Postictal spectroscopy and imaging findings mimicking brain tumor recurrence

Post-ictal changes presenting as late pseudoprogression on MRI and PET in a patient with diffuse glioma: Case report and brief literature review

Following completion of adjuvant radiation and chemotherapy imaging surveillance forms a major role in the management of diffuse gliomas. The primary role of imaging is to detect recurrences earlier than clinical symptomatology. Magnetic resonance imaging (MRI) is considered the gold standard in follow-up protocols owing to better soft tissue delineation and multiparametric nature. True recurrence can often mimic treatment-related changes, it is of paramount importance to differentiate between the two entities as the clinical course is divergent. Addition of functional sequences like perfusion, spectroscopy and metabolic imaging can provide further details into the microenvironment. In equivocal cases, a follow-up short interval imaging might be obtained to settle the diagnostic dilemma. Here, we present a patient with diagnosis of recurrent oligodendroglioma treated with adjuvant chemoradiation, presenting with seizures five years post-completion of chemotherapy for recurrence. On MRI, subtle new onset gyral thickening of the left frontal region with mild increase in perfusion and patchy areas of raised choline. FET-PET (fluoro-ethyltyrosine) showed an increased tumour-to-white matter (T/Wm) ratio favouring tumour recurrence. Based on discussion in a multi-disciplinary joint clinic, short interval follow-up MRI was undertaken at two months showing decrease in gyral thickening and resolution of enhancing areas in left frontal lobe. Repeat imaging one year later demonstrated stable disease status without further new imaging findings. Given the changes resolving completely without any anti-tumoral intervention, we conclude this to be peri-ictal pseudoprogression, being the second such case described in India.

Seizure-induced reversible MRI abnormalities in patients with single seizures: a systematic review

Differentiating seizure-induced reversible MRI abnormalities from MRI changes secondary to underlying cerebral pathologies can be challenging for clinicians in the investigation of seizures. The aim of this study was to delineate the characteristic features of reversible seizure-induced MRI abnormalities. A systematic search of the databases Medline (1946-2020), PubMed (1996-2020), and Embase (1947-2020) was performed in keeping with the Preferred Items Reporting for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All publications in English, including case reports, of single unprovoked seizure patients with seizure-induced MRI abnormalities demonstrating complete resolution, were included. Two authors extracted data using a predefined template and evaluated the quality of the included studies. MRI data were additionally reviewed by a neuroradiologist. All data were synthesised qualitatively. There were 11 publications altogether, yielding a total of 27 cases that were pertinent to our research question. Abnormalities were most commonly observed on T2-weighted sequences. The most commonly observed constellations of MRI features ("composite pattern") included the following: cortical or subcortical signal change with or without leptomeningeal enhancement, signal abnormality in the splenium of the corpus callosum, and hippocampal signal abnormality. Seizure-induced reversible MRI abnormalities were observed as early as six hours from seizure onset and resolved completely as early as five days from seizure onset. A key limitation of this systematic review was the variability and incomplete reporting of clinical data, especially with regards to seizure semiology and MRI sequences performed, which may have limited our ability to make more definitive conclusions. Seizure-induced reversible MRI changes may appear within hours of seizure onset and resolve within a variable time frame, ranging from days to weeks. Bilateral seizure-induced reversible MRI abnormalities tend to be associated with generalised seizures while unilateral seizure-induced reversible MRI abnormalities may be associated with focal seizures, usually ipsilateral to the seizure focus.

Peri-ictal pseudoprogression in patients with brain tumor

Recent advances in the treatment of malignant gliomas have highlighted the fact that the appearance of new contrast-enhancing lesions on magnetic resonance imaging (MRI) is not always indicative of tumor recurrence. It has been suggested that transient seizure-related MRI changes could mimic disease progression (peri-ictal pseudoprogression [PIPG]). However, the clinical and MRI features associated with this situation have not been well described. Here, we consulted the databases of 6 institutions to identify patients with brain tumor who presented during the follow-up period transient MRI lesions wrongly suggesting tumor progression in a context of epileptic seizures. Ten patients were identified. All patients but 1 were long-term survivors who had initially been treated with radiotherapy. The PIPG episode occurred after a median interval of 11 years after radiotherapy. MRI features were highly similar across patients and consisted of transient focal cortical and/or leptomeningeal enhancing lesions that erroneously suggested tumor progression. All patients improved after adjustment of their antiepileptic drugs and transient oral corticosteroids, and MRI findings were normalized 3 months after the PIPG episode. Two patients demonstrated several seizure relapses with the same clinicoradiological pattern. After a median follow-up period of 3.5 years after the initial PIPG episode, only 1 patient presented with a tumor recurrence. In conclusion, in patients with brain tumor, especially in long-term survivors of radiotherapy, the appearance of new cortical and/or leptomeningeal contrast-enhancing lesions in a context of frequent seizures should raise the suspicion of PIPG. This phenomenon is important to recognize in order to avoid futile therapeutic escalation.

Single-voxel magnetic resonance spectroscopy of brain tissue adjacent to arachnoid cysts of epileptic patients

Intracranial arachnoid cysts (ACs) are usually asymptomatic, benign developmental anomalies. The most frequent clinical manifestations are cranial expansion, hydrocephaly, headache, epileptic seizures, psychomotor retardation, and aphasia. It is unknown whether there is a correlation between intracranial AC and epileptic seizures without obvious intracranial pressure signs. In vivo magnetic resonance spectroscopy is a technique used for the noninvasive investigation of the various metabolites of cerebral biochemical reactions. Magnetic resonance spectroscopy is also being used increasingly commonly in epileptogenic situations as a noninvasive technique. The purpose of this study was to evaluate the proton magnetic resonance spectroscopic pattern of the contents of tissue adjacent to AC and to determine whether there are any characteristic spectral patterns that may be helpful in evaluating whether these lesions are epileptogenic foci. In conclusion, although the number of cases was limited, this finding may be seen as indicating that there is no association between AC and epilepsy.