Christine Denby

A disproportionate role for the fornix and mammillary bodies in recall versus recognition memory

Uncovering the functional relationship between temporal lobe amnesia and diencephalic amnesia depends on determining the role of the fornix, the major interlinking fiber tract. In this study relating fornix volume with memory, we made magnetic resonance imaging–based volume estimates of 13 brain structures in 38 individuals with surgically removed colloid cysts. Fornix status was assessed directly by overall volume and indirectly by mammillary body volume (which atrophies after fornix damage). Mammillary body volume significantly correlated with 13 out of 14 tests of episodic memory recall, but correlated poorly with recognition memory. Furthermore, as the volumes of the left fornix and the left mammillary bodies decreased, the difference between recall and recognition scores increased. No other structure was consistently associated with memory. These findings support models of diencephalic memory mechanisms that require hippocampal inputs for recall, but not for key elements of recognition.

Voxel based morphometry of grey matter abnormalities in patients with medically intractable temporal lobe epilepsy: effects of side of seizure onset and epilepsy duration

Objectives: To investigate the use of whole brain voxel based morphometry (VBM) and stereological analysis to study brain morphology in patients with medically intractable temporal lobe epilepsy; and to determine the relation between side, duration, and age of onset of temporal lobe epilepsy, history of childhood febrile convulsions, and grey matter structure. Methods: Three dimensional magnetic resonance images were obtained from 58 patients with left sided seizure onset (LSSO) and 58 patients with right sided seizure onset (RSSO), defined using EEG and foramen ovale recordings in the course of presurgical evaluation for temporal lobectomy. Fifty eight normal controls formed a comparison group. VBM was used to characterise whole brain grey matter concentration, while the Cavalieri method of modern design stereology in conjunction with point counting was used to estimate hippocampal and amygdala volume. Age and sex were used as confounding covariates in analyses. Results: LSSO and RSSO patients showed significant reductions in volume (using stereology) and grey matter concentration (using VBM) of the hippocampus, but not of the amygdala, in the presumed epileptogenic zone when compared with controls, but hippocampal (and amygdala) volume and grey matter concentration were not related to duration or age of onset of epilepsy. LSSO and RSSO patients with a history of childhood febrile convulsions had reduced hippocampal volumes in the presumed epileptogenic zone compared with patients without such a history. Left amygdala volume was also reduced in LSSO patients with a history of childhood convulsions. VBM results indicated bilateral thalamic, prefrontal, and cerebellar GMC reduction in patients, which correlated with duration and age of onset of epilepsy. Conclusions: Hippocampal sclerosis is not necessarily the consequence of recurrent temporal lobe seizures. A major cause of hippocampal sclerosis appears to be an early aberrant neurological insult, such as childhood febrile seizures. Secondary brain abnormalities exist in regions outside the presumed epileptogenic zone and may result from recurrent seizures.

Dissociation Between Recall and Recognition Memory Performance in an Amnesic Patient with Hippocampal Damage Following Carbon Monoxide Poisoning

Abstract Some patients with relatively selective hippocampal damage have shown proportionate recall and recognition deficits. Moreover, familiarity as well as recollection have been found to be impaired in some of these patients. In contrast, other patients with apparently similar damage presented with relatively preserved recognition despite having severely impaired recall, and some of these patients have been shown to have preserved familiarity. We report here the case of an amnesic patient who suffered bilateral hippocampal damage and temporoparietal atrophy after carbon monoxide poisoning. On tests matched for difficulty, his recall performance was more severely impaired than his recognition memory, for verbal as well as for visual materials. Moreover, he performed within the range of healthy matched subjects on nine recognition tests out of ten. In a task using the process dissociation procedure, the patients familiarity was preserved although his recollection was impaired. These findings indicate that recall and recognition memory can be dissociated in amnesic patients with hippocampal lesions even when temporoparietal cortical atrophy is also present.

