Kathryn A. Hirschorn

MRI hippocampal volumes and memory function before and after temporal lobectomy

We investigated the relationship between preoperative MRI hippocampal volumes and clinical neuropsychological memory test data obtained before and after temporal lobectomy and amygdalohippocampectomy for intractable epilepsy in 44 left (LTL) and 36 right (RTL) temporal lobectomy patients. In LTL patients, the difference (right minus left hippocampal volume) between hippocampal volumes (DHF) was significantly (p < 0.001) correlated (r = 0.61) with postoperative verbal memory change as measured by a delayed memory percent retention score from the Wechsler Memory Scale-Revised, Logical Memory subtest. DHF was also positively associated with postoperative memory for abstract geometric designs in LTL patients (r = 0.49, p < 0.005). Resection of a relatively nonatrophic left hippocampus was associated with poorer verbal and visual memory outcome. In RTL patients, larger right adjusted (for total intracranial volume) hippocampal volume was associated with decline in visual-spatial learning, but not memory, following surgery. MRI hippocampal volume data appear to provide meaningful information in evaluating the risk for memory impairment following temporal lobectomy.

MRI in the presurgical evaluation of patients with frontal lobe epilepsy and children with temporal lobe epilepsy" pathologic correlation and prognostic importance*

We performed magnetic resonance imaging (MRI) using a high-field strength magnet (1.5 T) in two series of 53 patients with intractable partial epilepsy of frontal lobe or temporal lobe origin who subsequently received ablative surgery for their seizure disorder. In the first series of patients the pathologic correlation and prognostic importance of an MRI-identified lesion in the frontal lobe were assessed. Twenty-five percent of the patients with negative MRI studies and 67% of patients with neuroimaging abnormalities restricted to the frontal lobe, were seizure-free at a minimum duration of follow-up of 1 year. None of the patients with a multilobar MRI-detected abnormality was seizure-free postoperatively. In the second study the sensitivity and specificity of MRI-based hippocampal volumetry was determined in pediatric patients with partial epilepsy of temporal lobe origin unrelated to foreign-tissue pathology. Hippocampal formation atrophy in the epileptic temporal lobe was identified in 63% of patients. The sensitivity and specificity of hippocampal volumetry was 100% in patients with mesial temporal sclerosis. The presence of an MRI-detected epileptogenic lesion in the frontal lobe and hippocampal formation atrophy in the temporal lobe may correlate with the underlying pathology and affect the identification of potential candidates for epilepsy surgery.

Quantitative MRI hippocampal volumes: association with onset and duration of epilepsy, and febrile convulsions in temporal lobectomy patients☆

The relationships between preoperatively acquired MRI-based hippocampal volumes (HV), seizure disorder onset and duration, and early childhood febrile convulsions were investigated retrospectively with data from 72 left and 56 right temporal lobectomy patients. Patients with lesional pathology and heterotopic abnormalities were excluded. Age at development of spontaneous seizures unprovoked by an acute illness defined age of seizure disorder onset. Age of onset was subtracted from age at neurosurgery to determine duration. MRI variables included in this study were the right and left HV divided by total intracranial volume (RAHV, LAHV), and the right-left hippocampal difference (DHF). Partial correlations were used to better isolate relationships with onset of recurrent seizures corrected for age at surgery, and age at neurosurgery corrected for age of recurrent seizure onset. Partial correlations between age at neurosurgery and volume were not significant in either group. LAHV (r = 0.42, P < 0.0003) and DHF (r = -0.49, P < 0.0001) were correlated with age of onset in the left lobectomy group. Correlations in the right lobectomy group were not significant. The presence of a febrile convulsion was associated with smaller LAHV (F(1,70) = 10.54, P < 0.002) and larger DHF (F(1,70) = 11.36, P < 0.002) in left temporal lobectomy patients. The presence of a febrile convulsion in the right temporal group was associated with a slightly smaller DHF (F(1,56) = 5.90, P < 0.02), and slightly smaller RAHV (F(1,56) = 4.49, P < 0.04). These data suggest that hippocampal atrophy remains stable over the duration of temporal lobe onset seizure disorders, and is associated with early onset of recurrent seizures in left temporal patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Intractable frontal lobe epilepsy: pathological and MRI features

