A magnetization transfer imaging study in patients with temporal lobe epilepsy and interictal psychosis

Increased cortical thickness in nodes of the cognitive control and default mode networks in psychosis of epilepsy

OBJECTIVE

To explore the cortical morphological associations of the psychoses of epilepsy.

METHODS

Psychosis of epilepsy (POE) has two main subtypes - postictal psychosis and interictal psychosis. We used automated surface-based analysis of magnetic resonance images to compare cortical thickness, area, and volume across the whole brain between: (i) all patients with POE (n = 23) relative to epilepsy-without psychosis controls (EC; n = 23), (ii) patients with interictal psychosis (n = 10) or postictal psychosis (n = 13) relative to EC, and (iii) patients with postictal psychosis (n = 13) relative to patients with interictal psychosis (n = 10).

RESULTS

POE is characterised by cortical thickening relative to EC, occurring primarily in nodes of the cognitive control network; (rostral anterior cingulate, caudal anterior cingulate, middle frontal gyrus), and the default mode network (posterior cingulate, medial paracentral gyrus, and precuneus). Patients with interictal psychosis displayed cortical thickening in the left hemisphere in occipital and temporal regions relative to EC (lateral occipital cortex, lingual, fusiform, and inferior temporal gyri), which was evident to a lesser extent in postictal psychosis patients. There were no significant differences in cortical thickness, area, or volume between the postictal psychosis and EC groups, or between the postictal psychosis and interictal psychosis groups. However, prior to correction for multiple comparisons, both the interictal psychosis and postictal psychosis groups displayed cortical thickening relative to EC in highly similar regions to those identified in the POE group overall.

SIGNIFICANCE

The results show cortical thickening in POE overall, primarily in nodes of the cognitive control and default mode networks, compared to patients with epilepsy without psychosis. Additional thickening in temporal and occipital neocortex implicated in the dorsal and ventral visual pathways may differentiate interictal psychosis from postictal psychosis. A novel mechanism for cortical thickening in POE is proposed whereby normal synaptic pruning processes are interrupted by seizure onset.

Neurobiological mechanisms of psychosis in epilepsy: Findings from neuroimaging studies

Despite the high prevalence and clinical importance of comorbid psychosis in epilepsy, its neurobiological mechanisms remain understudied. This narrative mini-review aims to provide an overview of recent updates in in vivo neuroimaging studies on psychosis in epilepsy, including structural and diffusion magnetic resonance imaging (MRI) and functional and molecular imaging, and to discuss future directions in this field. While the conventional morphological analysis of structural MRI has provided relatively inconsistent results, advanced methods, including brain network analysis, hippocampal subregion volumetry, and machine learning models, have recently provided novel findings. Diffusion MRI, for example, has revealed a reduction in white matter integrity mainly in the frontal and temporal lobes, as well as a disruption of brain white matter networks. Functional neuroimaging, such as perfusion single-photon emission computed tomography (SPECT) or fluorodeoxyglucose positron emission tomography (FDG-PET), often identifies hyperactivity in various brain regions. The current limitations of these more recent studies may include small and sometimes heterogeneous samples, insufficient control groups, the effects of psychoactive drugs, and the lack of longitudinal analysis. Further investigations are required to establish novel treatments and identify clinical diagnostic or disease-monitoring biomarkers in psychosis in epilepsy.

Disrupted White Matter Integrity and Structural Brain Networks in Temporal Lobe Epilepsy With and Without Interictal Psychosis

Background: Despite the importance of psychosis as a comorbidity of temporal lobe epilepsy (TLE), the underlying neural mechanisms are still unclear. We aimed to investigate abnormalities specific to psychosis in TLE, using diffusion MRI parameters and graph-theoretical network analysis.

Material and Methods: We recruited 49 patients with TLE (20 with and 29 without interictal schizophrenia-like psychosis) and 42 age-/gender-matched healthy controls. We performed 3-tesla MRI scans including 3D T1-weighted imaging and diffusion tensor imaging in all participants. Among the three groups, fractional anisotropy (FA), mean diffusivity (MD), and global network metrics were compared by analyses of covariance. Regional connectivity strength was compared by network-based statistics.

