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Perminder S Sachdev

Publications and source records attributed to Perminder S Sachdev.

31 records · Page 2Linked to original sources
PubMed2005

Periodic limb movements and other movement disorders in sleep: neuropsychiatric dimensions.

Movement disorders such as Parkinson's disease and Tourette's syndrome, primarily manifest during wakefulness, intrude into sleep. There are some disorders, however, such as periodic limb movements in sleep, restless legs syndrome, paroxysmal nocturnal dystonia, bruxism, and somnambulism, which occur primarily during sleep. The diagnosis and management of these disorders pose a challenge to neuropsychiatric practice, not only because they may be difficult to distinguish from other neuropsychiatric disorders, but also because psychiatric disorders are often co-morbid with them. Study of these disorders is necessary for an understanding of the interaction of sleep and movement, and how disturbance in one may affect the other.

Adult↗
PubMed2005

Obsessive-compulsive behaviour: a disorder of decision-making.

OBJECTIVE: Compulsive individuals are habitually indecisive, and indecision reaches its pathological apex in obsessive-compulsive disorder (OCD). With the increasing interest in the neurobiology of decision-making, it may be useful to conceptualize OCD as a disorder of decision-making. METHOD: A selective review of the neurobiological studies of the decision-making process was performed, and the convergence with the understanding of the neurobiology of OCD examined. RESULTS: The dorsolateral, orbitofrontal and anterior cingulate cortices are engaged in multiregion neural subsystems that interact with each other to retain information online, manipulate options, make choices and maintain goals. These interact with the limbic regions, especially the amygdala, in relation to history of reward and emotional valence relating to a choice, and the basal ganglia for behavioural execution. Abnormalities in these regions also characterize OCD and related disorders, therefore leading to problems in making some decisions that are affect-laden by nature or association. CONCLUSION: Conceptualizing OCD as a disorder of decision-making leads to new approaches for its investigation, and novel strategies for both physical and behavioural-cognitive treatments.

Affect↗
PubMed2005

An emotional Stroop functional MRI study of euthymic bipolar disorder.

OBJECTIVE: To identify the brain regions associated with emotional processing in euthymic bipolar patients. METHODS: The study examined 12 euthymic bipolar patients using functional magnetic resonance imaging (fMRI) while performing an emotional Stroop (eStroop) task. The task comprised emotionally valent and neutral words presented in alternating blocks that was designed to implicitly induce affect. In conjunction with fMRI, galvanic skin responses (GSR) were measured to monitor arousal. RESULTS: Euthymic bipolar patients had diminished activation in response to the affective stimuli in both cortical and subcortical brain regions when compared with healthy subjects. In particular, patients had less activation in the left ventral prefrontal cortex suggesting a potential trait deficit. Patients were slower to react than healthy controls, but did not differ with respect to accuracy. CONCLUSIONS: Euthymic bipolar patients are perhaps constrained in their ability to engage affective processing. Diminished ventral prefrontal cortex activation corroborates previous reports of a potential trait deficit, suggesting that 'all is not well in euthymia', although the effects of medication cannot be overlooked.

Adult↗
PubMed2005

Regional cerebral blood flow deficits in mild Alzheimer's disease using high resolution single photon emission computerized tomography.

In spite of its wide availability, single photon emission computerized tomography (SPECT) scanning is uncommonly used in the assessment of Alzheimer's disease (AD) and related dementias. In light of recent advances in scanning protocols and image analysis, SPECT needs to be re-examined as a tool in the diagnosis of dementia. A total of 18 subjects with early AD and 10 healthy elderly control subjects were examined with high resolution SPECT during the performance of a simple word discrimination task. SPECT images were coregistered with individual magnetic resonance imaging scans, allowing delineation of predetermined neuroanatomical Regions of Interest (ROI). There was a gradation of regional cerebral blood flow (rCBF) values in both groups, with the lowest values being in the hippocampus and the highest in the striatum, thalamus and cerebellum. Compared to healthy controls, AD subjects demonstrated lower relative rCBF in parietal and prefrontal cortices. Analysis of individual ROI demonstrated bilateral reduction of rCBF in prefrontal poles, posterior temporal and anterior parietal cortex, and unilateral reduction of rCBF in left dorsolateral prefrontal cortex, right posterior parietal cortex and the left cingulate body. There were no significant differences for hippocampal, occipital or basal ganglia rCBF. Discriminant function analysis indicated that rCBF in the prefrontal polar regions achieved the best classification of cases. SPECT has utility in the diagnostic assessment of AD if standardized and semiquantitative techniques are used.

Aged↗
PubMed2005

Long-term outcome of neurosurgery for the treatment of resistant depression.

