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L Anne Mitchell

Publications and source records attributed to L Anne Mitchell.

8 recordsLinked to original sources
PubMed2005

Early seizures after temporal lobectomy predict subsequent seizure recurrence.

Patients are understandably anxious if seizures occur immediately after temporal lobectomy. Such "neighborhood" seizures are commonly regarded as irrelevant to seizure outcome and discounted in outcome measurement. We conducted an in-depth examination of early postoperative seizures (<28 days) and outcome. The risk of recurrence at one postoperative year was calculated using Poisson regression, and statistical adjustments were made for preoperative pathology. Of 321 patients, 69 (22%) experienced early postoperative seizures. These early seizures were associated with subsequent seizure recurrence (rate ratio [RR] 5.9; 95% confidence interval [CI], 4.1-8.4). Among patients with early seizures, the only significant factor was the presence of seizure precipitants, which was associated with a lower recurrence risk. However, when compared with patients with no early seizures, those with precipitants to early seizures had a higher risk of recurrence (RR, 3.0; 95% CI, 1.8-5.2). The risk was higher again for patients without precipitants to early seizures (RR, 7.6; 95% CI, 5.0-11.5). Early seizures and other seizure recurrences in the first postoperative year did not differ in their effect on subsequent outcome (X(2) [3] = 3.4, p = 0.33). We conclude that early postoperative seizures are associated with subsequent seizure recurrence. These findings have implications for patient counseling and the measurement of outcome.

Anterior Temporal Lobectomy↗
PubMed2004

Temporal lobectomy: long-term seizure outcome, late recurrence and risks for seizure recurrence.

There is little information available relevant to long-term seizure outcome after anterior temporal lobectomy, particularly at extended postoperative periods. The aim of this study was an in-depth examination of patterns of longitudinal outcome and potential risk factors for seizure recurrence after lobectomy, utilizing a large patient sample with long follow-up. Included were 325 patients who underwent anterior temporal lobectomy between 1978 and 1998 (mean follow-up 9.6 +/- 4.2 years). Retrospective data were analysed using survival analysis and multivariate regression with Cox proportional hazard models. The probability of complete seizure freedom at 2 years post-surgery was 55.3% [95% confidence interval (CI) 50-61]; at 5 years, 47.7% (95% CI 42-53); and at 10 postoperative years it was 41% (95% CI 36-48). Patients with discrete abnormalities preoperatively (i.e. lesions and hippocampal sclerosis) had a significantly higher probability of seizure freedom than patients without obvious abnormality. The latter group had a pattern of recurrence similar to that in patients with lesions outside the area of excision. After adjustment for preoperative pathology, only the presence of preoperative secondarily generalized seizures had a significant association with recurrence [occasional preoperative generalized seizures, hazard ratio (HR) 1.6, 95% CI 1.1-2.3; frequent seizures, HR 2.0, 95% CI 1.4-2.9 compared with absence of preoperative generalized seizures]. Duration of preoperative epilepsy, age of seizure onset and age at surgery did not have an effect on outcome. Patients with two seizure-free postoperative years had a 74% (95% CI 66-81) probability of seizure freedom by 10 postoperative years. This late seizure recurrence was not associated with any identified risk factors. Specifically, patients with hippocampal sclerosis were not at higher risk. Surprisingly, complete discontinuation of anti-epileptic drugs (AEDs) after two postoperative years was not associated with an increased risk of recurrence (HR 1.03, 95% CI 0.5-2.1). This may be because selection of patients for AED discontinuation is biased towards those individuals perceived as 'low risk'. The results of this study indicate that the lack of an obvious abnormality or the presence of diffuse pathology, and preoperative secondarily generalized seizures are risk factors for recurrence after surgery. Late recurrence after initial seizure freedom is not a rare event; risk factors specific to this phenomenon are as yet unidentified.

Adolescent↗
PubMed2004

Glioneuronal tumours in neurofibromatosis type 1: MRI-pathological study.

