Quantitative serial T2 relaxometry: a prospective evaluation in solitary cerebral cysticercosis

Neurocysticercosis-related Seizures: Imaging Biomarkers

Neurocysticercosis (NCC)-a parasitic CNS infection endemic to developing nations-has been called the leading global cause of acquired epilepsy yet remains understudied. It is currently unknown why a large proportion of patients develop recurrent seizures, often following the presentation of acute seizures. Furthermore, the presentation of NCC is heterogenous and the features that predispose to the development of an epileptogenic state remain uncertain. Perilesional factors (such as oedema and gliosis) have been implicated in NCC-related ictogenesis, but the effects of cystic factors, including lesion load and location, seem not to play a role in the development of habitual epilepsy. In addition, the cytotoxic consequences of the cyst's degenerative stages are varied and the majority of research, relying on retrospective data, lacks the necessary specificity to distinguish between acute symptomatic and unprovoked seizures. Previous research has established that epileptogenesis can be the consequence of abnormal network connectivity, and some imaging studies have suggested that a causative link may exist between NCC and aberrant network organisation. In wider epilepsy research, network approaches have been widely adopted; studies benefiting predominantly from the rich, multimodal data provided by advanced MRI methods are at the forefront of the field. Quantitative MRI approaches have the potential to elucidate the lesser-understood epileptogenic mechanisms of NCC. This review will summarise the current understanding of the relationship between NCC and epilepsy, with a focus on MRI methodologies. In addition, network neuroscience approaches with putative value will be highlighted, drawing from current imaging trends in epilepsy research.

T2 relaxometry helps prognosticate seizure outcome in patients with solitary cerebral cysticercosis

OBJECTIVE

Correlate serial T2 relaxometry (T2R) values with long term seizure outcome in patients with solitary cerebral cysticercosis (SCC) in order to establish its usefulness as a prognostic marker in these patients.

METHODS

Patients with new-onset seizures due to SCC were imaged serially using a pre-determined MRI protocol at enrolment and after 3, 6, 12 and 24months. T2 relaxometry was performed using a dual echo sequence with maps generated manually from the measured image intensities at the level of the lesion. Patients were randomised to receive albendazole plus antiepileptic drugs, or only antiepileptic treatment ("controls"). At each visit, as well as four years after study initiation, patients were reviewed for seizure recurrence. Clinical and radiological outcomes were assessed by physicians blinded to treatment received.

RESULTS

Of 123 patients recruited, 77 had at least four MRIs and >12month follow-up, and were included for analysis. Baseline clinical and demographic parameters as well as antiepileptic treatment were similar between albendazole and control groups. T2 values from the lesion were higher than normal parenchyma initially, and fell to approach normal over six months. Controls had higher T2 values from the lesion centre and wall at six months than those who received albendazole. However no difference was seen in T2 values from perilesional parenchyma between treatment and control groups, indicating lack of modulation of the development of perilesional gliosis by albendazole therapy. Patients with seizures persisting >6months after enrolment had higher perilesional T2 values than those who were seizure-free. A rise in perilesional T2 value at 12months is probably due to gliosis. A later stage of degeneration was associated with a reduced likelihood of seizure relapse.

SIGNIFICANCE

T2 relaxometry at three and six months after seizure onset can identify patients likely to have seizures beyond six months after onset. Persistently abnormal T2 values in patients with poorer outcomes reflect the development of perilesional gliosis.