Magnetic Resonance Imaging and 31 P Spectroscopy of an Interictal Cortical Spike Focus in the Rat

Summary:Purpose: In this study, hippocampal metabolite alterations in 1 H-MR spectroscopy ( 1 H-MRS) were correlated to the findings of intensive video-EEG monitoring and duration of seizure symptoms in patients with temporal lobe epilepsy (TLE).Methods: The 14 patients with mesial TLE and no pathological findings in imaging were investigated by 1 H-MRS. Seizures were analyzed by: number of clinical seizures in 24 h, exact duration of clinical symptoms in 24 h, frequency of interictal epileptiform discharges (IEDs) and ictal activity, duration of ictal activity, and IEDs occurring within 24 h in intensive EEG monitoring. Pearson Correlation Coefficient (PCC) was calculated between spectral metabolite alterations and the parameters mentioned above. Results:In the analysis, a negative correlation was found between total (t) NAA values and degree of IEDs in EEG (p = 0.04); a positive correlation was found between Cr levels and duration of seizure symptoms registered by video monitoring (p = 0.01).Conclusions: Our study shows that, in some patients, 1 H-MRS is able to refer the severity of TLE. The degree of tNAA reduction in 1 H-MRS, probably indicating neuronal dysfunction, is associated with interictal spiking in intensive EEG monitoring. Duration of seizure symptoms associated with increased Cr peaks probably reflects increased gliosis.

Section: Discussionmentioning

confidence: 99%

¹H‐MR Spectroscopy Indicates Severity Markers in Temporal Lobe Epilepsy: Correlations between Metabolic Alterations, Seizures, and Epileptic Discharges in EEG

Hammen

Schwarz

Doelken³

et al. 2007

“…However, these studies demonstrated decreased phosphocreatine levels without changes in the levels of ATP and pioneered the idea that NMR techniques can be used for in vivo detection of seizure consequences. The first MRI studies in epilepsy models were conducted in the early 1990s (Karlik et al, 1991; King et al, 1991). Status epilepticus was induced by chemical convulsants such as kainate or pilocarpine, and animals were followed with MRI for a few days.…”

Section: Mri Studies In Animal Models Of Acquired Epilepsy—focus On Smentioning

confidence: 99%

Magnetic Resonance Imaging in Animal Models of Epilepsy—Noninvasive Detection of Structural Alterations

Gröhn¹,

Pitkänen²

2007

Summary: Small animal magnetic resonance imaging (MRI) has opened a window through which brain abnormalities can be observed over time in rodents noninvasively. We review MRI studies done during epileptogenesis triggered by status epilepticus in rat. Most of these studies have used quantitative T2, diffusion, and/or volumetric MRI. The goal has been to identify the distribution and severity of structural lesions during the epileptogenic process, that is, soon after status epilepticus, during epileptogenesis, and after the appearance of spontaneous seizures. Data obtained demonstrate that MRI can be used to associate the development of brain pathology with the evolution of clinical phenotype. MRI can also be used to select animals to preclinical studies based on the severity and/or distribution of brain damage, thus making the study population more homogeneous, for example, for assessment of novel antiepileptogenic or neuroprotective treatments. Importantly, follow-up data collected emphasize interindividual differences in the dynamics of development of abnormalities that could have remained undetected in a typical histologic analysis providing a snapshot to brain pathology. A great future challenge is to take advantage of interanimal variability in MRI in the development of surrogate markers for epilepsy or its comorbidities such as memory impairment. Understanding of molecular and cellular mechanisms underlying changes in various MRI techniques will help to better understand complex progressive pathological processes associated with epileptogenesis and epilepsy. Key Words: Epilepsy-EpileptogenesisMagnetic resonance imaging-Animal models.Epilepsies are a heterogeneous group of neurological disorders that can be divided into symptomatic, presumed symptomatic, and idiopathic epilepsies based on the underlying etiology (Engel, 2002). They are characterized by a transient and recurrent failure of normal brain function and simultaneous activation of a large population of neurons resulting in electrographic and/or behavioral seizure activity (Engel, 1989). Epileptic process in symptomatic epilepsies often includes an initial brain damaging insult such as head trauma, stroke, brain infection, or status epilepticus. This is followed by a latency period that can last from a few weeks to several years, during which a large number of various neurobiological changes can take place, including neuronal death, gliosis, neurogenesis, axonal sprouting and injury, reorganization of extracellular matrix, and vascular changes. These alterations eventually lead to the appearance of spontaneous seizures, that is, development of epilepsy. Experimental evidence suggests that some of these cellular changes can continue even after epilepsy diagnosis (Pitkanen and Sutula, 2002 In the present review, we will mainly focus on structural magnetic resonance imaging (MRI) in animal models of symptomatic epilepsies, including quantitative relaxation and diffusion MRI studies, while other publications in this supplement will more widely cover top...

“…31 P MRS may be used in combination with other MRS techniques such as 1 H MRS for the identification of the ictal event itself as an energy exhaustive process. However, it is unlikely that any significant (measurable) change in the pool of high‐energy metabolites occurs during interictal spiking (without an ictal event) that is detectable presently on MRS or MRI (Karlik et al, 1991).…”

Section: P Mrs‐early Studiesmentioning

confidence: 99%

Magnetic Resonance Spectroscopy in Animal Models of Epilepsy

Hiremath¹,

Najm²

2007

Summary:The noninvasive localization of the epileptogenic zone continues to be a challenge in many patients that present as candidates for possible epilepsy surgery. Magnetic resonance imaging (MRI) techniques provide accurate anatomical definition, but despite their high resolution, these techniques fail to visualize the pathological neocortical and hippocampal changes in a sizable number of patients with focal pathologies. Further, visualized lesions on MRI may not all produce seizures. One of the keys to the understanding of the epileptogenic zone lies in the recognition of the metabolic alterations that occur in the setting of epileptic seizures. Magnetic resonance spectroscopy (MRS) is a valuable tool that can be used to study the metabolic changes seen in both acute and chronic animal models of epilepsy. Such study allows for the identification of epileptic tissue with high sensitivity and specificity. We present here a review of the use of MRS in animal models of epilepsy.