Between 1973 and 1995, a total of 76 patients were treated with bilateral stereotactic, orbitomedial lesions for resistant severe depression at the Neuropsychiatric Institute, Sydney, Australia. On follow up after a mean 14.4 years, 24 (31.6%) subjects were confirmed dead, with six having committed suicide. Of the 52 patients still alive (mean age 62.9 years), 23 were interviewed in detail, and lesions verified in 18 with magnetic resonance imaging (MRI). On a 6-point global outcome rating scale, rated by consensus between two independent psychiatrists, five (22.7%) were judged to be completely recovered and another 11 (50%) showed significant improvement. The improvement was noted within days or weeks of the surgery. Adverse effects were epilepsy (2 subjects), marked personality change (1), weight gain (2), and mild personality change (5). Any reported cognitive impairment was mild. No definite predictors of improvement were identified.

Adult↗
PubMed2004

Prevalence of mild cognitive impairment in 60- to 64-year-old community-dwelling individuals: The Personality and Total Health through Life 60+ Study.

This epidemiological study aimed at determining the prevalence of mild cognitive impairment (MCI) in 60- to 64-year-old individuals using different diagnostic criteria. Community dwelling individuals (n = 2,551) in the age range of 60-64 years were recruited randomly through the electoral roll. They were screened using the MMSE and a short cognitive battery, and those who screened positive underwent detailed medical and cognitive assessments. Extant MCI-related diagnoses were established by consensus. Predictive regression models on the sub-sample were used to determine population prevalence for the diagnoses. Of the 224 subjects who screened positive for MCI, 112 underwent a detailed assessment and 74% met the criteria for at least one recognised diagnosis of mild cognitive deficit (MCI and related diagnoses). By predictive regression modelling, the prevalence of any MCI diagnosis was 13.7% (95% CI 9.1-30.2) in the population of 60- to 64-year-olds. The estimated prevalence rates for specific diagnoses were: MCI 3.7%, ageing-associated cognitive decline 3.1%, Clinical Dementia Rating score (0.5) 2.8%, age-associated memory impairment 1%, other cognitive disorders 0.9%, and mild neurocognitive disorder 0.6%. Agreement on 'caseness' between various proposed diagnoses was at best fair and generally poor. Memory and other cognitive problems not meeting the threshold for dementia are relatively common in 60- to 64-year-old individuals living in the community. The prevalence rate varies up to six-fold according to the diagnostic criteria applied, with limited overlap between diagnoses. There is an urgent need for standardization of the criteria.

Activities of Daily Living↗
PubMed2004

Extent and distribution of white matter hyperintensities in stroke patients: the Sydney Stroke Study.

BACKGROUND AND PURPOSE: White matter hyperintensities (WMHs) on T2-weighted MRI are common in stroke patients and healthy elderly individuals. The detailed anatomical distribution of these lesions in stroke patients has not been examined. METHODS: A total of 112 stroke or transient ischemic attack patients and 87 matched control subjects from the Sydney Stroke Study underwent MRI scans that included a T2-weighted fluid-attenuated inversion recovery (FLAIR) sequence. WMHs were delineated from each FLAIR MRI by an automated method. Region of interest and voxel-wise statistical parametric mapping approaches were applied to examine the volume, distribution, and severity of WMHs of the patient and control groups, and subgroups with large or lacunar infarcts. RESULTS: Stroke subjects had significantly more WMHs than controls in all brain regions except the occipital lobe and in all arterial territories except the anterior callosal and anterior medial lenticulostriate. In the frontotemporal regions, average WMH volumes in patients were >3.5x those in controls. The total number of discrete WMHs was not different in the 2 groups, but stroke patients had more large (>20 mm) and high-intensity lesions. Subjects with lacunar infarcts had more WMHs than those with large infarcts, who, in turn, had more WMHs than control subjects. Lacunar infarction subjects had more WMHs than subjects with large thromboembolic or cardioembolic strokes. Those with anterior arterial territory infarction had more WMHs in the frontal regions. Subjects with single or multiple lacunes did not differ in volumes of WMHs. CONCLUSIONS: Stroke patients have significantly more WMHs in nearly every brain region than healthy controls. Those with lacunar infarcts are particularly affected. WMHs represent a significant proportion of the ischemic lesion burden in stroke and transient ischemic attack patients.

Aged↗
PubMed2004

Magnetic resonance spectroscopy in cognitive research.

The neurophysiological basis of cognition is relatively unexplained, with most studies reporting weak relationships between cognition and measures of brain function, such as event-related potentials, brain size and cerebral blood flow. Magnetic resonance spectroscopy (MRS) is an in vivo method used to detect neurochemicals within the brain that are relevant to certain brain processes. The most widely used methods are 1H-MRS and 31P-MRS, which detect compounds that contain hydrogen and phosphorus, respectively. Recent studies have shown that the absolute concentrations or ratios of these neurochemicals, in particular N-acetyl aspartate (NAA), which is associated with neuronal viability, correlate with performance on neuropsychological tests or other measures of cognitive function in normal subjects. Many studies in adults and children have shown a relationship between neurometabolite values and cognitive status or extent of cognitive dysfunction in various neurological and neuropsychiatric disorders. We review these studies and conclude that MRS has potential applications for the study of cognitive processes in health and disease and may be used clinically for differential diagnosis, the early detection of pathology and the examination of longitudinal change.

