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K J Black

Publications and source records attributed to K J Black.

At least 19 recordsLinked to original sources
PubMed2004

Pathophysiology of parkinsonism due to hydrocephalus.

We report a patient with hydrocephalus who developed levodopa responsive parkinsonism and severe bradyphrenia associated with shunt malfunction and revision. Magnetic resonance imaging revealed periaqueductal edema involving medial substantia nigra. [18F]dopa positron emission tomography demonstrated reduced uptake in the caudate and putamen with relative sparing of the posterior putamen. Hydrocephalus associated with shunt malfunction can cause a distinct parkinsonian syndrome with greater dysfunction of projections from the medial substantia nigra to anterior striatum than in idiopathic Parkinson's disease.

Adult↗
PubMed2003

Long term treatment and disease severity change brain responses to levodopa in Parkinson's disease.

OBJECTIVES: Degeneration of nigrostriatal neurons and subsequent striatal dopamine deficiency produce many of the symptoms of Parkinson disease (PD). Initially restoration of striatal dopamine with oral levodopa provides substantial benefit, but with long term treatment and disease progression, levodopa can elicit additional clinical symptoms, reflecting altered effects of levodopa in the brain. The authors examined whether long term treatment affects the brain's response to levodopa in the absence of these altered clinical responses to levodopa. METHODS: Positron emission tomography (PET) measurements were used of brain-blood flow before and after an acute dose of levodopa in three groups: PD patients treated long term with levodopa without levodopa induced dyskinesias, levodopa naive PD patients, and controls. RESULTS: It was found that the PD group treated long term responded to acute levodopa differently from controls in left sensorimotor and left ventrolateral prefrontal cortex. In both regions, the treated PD group had decreased blood flow whereas the control group had increased blood flow in response to levodopa. Levodopa naive PD patients had little or no response to levodopa in these regions. Within the treated PD group, severity of parkinsonism correlated with the degree of abnormality of the sensorimotor cortex response, but not with the prefrontal response. CONCLUSIONS: It is concluded that long term levodopa treatment and disease severity affect the physiology of dopaminergic pathways, producing altered responses to levodopa in brain regions associated with motor function.

Administration, Oral↗
PubMed2001

Template images for nonhuman primate neuroimaging: 1. Baboon.

Coregistration of functional brain images across many subjects offers several experimental advantages and is widely used for studies in humans. Voxel-based coregistration methods require a high-quality 3-D template image, preferably one that corresponds to a published atlas. Template images are available for human, but we could not find an appropriate template for neuroimaging studies in baboon. Here we describe the formation of a T1-weighted structural MR template image and a PET blood flow template, derived from 9 and 7 baboons, respectively. Custom software aligns individual MR images to the MRI template; human supervision is needed only to initially estimate any gross rotational misalignment. In these aligned individual images, internal subcortical fiducial points correspond closely to a photomicrographic baboon atlas with an average error of 1.53 mm. Cortical test points showed a mean error of 1.99 mm compared to the mean location for each point. Alignment of individual PET blood flow images directly to the PET template was compared to a two-step alignment process via each subject's MR image. The two transformations were identical within 0.41 mm, 0.54 degrees, and 1.0% (translation, rotation, and linear stretch; mean). These quantities provide a check on the validity of the alignment software as well as of the template images. The baboon structural MR and blood flow PET templates are available on the Internet (purl.org/net/kbmd/b2k) and can be used as targets for any image registration software.

Animals↗
PubMed2001

Template images for nonhuman primate neuroimaging: 2. Macaque.

Neuroimaging studies are increasingly performed in macaque species, including the pig-tailed macaque (Macaca nemestrina). At times experimental questions can be answered by analysis of functional images in individual subjects and reference to a structural image in that subject. However, coregistration of functional brain images across many subjects offers the experimental advantage of enabling voxel-based analysis over multiple subjects and is therefore widely used in human studies. Voxel-based coregistration methods require a high-quality 3D template image. We created such templates, derived from T1-weighted MRI and blood-flow PET images from 12 nemestrina monkeys. We designed the macaque templates to be maximally compatible with the baboon template images described in a companion paper, to facilitate cross-species comparison of functional imaging data. Here we present data showing the reliability and validity of automatic image registration to the template. Alignment of selected internal fiducial points was accurate to within 1.9 mm overall (mean) even across species. The template images, along with copies aligned to the UCLA nemestrina brain atlas, are available on the Internet (purl.org/net/kbmd/n2k) and can be used as targets with any image registration software.

Animals↗
PubMed2000

Response to levodopa challenge in Tourette syndrome.

