Nuclear magnetic resonance imaging, a new approach to the investigation of refractory temporal lobe epilepsy

Partial seizures in children: clinical features, medical treatment, and surgical considerations

Partial seizures are not uncommon in children. They are classified into two types: simple partial, without impairment of consciousness, and complex partial, with impaired consciousness. For both types, the hallmark is onset of the seizure from a portion of one cerebral hemisphere, as indicated by focal spikes or sharp waves on EEG. The symptoms of simple partial seizures may include focal motor or somatosensory phenomena, special sensory phenomena, autonomic symptoms, or psychic symptoms, and these symptoms may occur alone or they may progress into a complex partial seizure with alteration of consciousness. The complex partial phase may include simply an arrest of ongoing activity with altered awareness and a blank empty stare, or there may also be automatisms, including movements which are gestural, alimentary, mimicking, verbal, or ambulatory. Automatisms are predominantly seen in complex partial seizures arising from temporal areas, but they also may be seen in seizures with extratemporal onset. If the epileptic discharge spreads throughout both cerebral hemispheres, the child will have a secondarily generalized tonic-clonic convulsion. EEG should be performed in any child who is suspected of having partial seizures. If there are focal spikes or sharp waves, then there is strong supportive evidence for a diagnosis of partial seizures in the proper clinical setting. It should be remembered, however, that a normal routine EEG cannot be used to "rule out" a diagnosis of epilepsy in patients who have episodes that sound like simple or complex partial seizures. An underlying etiology may be found in a significant percentage of children with partial seizures. Most of these etiologies are static, and the seizures are the result of a previous cerebral insult, but some patients may have slow-growing gliomas or other mass lesions. MRI or CT is indicated in essentially any child with partial seizures. Medical treatment is based on the idea of using single drugs to maximally tolerated doses, if needed, before beginning with two-drug regimens. If the child continues to have seizures despite aggressive trials of medication, then it is important to consider epilepsy surgery, either temporal lobectomy or other cortical resection. When children are identified as candidates for epilepsy surgery, they should be referred to specialized centers for further testing.(ABSTRACT TRUNCATED AT 400 WORDS)

Severe epilepsy: diagnostic and epidemiological aspects

Epidemiological parameters of epilepsy have been estimated in a large number of studies. Reported annual incidence rates for recurrent seizures vary between 30 and 50/100,000, and prevalence rates in most studies between 500 and 1000/100,000. Varying findings are mostly due to different case ascertainment methods and definitions of epilepsy applied in different surveys. These aspects will be discussed in this paper. A special emphasis is laid on differential diagnosis of seizure disorders, and on the prevalence and causes of complex partial epilepsy. This epileptic disorder is one of the most common forms of epilepsy, and also difficult to treat in many cases. Many recent reports show that prognosis of seizures in patients with epilepsy is better than suggested in earlier studies. However, 25-30% of epileptics seem to have frequent (greater than 1/month) seizures. Our own study, in accordance with earlier findings suggests that prevalence of patients with severe complex partial epilepsy is about 80-90/100,000. Available literature provides several predictive factors for the prognosis of seizures and assessment of prognosis is possible quite early after the onset of seizures. Treatment choices for patients with intractable epilepsy will be discussed.

Nuclear magnetic resonance relaxometry in a penicillin model of focal epilepsy

Magnetic resonance imaging (MRI) is effective in demonstrating pathologic lesions in patients with epilepsy. It has been suggested that MRI might also reveal functional abnormalities at an interictal epileptic focus when no gross structural change such as gliosis or tumor is present. Experimental epileptic foci were produced by topical application of penicillin to the cortex of rats. In vitro proton nuclear magnetic resonance (NMR) relaxometry of tissue excised from the experimental foci revealed an increase in spin-echo relaxation time as compared to that in control tissue. The elevated relaxation times occurred in tissue samples from areas of active electroencephalographic (EEG) spiking. This is the first direct demonstration of an alteration in proton magnetic resonance parameters by functional abnormalities (focal interictal spike activity) in the brain, supporting the concept that MRI might be similarly affected.