Animals↗
PubMed2003

Psychotic disorder and traumatic brain injury.

Traumatic brain injury (TBI) can result in serious and disabling neuropsychiatric disorders, such as cognitive deficits and personality change, as well as severe and chronic psychosis. This review focuses on the relationship between TBI and schizophrenia-like psychosis (SLP) including its epidemiology, diagnostic criteria, clinical presentation, psychopathology, risk factors, and pathophysiology. The relationships between post-traumatic epilepsy and SLP, and brain trauma and schizophrenia, are also discussed. The risk of SLP does increase after TBI. The clinical presentation has considerable overlap with primary schizophrenic disorder, with a prominence of persecutory and other delusions and auditory hallucinations, as well as a lack of negative symptoms. The onset is often gradual, with a subacute or chronic course. More severe and diffuse brain injury, especially of the temporal and frontal lobes, is the most prominent risk factor. Genetic load may also play a role, but presence of epilepsy could be a protective factor. Further large and systematic longitudinal studies are needed.

Brain Injuries↗
PubMed2003

Homocysteine as a risk factor for cognitive impairment in stroke patients.

BACKGROUND: Elevated total homocysteine (tHcy) levels are associated with an increased risk of cerebrovascular disease. It is uncertain whether tHcy is also an independent risk factor for cognitive impairment. METHODS: We examined 95 stroke subjects 3 months after their strokes, and 55 healthy comparison subjects, with a detailed neuropsychological assessment, and MRI brain scans in a proportion (n = 97). Baseline measurements of tHcy, serum folate and B(12), creatinine and plasma fibrinogen levels were obtained. RESULTS: tHcy levels were higher in the stroke subjects by a mean 34%. These levels were significantly correlated with the first factor of a principal component analysis of the neuropsychological data, after controlling for age, folate, B(12) and creatinine levels. The correlation of Hcy levels was particularly significant with frontal-executive functioning and attention. tHcy levels were significantly correlated with number of infarcts and total stroke volume in the stroke group, but not with T(2)-weighted deep white matter hyperintensity scores, after correction for age. In the control group, tHcy levels were significantly correlated with ventricle-to-brain ratios as measures of brain atrophy. CONCLUSION: This study provides evidence that high tHcy levels are associated with cognitive impairment, in particular that of frontal-executive function. The major component of this association is accounted for by small and large strokes, but non-vascular neurotoxic effects of tHcy also appear to play a role. tHcy must receive greater attention as a risk factor for cognitive impairment.

Aged↗
PubMed2002

Effects of different frequencies of transcranial magnetic stimulation (TMS) on the forced swim test model of depression in rats.

BACKGROUND: Repetitive transcranial magnetic stimulation has been demonstrated in humans as well as in animal models to have an antidepressant effect, but the optimal frequency of stimulation is not known. We examined this question in a rat model of depression. METHODS: Young male Sprague-Dawley rats were allocated to two placebo (restraint and sham transcranial magnetic stimulation), one active control (imipramine), and four transcranial magnetic stimulation groups at 1, 5, 15 and 25 Hz and 1000 stimuli each. The Porsolt Swim Test was performed on day 1 (experiment 1). In an extension (experiment 2), the treatments were repeated on days 2 through 5, and the Swim Test repeated on days 3, 5, and 7. RESULTS: After one treatment session, all transcranial magnetic stimulation groups had significantly reduced immobility times compared with sham stimulation (p =.000), but the higher frequencies (15 and 25 Hz) did not differ significantly from lower (1 and 5 Hz) frequencies. After three sessions, all transcranial magnetic stimulation groups were different from placebo, and the rapid transcranial magnetic stimulation groups had lower immobility times than the slow transcranial magnetic stimulation groups (p =.035). After five sessions, only 15- and 25-Hz groups were different from control, and on day 7, only the 25-Hz group had reduced immobility. There was an overall difference between fast and slow transcranial magnetic stimulation (p =.010), and 1 Hz was different from the other three transcranial magnetic stimulation conditions (p =.016). CONCLUSIONS: Repetitive transcranial magnetic stimulation reduces immobility time in the Forced Swim Test model of depression, suggesting an antidepressant effect, which is evident at a range (1-25 Hz) of frequencies. With repeated administration, the findings suggest that the antidepressant effect of the higher frequencies, as for imipramine, is likely to be sustained, although the model used for this (i.e., repeating the Swim Test) requires further validation.

Animals↗