Results: Compared to controls, TLE patients showed significant temporal and extra-temporal changes in FA, and MD, which were more severe and widespread in patients with than without psychosis. We observed distinct differences between TLE patients with and without psychosis in the anterior thalamic radiation (ATR), inferior fronto-occipital fasciculus (IFOF), and inferior longitudinal fasciculus (ILF). Similarly, for network metrics, global, and local efficiency and increased path length were significantly reduced in TLE patients compared to controls, but with more severe changes in TLE with psychosis than without psychosis. Network-based statistics detected significant differences between TLE with and without psychosis mainly involving the left limbic and prefrontal areas.

Conclusion: TLE patients with interictal schizophrenia-like psychosis showed more widespread and severe white matter impairment, involving the ATR, IFOF and ILF, as well as disrupted network connectivity, particularly in the left limbic and prefrontal cortex, than patients without psychosis.

Enlarged hippocampal fissure in psychosis of epilepsy

Psychosis of epilepsy (POE) can be a devastating condition, and its neurobiological basis remains unclear. In a previous study, we identified reduced posterior hippocampal volumes in patients with POE. The hippocampus can be further subdivided into anatomically and functionally distinct subfields that, along with the hippocampal fissure, have been shown to be selectively affected in other psychotic disorders and are not captured by gross measures of hippocampal volume. Therefore, in this study, we compared the volume of selected hippocampal subfields and the hippocampal fissure in 31 patients with POE with 31 patients with epilepsy without psychosis. Cortical reconstruction, volumetric segmentation, and calculation of hippocampal subfields and the hippocampal fissure were performed using FreeSurfer. The group with POE had larger hippocampal fissures bilaterally compared with controls with epilepsy, which was significant on the right. There were no significant differences in the volumes of the hippocampal subfields between the two groups. Our findings suggest abnormal development of the hippocampus in POE. They support and expand the neurodevelopmental model of psychosis, which holds that early life stressors lead to abnormal neurodevelopmental processes, which underpin the onset of psychosis in later life. In line with this model, the findings of the present study suggest that enlarged hippocampal fissures may be a biomarker of abnormal neurodevelopment and risk for psychosis in patients with epilepsy.

Bilateral volume reduction in posterior hippocampus in psychosis of epilepsy

OBJECTIVE

Psychosis of epilepsy (POE) occurs more frequently in temporal lobe epilepsy, raising the question as to whether abnormalities of the hippocampus are aetiologically important. Despite decades of investigation, it is unclear whether hippocampal volume is reduced in POE, perhaps due to small sample sizes and methodological limitations of past research.

METHODS

In this study, we examined the volume of the total hippocampus, and the hippocampal head, body and tail, in a large cohort of patients with POE and patients with epilepsy without psychosis (EC). One hundred adults participated: 50 with POE and 50 EC. Total and subregional hippocampal volumes were manually traced and compared between (1) POE and EC; (2) POE with temporal lobe epilepsy, extratemporal lobe epilepsy and generalised epilepsy; and (3) patients with POE with postictal psychosis (PIP) and interictal psychosis (IP).

RESULTS

Compared with EC the POE group had smaller total left hippocampus volume (13.5% decrease, p<0.001), and smaller left hippocampal body (13.3% decrease, p=0.002), and left (41.5% decrease, p<0.001) and right (36.4% decrease, p<0.001) hippocampal tail volumes. Hippocampal head volumes did not differ between groups.

CONCLUSION

Posterior hippocampal volumes are bilaterally reduced in POE. Volume loss was observed on a posteroanterior gradient, with severe decreases in the tail and moderate volume decreases in the body, with no difference in the hippocampal head. Posterior hippocampal atrophy is evident to a similar degree in PIP and IP. Our findings converge with those reported for the paradigmatic psychotic disorder, schizophrenia, and suggest that posterior hippocampal atrophy may serve as a biomarker of the risk for psychosis, including in patients with epilepsy.

