correlation between MRI and SPECT in 30.7% (n = 8). SPECT and EEG were in agreement in 57.7% (n = 15). MRI, SPECT and EEG were congruent in 26.9% (n = 7). These results support the usefulness of interictal brain SPECT and MRI in detecting lateralized abnormalities in temporal lobe epilepsy. On the other hand, in two cases, interictal SPECT correlated poorly with surface EEG. This functional method should not be used isolately in the detection of temporal lobe foci. MRI is more useful than CT as a neuroimaging technique in temporal lobe epilepsy. It may detect small structural lesions and mesial temporal lobe sclerosis which are not easily seen with traditional CT scanning.

Postictal switch in blood flow distribution and temporal lobe seizures

The ictal increase of regional cerebral blood flow has yet to be fully utilised in the investigation of focal seizures. Although single photon emission tomography (SPECT) is being increasingly used in the localisation of epileptic foci, the evolution and time courses of the peri-ictal perfusion changes have yet to be clarified. We performed serial SPECT studies in the interictal, ictal and immediate postictal states in 12 patients with refractory temporal lobe epilepsy to define the patterns and duration of peri-ictal cerebral blood flow changes. Visual analysis showed a constant pattern of unilateral global increases in temporal lobe perfusion during seizures which suddenly switched to a pattern of relative mesial temporal (hippocampal) hyperperfusion and lateral temporal hypoperfusion in the immediate postictal period. Quantitative analysis confirmed the visual assessment. Lateral temporal cortex ictal/normal side to side ratios were increased by mean 35.1% (95% confidence interval 21.8% to 48.4%) more in the ictal studies than in the interictal studies and mesial temporal cortex ratios increased by mean 30.8% (22.4% to 39.2%). In the postictal state, however, lateral temporal ratios were reduced by mean 7.7% (-15.8% to 0.4%) compared with interictal values, whereas mesial temporal perfusion was maintained compared with the interictal studies. These observations provide critical information for interpreting scans which can be used in the localisation of epileptic foci. This postictal switch in blood flow patterns may reflect the underlying metabolic processes of neuronal activation and recovery and have implications for understanding the neurobiology of human epileptic seizures.