Medial forebrain bundle stimulation as a pathophysiological mechanism for hypomania in subthalamic nucleus deep brain stimulation for Parkinson's disease

OBJECTIVE

Hypomania accounts for approximately 4% to 13% of psychotropic adverse events during subthalamic nucleus (STN) deep brain stimulation (DBS) for Parkinson's disease. Diffusion of current into the inferior and medial "limbic" STN is often reported to be the cause. We suggest a different explanation, in which the coactivation of the medial forebrain bundle (MFB), outside the STN, leads to hypomania during STN DBS.

METHODS

Six patients with advanced Parkinson's disease (age, 54 +/- 11 years) underwent bilateral STN DBS surgery. Preoperative diffusion tensor imaging scans for fiber tracking of the MFB were conducted on a 3T magnetic resonance imaging scanner. After implantation, the electrode positions were determined with computed tomography and integrated in a diffusion tensor imaging software environment.

RESULTS

The medial STN was shown to send tributaries to the MFB using it as a pathway to connect to the reward circuitry. One patient, who had a transient, stimulation-induced acute hypomanic episode, showed a direct contact between 1 active electrode contact and these putative limbic STN tributaries to the MFB unilaterally on the left. In 5 asymptomatic patients, the active contacts were between 2.9 and 7.5 mm distant from the MFB or its limbic STN tributaries.

CONCLUSION

We hypothesize that STN DBS-induced reversible acute hypomania might be elicited by inadvertent and unilateral coactivation of putative limbic STN tributaries to the MFB. These findings may provide insight into the neural pathways of hypomania and may facilitate future investigations of the pathophysiology of mood disorders.

Hypomania as an adverse effect of subthalamic nucleus stimulation: report of two cases

Mania following subthalamic nucleus (STN) deep brain stimulation (DBS) is well described and obvious to both the patient and their physician. The authors describe two patients who developed hypomania following STN-DBS but were unaware of their mood disturbance. Two Parkinson's patients with no previous mood disorders received bilateral STN electrodes. Both experienced dramatic improvement in their motor function and neither complained of any side effects. Their families reported detrimental hypomanic behaviour. Readjusting the stimulation parameters resolved the hypomania with continued motor benefits. The authors draw attention to potential adverse effects of STN-DBS that might be neglected by patients.

Regional cerebral glucose metabolism in never-medicated patients with schizophrenia

OBJECTIVE

The purpose of this study was to assess regional cerebral glucose metabolism in patients with schizophrenia who had never received antipsychotic medication and whose olfactory identification ability had been assessed. Two hypotheses were examined. First, the patients were compared with normal controls to determine whether differences in regional cerebral metabolism were apparent. Second, regional rates of metabolism were correlated with olfactory ability and the relation between them determined.

METHODS

The patient (n = 26) and control (n = 32) subjects were scanned at rest using positron emission tomography (PET) after administration of 18F-fluorodeoxyglucose (FDG). In addition, the University of Pennsylvania Smell Identification Test was administered to each patient.

RESULTS

Patients with schizophrenia had reduced rates of glucose metabolism in the right and left thalamus that reached significance if not corrected for multiple comparisons. However, if a Bonferroni correction was applied over the 27 regions of interest, the differences were not significant. Scores on the Smell Identification Test were negatively correlated with 8 regions of interest. When scores were analyzed using multiple regression, the left frontal cortex and the medial parietal cortex were significant predictors.

CONCLUSIONS

The finding of reduced metabolism in the thalami is consistent with some of the previous literature, whereas the negative correlations between specific regions and olfactory function are not consistent with studies using activation paradigms.

Olfactory deficits in schizophrenia are not a function of task complexity

The purpose of the current study was to determine if olfactory identification deficits in patients with schizophrenia were related to task complexity. Given that we had previously reported that male patients with schizophrenia are the most impaired on olfactory identification tests (the University of Pennsylvania Smell Identification Test, UPSIT), we wished to determine whether a similar deficit would exist for this group on a task of similar format and complexity, the Colour Identification Test (CIT). Sixty-five neuroleptically medicated patients with a DSM-III-R diagnosis of schizophrenia and 30 normal control subjects participated. The dependent measures were scores on the UPSIT and CIT. Overall, patients with schizophrenia had significantly lower USPIT scores than did the normal control subjects whereas no mean difference was observed for colour identification. Male patients with schizophrenia had olfactory identification deficits but performed comparably to all other groups on the CIT. Furthermore, microsmic patients with schizophrenia had CIT scores that did not differ from normal control subjects. Finally, CIT and UPSIT scores were not significantly correlated for the study sample as a whole. The results of this study suggest that the olfactory identification deficits observed in patients with schizophrenia likely reflect abnormalities of brain areas involved in olfactory pathways and are not a function of task complexity.