Magnetic resonance imaging in epilepsy: a controlled study

The authors present a study of 50 patients with epilepsy and 14 healthy controls using a standardized magnetic resonance imaging (MRI) technique. Gross inspection of MRI scans identified major cerebral pathology and supplemented computerized tomography (CT) data. With further analysis of spin-lattice (T1) relaxation times, significant differences from controls emerged in epilepsy patients, even with normal CT scans, particularly in the temporal lobes. Patients with generalized seizures had increased T1 values in the thalamus. Also prolonged T1 in patients with focal seizures was noted on the ipsilateral side. These results of MRI imaging are discussed in relation to other imaging modalities in epilepsy. Further, the potential benefit of MRI in localization of seizure focus and specific pathophysiological mechanisms in seizure disorders are considered.

Magnetic resonance imaging in psychiatry

Magnetic resonance imaging (MRI) is a relatively new radiological technique that may be useful in the study of psychiatric illness. MRI gives detailed structural information about the brain and also allows quantification of functional change. Current areas of study relevant to psychiatry include: schizophrenia, dementia, epilepsy and, to a lesser extent, alcohol and affective disorders. The authors review the basic principles of MRI, discuss the recent application to psychiatry, indicate its potential advantages and comment on the current limitations of this imaging modality.

Correlations between cerebral blood flow variations and clinical parameters in temporal lobe epilepsy: an interictal study

Regional cerebral blood flow (rCBF) measurements were determined by the intravenous Xenon 133 technique in 80 patients suffering from temporal lobe epilepsy. All the patients had a normal CT scan. Three subgroups were differentiated, according to EEG and all-night polygraphic recordings: temporal lobe epilepsy with left (N = 25) or right (N = 25) EEG epileptic abnormalities and temporal lobe epilepsy with EEG abnormalities in both temporal regions with asynchronous occurrence (n = 30). In comparison with a control group (n = 20), there was (1) a marked reduction of blood flow in the temporal region corresponding to the site of the epileptic focus and (2) a reduction in blood flow in distant brain areas and the contralateral hemisphere. The rCBF decrease was highly correlated (p less than 0.001) with the disease severity (taking into account the complex partial seizure frequency and the number of secondary generalised seizures). Differences were found in the rCBF decrease between left and right temporal lobe epilepsy.

Magnetic resonance imaging in temporal lobe epilepsy: pathological correlations

A retrospective single-blind study assessing the value of magnetic resonance imaging (MRI) in 48 patients treated surgically for temporal lobe epilepsy was carried out. The imaging findings were correlated with the surgical findings in all cases. Abnormal MRI signals were detected in 34 of 48 (71%) epileptic patients and in 3 of 48 (6.2%) normal or disease control subjects. Twelve patients had structural foreign-tissue lesions, all detected by MRI. Of 14 patients with severe gliosis of the neocortex and/or mesial temporal structures, 11 had abnormal MRI scans. In patients with mild or moderate gliosis of mesial temporal structures, 6 of 12 had abnormal MRI scans. These results indicate that MRI is a sensitive technique for localizing foreign-tissue lesions, mesial temporal sclerosis, and gliosis in patients with intractable temporal lobe seizures.

Functional and morphological abnormalities in temporal lobe epilepsy: a comparison of interictal and ictal EEG, CT, MRI, SPECT and PET

Ten patients suffering from drug-resistant complex partial seizures, with EEG abnormalities in the temporal region, were studied by means of non-invasive electrophysiological techniques (video-monitored, 16-channel, prolonged surface and sphenoidal EEG) as well as by imaging techniques (CT, MRI, SPECT and PET). Analysis of interictal and ictal EEG indicated the localization of epileptic activity in one side in eight cases. CT demonstrated focal abnormalities in three, SPECT in five unequivocally (in another four questionably, with the same lateralization as indicated by PET), MRI in eight, and PET in all cases. While only EEG provided specific diagnostic information, the focus definition was consistently good on PET images, poor on CT scans, and generally good but less consistent on MRI.