A multidimensional investigation of sleep and biopsychosocial profiles with associated neural signatures

Sleep is essential for optimal functioning and health. Interconnected to multiple biological, psychological and socio-environmental factors (i.e., biopsychosocial factors), the multidimensional nature of sleep is rarely capitalized on in research. Here, we deployed a data-driven approach to identify sleep-biopsychosocial profiles that linked self-reported sleep patterns to inter-individual variability in health, cognition, and lifestyle factors in 770 healthy young adults. We uncovered five profiles, including two profiles reflecting general psychopathology associated with either reports of general poor sleep or an absence of sleep complaints (i.e., sleep resilience) respectively. The three other profiles were driven by sedative-hypnotics-use and social satisfaction, sleep duration and cognitive performance, and sleep disturbance linked to cognition and mental health. Furthermore, identified sleep-biopsychosocial profiles displayed unique patterns of brain network organization. In particular, somatomotor network connectivity alterations were involved in the relationships between sleep and biopsychosocial factors. These profiles can potentially untangle the interplay between individuals' variability in sleep, health, cognition and lifestyle - equipping research and clinical settings to better support individual's well-being.

A multidimensional investigation of sleep and biopsychosocialprofiles with associated neural signatures

Sleep is essential for optimal functioning and health. Interconnected to multiple biological, psychological and socio-environmental factors (i.e., biopsychosocial factors), the multidimensional nature of sleep is rarely capitalized on in research. Here, we deployed a data-driven approach to identify sleep-biopsychosocial profiles that linked self-reported sleep patterns to inter-individual variability in health, cognition, and lifestyle factors in 770 healthy young adults. We uncovered five profiles, including two profiles reflecting general psychopathology associated with either reports of general poor sleep or an absence of sleep complaints (i.e., sleep resilience) respectively. The three other profiles were driven by sedative-hypnotics-use and social satisfaction, sleep duration and cognitive performance, and sleep disturbance linked to cognition and mental health. Furthermore, identified sleep-biopsychosocial profiles displayed unique patterns of brain network organization. In particular, somatomotor network connectivity alterations were involved in the relationships between sleep and biopsychosocial factors. These profiles can potentially untangle the interplay between individuals' variability in sleep, health, cognition and lifestyle - equipping research and clinical settings to better support individual's well-being.

ENIGMA-Sleep: Challenges, opportunities, and the road map

Neuroimaging and genetics studies have advanced our understanding of the neurobiology of sleep and its disorders. However, individual studies usually have limitations to identifying consistent and reproducible effects, including modest sample sizes, heterogeneous clinical characteristics and varied methodologies. These issues call for a large-scale multi-centre effort in sleep research, in order to increase the number of samples, and harmonize the methods of data collection, preprocessing and analysis using pre-registered well-established protocols. The Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) consortium provides a powerful collaborative framework for combining datasets across individual sites. Recently, we have launched the ENIGMA-Sleep working group with the collaboration of several institutes from 15 countries to perform large-scale worldwide neuroimaging and genetics studies for better understanding the neurobiology of impaired sleep quality in population-based healthy individuals, the neural consequences of sleep deprivation, pathophysiology of sleep disorders, as well as neural correlates of sleep disturbances across various neuropsychiatric disorders. In this introductory review, we describe the details of our currently available datasets and our ongoing projects in the ENIGMA-Sleep group, and discuss both the potential challenges and opportunities of a collaborative initiative in sleep medicine.

0287 Motivated Performance While Sleep Deprived: Neurobehavioral Correlates of Attentional Effort Deployment

Introduction

Sleep deprivation (SD) has a negative impact on the motivation to exert effort. This may contribute to the decline in attentional performance observed under SD. In this study we examined how SD affects motivated performance and effort-based decision making. Particularly, we used functional magnetic resonance imaging (fMRI) to uncover the neural mechanisms underlying the interplay between SD and motivated behavior.

Methods

Twenty-seven healthy subjects were tested once after a night of sleep in the lab (9h Time in Bed; Rested Wakefulness = RW), and once after a night of total sleep deprivation (SD). Participants performed an effortful attention task with different incentive levels (0, 10, or 50 cents/fast and correct response). Behavioral performance and fMRI data were collected during task performance. Subsequently, participants performed an effort-based choice task, during which they could choose to earn additional rewards for performing the attention task for a longer duration.