Metabolic subtypes in patients with schizophrenia

Patterns of regional cerebral glucose metabolism were examined in a group of patients with schizophrenia (n = 17) and normal controls (n = 16) to determine if different metabolic profiles were present. For the patients with schizophrenia, two profiles were found. The first was characterized by a normal "shape" but overall reductions in cerebral metabolism. The second had focal reductions in frontal metabolism. This latter group also had significantly larger frontal horns than the other schizophrenic group. The two groups with schizophrenia did not differ on other attributes or clinical variables. These results are discussed in terms of our understanding of heterogeneity in schizophrenia and etiology.

Olfactory deficits in neuroleptic naive patients with schizophrenia

Because previous studies have shown deficits in olfactory identification for male patients with schizophrenia, either withdrawn from or receiving neuroleptic medication, the purpose of the current study was to determine if such deficits occurred in male patients who had never received neuroleptics. A sample of male (n = 30) and female (n = 10) patients as well as age appropriate controls (males, n = 28, females, n = 30) was assessed in terms of olfactory acuity and identification ability. No differences were found in olfactory acuity, but an olfactory identification deficit was present in 31% of the male patients with schizophrenia. As the olfactory pathways project through the limbic system and to the orbitofrontal cortex, odour identification may be a measure of the functional integrity of these structures. Therefore, these results suggest that for a sub-sample of male patients, the functional integrity of these structures is compromised.

Structural brain imaging abnormalities associated with schizophrenia and partial trisomy of chromosome 5

Chromosomal abnormalities occurring in association with mental illness provide a unique opportunity to study the interaction of genetic abnormalities and the brain in mental illness. Four individuals from a family in which schizophrenia was found to cosegregate with a partial trisomy of chromosome 5 were studied with computed tomography and magnetic resonance imaging. Temporal lobe atrophy was found in the two trisomic males and in the asymptomatic balanced translocation female. In addition, a large cavum septum pellucidum and a cavum vergae were found in the older trisomic individual. Scans from the normal male were free of abnormalities. These results suggest that molecular studies of the translocation breakpoints in this chromosomal abnormality may be of interest, and encourage further studies of brain structure in other chromosomal abnormalities associated with psychosis.

A comparison of the matching of emotional information by depressive and organic patients

The ability to match complex emotional stimuli was assessed in depressed and organic neuropsychiatric patients. Subjects were 13 nonorganic-depressed, 13 organic-depressed, 10 organic-nondepressed, and 10 nonorganic-nondepressed right-handed adults. They were required to match pictures, sentences, and faces on the basis of emotional content in order to determine whether depression resulted in difficulties in analyzing emotional information consistent with those seen in organic patients. Depression produced an error pattern for the matching of complex emotional information that was suggestive of right hemisphere dysfunction. It was unclear if this was due to emotional processing defects or a more generalized deficit in conceptual processes.

Primacy and recency effects in the assessment of memory using the Rey Auditory Verbal Learning Test

The present study examined the manifestation of the primacy and recency effects in patients with anterior brain damage, posterior brain damage, and psychiatric inpatients with no known organic impairment. All three groups of patients demonstrated both a primacy and a recency effect on the Rey Auditory Verbal Learning Test (RAVLT). Differences among the three groups with respect to the magnitude of primacy and recency as well as with other variables reflecting free recall were nonsignificant. These findings limit the use of primacy and recency for the differentiation of memory deficits due to organic and nonorganic causes.

Regional metabolism in microsmic patients with schizophrenia

The cerebral glucose metabolism of eight patients with schizophrenia and an olfactory agnosia was compared with that of eight normosmic patients with schizophrenia and eight normal controls. Since all patients were scanned while on their current medication regimen, the duration and dosage of the medication of the two patient groups were compared. Similarly, duration and dosage were correlated with absolute regional metabolic rates. No significant effects were found in these analyses. The patients with schizophrenia had significantly lower rates of frontal metabolism than the normal controls. However, the patients with schizophrenia and an olfactory agnosia had a lower right basal ganglia and thalamic metabolism than the normosmic patients with schizophrenia.

