Chandrasekharan Kesavadas

Seizure Outcome after Anterior Temporal Lobectomy and Its Predictors in Patients with Apparent Temporal Lobe Epilepsy and Normal MRI

Summary:  Purpose: Very little reliable information is available regarding the role of anterior temporal lobectomy (ATL), optimal presurgical evaluation strategy, post‐ATL seizure outcome, and the factors that predict the outcome in patients with medically refractory temporal lobe epilepsy (TLE) and normal high‐resolution magnetic resonance imaging (MRI). To be cost‐effective, epilepsy surgery centers in developing countries will have to select candidates for epilepsy surgery by using the locally available technology and expertise.

Utility of susceptibility-weighted MRI in differentiating Parkinson's disease and atypical parkinsonism

IntroductionNeuropathological studies report varying patterns of brain mineralization in Parkinson’s diseases (PD), progressive supranuclear palsy (PSP), and Parkinson variant of multiple system atrophy (MSA-P). Susceptibility-weighted imaging (SWI) is the ideal magnetic resonance imaging (MRI) technique to detect mineralization of the brain. The purpose of this study was to test if SWI can differentiate PD, PSP, and MSA-P.MethodsEleven patients with PD, 12 with PSP, 12 with MSA-P, and 11 healthy controls underwent SWI of the brain. Hypointensity of putamen, red nucleus, substantia nigra, and dentate nucleus in all groups were measured using an objective grading scale and scored from 0 to 3.ResultsIn PSP, hypointensity score of red nucleus was higher than that in MSA-P (p = 0.001) and PD (p = 0.001), and a score of ≥2 differentiated the PSP group from the PD and MSA-P groups. Putaminal hypointensity score was higher in PSP when compared to that in PD (p = 0.003), and a score of ≥2 differentiated PSP from PD groups. SWI hypointensity scores of red nucleus and putamen had an excellent intrarater and interrater correlation. Substantia nigra hypointensity score of the PSP group was higher than that of the MSA-P (p = 0.004) and PD (p = 0.006) groups, but the scores had only a moderate intrarater and interrater correlation.ConclusionsSWI shows different patterns of brain mineralization in clinically diagnosed groups of PD, PSP, and MSA-P and may be considered as an additional MR protocol to help differentiate these conditions.

Clinical and functional outcome and factors predicting prognosis in osmotic demyelination syndrome (central pontine and/or extrapontine myelinolysis) in 25 patients

Aims To assess the functional and clinical outcome in a sizeable cohort of patients with osmotic demyelination syndrome (ODS) and to characterise the factors which could predict the final outcome. Methods Twenty five consecutive patients with ODS formed the study cohort. The diagnosis of ODS was based on clinical features with corroborating imaging findings. Two functional scales—Functional Independent Measure (FIM) and Disability Rating Scale (DRS)—were applied to assess the functional status at the time of admission, discharge and last follow-up. Patients who became independent for activities of daily living (ADL) at last follow-up were classified as favourable outcome, and those who died or became dependent for ADL were classified as a poor outcome group respectively. The Fisher exact test and Mann–Whitney U test were used to assess categorical and continuous variables respectively. Results The mean age at diagnosis was 53±14 years. Five (20%) had central pontine myelinolysis, seven (28%) had extrapontine myelinolysis, and 13 (52%) had both. Hyponatraemia and hypokalaemia were noted in 20 (80%) and 10 (40%) patients respectively. Six (24%) received intravenous methylprednisolone. Eleven (46%) had a favourable outcome at a mean follow-up of 2.2±2.5 years. Hyponatraemia ≤115 mEq (p=0.04), associated hypokalaemia (p=0.04) and low Glasgow Coma Scale (GCS) (p=0.008) at presentation were predictive of poor outcome. The mean FIM score at admission (p=0.05) and at discharge (p=0.01), and mean DRS at admission (p=0.05) were predictive of poor outcome. Conclusions Higher GCS scores, better scores in functional scales in hospital, less severe hyponatraemia and absence of superadded hypokalaemia predicted favourable outcome.