Results

As expected, attentional performance was worse in the SD session compared to the RW session. In addition, performance improved as a function of incentive level both in the RW and the SD session. This reward-effect was accompanied by increased activation in attention-related brain areas, and increased arousal-related thalamus activation. This reward-modulation was more extensive during RW than SD, particularly in the anterior cingulate cortex (ACC) and anterior insula (aIns; both areas involved in effort regulation). Results from the decision making task were less willing to perform the attention task for a further duration after SD compared to RW.

Conclusion

Results show that performance decline after SD is reward-dependent and willingness to perform is reduced. Reward modulation of attention-related brain activation is reduced, particularly in areas that are associated with effort regulation (i.e. ACC and aIns). These findings indicate that motivational factors contribute to decline of vigilance following sleep deprivation.

Support

This work was supported by grants awarded to Dr. Michael Chee from the National Medical Research Council (NMRC/STaR/0015/2013), and the Far East Organization.

0095 Sleep Boosts Schema-Related Memory Consolidation and Inference

Introduction

A schema is a previously learned framework of information that helps the learning and retention of new, but related material. We examined how sleep, compared to staying awake following the acquisition of a schema, and thereafter novel material, affects the consolidation of new memoranda that were either embedded or not into the learned schema. We also tested if sleep affects the inference of hierarchy within these memoranda.

Methods

54 adolescents (mean age 16.6 years; 26 males) learned the age hierarchy of 7 galaxies by viewing adjacent pairs, one at a time e.g. A-B, D-E, and making transitive inferences (If B>C and C>D then B>D). Once this schema was learned to criterion, participants learned two new sets of galaxies: one set comprised 5 galaxies from the schema and 4 new, intercalated galaxies; the other contained 9 unfamiliar galaxies (schema & no-schema conditions). Memory for galaxy ordering was tested immediately after learning and again after 12-hours. One group(n=25) was kept awake in the day, while the other group (n=29) slept overnight for 8-h. Memory was tested for galaxies that were directly adjacent e.g. A-B, as well as for ‘inference pairs’ that were two apart: e.g.:(B-D, C-E).

Results

Change in memory following the respective 12-hour intervals was analyzed using a mixed ANOVA with schema (schema, no-schema) and pair-type (adjacent, inference) as within-subject factors and sleep group (sleep/awake) as the between-subjects factor. There were significant main effects of sleep and pair type as well as a significant interaction, where schema-related memory was better preserved in the sleep group. This group also had higher performance for inference pairs embedded within the original schema.

Conclusion

Sleep benefitted the consolidation of new memoranda embedded in a schema. This benefit was stronger for non-adjacent inference pairs suggesting that sleep boosts insight into non-explicitly declared, hierarchically organized information.

Support

Supported by NMRC/STaR/0015/2013 and NRF2016-SOL002-001

0092 A Daytime Nap Restores Hippocampal Function and Improves Declarative Learning

Introduction

Daytime naps have been shown to improve learning outcomes. One theory underlying enhanced encoding following a nap is via the synaptic downscaling of neurons potentiated during wake - a process facilitated by slow oscillations. In this study, we sought to investigate neural mechanisms underlying enhanced encoding following a nap compared to a waking period using a combination of PSG and fMRI methods.

Methods

40 healthy undergraduates (M=23.3y, SD=2.96y; 10 males) who slept normally the previous night encoded word pair lists across 2 runs in an MRI scanner at 1PM and 4.30PM. In between encoding sessions, participants either stayed awake and watched a documentary (Wake group; N=20), or napped for 90-min while undergoing polysomnography (Nap group; N=20). Approximately 40min after each encoding session, memory of these word lists were assessed in a cued-recall fashion. Performance in each session was measured by percentage of correct responses.

Results

There were no baseline differences in encoding performance. However, a Session x Group interaction effect (p<0.001) was observed whereby performance significantly improved only in the Nap group in the second encoding session (Nap:20±19% vs. Wake:-1±13%). Concurrent to this, fMRI analyses revealed a Session x Run x Group interaction effect in the hippocampus (p=0.002) whereby hippocampal activation during encoding of the word lists increased only in the Nap group. In addition, although there was no association between degree of performance improvement in the nap group with duration of sleep or the various sleep stages (N1,N2,N3,REM), spindle count (12-15Hz) in the Nap group correlated significantly with both performance improvement (rs=0.46) and increase in hippocampal activation (rs=0.46).

Conclusion

These results confirm the benefit of a nap on encoding processes. Hippocampal activation also increased following the nap, which could indicate renewed hippocampal capacity to store new information. While we hypothesized that slow wave sleep would aid in this transfer, we instead found a relationship between spindle count and both degree of performance improvement and increase in hippocampal activation. The interplay between NREM sleep oscillations, hippocampal downscaling and encoding performance could be more complex than originally thought.