Systematic review of structural and functional brain alterations in psychosis of epilepsy

This systematic review critically assesses structural and functional neuroimaging studies of psychosis of epilepsy (POE). We integrate findings from 18 studies of adults with POE to examine the prevailing view that there is a specific relationship between temporal lobe epilepsy (TLE) and POE, and that mesial temporal lobe pathology is a biomarker for POE. Our results show: (1) conflicting evidence of volumetric change in the hippocampus and amygdala; (2) distributed structural pathology beyond the mesial temporal lobe; and (3) changes in frontotemporal functional network activation. These results provide strong evidence for a revised conceptualisation of POE as disorder of brain networks, and highlight that abnormalities in mesial temporal structures alone are unlikely to account for its neuropathogenesis. Understanding POE as a disease of brain networks has important implications for neuroimaging research and clinical practice. Specifically, we suggest that future neuroimaging studies of POE target structural and functional networks, and that practitioners are vigilant for psychotic symptoms in all epilepsies, not just TLE.

Interictal psychosis following temporal lobe surgery: dentate gyrus pathology

BACKGROUND

De novo interictal psychosis, albeit uncommon, can develop in patients following temporal lobe surgery for epilepsy. Pathological alterations of the dentate gyrus, including cytoarchitectural changes, immaturity and axonal reorganization that occur in epilepsy, may also underpin co-morbid psychiatric disorders. Our aim was to study candidate pathways that may be associated with the development of interictal psychosis post-operatively in patients with hippocampal sclerosis (HS).

METHOD

A total of 11 patients with HS who developed interictal psychosis (HS-P) post-operatively were compared with a matched surgical HS group without psychosis (HS-NP). Resected tissues were investigated for the extent of granule cell dispersion, mossy fibre sprouting and calbindin expression in the granule cells. We quantified doublecortin, mini-chromosome maintenance protein 2 (MCM2) and reelin-expressing neuronal populations in the dentate gyrus as well as the distribution of cannabinoid type 1 receptor (CBR1).

RESULTS

The patterns of neuronal loss and gliosis were similar in both groups. HS-P patients demonstrated less mossy fibre sprouting and granule cell dispersion (p < 0.01) and more frequent reduction in calbindin expression in granule cells. There were no group differences in the densities of immature MCM2, doublecortin and reelin-positive cells. CBR1 labelling was significantly lower in Cornu ammonis area CA4 relative to other subfields (p < 0.01); although reduced staining in all hippocampal regions was noted in HS-P compared with HS-NP patients, the differences were not statistically significant.

CONCLUSIONS

The alterations in dentate gyrus pathology found in HS-P patients could indicate underlying differences in the cellular response to seizures. These mechanisms may predispose to the development of psychosis in epilepsy and warrant further investigation.

MTR abnormalities in subjects at ultra-high risk for schizophrenia and first-episode schizophrenic patients compared to healthy controls

BACKGROUND

Neuroimaging studies have suggested gray (GM) and white matter (WM) abnormalities in early stages of schizophrenia. We aimed at evaluating subtle parenchymal alterations in individuals at ultra-high risk (UHR) for transition into psychosis and first-episode schizophrenic (FES) patients by measuring the magnetization transfer ratio (MTR).

METHODS AND MATERIAL

In a cross-sectional study magnetization transfer images and high-resolution volumetric T1-weighted images were acquired in 70 age- and gender-matched subjects (25 UHR subjects, 16 FES patients and 29 controls) in a 1.5Tesla scanner. Following normalization of MTR-maps the intensity histograms were analyzed by performing a Kruskal-Wallis-test.

RESULTS

Gray matter MTR decreases were depicted in UHR subjects solely, involving the cingulate gyrus and precentral cortex. WM MTR alterations were more pronounced in FES than in UHR patients and exclusively affected the frontal lobe bilaterally. In addition, UHR subjects showed bilateral MTR decreases at the stria terminalis though statistically significant only on the left side (p=0.018.)