Concepts and controversies in nonketotic hyperglycemia-induced hemichorea: Further evidence from susceptibility-weighted MR imaging

Hyperglycemia‐induced hemichorea can show T1 hyperintensity of the contralateral striatum on MRI. This is thought to be due to petechial hemorrhages or gemistocytic astrocyte accumulation. This study explores the utility of susceptibility‐weighted imaging (SWI) and diffusion‐weighted imaging (DWI) in identifying the nature of these lesions. Three patients underwent MR imaging of the brain with SE T1, F SE T2, DWI, and SWI. T1 images showed hyperintensity predominantly involving the contralateral striatum, where mild (two cases) to moderate (one case) restricted diffusion (low apparent diffusion coefficient [ADC]) was detected on DWI. SWI demonstrated bilateral symmetrical hypointensities in the first two cases, suggesting age associated mineralization. In addition, increased susceptibility change (hypointensity) was also noted in the right putamen in the first and the third cases, suggesting paramagnetic mineral deposition. T1 hyperintensity may be from the protein hydration layer inside the cytoplasm of swollen gemistocytes appearing after an acute cerebral injury. These astrocytes also express metallothionein with zinc, which is thought to be the cause of asymmetric hypointensity of the posterior putamen on SWI. ADC values were thought to be useful for prognostication; however, they should be interpreted cautiously in the presence of susceptibility changes. J. Magn. Reson. Imaging 2009;29:699–703.

Applications of 3D CISS sequence for problem solving in neuroimaging.

Three-dimensional (3D) constructive interference in steady state (CISS) is a gradient-echo MRI sequence that is used to investigate a wide range of pathologies when routine MRI sequences do not provide the desired anatomic information. The increased sensitivity of the 3D CISS sequence is an outcome of the accentuation of the T2 values between cerebrospinal fluid (CSF) and pathological structures. Apart from its well-recognized applications in the evaluation of the cranial nerves, CSF rhinorrhea and aqueduct stenosis, we have found the CISS sequence to be useful for the cisternal spaces, cavernous sinuses and the ventricular system, where it is useful for detecting subtle CSF-intensity lesions that may be missed on routine spin-echo sequences. This information helps in the management of these conditions. After a brief overview of the physics behind this sequence, we illustrate its clinical applications with representative cases and discuss its potential role in imaging protocols.

Calcified neurocysticercosis lesions and hippocampal sclerosis: Potential dual pathology?

In areas where cysticercosis is endemic, calcified neurocysticercosis lesion(s) (CNL) and hippocampal sclerosis (HS) commonly coexist in patients with localization‐related epilepsies. To understand the pathogenesis of HS associated with CNL, we compared the characteristics of three groups of patients with antiepileptic drug–resistant epilepsies: CNL with HS, CNL without HS (CNL alone), and HS without CNL (HS alone). In comparison to patients with CNL alone, those with CNL with HS had CNL more frequently located in the ipsilateral temporal lobe. Those with CNL with HS had a lower incidence of febrile seizures, older age at initial precipitating injury and at onset of habitual complex partial seizures, and more frequent clustering of seizures and extratemporal/bitemporal interictal epileptiform discharges as compared to patients with HS alone. Our study illustrates that HS associated with CNL might have a different pathophysiologic basis as compared to classical HS.

Susceptibility weighted imaging in cerebral hypoperfusion—can we predict increased oxygen extraction fraction?

IntroductionIncreased concentrations of deoxyhemoglobin within veins can induce susceptibility changes resulting in increased conspicuity in susceptibility weighted imaging (SWI). Compensatory mechanisms following reduced cerebral perfusion due to carotid occlusive disease may not be sufficient to meet demands of ischemic tissue and increased tissue oxygen extraction ratio results in relative increase in deoxyhemoglobin levels in the venous blood draining affected hemisphere. We assessed whether patients with carotid disease display prominence of veins over affected cerebral hemisphere.MethodsEighteen patients with unilateral carotid occlusion or critical carotid stenosis proven by magnetic resonance angiography (MRA) were selected. The medical records and MRI findings including SWI and MRA were reviewed. The SWI images were studied for the presence of asymmetry of veins over the cerebral hemispheres and were correlated with the site and severity of stenosis or occlusion. The veins were assumed to be conspicuous and asymmetric if there were more numerous veins and/or large veins with greater signal loss observed compared with opposite normal hemisphere.ResultsIn about half of patients, prominence of veins was noted in the cerebral hemisphere ipsilateral to side of occlusion. This was not observed in patients with significant extracranial carotid stenosis. The SWI abnormalities were seen extending beyond the boundaries of occluded vascular territory. There was good agreement between two observers in all the patients who showed positive finding. Also there was no interobserver variation in patients with negative findings.ConclusionThe increased susceptibility arising out of increased deoxyhemoglobin to oxyhemoglobin ratio leads to visualization of prominent veins over the affected cerebral hemisphere on SWI.