Support

National Medical Research Council, Singapore (NMRC/STaR/015/2013) and the Far East Organization.

Sleep Restriction Impairs Vocabulary Learning when Adolescents Cram for Exams: The Need for Sleep Study

STUDY OBJECTIVES

The ability to recall facts is improved when learning takes place at spaced intervals, or when sleep follows shortly after learning. However, many students cram for exams and trade sleep for other activities. The aim of this study was to examine the interaction of study spacing and time in bed (TIB) for sleep on vocabulary learning in adolescents.

METHODS

In the Need for Sleep Study, which used a parallel-group design, 56 adolescents aged 15-19 years were randomly assigned to a week of either 5 h or 9 h of TIB for sleep each night as part of a 14-day protocol conducted at a boarding school. During the sleep manipulation period, participants studied 40 Graduate Record Examination (GRE)-type English words using digital flashcards. Word pairs were presented over 4 consecutive days (spaced items), or all at once during single study sessions (massed items), with total study time kept constant across conditions. Recall performance was examined 0 h, 24 h, and 120 h after all items were studied.

RESULTS

For all retention intervals examined, recall of massed items was impaired by a greater amount in adolescents exposed to sleep restriction. In contrast, cued recall performance on spaced items was similar between sleep groups.

CONCLUSIONS

Spaced learning conferred strong protection against the effects of sleep restriction on recall performance, whereas students who had insufficient sleep were more likely to forget items studied over short time intervals. These findings in adolescents demonstrate the importance of combining good study habits and good sleep habits to optimize learning outcomes.

Lack of Evidence for Regional Brain Volume or Cortical Thickness Abnormalities in Youths at Clinical High Risk for Psychosis: Findings From the Longitudinal Youth at Risk Study

There is cumulative evidence that young people in an "at-risk mental state" (ARMS) for psychosis show structural brain abnormalities in frontolimbic areas, comparable to, but less extensive than those reported in established schizophrenia. However, most available data come from ARMS samples from Australia, Europe, and North America while large studies from other populations are missing. We conducted a structural brain magnetic resonance imaging study from a relatively large sample of 69 ARMS individuals and 32 matched healthy controls (HC) recruited from Singapore as part of the Longitudinal Youth At-Risk Study (LYRIKS). We used 2 complementary approaches: a voxel-based morphometry and a surface-based morphometry analysis to extract regional gray and white matter volumes (GMV and WMV) and cortical thickness (CT). At the whole-brain level, we did not find any statistically significant difference between ARMS and HC groups concerning total GMV and WMV or regional GMV, WMV, and CT. The additional comparison of 2 regions of interest, hippocampal, and ventricular volumes, did not return any significant difference either. Several characteristics of the LYRIKS sample like Asian origins or the absence of current illicit drug use could explain, alone or in conjunction, the negative findings and suggest that there may be no dramatic volumetric or CT abnormalities in ARMS.

Stimulus repetition and hemodynamic response refractoriness in event-related fMRI

We investigated the extent of hemodynamic recovery following the paired presentation of either identical or different faces at two different inter-stimulus intervals (ISI). Signal recovery was consistently better at an ISI of 6 sec compared to 3 sec. Significantly less signal recovery was associated with identical faces compared to different faces in bilateral mid-fusiform and right prefrontal regions but not in the calcarine and posterior fusiform regions. Repetition suppression effects contributed significantly to incomplete signal recovery in a region-specific manner. Simulations using empirically derived data suggest that experiments with shorter ISI (average 4.5-6.0 sec) are as sensitive as experiments with intermediate ISI (average 9 sec) in detecting response differences if experimental duration is equivalent. However, designs using intermediate ISI may be more appropriate if the expected difference in responses is small and if the number of suitable stimuli is limited.

Seeing how we think about words using BOLD contrast fMR imaging

This review examines how blood oxygen level-dependent functional magnetic resonance imaging (fMRI) may be harnessed to study the brain when it engages in language processing tasks. This method makes clinical and scientific contributions to understanding language function. Issues such as the lateralisation of language function, brain plasticity in health, ageing and neurological disease, and as well as how 2 different languages are processed, may all be evaluated by fMRI.

