Frederick Andermann

Bio: Frederick Andermann is an academic researcher from Montreal Neurological Institute and Hospital. The author has contributed to research in topics: Epilepsy & Temporal lobe. The author has an hindex of 90, co-authored 365 publications receiving 25638 citations. Previous affiliations of Frederick Andermann include McGill University & Montreal Children's Hospital.

The role of the limbic system in experiential phenomena of temporal lobe epilepsy

Abstract: Experiential phenomena occurring in spontaneous seizures or evoked by brain stimulation were reported by 18 of 29 patients with medically intractable temporal lobe epilepsy who were investigated with chronic, stereotaxically implanted intracerebral electrodes. The phenomena mainly consisted of perceptual (visual or auditory) hallucinations or illusions, memory flashbacks, illusions of familiarity, forced thinking, or emotions. Experiential phenomena did not occur unless a seizure discharge or electrical stimulation involved limbic structures. For such phenomena to occur, seizure discharge or electrical stimulation did not have to implicate temporal neocortex. This was true even for perceptual experiential phenomena. Many experiential responses elicited by electrical stimulation, particularly when applied to the amygdala, were not associated with electrical afterdischarge. Limbic activation by seizure discharge or electrical stimulation may add an affective dimension to perceptual and mnemonic data processed by the temporal neocortex, which may be required for endowing them with experiential immediacy.

Anatomic basis of amygdaloid and hippocampal volume measurement by magnetic resonance imaging

Abstract: Both the amygdala and the hippocampus are involved in the pathogenesis of a number of neurologic conditions, including temporal lobe epilepsy, postanoxic amnesia, and Alzheimer9s disease. To enhance the investigation and management of patients with these disorders, we developed a protocol to measure the volumes of the amygdala and as much of the hippocampus as possible (approximately 90 to 95%) using high-resolution MRI. We present the anatomic basis of these two protocols and our results in normal control subjects. These volumetric studies of the amygdala may clarify the role of this structure in the pathogenesis of temporal lobe epilepsy.

Intrinsic epileptogenicity of human dysplastic cortex as suggested by corticography and surgical results

Abstract: Cortical dysplastic lesions (CDyLs) are often associated with severe partial epilepsies. We describe the electrographic counterpart of this high degree of epileptogenicity, manifested by continuous or frequent rhythmic epileptogenic discharges recorded directly from CDyLs during intraoperative electrocorticography (ECoG). These ictal or continuous epileptogenic discharges (I/CEDs) assumed one of the following three patterns: (1) repetitive electrographic seizures, (2) repetitive bursting discharges, or (3) continuous or quasicontinuous rhythmic spiking. One or more of these patterns were present in 23 of 34 patients (67%) with intractable partial epilepsy associated with CDyLs, and in only 1 of 40 patients (2.5%) with intractable partial epilepsy associated with other types of structural lesions. I/CEDs were usually spatially restricted, thus contrasting with the more widespread interictal ECoG epileptic activity, and tended to colocalize with the magnetic resonance imaging-defined lesion. Completeness of excision of cortical tissue displaying I/CEDs correlated positively with surgical outcome in patients with medically intractable seizures; i.e., three-fourths of the patients in whom it was entirely excised had favorable surgical outcome; in contrast, uniformly poor outcome was observed in those patients in whom areas containing I/CEDs remained in situ. We conclude that CDyLs are highly and intrinsically epileptogenic, and that intraoperative ECoG identification of this intrinsically epileptogenic dysplastic cortical tissue is crucial to decide the extent of excision for best seizure control.

Familial agenesis of the cerebellar vermis A syndrome of episodic hyperpnea, abnormal eye movements, ataxia, and retardation

Abstract: SOME TWO YEARS AGO we investigated a child with profound psychomotor retardation who had had an occipital meningoencephalocele removed at birth. Contrast studies were carried out which showed a large midline defect in the posterior fossa and absence of the vermis. At the time we disregarded the nurses’ comments about the child’s abnormal breathing. A year later, Dr. P. P. Demers referred this patient’s baby brother to us because he was concerned about his abnormal breathing and xetarded development. It was then found that a third and older child in this family was Tetarded, ataxic, and breathing abnormally. Finally we were able to trace yet another sibling who had died in fancy and who, at autopsy, proved to have agenesis of the vermis. This .diagnosis was then confirmed in the two affected living children by contrast studies. From this investigation there emerged a familial syndrome of episodic hyperpnea, abnormal eye movements, ataxia, and mental retardation associated with a common malformation in the four affected siblings, agenesis of the vermis. This syndrome has not previously been described in the literature. The affected children will be presented in the order in which the abnormality was identified, which happens to be in reverse to the birth order (Fig. 1).

The spectrum of SCN1A-related infantile epileptic encephalopathies

Abstract: The relationship between severe myoclonic epilepsy of infancy (SMEI or Dravet syndrome) and the related syndrome SMEI-borderland (SMEB) with mutations in the sodium channel alpha 1 subunit gene SCN1A is well established. To explore the phenotypic variability associated with SCN1A mutations, 188 patients with a range of epileptic encephalopathies were examined for SCN1A sequence variations by denaturing high performance liquid chromatography and sequencing. All patients had seizure onset within the first 2 years of life. A higher proportion of mutations were identified in patients with SMEI (52/66; 79%) compared to patients with SMEB (25/36; 69%). By studying a broader spectrum of infantile epileptic encephalopathies, we identified mutations in other syndromes including cryptogenic generalized epilepsy (24%) and cryptogenic focal epilepsy (22%). Within the latter group, a distinctive subgroup designated as severe infantile multifocal epilepsy had SCN1A mutations in three of five cases. This phenotype is characterized by early onset multifocal seizures and later cognitive decline. Knowledge of an expanded spectrum of epileptic encephalopathies associated with SCN1A mutations allows earlier diagnostic confirmation for children with these devastating disorders.