Differences in neuropsychological performance in psychiatric, anterior- and posterior-cerebral dysfunctioning groups

The neuropsychological performance of psychiatric, anterior- and posterior-cerebral dysfunctioning groups was compared using both raw scores and scores statistically adjusted for the effects of age, education, gender, and overall level of intellectual functioning. Between 5% and 37% of the variance of the subtests of the WAIS-R and between 9% and 58% of the variance associated with the neuropsychological variables was accounted for by the demographic variables. Using raw scores, ten of the twenty-five tests showed significant overall differences among the groups, while only five of the contrast using adjusted scores were significant. Anterior- and posterior-cerebral dysfunctioning groups generally were significantly more impaired than the psychiatric group. Memory and problem-solving variables were the most sensitive to the removal of demographic variance, while psychomotor test scores were the most robust. Differences among cerebrally impaired and psychiatric groups may be obscured by demographic variables or levels of general intellectual functioning.

Neuropsychological performance in psychiatric patients with or without documented brain dysfunction

The current study examined neuropsychological performance of schizophrenic and depressed patients with and without structural or EEG signs of brain dysfunctioning. The neuropsychological test battery was designed to sample intellectual functioning, psychomotor skills, nonverbal memory, and novel problem solving ability. Patients were classified into four groups: schizophrenics without signs of brain dysfunctioning, schizophrenics with signs of brain dysfunctioning, depressed without signs of brain dysfunctioning, and depressed with signs of brain dysfunctioning. The Trail Making Test--Parts A & B, the difference between these two components of the Trail Making Test, the World Fluency Test and a Laterality Index based on the age scale scores of the WAIS significantly discriminated between patients with and without brain dysfunction. Using these variables and a Linear Discriminant Function Analysis, we found that 84.5% of our subjects could be correctly classified. Substantially fewer patients could be correctly classified with respect to their psychiatric diagnosis (i.e., 66.7% correct classification). In fact, only the PIQ from the WAIS-R showed significant differences between the depressed and schizophrenic subjects. Poor neuropsychological performance was interpreted as showing more than the behavioral disorganization associated with psychiatric states and was felt to be related to the presence of objective signs of brain dysfunctioning.

Olfactory deficits in schizophrenia

Olfactory discrimination was measured in patients with schizophrenia who were on neuroleptic medication and was compared with other psychiatric patients receiving neuroleptics and normal controls. The performance of the patients with schizophrenia was significantly lower than the psychiatric and normal controls. The latter two groups performed at equivalent levels. The findings are discussed with respect to olfactory deficits found in patients with cerebral lesions and with abnormalities of specific neurotransmitter systems.

Temporal lobe involvement in multiple sclerosis patients with psychiatric disorders

Patients with multiple sclerosis (MS) frequently develop psychiatric disturbances. The clinical histories and magnetic resonance imaging results from eight patients with MS and psychiatric disorders were compared with those from eight control MS patients matched for age, sex, duration and severity of illness, and clinical course. Both groups had widespread lesions on the magnetic resonance imaging scans; however, the psychiatric group had more clinically defined sites of MS involvement, possibly indicating a difference in the biologic activity of the lesions in this group. The total lesion area was not different between the groups. However, the distribution of lesions did differ; the psychiatric group had significantly more temporal lobe involvement than the control group. These results indicate a role for the cerebral lesions themselves, particularly those in the temporal lobes, in the genesis of psychiatric disorders in MS.

Clinical utility of three measures of frontal lobe dysfunction in neuropsychiatric samples

The utility of the Word Fluency Test, Wisconsin Card-Sorting Test, and a shorter form of the Categories Test as screening instruments for detecting frontal lobe dysfunction in a neuropsychiatric setting was examined. On the basis of clinical and neurological examination, patients were assigned to one of three groups: frontal lobe injured, brain impaired excluding the frontal areas, and psychiatric with no evidence of brain dysfunctioning. It was possible to assign correctly 66.3% of the patients to their respective groups. The Word Fluency Test made the strongest contribution to the prediction of the presence of frontal lobe pathology, even when the effects of age and postmorbid intellectual functioning were controlled. The results were consistent with the interpretation of lowered verbal fluency and deficits in the capacity to suppress habitual behaviour as a major feature of frontal lobe dysfunctioning.