Relative language proficiency modulates BOLD signal change when bilinguals perform semantic judgments. Blood oxygen level dependent

The effect of relative language proficiency on the spatial distribution and magnitude of BOLD signal change was evaluated by studying two groups of right-handed English-Mandarin bilingual participants with contrasting language proficiencies as they made semantic judgments with words and characters. Greater language proficiency corresponded to shorter response times and greater accuracy in the semantic judgment task. Within the left prefrontal and parietal regions, the change in BOLD signal was smaller in a participant's more proficient language. The least proficient performance was associated with right, in addition to left, inferior frontal activation. The results highlight the importance of taking into consideration nature of task and relative language proficiency when drawing inferences from functional imaging studies of bilinguals.

Overlap and dissociation of semantic processing of Chinese characters, English words, and pictures: evidence from fMRI

The functional anatomy of Chinese character processing was investigated using fMRI. Right-handed Mandarin-English bilingual participants made either semantic or perceptual size judgements with characters and pictures. Areas jointly activated by character and picture semantic tasks compared to size judgement tasks included the left prefrontal region (BA 9, 44, 45), left posterior temporal, left fusiform, and left parietal regions. Character processing produced greater activation than picture processing in the left mid and posterior temporal as well as left prefrontal regions. The lateral occipital regions were more active during picture semantic processing than character semantic processing. A similar pattern of activation and contrasts was observed when English words and pictures were compared in another set of bilingual participants. However, there was less contrast between word and picture semantic processing than between character and picture processing in the left prefrontal region. When character and word semantic processing were compared directly in a third group, the loci of activation peaks was similar in both languages but Chinese character semantic processing was associated with a larger MR signal change. The semantic processing of Chinese characters, English words, and pictures activates a common semantic system within which there are modality-specific differences. The semantic processing of Chinese characters more closely resembles English words than pictures.

Auditory and visual word processing studied with fMRI

Brain activations associated with semantic processing of visual and auditory words were investigated using functional magnetic resonance imaging (fMRI). For each form of word presentation, subjects performed two tasks: one semantic, and one nonsemantic. The semantic task was identical for both auditory and visual presentation: single words were presented and subjects determined whether the word was concrete or abstract. In the nonsemantic task for auditory words, subjects determined whether the word had one syllable or multiple syllables. In the nonsemantic task for visual words, subjects determined whether the word was presented in lower case or upper case. There was considerable overlap in where auditory and visual word semantic processing occurred. Visual and auditory semantic tasks both activated the left inferior frontal (BA 45), bilateral anterior prefrontal (BA 10, 46), and left premotor regions (BA 6) and anterior SMA (BA 6, 8). Left posterior temporal (middle temporal and fusiform gyrus) and predominantly right-sided cerebellar activations were observed during the auditory semantic task but were not above threshold during visual word presentation. The data, when averaged across subjects, did not show obligatory activation of left inferior frontal and temporal language areas during nonsemantic word tasks. Individual subjects showed differences in the activation of the inferior frontal region while performing the same task, even though they showed similar response latency and accuracy.

Dorsolateral prefrontal cortex and the implicit association of concepts and attributes

The Implicit Association Test (IAT) examines the differential association of two object categories (e.g. flower and insect) with attribute categories (e.g. pleasant and unpleasant). When items from congruent categories (e.g. flower + pleasant) share a response key, performance is faster and more accurate than when items from incongruent categories (e.g. insect + pleasant) share a key. Performing incongruent word classification engages inhibitory processes to overcome the prepotent tendency to map emotionally congruent items to the same response key. Using fMRI on subjects undergoing the IAT, we show that the left dorsolateral prefrontal cortex, and to a lesser extent the anterior cingulate cortex, mediate inhibitory processes where manipulation of word association is required.

Culture positive tuberculous meningitis: clinical indicators of poor prognosis

Few studies have evaluated culture positive tuberculous meningitis (TBM) as a group. We evaluated certain clinical factors in culture positive TBM which could be associated with a poorer outcome. Out of 40 consecutive TBM patients seen over a period of 4 years in a tertiary referral hospital, 18 culture positive and non-human immunodeficiency virus (HIV) related cases were studied. The mean age was 37.9 +/- 14.9 years (range 9-63); five were males and 13 females. None had any associated active chronic medical illness. Patients (44.4%) started on antituberculous treatment within 24 h of admission. Treatment was initiated at a median time of 48 h upon admission in hospital. Univariate analysis revealed a significant correlation between hydrocephalus (P = 0.007) and poor morbidity and mortality. The other clinical factors were not statistically significant: age (P = 0.36): sex (P = 0.49); symptom duration (P = 0.69); BCG vaccination (P = 0.65); cerebral infarct (P = 0.63); extrameningeal spread (P = 1.00); steroids (P = 1.00); time to treatment (P = 0.94) and stage of disease (P = 0.11). Hydrocephalus was the only significant factor predisposing culture positive TBM patients to a poorer outcome. There was also a trend towards a poorer prognosis in those with advanced stage of the disease.