Corpora amylacea in mesial temporal lobe epilepsy: clinico-pathological correlations.

PURPOSE To investigate the electro-clinical significance of premature accumulation of corpora amylacea (CoA) in the resected hippocampus of patients with medically refractory mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). METHODS We compared the clinical and EEG characteristics, and post-operative seizure outcome of 373 (mean age 29.4 years, range 7-55 years) surgically treated MTLE-HS patients with (MTLE-HS-CoA(+), n=129 [34.5%]) and without (MTLE-HS-CoA(-), n=244 [65.5%]) CoA. RESULTS Age at surgery was significantly higher and duration of epilepsy before surgery was significantly longer for MTLE-HS-CoA(+) patients compared to MTLE-HS-CoA(-) patients. Although the distribution of interictal epileptiform EEG abnormalities did not differ, type 1 ictal EEG pattern was more frequent in MTLE-HS-CoA(+) patients. Among the 21 patients with major interictal psychosis detected prior to epilepsy surgery, 19 (90.5%) belonged to MTLE-HS-CoA(+) group. Schizophrenia-like psychosis was most prevalent. The post-operative seizure-free outcome was comparable, but significantly more MTLE-HS-CoA(-) patients were free of antiepileptic drugs. CONCLUSIONS Overall, our observations support the hypothesis that the pathological process in MTLE-HS is progressive. MTLE-HS-CoA(+) patients are predisposed to increased psychiatric morbidity. In vivo detection of hippocampal CoA accumulation in the future will help us to understand the neurobiological significance of this phenomenon.

Evolution and long term outcome in patients presenting with large demyelinating lesions as their first clinical event

OBJECTIVES To describe the long term evolution and outcome of a homogeneous cohort of patients (n=14) with large demyelinating lesions (LDLs) as the first clinical event from a group of idiopathic inflammatory demyelinating diseases of central nervous system. METHODS Detailed review of LDLs from December 2002-January 2007 was made. Patients had at least two magnetic resonance imaging (MRI) and minimum follow-up of 2years. The disability was assessed using Estimated Expanded Disability Status Scale (EDSS) and Rappaport Disability Rating Scale (DRS) at onset and last follow-up. RESULTS Fourteen consecutive LDL patients (male=7), with mean age 32.7years and mean follow-up of 45.5months were included. Motor deficits (79%) and cognitive symptoms (43%) marked the onset, none had optic neuritis. All except two responded to steroids. Follow-up MRI showed complete resolution in 43%, 57% showing marked reduction in size. On follow-up, 2 relapsed. Mean EDSS and DRS at presentation were 5.93 and 9.07 and at last follow-up were 1.75 and 2.25 (p<0.001). CONCLUSIONS Our data suggests that, patients presenting with LDLs as their first clinical event behaves distinctly in their presentation, imaging characteristics, prognosis and long term outcome as compared to MS and ADEM. Albeit significant disability at the onset, these patients show an excellent response to treatment with good functional recovery in long term and rare relapses.

Calcified neurocysticercosis lesions and antiepileptic drug–resistant epilepsy: A surgically remediable syndrome?

In contrast to the well‐recognized association between acute symptomatic seizures and neurocysticercosis, the association between antiepileptic drug (AED)–resistant epilepsy and calcified neurocysticercosis lesions (CNLs) is poorly understood. We studied the association between AED‐resistant epilepsy and CNLs, including the feasibility and outcome of resective surgery.