Implications of normal brain development for the pathogenesis of schizophrenia

Abstract: • Recent research on schizophrenia has demonstrated that in this disorder the brain is not, strictly speaking, normal. The findings suggest that nonspecific histopathology exists in the limbic system, diencephalon, and prefrontal cortex, that the pathology occurs early in development, and that the causative process is inactive long before the diagnosis is made. If these findings are valid and not epiphenomena, then the pathogenesis of schizophrenia does not appear to fit either traditional metabolic, posttraumatic, or neurodegenerative models of adult mental illness. The data are more consistent with a neurodevelopmental model in which a fixed "lesion" from early in life interacts with normal brain maturational events that occur much later. Based on neuro-ontological principles and insights from animal research about normal brain development, it is proposed that the appearance of diagnostic symptoms is linked to the normal maturation of brain areas affected by the early developmental pathology, particularly the dorsolateral prefrontal cortex. The course of the illness and the importance of stress may be related to normal maturational aspects of dopaminergic neural systems, particularly those innervating prefrontal cortex. Some implications for future research and treatment are considered.

Androgen receptor gene mutations in X-linked spinal and bulbar muscular atrophy.

Abstract: X-linked spinal and bulbar muscular atrophy (Kennedy's disease) is an adult-onset form of motorneuron disease which may be associated with signs of androgen insensitivity. We have now investigated whether the androgen receptor gene on the proximal long arm of the X chromosome is a candidate gene for this disease. In patient samples we found androgen receptor gene mutations with increased size of a polymorphic tandem CAG repeat in the coding region. These amplified repeats were absolutely associated with the disease, being present in 35 unrelated patients and none of 75 controls. They segregated with the disease in 15 families, with no recombination in 61 meioses (the maximum log likelihood ratio (lod score) is 13.2 at a recombination rate of 0). The association is unlikely to be due to linkage disequilibrium, because 11 different disease alleles were observed. We conclude that enlargement of the CAG repeat in the androgen receptor gene is probably the cause of this disorder.

From sensation to cognition.

Abstract: Sensory information undergoes extensive associative elaboration and attentional modulation as it becomes incorporated into the texture of cognition. This process occurs along a core synaptic hierarchy which includes the primary sensory, upstream unimodal, downstream unimodal, heteromodal, paralimbic and limbic zones of the cerebral cortex. Connections from one zone to another are reciprocal and allow higher synaptic levels to exert a feedback (top-down) influence upon earlier levels of processing. Each cortical area provides a nexus for the convergence of afferents and divergence of efferents. The resultant synaptic organization supports parallel as well as serial processing, and allows each sensory event to initiate multiple cognitive and behavioural outcomes. Upstream sectors of unimodal association areas encode basic features of sensation such as colour, motion, form and pitch. More complex contents of sensory experience such as objects, faces, word-forms, spatial locations and sound sequences become encoded within downstream sectors of unimodal areas by groups of coarsely tuned neurons. The highest synaptic levels of sensory-fugal processing are occupied by heteromodal, paralimbic and limbic cortices, collectively known as transmodal areas. The unique role of these areas is to bind multiple unimodal and other transmodal areas into distributed but integrated multimodal representations. Transmodal areas in the midtemporal cortex, Wernicke's area, the hippocampal-entorhinal complex and the posterior parietal cortex provide critical gateways for transforming perception into recognition, word-forms into meaning, scenes and events into experiences, and spatial locations into targets for exploration. All cognitive processes arise from analogous associative transformations of similar sets of sensory inputs. The differences in the resultant cognitive operation are determined by the anatomical and physiological properties of the transmodal node that acts as the critical gateway for the dominant transformation. Interconnected sets of transmodal nodes provide anatomical and computational epicentres for large-scale neurocognitive networks. In keeping with the principles of selectively distributed processing, each epicentre of a large-scale network displays a relative specialization for a specific behavioural component of its principal neurospychological domain. The destruction of transmodal epicentres causes global impairments such as multimodal anomia, neglect and amnesia, whereas their selective disconnection from relevant unimodal areas elicits modality-specific impairments such as prosopagnosia, pure word blindness and category-specific anomias. The human brain contains at least five anatomically distinct networks. The network for spatial awareness is based on transmodal epicentres in the posterior parietal cortex and the frontal eye fields; the language network on epicentres in Wernicke's and Broca's areas; the explicit memory/emotion network on epicentres in the hippocampal-entorhinal complex and the amygdala; the face-object recognition network on epicentres in the midtemporal and temporopolar cortices; and the working memory-executive function network on epicentres in the lateral prefrontal cortex and perhaps the posterior parietal cortex. Individual sensory modalities give rise to streams of processing directed to transmodal nodes belonging to each of these networks. The fidelity of sensory channels is actively protected through approximately four synaptic levels of sensory-fugal processing. The modality-specific cortices at these four synaptic levels encode the most veridical representations of experience. Attentional, motivational and emotional modulations, including those related to working memory, novelty-seeking and mental imagery, become increasingly more pronounced within downstream components of unimodal areas, where they help to create a highly edited subjective version of the world. (ABSTRACT TRUNCATED)