Biomedical subjects

Kenneth Perrine

Publications and source records attributed to Kenneth Perrine.

5 recordsLinked to original sources

PubMed2006

Metabolic brain networks associated with cognitive function in Parkinson's disease.

The motor manifestations of Parkinson's disease (PD) have been linked to an abnormal spatial covariance pattern involving basal ganglia thalamocortical pathways. By contrast, little is known about the functional networks that underlie cognitive dysfunction in this disorder. To identify such patterns, we studied 15 non-demented PD patients using FDG PET and a voxel-based network modeling approach. We detected a significant covariance pattern that correlated (p<0.01) with performance on tests of memory and executive functioning. This PD-related cognitive pattern (PDCP) was characterized by metabolic reductions in frontal and parietal association areas and relative increases in the cerebellar vermis and dentate nuclei. To validate this pattern, we analyzed data from 32 subsequent PD patients of similar age, disease duration and severity. Prospective measurements of PDCP activity predicted memory performance (p<0.005), visuospatial function (p<0.01), and perceptual motor speed (p<0.005) in this validation sample. PDCP scores additionally exhibited an excellent degree of test-retest reliability (intraclass correlation coefficient, ICC=0.89) in patients undergoing repeat FDG PET at an 8-week interval. Unlike the PD-related motor pattern, PDCP expression was not significantly altered by antiparkinsonian treatment with either intravenous levodopa or deep brain stimulation (DBS). These findings substantiate the PDCP as a reproducible imaging marker of cognitive function in PD. Because PDCP expression is not altered by routine antiparkinsonian treatment, this measure of network activity may prove useful in clinical trials targeting the progression of non-motor manifestations of this disorder.

Brain↗

PubMed2005

Brain stimulation reveals critical auditory naming cortex.

One challenge in dominant temporal lobe epilepsy surgery is to remove sufficient epileptogenic tissue without compromising post-operative language functioning. Pre-resection electrical stimulation mapping enables identification of language areas that can be spared from resection, and also provides a unique opportunity to investigate brain-language relationships. Visual object naming is the gold standard for identifying 'essential' language cortex; however, sparing visual naming (VN) sites has not reliably prevented post-operative language decline. In addition to visual object naming, we included a more 'ecologically valid' auditory description naming task in our pre-resection cortical mapping protocol. Of the seven patients who had auditory naming (AN) sites removed, six declined post-operatively, whereas of the 12 patients who did not have AN sites removed, only 3 declined post-operatively (P = 0.02), suggesting an association between AN site removal and post-operative naming decline. Interestingly, although VN sites were preserved in all patients, AN site removal resulted in decline in both auditory and VN tasks. These findings not only have potentially critical clinical significance, but also argue for modality specificity, with considerable integration within the semantic system.

Adolescent↗

PubMed2004

Dexmedetomidine and neurocognitive testing in awake craniotomy.

Patients are selected for awake craniotomy when the planned procedure involves eloquent areas of the brain, necessitating an awake, cooperative patient capable of undergoing neurocognitive testing. Different anesthetic combinations, including neurolept, propofol with or without opioid infusions, and asleep-awake-asleep techniques, have been reported for awake craniotomy. In all these techniques, respiratory depression has been reported as a complication. In this case series dexmedetomidine, the highly selective alpha-2 adrenoreceptor agonist, was selected for its lack of respiratory depression as well as its sedative and analgesic properties. The charts of 10 consecutive patients who underwent awake craniotomy with dexmedetomidine infusion were reviewed. Five of the patients underwent "asleep-awake" technique with a laryngeal mask airway and volatile agent. Five patients received moderate to conscious sedation. All patients received a dexmedetomidine load of 0.5 to 1.0 microg/kg over 20 minutes followed by an infusion at rates of 0.01 to 1.0 microg/kg per hour. Four patients had extensive sensory and motor testing, and six underwent neurocognitive testing, including naming, reading, counting, and verbal fluency. There were no permanent neurologic deficits, except one patient who had an exacerbation of preoperative language difficulties. Dexmedetomidine appears to be a useful sedative for awake craniotomy when sophisticated neurologic testing is required.

Adrenergic alpha-Agonists↗

PubMed2002

Relationships among the metabolic patterns that correlate with mnemonic, visuospatial, and mood symptoms in Parkinson's disease.

OBJECTIVE: A multivariate analysis of baseline brain metabolism was used to investigate the relationships among pathophysiological mechanisms responsible for cognitive dysfunction and dysphoria in nondemented patients with Parkinson's disease. METHOD: Using [(18)F]fluorodeoxyglucose positron emission tomography and neuropsychological tests, the authors studied 15 nondemented patients who had Parkinson's disease without major depression (DSM-III-R). Their mean age was 59.2 years (SD=9.2), the mean rating of Parkinson's disease stage (Hoehn and Yahr scale) was 3.3 (SD=0.9), and all had Mini-Mental State Examination scores of 24 or higher. To identify specific regional patterns of brain metabolism associated with abnormal cognitive and mood functioning, the data were analyzed by using brain-behavior partial least squares. This multivariate voxel-based analysis allowed detection of significant topographic patterns of metabolic activity and quantification of the extent to which each topographic pattern correlated with scores on mnemonic, visuospatial, and dysphoric tests. RESULTS: Two significant, independent topographic patterns were identified. Pattern 1 included parieto-occipito-temporal and medial temporal brain regions, and pattern 2 included the lateral frontal and anterior limbic cortex. Patterns 1 and 2 exhibited a double dissociation in their behavioral correlates: pattern 1 correlated with both visuospatial and mnemonic functioning but not with dysphoria; pattern 2 correlated with dysphoria but not with the cognitive measures. CONCLUSIONS: The authors used the independence of topographic patterns and the size of correlations between topographic patterns and behavior to infer relationships among the pathophysiological processes responsible for the correlations. The finding that mildly abnormal mnemonic and visuospatial functioning correlated with the same topographic pattern suggests that a common pathophysiology underlies this marker of cognition in Parkinson's disease. By contrast, the independence of the two topographic patterns supports the notion that different mechanisms underlie cognitive and dysphoric symptoms in nondemented patients with Parkinson's disease.

Adult↗

PubMedDate not supplied

Mapping the functional anatomy of sentence comprehension and application to presurgical evaluation of patients with brain tumor.

BACKGROUND AND PURPOSE: The main clinical indication for functional MR imaging (fMRI) has been to preoperatively map the cortex. Motor paradigms to activate the cortex are simple and robust; however, language tasks show greater variability and difficulty. The aim of this study was to develop a language task with an adequate control task to engage the areas of the posterior temporal lobe responsible for sentence comprehension. METHODS: We performed a cloze paradigm requiring silent reading of a visually presented sentence-completion task based on semantic meaning versus a letter-scanning epoch requiring the completion of nonlinguistic strings or a rest period. Before this task was clinically used in two patients epilepsy and cavernous angioma, its feasibility and accuracy were tested in 14 healthy right-handed participants. RESULTS: Results showed significant activation of the posterior temporal cortex, including a broad area across the posterior left temporal cortex extending into the inferior parietal lobule. When the sentence completion-minus-letter string task was compared with the sentence completion-minus-rest task, increased activation was present in the posterior temporal lobe. CONCLUSION: Decreased significant activation during the sentence completion-minus-rest contrast may be attributed to increased noise from intersubject variability in the rest period. Our results suggest that this task elucidates areas important to reading comprehension in the posterior and inferior temporal regions that verbal fluency and auditory discrimination tasks do not. Data from two cases are summarized to exemplify the input of this task for neurosurgery.

Adult↗