A dopaminergic excess has been commonly postulated in the pathophysiology of tics, and an early report described acute worsening of tics with levodopa. However, dopamine agonists sometimes improve tics. We undertook this pilot study to determine whether people with tics could tolerate an acute dose of levodopa. Six adults with Tourette syndrome (TS) who had never been treated with neuroleptics took 150 mg levodopa by mouth under single-blind conditions after carbidopa pretreatment. All six subjects reported a decrease in self-rated tic severity (mean -40%, p <0.05), and three spontaneously asked if they could be prescribed levodopa for chronic treatment. Blinded videotape ratings of motor tic severity improved by 37% (p <0.02). A large, placebo-controlled trial will be required to confirm these findings, which raise important questions concerning the relationship of tic expression to dopaminergic activity.

Adult↗
PubMed2000

Dopa-induced blood flow responses in nonhuman primates.

Initially, treatment with the dopamine precursor levodopa provides substantial symptomatic relief for patients with Parkinson's disease (PD). However, as the disease progresses, side effects such as involuntary movements or psychosis may accompany the response to medication. The mechanisms underlying these actions of levodopa remain unclear. To develop methodology for longitudinal studies of the effects of PD and levodopa treatment in living nonhuman primates, we first studied the effects of an acute dose of levodopa on regional brain activity in sedated baboons using positron emission tomography. We found that levodopa significantly decreased regional cerebral blood flow (rCBF) bilaterally in putamen and right cingulate and increased rCBF in right lateral temporal cortex and bilateral frontal cortex. We then performed similar studies on a nemestrina in awake and sedated states to determine whether these responses were affected by sedation. Interestingly, the directions of the rCBF responses in the putamen and temporal cortex were reversed depending on the presence or absence of sedation. Specifically, responses were decreased in sedated animals, but increased dose-dependently in the awake nemestrina. These findings have important implications for the interpretation of studies that use anesthesia. The responses in the awake nemestrina were most similar to those reported in humans and thus may be the most useful model system. Future imaging studies using selective dopaminergic agents in awake animals may permit the identification of relatively specific agonist-mediated pathways and may help separate the mechanisms that mediate levodopa's benefit from those that produce its unwanted side effects.

Anesthetics, Dissociative↗
PubMed2000

Dopamine D(1) agonist activates temporal lobe structures in primates.

Changes in the function of dopamine D(1)-influenced neuronal pathways may be important to the pathophysiology of several human diseases. We recently developed methods for averaging functional imaging data across nonhuman primate subjects; in this study, we apply this method for the first time to map brain responses to experimental dopamine agonists in vivo. Here we report the use of positron emission tomography (PET) in seven normal baboons to measure the regional cerebral blood flow (rCBF) responses produced by an acute dose of the dopamine D(1) full agonist SKF82958. The most significant rCBF increases were in bilateral temporal lobe, including amygdala and superior temporal sulcus (6-17%, P < 0.001). Blood flow decreased in thalamus, pallidum, and pons (4-7%, P = 0.001). Furthermore the rCBF responses were dose-dependent and had a half-life of approximately 30 min, similar to that reported for the drug's antiparkinsonian effects. Absolute whole-brain blood flow did not change, suggesting that these local changes in rCBF reflect neuronal rather than direct vascular effects of the agonist. The prominent temporal lobe response to a D(1) agonist supports and extends our recent observations that levodopa produces prominent amygdala activation both in humans and in other primates. We speculate that levodopa may exert its known effects on mood in humans through increased amygdala activity, mediated in part by D(1) receptors.

Animals↗
PubMed1999

On the efficiency of stereologic volumetry as commonly implemented for three-dimensional digital images.

The aim of the study was to demonstrate, for certain ideal shapes (right cylinders) and for representative neuroanatomical images, that stereologic volumetry of three-dimensional images is more efficient when the sampling grid is placed randomly on each cross-section rather than identically across sections. As an example, the special case of mathematical right cylinders is presented, and an informal proof is provided. For neuroanatomical images, a custom computer program estimated volume with either the fixed- or random-grid method, using the same cross-sectional slices and first-slice test grid position for each method. The slice spacing, grid size, and starting grid position were randomly varied within practical constraints for 100,000 trials in each image. For right cylinders, the random-grid method is always more efficient than the fixed-grid method. For the neuroanatomic images tested, relative variance was up to three times higher for the fixed-grid method than for the random-grid method, especially for test grids with few grid intersections ('hits') per section. With the random-grid method, relative variance is primarily dependent on the total number of hits rather than on the distribution of hits per section. Implementation of the random-grid method for stereologic volumetry in three-dimensional images should in general improve sampling efficiency.