The clinical, pathological, and at least one year follow-up of 48 patients with intractable frontal lobe partial epilepsy who underwent surgical treatment for their seizure disorder were reviewed. The group consisted of 27 males and 21 females. Preoperative magnetic resonance imaging (MRI) was normal (26 patients), demonstrated focal frontal lobe (16 patients) or multilobar signal abnormalities (6 patients). Postoperatively patients were divided into one of four groups based upon the degree of seizure activity (Class I: seizure free, Class IV: little to no improvement, Classes II/III: intermediate). Eight patients with tumors (low grade gliomas) were Class I (N = 6) or Class II (N = 2) postoperatively. The remaining six patients with focal, completely resected pathological lesions (e.g. tubers, contusions, etc.) also had Class I or Class II outcomes. Of the 31 patients with the pathological diagnosis of gliosis, the outcome was dependent on the MRI appearance. Preoperative MRI scans of these patients were normal (N = 23), or had focal frontal lobe (N = 2) or multilobar (N = 6) abnormalities. The gliosis patients with unilateral frontal MRI lesions had a good outcome (Class I or II) while those with multilobar MRI abnormalities were all Class IV. Successful outcome correlated strongly with both focal frontal lobe MRI and pathological abnormalities in contrast to the less favorable results seen in patients with normal head MRI scans and gliosis or no pathological abnormality on pathological examination. Multilobar MRI abnormalities invariably had the poorest outcome of all patient groups. Thus presurgical MRI is an important tool and predictor of surgical outcome in patients with frontal lobe epilepsy.

Surgery for focal epilepsy in the older patient

Eight of the 237 patients who received a surgical procedure for intractable partial epilepsy at the Mayo Clinic during a 3-year period were 50 years of age or older. All patients had disabling partial seizures of several years in duration that were refractory to anti epileptic drug medication. A neuroimaging-identified epileptogenic lesion prompted referral for surgical treatment in three patients. The only clinically significant morbidity associated with surgery in the eight patients was a transient exacerbation of an aphasia in a patient who underwent a left frontal corticectomy. All eight patients had a favorable seizure outcome, and three patients postoperatively are seizure free. Epilepsy surgery may be an appropriate alternate therapy for select patients in the sixth decade of life or older with medically refractory partial seizures.

Traditional and computerized assessment procedures applied to the evaluation of memory change after temporal lobectomy.

After establishing that 40 temporal lobectomy patients (20 right, 20 left) demonstrated the same pattern of memory compromise as has been reported in prior studies, we examined the sensitivity of computerized tests of everyday memory skills to the cognitive change associated with temporal resection. Multiple cognitive deficits occur after left, but not after right, temporal lobectomies. Memory impairment after surgery is not limited to traditionally structured memory tests but is also evident on tasks designed to simulate activities of daily life.

Gadolinium‐DTPA‐enhanced magnetic resonance imaging in intractable partial epilepsy

We performed magnetic resonance imaging (MRI), before and after the administration of gadolinium-DTPA (Gd-DTPA), in 23 patients with medically refractory partial epilepsy who subsequently had surgical treatment for their seizure disorder. In most patients, 61%, unenhanced and enhanced MRI studies were negative. In 26% the unenhanced image was positive, and the abnormality enhanced with Gd-DTPA. In 13% the unenhanced MR image was positive, but the abnormality did not enhance with Gd-DTPA. Gd-DTPA does not appear to increase the diagnostic yield of MRI in the presurgical evaluation of patients with partial epilepsy if the unenhanced MRIs are normal.