CONCLUSION

Our results indicate GM affection earlier on during disease progression as well as cumulative WM affection within frontal lobes during transition from UHR to FES. MTR reductions at the stria terminalis of UHR patients points to the involvement of the extended amygdala in the prodromal disease stage.

Resting-state EEG source localization and functional connectivity in schizophrenia-like psychosis of epilepsy

Background

It is unclear whether, like in schizophrenia, psychosis-related disruption in connectivity between certain regions, as an index of intrinsic functional disintegration, occurs in schizophrenia-like psychosis of epilepsy (SLPE). In this study, we sought to determine abnormal patterns of resting-state EEG oscillations and functional connectivity in patients with SLPE, compared with nonpsychotic epilepsy patients, and to assess correlations with psychopathological deficits.

Methodology/Principal Findings

Resting EEG was recorded in 21 patients with focal epilepsy and SLPE and in 21 clinically-matched non-psychotic epilepsy controls. Source current density and functional connectivity were determined using eLORETA software. For connectivity analysis, a novel nonlinear connectivity measure called “lagged phase synchronization” was used. We found increased theta oscillations in regions involved in the default mode network (DMN), namely the medial and lateral parietal cortex bilaterally in the psychotic patients relative to their nonpsychotic counterparts. In addition, patients with psychosis had increased beta temporo-prefrontal connectivity in the hemisphere with predominant seizure focus. This functional connectivity in temporo-prefrontal circuits correlated with positive symptoms. Additionally, there was increased interhemispheric phase synchronization between the auditory cortex of the affected temporal lobe and the Broca's area correlating with auditory hallucination scores.

Conclusions/Significance

In addition to dysfunction of parietal regions that are part of the DMN, resting-state disrupted connectivity of the medial temporal cortex with prefrontal areas that are either involved in the DMN or implicated in psychopathological dysfunction may be critical to schizophrenia-like psychosis, especially in individuals with temporal lobe epilepsy. This suggests that DMN deficits might be a core neurobiological feature of the disorder, and that abnormalities in theta oscillations and beta phase synchronization represent the underlying neural activity.

Neuroanatomical correlates of psychosis in temporal lobe epilepsy: voxel-based morphometry study

BACKGROUND

Temporal lobe epilepsy is associated with a significant risk of psychosis but there are only limited studies investigating the underlying neurobiology.

AIMS

To characterise neuroanatomical changes in temporal lobe epilepsy and comorbid psychosis.

METHOD

The study population comprised all individuals with temporal lobe epilepsy on the epilepsy database at the National Centre for Epilepsy and Epilepsy Neurosurgery in Ireland (Beaumont Hospital) between 2002 and 2006. Ten people with temporal lobe epilepsy with psychosis were matched for age, gender, handedness, epilepsy duration, seizure laterality, severity of epilepsy and anti-epileptic medication with ten comparison participants with temporal lobe epilepsy only. Participants received a magnetic resonance imaging scan and voxel-based morphometry analyses were applied to grey and white matter anatomy.

RESULTS

Significant grey matter reduction was found bilaterally in those with temporal lobe epilepsy with psychosis in the temporal lobes in the inferior, middle and superior temporal gyri and fusiform gyri, and unilaterally in the left parahippocampal gyrus and hippocampus. Significant extratemporal grey matter reduction was found bilaterally in the insula, cerebellum, caudate nuclei and in the right cingulum and left inferior parietal lobule. Significant white matter reduction in those with temporal lobe epilepsy with psychosis was found bilaterally in the hippocampus, parahippocampal/fusiform gyri, middle/inferior temporal gyri, cingulum, corpus callosum, posterior thalamic radiation, anterior limb of internal capsule and white matter fibres from the caudate nuclei, and unilaterally in the left lingual gyrus and right midbrain and superior temporal gyrus.

CONCLUSIONS

Significant grey and white matter deficits occur in temporal lobe epilepsy with psychosis. These encompass the medial temporal lobe structures but also extend to lateral temporal and extratemporal regions. Some of these deficits overlap with those found in schizophrenia.