Persistent seizures following left temporal lobe surgery are associated with posterior and bilateral structural and functional brain abnormalities

PURPOSE To perform a quantitative MRI and retrospective electrophysiological study to investigate whether persistent post-surgical seizures may be due to brain structural and functional abnormalities in temporal lobe cortex beyond the margins of resection and/or bilateral abnormalities in patients with temporal lobe epilepsy (TLE). METHODS In 22 patients with left TLE and histopathological evidence of hippocampal sclerosis, we compared pre-surgical brain morphology between patients surgically remedied (Engels I) and patients with persistent post-surgical seizures (PPS, Engels II-IV) using voxel-based morphometry (VBM). Routine pre-surgical EEG and invasive and non-invasive telemetry investigations were additionally compared between patient groups. RESULTS Results indicated widespread structural and functional abnormalities in patients with PPS relative to surgically remedied patients. In particular, patients with PPS had significantly reduced volume of the ipsilateral posterior medial temporal lobe and contralateral medial temporal lobe relative to surgically remedied patients. Furthermore, successful surgery was associated with clear anterior (89%) and unilateral (100%) temporal lobe EEG abnormalities, whilst PPS were associated with widespread ipsilateral (91%) and bilateral (82%) temporal lobe abnormalities. DISCUSSION We suggest that these preliminary data support the hypothesis that PPS after temporal lobe surgery are due to functionally connected epileptogenic cortex remaining in the ipsilateral posterior temporal lobe and/or in temporal lobe contralateral to resection.

Memory loss resulting from fornix and septal damage: impaired supra-span recall but preserved recognition over a 24-hour delay.

Despite increasing evidence that the fornix is important for memory, uncertainty remains about the exact nature of subsequent impairments arising from damage to this tract. This uncertainty is often created by pathology in additional brain structures. The present study involved a young man, DN, who had almost complete bilateral loss of the rostral columns of the fornix and much of the surrounding septum in the left hemisphere following the surgical removal of a cavernous angioma. Quantitative MRI analyses of structure size, normalized to intracranial volume, showed no difference in any of the additional brain regions measured, apart from those areas removed to expose the tumor. DN showed a marked, stable anterograde memory impairment that was still present 4 years postsurgery. In contrast, DN performed within normal levels on most tests of recognition memory. This sparing was most striking when given a 24-hr delay between study and test of the Warrington Recognition Memory Test. This recall/recognition dissociation provides further evidence for neuroanatomical divisions within recognition memory processes.

Foramen ovale Recordings: A Presurgical Investigation in Epilepsy

The aim of our study was to determine when foramen ovale recordings add useful information to scalp EEG recordings and magnetic resonance imaging (MRI) with hippocampal measurements. We evaluated the outcome of 79 patients with non-lesional partial epilepsy with presumed temporal seizure onset. Ictal foramen ovale recordings were performed in 16 patients with normal MRI (‘MRI-negative group’) and 41 patients with lateralizing MRI but non-lateralizing scalp EEG (‘discordant group’). 22 patients with concordant MRI and scalp EEG were not investigated with foramen ovale recordings (‘concordant group’). The seizure-free rate was higher in concordant than discordant patients despite additional investigation with foramen ovale electrodes (71 and 55% seizure free, respectively). No useful localizing information was added with foramen ovale recordings in MRI-negative patients.

Impairment in material-specific long-term memory following unilateral mediodorsal thalamic damage and presumed partial disconnection of the mammillo-thalamic tract

Neuropsychological findings suggest material-specific lateralization of the medial temporal lobes role in long-term memory, with greater left-sided involvement in verbal memory, and greater right-sided involvement in visual memory. Whether material-specific lateralization of long-term memory also extends to the anteromedial thalamus remains uncertain. We report two patients with unilateral right (OG) and left (SM) mediodorsal thalamic pathology plus probable correspondingly lateralized damage of the mammillo-thalamic tract. The lesions were mapped using high-resolution structural magnetic resonance imaging and schematically reconstructed. Mean absolute volume estimates for the mammillary bodies, hippocampus, perirhinal cortex, and ventricles are also presented. Estimates of visual and verbal recall and item recognition memory were obtained using the Doors and People, the Rey Complex Figure Test, and the Logical Memory subtests of the Wechsler Memory Scales. Each patients performance was compared to a group of healthy volunteers matched for demographic characteristics, premorbid IQ, and current levels of functioning. A striking double dissociation was evident in material-specific long-term memory, with OG showing significant impairments in visual memory but not verbal memory, and SM showing the opposite profile of preserved visual memory and significantly impaired verbal memory. These impairments affected both recall and item recognition. The reported double dissociation provides the strongest evidence yet that material-specific lateralization of long-term memory also extends to the anteromedial thalamus. The findings are also discussed in relation to proposals that distinct anatomical regions within the medial temporal lobe, anteromedial thalamus, and associated tracts make qualitatively different contributions to recall and item recognition.

Jazz, guitar, and neurosurgery: the Pat Martino case report.