Neurofibromatosis type 1 (NF1) is an inherited disorder in which affected individuals develop both benign and malignant tumours at an increased frequency. Glioneuronal tumours, such as ganglioglioma and dysembryoplastic neuroepithelial tumour, have been previously reported in patients with NF1. We describe two patients with glioneuronal tumours and typical clinical features of NF1. Molecular analysis of these tumours did not demonstrate loss of the NF1 gene by fluorescence in situ hybridization (FISH) or immunohistochemistry analysis, suggesting they might not be causally associated with gross defects in NF1 expression. Because of the excellent prognosis following the resection of these tumours, it is important to distinguish them from other NF1-associated tumours.

Adult↗
PubMed2003

Correlation between language organization and diffusion tensor abnormalities in refractory partial epilepsy.

PURPOSE: Atypical language organization is more frequently found in patients with refractory partial epilepsy than in healthy controls; however, the reasons for this are not well known. Here we assess the relation between language laterality index (LI) and white-matter tract changes. METHODS: Nine patients with refractory partial epilepsy were assessed with a 3-T GE scanner. Functional magnetic resonance imaging (fMRI) of language and diffusion tensor imaging (DTI) were acquired. For the fMRI, a noun-verb generation task was performed, all images were motion corrected, and activated pixels in classic language areas were counted. The DTI images were acquired in six standard directions with an initial non-diffusion-weighted scan. The "average anisotropy" was determined in a region of interest in the frontal lobe, temporal lobe, and parietal lobe white matter. An asymmetry index (AI) was calculated for language and DTI. Atypical language lateralization was diagnosed if the lateralization index (LI)-language was smaller than 0.4. RESULTS: Two of the nine patients had atypical language localization (LI-language, -0.6, and 0.3); both had left temporal DTI asymmetry (LI-DTI, -0.3 and -0.2). The remaining seven patients had typical language localization, and no marked DTI abnormalities. Asymmetry in temporal lobe DTI correlated with LI-language (r= 0.8; p = 0.006). CONCLUSIONS: Atypical language lateralization in patients with partial epilepsy may be associated with white-matter tract abnormalities.

Adolescent↗
PubMed2003

MR imaging of epilepsy: state of the art at 1.5 T and potential of 3 T.

Shortly after being introduced in the nineteen eighties, magnetic resonance imaging (MRI) became a key tool for the investigation of patients with epilepsy, due to its ability to acquire high quality images. The strength of the magnetic field of a scanner is measured in tesla (T). This review addresses the clinical and research potential in epilepsy of MR imaging at 1.5 T and 3 T. A typical clinical scanning protocol at 1.5 T for a patient with refractory epilepsy may include T1- and T2-weighted imaging, fluid-attenuated inversion recovery (FLAIR) imaging, and a 3D volume acquisition sequence. A research protocol may add quantification of structural imaging, such as volumetric assessment and T2-relaxometry, together with functional measures, such as MR-spectroscopy, functional MRI and diffusion weighted sequences. MR-spectroscopy assesses the metabolites of the seizure focus and other brain areas. Functional MRI allows localisation of cognitive and sensori-motor function and the ability to assess the spatial relationship of these functions to the seizure focus. Whereas these techniques can be performed at 1.5 T, particularly MR-spectroscopy and functional MRI benefit from increased magnetic field-strength. Higher magnetic field-strength is associated with a higher signal-to-noise ratio (SNR). The increased SNR can allow shorter imaging times for a given resolution, higher resolution for a given imaging time, or combination of both. The use of higher magnetic field-strengths is therefore indicated for the (fast) imaging of ill subjects, for long protocols, including structural, metabolic and functional imaging, and for novel applications, such as continuous EEG recording and functional MRI for the detection of the seizure focus. Disadvantages of MR imaging in epilepsy at a high field-strength of 3 T and above are, apart from engineering and technical challenges, the greater energy deposition into tissue and increased susceptibility to artefacts. So far, magnets of 3 T and above have been used mainly for research applications, however the benefits of high field-strength for MR spectroscopy and functional MRI, and the usefulness of these techniques for the investigation of epilepsy patients are obvious incentives for the use of 3 T systems in routine clinical investigations.