Neuropsychiatric evaluations of postictal behavioral changes

Postictal behavioral changes (PBCs), including psychosis, aggression, and mood change, are commonly observed in patients with epilepsy. Recognition and description of the clinical manifestations of PBCs would help in understanding and treating patients. Additionally, various quantified objective scales that are widely available in clinical psychiatry could be used to assess the clinical symptoms of PBCs. There are few reports in which objective rating scales have been used to assess neuropsychiatric symptoms in patients with epilepsy. However, there have been a small number of studies on interictal psychosis and depression in which either the Brief Psychiatric Rating Scale or the Hamilton Depression Scale was used. These inventories are likely to be useful for the assessment of PBCs. Other rating scales used for schizophrenia, depression, mania, and aggressive behavior are reviewed here. The author suggests that cross-sectional and longitudinal neuropsychiatric measurement combined with other modalities, including functional neuroimaging, could provide clues to the pathophysiology of PBCs.

Working memory abnormalities in chronic interictal epileptic psychosis and schizophrenia revealed by magnetoencephalography

Working memory (WM) deficits are considered a core cognitive dysfunction in schizophrenia. To determine cognitive abnormalities in chronic interictal psychosis (CIP), and to assess whether these abnormalities are distinguishable from those seen in schizophrenia in terms of WM deficits, we used magnetoencephalography during a WM task performed by patients with CIP, nonpsychotic epilepsy, and schizophrenia and by healthy subjects. Multiple Source Beamformer and Brain-Voyager were used for analysis. In both patients with CIP and those with schizophrenia, we found dorsolateral prefrontal hyperactivation and left inferior temporal hypoactivation, as indicated by alpha event-related desynchronization and synchronization, respectively. Patients with schizophrenia also showed alpha2 event-related desynchronization in the mid-prefrontal cortex relative to healthy controls. Direct comparison of patients with CIP and schizophrenia rendered no difference in source-power changes. Our findings indicate similar functional cognitive abnormalities in CIP and schizophrenia in the prefrontal and left temporal cortex, which supports the possibility that these disorders share common underlying pathophysiological mechanisms.

Brain pathology in first-episode psychosis: magnetization transfer imaging provides additional information to MRI measurements of volume loss

Background

Loss of brain volume in first-episode psychosis can be detected using conventional magnetic resonance imaging (MRI), but subtle changes – not leading to reduction in volume – that may contribute to clinical and cognitive abnormalities, may go undetected. Magnetization transfer imaging (MTI), a technique more sensitive to subtle neuropathological changes than conventional MRI, could yield important information on the extent and nature of structural abnormalities.

Methods

Forty-eight patients (33 males) from a population-based sample with first-episode psychosis (41 with schizophrenia and 7 with schizoaffective psychosis) and 47 healthy volunteers (27 males) were studied. Differences in magnetization transfer ratio (MTR) and white and grey matter volumes between groups were investigated.

Results

In patients, MTR was reduced in right entorhinal cortex, fusiform, dentate and superior frontal gyri and in left superior frontal and inferior/rostral cingulate gyri. Grey matter volume was reduced in right insula, frontal operculum and middle and superior temporal gyri and in left middle temporal gyrus. Grey matter volume increases were seen in patients in the superior frontal gyrus. White matter volume loss was found adjacent to grey matter loss. In patients MTR was lower in all areas of volumetric differences between groups suggesting that both changes may be related. Similar findings were observed when patients with schizoaffective psychosis were removed from the analysis. The correlations between clinical and MRI parameters did not survive correction for multiple comparisons.

Conclusions

MTI frontal and temporal abnormalities suggesting neuroaxonal and myelin changes were more extensive in our patients than those detected with conventional MRI. Our findings also suggest that there is regional variation in the severity of structural brain abnormalities.