Processing of visually presented sentences in Mandarin and English studied with fMRI

Comprehension of visually presented sentences in fluent bilinguals was studied with functional magnetic resonance imaging (fMRI) using a set of conceptually similar sentences in two orthographically and phonologically distinct languages, Mandarin and English. Responses were monitored during scanning. Sentence comprehension in each language was compared to fixation in nine subjects and Tamil-like pseudo-word strings in five subjects. Spatially congruent activations in the prefrontal, temporal, and superior parietal regions and in the anterior supplementary motor area were observed for both languages and in both experiments at the individual and group levels of analysis. Proficient bilinguals exposed to both languages early in life utilize common neuroanatomical regions during the conceptual and syntactic processing of written language irrespective of their differences in surface features.

Mandarin and English single word processing studied with functional magnetic resonance imaging

The cortical organization of language in bilinguals remains disputed. We studied 24 right-handed fluent bilinguals: 15 exposed to both Mandarin and English before the age of 6 years; and nine exposed to Mandarin in early childhood but English only after the age of 12 years. Blood oxygen level-dependent contrast functional magnetic resonance imaging was performed while subjects performed cued word generation in each language. Fixation was the control task. In both languages, activations were present in the prefrontal, temporal, and parietal regions, and the supplementary motor area. Activations in the prefrontal region were compared by (1) locating peak activations and (2) counting the number of voxels that exceeded a statistical threshold. Although there were differences in the magnitude of activation between the pair of languages, no subject showed significant differences in peak-location or hemispheric asymmetry of activations in the prefrontal language areas. Early and late bilinguals showed a similar pattern of overlapping activations. There are no significant differences in the cortical areas activated for both Mandarin and English at the single word level, irrespective of age of acquisition of either language.

Right hemisphere language in a neurologically normal dextral: a fMRI study

Dextrals with right cerebral hemisphere dominance for language are rare. Eight neurologically intact dextrals underwent BOLD-fMRI while being presented auditory and visual words. Fortuitously, in one subject, right hemisphere activations with visually presented words were seen in the inferior frontal, premotor regions together with predominantly left cerebellar activation. These were a mirror image of activations obtained from the seven other dextrals. Also mirrored was temporal activation from auditory words which extended more posteriorly on the right side than the left. These results showing mirror organization of language were replicated in another scanning session and also by using a second word task. Although rare, mirrored organization of language can occur in normal dextrals without penalizing language function.

MRI of the fornix and mamillary body in temporal lobe epilepsy

We performed MRI on 27 patients with clinically proven temporal lobe epilepsy (TLE), all with prior EEG lateralisation, and 10 volunteers, studied to evaluate disparity in size arising from biological variation (group 1). Three-dimensional spoiled GRASS (3DSPGR) sequences provided 2-mm contiguous sections of the limbic system, enabling assessment of the hippocampus (HC), fornix (FN) and mamillary body (MB). Measurements of FN and MB width were made from a workstation. Any percentage difference in size was computed. In 19 cases there was unilateral abnormality in the HC (group 2); in 18 and 19 cases respectively there was a smaller FN and MB on the same side as the abnormal HC. This percentage difference in size was significantly greater than that in group 1 in the FN and MB in 17 and 17 cases respectively. Comparison of percentage difference computations for FN and MB between groups 1 and 2 showed high statistical significance (P < 0.0002). In 5 patients with clinical TLE the HC was normal on MRI (group 3). Unequal FN and MB sizes were found in 4, significant in 2. Comparison of percentage difference computations for FN and MB showed statistical significance (P < 0.0005 and P < 0.0003 respectively). There was no case of discordance between the sides of hippocampal abnormality and the smaller FN or MB or between the sides of smaller FN and MB. The strong concordance between the changes in the HC and those in the FN and MB suggests that this combination will play an important role in the assessment of TLE and limbic system abnormality.