Electroencephalography↗
PubMed2003

Anterior temporal changes on MR images of children with hippocampal sclerosis: an effect of seizures on the immature brain?

BACKGROUND AND PURPOSE: Ipsilateral loss of anterior temporal gray-white matter definition, due mainly to white matter signal intensity abnormality, is frequently seen on MR images of patients with hippocampal sclerosis. Our aim was to determine the prevalence and clinical correlations of these anterior temporal changes in pediatric cases of hippocampal sclerosis and to determine whether cumulative damage from seizures is important for their development. METHODS: We reviewed the MR images and clinical details of 54 children (age range, 1.5-19 years) with typical hippocampal sclerosis. Specific imaging features noted included hippocampal sclerosis, anterior temporal changes, anterior temporal atrophy, and extra-hippocampal abnormality. RESULTS: Thirty-one (57%) of 54 children with hippocampal sclerosis had associated ipsilateral anterior temporal changes. Ipsilateral anterior temporal atrophy was associated with anterior temporal changes (P <.03). Children whose images showed anterior temporal changes were younger at onset of epilepsy (P <.01) and younger at antecedent cerebral insult (P <.03) than those with normal anterior temporal lobes. Most (84%) children whose images showed anterior temporal changes had experienced the onset of epilepsy or antecedent cerebral insult before the age of 2 years (P <.0009). Eighty-one percent of children with anterior temporal changes shown on their images experienced seizures at the time of antecedent insult. CONCLUSION: Ipsilateral anterior temporal changes identical to those observed in adult cases are seen on the MR images of young children with hippocampal sclerosis, with a similar prevalence, and are associated with either epilepsy onset or seizure-related cerebral insult before the age of 2 years. We suggest that the loss of gray-white matter definition may represent a persistent immature appearance, including an abnormality of myelin or myelination, possibly a result of seizures occurring during maturation of the temporal pole.

Adolescent↗
PubMed2002

Ectopic posterior pituitary lobe and periventricular heterotopia: cerebral malformations with the same underlying mechanism?

BACKGROUND AND PURPOSE: Ectopic posterior pituitary lobe often occurs in children with growth hormone deficiency and is part of the spectrum associated with septo-optic dysplasia. Some cases of septo-optic dysplasia are caused by homozygous mutations in the homeobox gene HESX1, whereas heterozygous mutations are associated with milder phenotypes. To date, HESX1 is the only gene associated with ectopic posterior pituitary lobe. We describe an association between ectopic posterior pituitary lobe and periventricular heterotopia in four children without classic features of septo-optic dysplasia and suggest possible mechanisms on the basis of a review of pituitary embryology and recent molecular genetic advances. METHODS: Among 20 children with ectopic posterior pituitary lobe, four had associated periventricular heterotopia. We herein review the clinical and MR imaging findings of these four children. Mutation screening of HESX1 was performed in two. RESULTS: All four children had growth hormone deficiency. None had visual or neurologic disturbances. MR images showed a range of pituitary appearances, with scattered discrete periventricular heterotopia in each case. Other abnormalities were limited to small suprasellar lipomas and callosal dysgenesis. A heterozygous HESX1 mutation was present in one case. CONCLUSION: The coexistence of ectopic posterior pituitary lobe and periventricular heterotopia suggests they have a common underlying genetic basis that is due to gene expression at different locations and stages of development. The presence of a heterozygous HESX1 mutation in one case suggests this gene is important in the development of both ectopic posterior pituitary lobe and periventricular heterotopia and supports their place in the spectrum of septo-optic dysplasia. Further analysis of HESX1 and other genes in related developmental pathways will elucidate their roles in the development of both malformations.

Basic Helix-Loop-Helix Proteins↗