Delusions, illusions and hallucinations in epilepsy: 2. Complex phenomena and psychosis

In this second paper the clinical features and electrophysiological underpinnings of more complex psychotic states associated with epilepsy are reviewed. (a) Complex partial status epilepticus, in particular of temporal lobe origin, may result in mental states remarkably similar to those seen in the primary psychoses. This non-convulsive state is associated with prolonged epileptic discharges on intracranial stereoelectroencephalography (SEEG) in hippocampal and other mesial temporal structures, sometimes without abnormalities on the scalp EEG. Where hallucinatory or psychotic symptomatology does occurs, it can be considered an examples of an ictal psychosis. The phenomenology and electrophysiological features of this condition are reviewed. (b) Postictal psychosis is noted for its similarity to schizophrenia-like/paranoid and affective psychoses and there is convincing SEEG evidence that, for some cases at least, the psychosis is not in fact postictal but rather an ictal psychosis due to ongoing limbic seizure activity and a form of non-convulsive status epilepticus. It has been suggested that postictal psychosis should be divided into two sub-groups: the classical 'nuclear' postictal type and an atypical periictal type. (c) Interictal hallucinosis in epilepsy has been poorly studied, but is probably commoner than appreciated. To what extent it represents subclinical epileptic discharges (i.e. auras) is not known. It may interestingly also be associated with abnormal affective states in epilepsy. (d) The interictal psychosis of epilepsy is often indistinguishable from primary schizophrenia. It occurs more commonly in temporal lobe (limbic) epilepsy, in those with frequent seizures and only in patients with a long history of epilepsy (usually over 10 years). There is convincing SEEG evidence of frequent, semi-continuous and sometimes continuous epileptic activity in limbic structures at the time of psychotic and hallucinatory ideation and behaviour, suggesting that in some cases at least, the epileptic activity is the cause of the symptoms. Whether the psychosis is directly 'driven' by subclinical electrographic activity or is indirectly a consequence of function change induced by such activity is not clear. An intriguing question also arises as to whether similar electrophysiological changes could underpin psychosis in patients without epilepsy but evidence on this point is sparse. The effects of temporal lobe surgery on the psychoses of epilepsy are described and these might throw light on the mechanisms of epileptic psychosis. The principles of pharmacological therapy of epileptic hallucinosis and psychosis are outlined.

Schizophrenia and epilepsy: is there a shared susceptibility?

Individuals with epilepsy are at increased risk of having psychotic symptoms that resemble those of schizophrenia. More controversial and less searched is if schizophrenia is a risk factor for epilepsy. Here we review overlapping epidemiological, clinical, neuropathological and neuroimaging features of these two diseases. We discuss the role of temporal and other brain areas in the development of schizophrenia-like psychosis of epilepsy. We underline the importance of ventricular enlargement in both conditions as a phenotypic manifestation of a shared biologic liability that might relate to abnormalities in neurodevelopment. We suggest that genes implicated in neurodevelopment may play a common role in both conditions and speculate that recently identified causative genes for partial complex seizures with auditory features might help explain the pathophysiology of schizophrenia. These particularly include the leucine-rich glioma inactivated (LGI) family gene loci overlap with genes of interest for psychiatric diseases like schizophrenia. Finally, we conclude that LGI genes associated with partial epilepsy with auditory features might also represent genes of interest for schizophrenia, especially among patients with prominent auditory hallucinations and formal thought disorder.

Interictal psychoses in comparison with schizophrenia--a prospective study

PURPOSE

To prospectively investigate the incidence of interictal psychoses of epilepsy patients, and make a comparison between those with interictal psychoses and patients with schizophrenia in respect to their responses to antipsychotic drugs, as well as psychotic states.

METHODS

We undertook a two-part prospective investigation. In Part I, the psychotic episodes of 619 epilepsy patients were investigated, while 182 patients with psychotic syndromes were followed in Part II, of whom 59 were diagnosed with schizophrenia and 13 with epilepsy with interictal psychoses. The Positive and Negative Syndrome Scale was used for efficacy assessment.