OBJECTIVE We present the case of a professional jazz guitarist with temporal lobe epilepsy secondary to an arteriovenous cerebral malformation. CASE DESCRIPTION The patient underwent a left temporal lobectomy in 1980. After surgery, he presented with severe retrograde amnesia and complete loss of musical interest and capabilities. The patients musical abilities recovered over time, and he regained his previous virtuoso status. In 2007, his medical history, neuropsychologic functions, and structural magnetic resonance imaging study were examined and revealed a remarkable degree of recovery of memory and musical abilities in the context of extensive temporal lobe resection. The neuropsychologic findings and neuroanatomic features of the magnetic resonance imaging study were analyzed to try to understand the high degree of recovery of both long-term memory and musical processing abilities in this musician. CONCLUSIONS This case reveals the possibility of an unusual degree of cerebral plasticity and reorganization. Additionally, it emphasizes the question of musical virtuosity. This report shows that the musical capabilities of professional musicians, in specific cases, can completely recover even when much of the left temporal lobe has been removed.

The Frequency and Extent of Mammillary Body Atrophy Associated with Surgical Removal of a Colloid Cyst

BACKGROUND AND PURPOSE: Patients who have had a colloid cyst removed from the third ventricle sometimes experience some difficulty with day-to-day memory. This study provided quantitative MR imaging volume measures of 1 structure potentially responsible for mnemonic problems, the mammillary bodies. Additional volume estimates in structures connected to the mammillary bodies sought to determine the specificity of any atrophy. MATERIALS AND METHODS: Volume estimates of the mammillary bodies were performed on 38 patients after surgical removal of colloid cysts and 20 control subjects by the application of stereologic volume-estimation techniques. For the mammillary body measures, 2 groups of MR images were assessed (0.8- and 1.0-mm section thickness) to compare the sensitivity of each imaging sequence for detecting any atrophy. Other structures associated with memory processes, such as the hippocampus and fornix, were also assessed quantitatively to determine whether there was a correlation between mammillary body damage and atrophy in connecting structures. RESULTS: Our investigations established the superiority of 0.8-mm-volume scans over standard isotropic 1.0-mm-thick-volume scans for mammillary body assessments. Comparisons with 20 age-matched controls revealed that patients with colloid cysts frequently showed significant mammillary body atrophy (mean volume of colloid cysts, 0.037 cm3 right and 0.038 cm3 left; control subjects, 0.069 cm3 right and 0.067 cm3 left). In fact, every patient had a mammillary body volume below the control mean, and the majority of patients had a volume decrease of >1 SD (82% right, 74% left). Mammillary body volumes correlated with fornix volumes in the same patient group. CONCLUSIONS: Our results reveal the frequent presence of mammillary body atrophy in patients with surgical removal of colloid cysts and indicate that this atrophy is partly due to a loss of temporal lobe projections in the fornix.

Diabetes mellitus is associated with adverse structural and functional cardiac remodelling in chronic heart failure with reduced ejection fraction.

Background: Diabetes mellitus is associated with an increased risk of death and hospitalisation in patients with chronic heart failure. Better understanding of potential underlying mechanisms may aid the development of diabetes mellitus–specific chronic heart failure therapeutic strategies. Methods: Prospective observational cohort study of 628 patients with chronic heart failure associated with left ventricular systolic dysfunction receiving contemporary evidence-based therapy. Indices of cardiac structure and function, along with symptoms and biochemical parameters, were compared in patients with and without diabetes mellitus at study recruitment and 1 year later. Results: Patients with diabetes mellitus (24.2%) experienced higher rates of all-cause [hazard ratio, 2.3 (95% confidence interval, 1.8–3.0)] and chronic heart failure–specific mortality and hospitalisation despite comparable pharmacological and device-based therapies. At study recruitment, patients with diabetes mellitus were more symptomatic, required greater diuretic doses and more frequently had radiologic evidence of pulmonary oedema, despite higher left ventricular ejection fraction. They also exhibited echocardiographic evidence of increased left ventricular wall thickness and pulmonary arterial pressure. Diabetes mellitus was associated with reduced indices of heart rate variability and increased heart rate turbulence. During follow-up, patients with diabetes mellitus experienced less beneficial left ventricular remodelling and greater deterioration in renal function. Conclusion: Diabetes mellitus is associated with features of adverse structural and functional cardiac remodelling in patients with chronic heart failure.