Animals↗
PubMed1999

Diminished regional cerebral blood flow response to vibration in patients with blepharospasm.

OBJECTIVE: To determine whether patients with blepharospasm have abnormal sensorimotor processing similar to patients with writer's cramp. BACKGROUND: Blepharospasm is a focal dystonia manifest by involuntary, excessive blinking and squeezing of the eyes. Altered sensorimotor processing may contribute to the development of dystonic movements. Previously the authors demonstrated decreased vibration-induced cortical blood flow responses in hand primary sensorimotor area (PSA) in patients with hand dystonia. METHODS: In this prospective, case-control study, seven patients with blepharospasm were compared with seven normal subjects. PET measurements of regional blood flow were obtained using bolus administration of H(2)15O at rest or during sequential vibration of either the left or the right hand or side of the mouth. RESULTS: PSA activation decreased significantly in the patients with blepharospasm both ipsilateral (-68%; p = 0.0004) and contralateral to the side of facial stimulation (-56%; p = 0.0009). Patients had a 31% lower mean contralateral PSA response to hand vibration and a 51% smaller right supplementary motor area response to left-hand vibration than normal subjects, but these differences did not reach statistical significance. CONCLUSIONS: Patients with blepharospasm have abnormal sensorimotor processing in response to lower face vibration. They may also have abnormal brain responses to stimulation of clinically uninvolved parts of the body, but this requires confirmation.

Aged↗
PubMed1998

Altered thalamic response to levodopa in Parkinson's patients with dopa-induced dyskinesias.

Parkinson's disease (PD) is a progressive neurologic condition characterized by tremor, slowness, stiffness, and unstable posture. Degeneration of dopamine-producing neurons in the substantia nigra causes PD. Treatment with levodopa, a precursor of dopamine, initially ameliorates the clinical manifestations of PD. However, chronic levodopa treatment can produce severe involuntary movements (so-called dopa-induced dyskinesias or DID), limiting treatment. Pallidotomy, placement of a surgical lesion in the internal segment of the globus pallidus, reduces DID. Because this result is inconsistent with current theories of both basal ganglia function and DID, it prompted us to investigate the brain's response to levodopa. We measured regional cerebral blood flow response to levodopa with positron-emission tomography in 6 PD patients with DID, 10 chronically treated PD patients without DID, 17 dopa-naïve PD patients, and 11 normals. The dose of levodopa was chosen to produce clinical benefit without inducing DID. This strategy allowed us to examine the brain response to levodopa across groups without the confounding effect of differences in motor behavior. We found that the DID group had a significantly greater response in ventrolateral thalamus than the other groups. This was associated with decreased activity in primary motor cortex. These findings are consistent with increased inhibitory output from the internal segment of the globus pallidus to thalamus after levodopa administration. They provide a physiological explanation for the clinical efficacy of pallidotomy and new insights into the physiology of the basal ganglia.

Adult↗
PubMed1998

Putamen volume in idiopathic focal dystonia.

OBJECTIVE: To determine whether the volume of the putamen is abnormal in patients with idiopathic focal dystonia. BACKGROUND: The cause of adult-onset focal dystonia is unknown, but substantial evidence suggests that the putamen may be abnormal in this condition. Cell loss and gliosis have been suggested. We hypothesized that this might be reflected as abnormal putamen volume on MRI. DESIGN AND METHODS: A high-resolution MRI was acquired in 13 adults with cranial or hand dystonia and 13 normal individuals matched for age and sex. Putamen volume was measured using a stereologic method (Study 1). In a replication study, another rater measured putamen volume using manual tracing and direct voxel count (Study 2). Neither rater was aware of the diagnosis, and the order of measurement was random in each study. RESULTS: In Study 1, putamen measurements were reasonably accurate (coefficient of error, approximately 6%). The putamen was 13% larger in patients, both in absolute terms (p = 0.03) and after covarying total brain volume (p = 0.02). In Study 2, putamen volumes correlated with those measured in Study 1 (intraclass correlation coefficient, 0.68 to 0.83). The putamen was 8% larger in patients (p = 0.06) and was larger in the patient than in the matched control subject in 10 of 13 pairs (p = 0.046). CONCLUSION: We find no evidence of putaminal atrophy or degeneration in adult-onset idiopathic focal dystonia. In fact, in this group, the putamen is about 10% larger in patients than in matched control subjects. This finding may reflect a response to the dystonia or may relate to its cause.

Adult↗
PubMed1997

PET measurement of dopamine D2 receptor-mediated changes in striatopallidal function.