RESULTS

The average annual incidence of interictal psychosis was 0.42% during the 56-month study period. A significant difference was found between patients with schizophrenia and epilepsy patients with interictal psychoses in respect to results on the negative subscale of the PANSS at the initial examination (mean scores of 18.1 and 13.2, respectively, p = 0.004). The response rates one year later for these groups were 27.1% and 53.8%, respectively, which showed a trend of better response to the antipsychotic medication by the epilepsy group (p = 0.098). Initial and maximum doses of antipsychotic drugs used for epilepsy patients with interictal psychoses were significantly lower than those used for patients with schizophrenia (p = 0.008 and p = 0.006, respectively).

CONCLUSIONS

Schizophrenia and epileptic psychosis showed different symptom profiles. On average, epilepsy patients with interictal psychoses achieved higher remission rates with lower doses of antipsychotic drugs as compared to patients with schizophrenia in the present 1-year follow-up study.

Psychiatric outcome of surgery for temporal lobe epilepsy and presurgical considerations

In recent years, surgery has become a treatment option for some patients with intractable epilepsy, particularly those with temporal lobe epilepsy. Psychiatric disturbances may complicate the postsurgical outcome in some patients and de novo psychiatric symptoms have been reported. In many but not all epilepsy surgical centres, a psychiatric assessment is included as part of the presurgical evaluation of potential candidates for surgery. This review indicates that affective disorders, namely, depression and anxiety, and psychosis are the most frequently reported postsurgical psychiatric disturbances. Whilst there are no absolute psychiatric contraindications to surgery, certain pre-existing psychiatric conditions may need careful consideration as there may be a risk of postsurgical psychiatric complications. Routine pre- and postsurgical psychiatric evaluations in patients undergoing epilepsy surgery are recommended. Clinicians involved in the care of surgical candidates should be aware of the possible psychiatric complications following surgery and ensure that the psychiatric risks are discussed with the patient and family.

Magnetization transfer magnetic resonance imaging of the brain, spinal cord, and optic nerve

Magnetic resonance imaging is highly sensitive in revealing CNS abnormalities associated with several neurological conditions, but lacks specificity for their pathological substrates. In addition, MRI does not allow evaluation of the presence and extent of damage in regions that appear normal on conventional MRI sequences and that postmortem studies have shown to be affected by pathology. Quantitative MR-based techniques with increased pathological specificity to the heterogeneous substrates of CNS pathology have the potential to overcome such limitations. Among these techniques, one of the most extensively used for the assessment of CNS disorders is magnetization transfer MRI (MT-MRI). The application of this technique for the assessment of damage in macroscopic lesions, in normal-appearing white and gray matter, and in the spinal cord and optic nerve of patients with several neurological conditions is providing important in vivo information-dramatically improving our understanding of the factors associated with the appearance of clinical symptoms and the accumulation of irreversible disability. MT-MRI also has the potential to contribute to the diagnostic evaluation of several neurological conditions and to improve our ability to monitor treatment efficacy in experimental trials.

A neuropsychological study of patients with temporal lobe epilepsy and chronic interictal psychosis

PURPOSE

To characterize the pattern of cognitive deficits in patients with temporal lobe epilepsy (TLE) and interictal (schizophrenia-like) psychosis and to examine the relationship between neuropsychological deficits and Magnetization transfer imaging.

METHODS

Twenty patients with TLE and interictal psychosis were compared to 20 non-psychotic TLE patients. Patients were matched with respect to premorbid IQ, age and conventional MRI findings. A battery of neuropsychological tests was administered. The neuropsychological tests which showed significant group differences were used for correlational analysis with magnetization transfer ratio (MTR) which provides a quantitative measure of macromolecular structural integrity.

RESULTS

Patients with interictal psychosis were significantly more impaired on executive and semantic memory tasks than the non-psychotic TLE group. Vocabulary test scores correlated significantly with MTR reduction in the left fusiform gyrus in the psychotic but not the non-psychotic group.

DISCUSSION

In this study, patients with TLE and interictal psychosis were more cognitively impaired than non-psychotic TLE patients. Our findings suggest that the cognitive deterioration in these patients may occur as the illness progresses and the causes for this are probably multifactorial. Our study also provides further evidence that MTR may be useful in investigating structural correlates of cognitive impairment.