Speech and the dominant superior frontal gyrus: correlation of ictal symptoms, EEG, and results of surgical resection

Two patients with seizures characterized by speech arrest had astrocytoma in the superior frontal gyrus (SFG) of the left hemisphere. Preoperative video EEG monitoring of seizures using subdural electrode arrays showed that comprehension, crude vocalization, and limb and tongue movements were preserved during speech arrest. One patient had difficulty writing during seizures. Ictal EEG onset was localized to the SFG without involvement of Broca's area. Electrical stimulation of SFG electrodes reproduced the speech arrest and writing difficulty. Resection of this region reduced seizures but did not result in lasting speech deficit. Cessation of speech with electrical stimulation of the superior frontal gyrus occurs by interrupting control of muscles required for speaking, which occurs independently of simple 'negative' motor effects. We postulate that functional redundancy is the basis for resection of this region without producing significant speech deficits.

Hippocampal volumetry with magnetic resonance imaging: a cost-effective validated solution

PURPOSE

The clinical utility of hippocampal volumetry is well documented, but the materials and techniques required to perform the procedure are not widely available outside major research centers. We describe a personal computer-based method of volumetric data analysis.

METHODS

Using a 1.0-T scanner, we obtained 2-mm-thick tilted coronal MPRAGE magnetic resonance imaging (MRI) scans of 20 healthy volunteers aged 20-38 years. We used an inexpensive utility program to extract image information and an NIH Image for image analysis. The hippocampal formations were traced with a graphics tablet and landmarks described by Watson et al. (Neurology 1992;42:1743-50). Overlays of individual observers' tracings were used to fine tune the selection of landmarks and boundaries. Filled-in silhouette pairs generated from these "training tracings" were compared to determine how well observers could visually quantify area differences.

RESULTS

Visual detection of asymmetry of silhouette pairs was sensitive, but the magnitude of asymmetry was underestimated. We achieved intraobserver coefficients of variation of right/left volume ratios between 0.82 and 3.16 and an interobserver range of volume ratios of 6%. In 20 healthy controls aged 20-38 years, the mean right and left hippocampal volumes were 2,911 mm3 and 2,836 mm3, respectively. The lower limits of normal were 2,217 mm3 for the right and 2,178 mm3 for the left. The mean right/left hippocampal ratio was 1.03, and the limits of normal (3 SD) for this were 0.95 to 1.10.

CONCLUSIONS

Hippocampal volumetry can be performed reliably and economically. Our methodology makes it possible for different observers to generate consistent and comparable measurements.

Mesial temporal lobe epilepsy in Singapore

Mesial temporal lobe epilepsy due to mesial temporal sclerosis is a distinctive syndrome and a surgically remediable form of epilepsy. We present 26 Singaporean cases of mesial temporal lobe epilepsy defined by clinical, electroencephalographic and MR features and validated by good surgical outcome (12 seizure free, 5 with two or fewer seizures) in all 17 patients who have so far undergone surgery and who have been followed up for at least 6 months. Sixty-five percent of patients experienced their first seizure in the setting of a febrile illness. Seventy-three percent of patients had seizure onset before the age of 10 years and the median interval between seizure onset and intractability of seizures was 3.75 years. 80.7% of patients had an aura and an equal number had at least one lateralizing sign during their seizures. Sixty-four percent of patients had predominantly unilateral anterior temporal interictal spikes. Eighty-eight percent of patients had seizures which were lateralised on scalp ictal EEG. MRI abnormalities were most frequently seen in the head and body of the hippocampal formation. Asymmetric hippocampal atrophy was more common than hippocampal T2 or T2* signal changes. There is much similarity in characteristics of mesial temporal lobe epilepsy in our population compared to what has been published regarding Caucasian subjects.

Fulminant Guillain-Barré syndrome with quadriplegia and total paresis of motor cranial nerves as a result of segmental demyelination

Guillain-Barré syndrome (GBS) is a subacute demyelinating polyneuropathy with a monophasic course. Rarely, demyelination may be so severe as to produce electrically unexcitable nerves. We present a patient with fulminant onset of symptoms who was quadriplegic and had bilateral involvement of all motor cranial nerves. Serial EMGs indicated that segmental demyelination was responsible for these clinical findings.

Neuronal migration disorder presenting with epilepsy: a report of five illustrative cases

Neuronal migration disorders are an uncommon but well-recognised cause of medically intractable epilepsy. The increasing availability of magnetic resonance imaging of the brain has made it possible to diagnose this condition ante-mortem. There are several types of migration disorders, each with different radiological and clinical features. A case each of focal cortical dysplasia, focal subcortical heterotopia, double cortex syndrome, periventricular nodular heterotopia and closed lip schizencephaly is presented to highlight the distinctive features of each entity.