This study was designed to validate an in vivo measurement of the functional sensitivity of basal ganglia neuronal circuits containing dopamine D2 receptors. We hypothesized that a D2 agonist would decrease striatopallidal neuronal activity, and hence regional cerebral blood flow (rCBF) over the axon terminals in the globus pallidus. Quantitative pallidal blood flow was measured using positron emission tomography (PET) with bolus injections of H215O and arterial sampling in six baboons before and after intravenous administration of the selective D2 agonist U91356a. We also tested whether the response to U91356a was modified by previous acute administration of various antagonists. Another baboon had serial measurements of blood flow under identical conditions, but received no dopaminergic drugs. In all animals that received U91356a, pallidal flow decreased in a dose-related manner. Global CBF had a similar response, but the decline in pallidal flow was greater in magnitude and remained significant after accounting for the global effect. A D2 antagonist, but not antagonists of D1, serotonin-2, or peripheral D2 receptors, prevented this decrease. This work demonstrates and validates an in vivo measure of the sensitivity of D2-mediated basal ganglia pathways. It also supports the hypothesis that activation of the indirect striatopallidal pathway, previously demonstrated using nonselective D2-like agonists, can be mediated specifically by D2 receptors. We speculate that the U91356a-PET technique may prove useful in detecting functional abnormalities of D2-mediated dopaminergic function in diseases such as parkinsonism, dystonia, Tourette syndrome, or schizophrenia.

Aminoquinolines↗
PubMed1997

Decreased [18F]spiperone binding in putamen in idiopathic focal dystonia.

In this study we have investigated the pathophysiology of two idiopathic focal dystonias: hand cramp with excessive cocontractions of agonist and antagonist hand or forearm muscles during specific tasks, such as writing, and facial dystonia manifested by involuntary eyelid spasms (blepharospasm) and lower facial and jaw spasms (oromandibular dystonia). We used positron emission tomography (PET) to measure the in vivo binding of the dopaminergic radioligand [18F]spiperone in putamen in 21 patients with these two focal dystonias and compared the findings with those from 13 normals. We measured regional cerebral blood flow and blood volume in each subject as well as the radiolabeled metabolites of [18F]spiperone in arterial blood. A stereotactic method of localization, independent of the appearance of the images, was used to identify the putamen in all of the PET images. We analyzed the PET and arterial blood data with a validated nonsteady-state tracer kinetic model representing the in vivo behavior of the radioligand. An index of binding called the combined forward rate constant was decreased by 29% in dystonics, as compared with normals (p < 0.05). There were no significant differences between dystonics and normals in regional blood flow, blood volume, nonspecific binding, permeability-surface area product of [18F]spiperone or the dissociation rate constant. These findings are consistent with a decrease of dopamine D2-like binding in putamen and are the first demonstration of a receptor abnormality in idiopathic dystonia. These results have important implications for the pathophysiology of dystonia as well as for function of the basal ganglia.

Adult↗
PubMed1997

Personality disorder scores improve with effective pharmacotherapy of depression.

INTRODUCTION: We hypothesized that the probability of personality disorder ('PROB') predicted by the Temperament and Character Inventory ('TCI') would decline after successful pharmacotherapy of depression. METHODS: We administered a computerized version of the TCI to 15 patients with DSM-III-R major depression, before and after treatment with serotonergic antidepressants. RESULTS: PROB declined from 58.9% +/- 18.0% to 42.4% +/- 22.8% (P < 0.003), due to a significant increase in the Self-Directedness scale. This change in PROB correlated with improvement in self-rated severity of depression (P < 0.02). CONCLUSION: TCI prediction of personality disorder is susceptible to state effects of depression.

Adult↗
PubMed1997

MPTP induces dystonia and parkinsonism. Clues to the pathophysiology of dystonia.

The pathophysiology of dystonia is unclear, but several clues implicate striatal dopamine dysfunction. In contrast, the causal relationship between striatal dopamine deficiency and parkinsonism is well defined. We now suggest that parkinsonism or dystonia may occur following striatal dopamine deficiency. Baboons treated with intracarotid 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) developed transient hemidystonia prior to hemiparkinsonism. The day after MPTP treatment, most animals had spontaneous ipsilateral turning. Within a few days, all developed contralateral hemidystonia, with the arm and leg extended and externally rotated. This transient dystonia preceded hemiparkinsonism with flexed posture, bradykinesia, and postural tremor that persisted for up to 1.5 years. Dystonia corresponded temporally with a decreased striatal dopamine content and a transient decrease in D2-like receptor number. The time course of dystonia and parkinsonism is analogous to lower limb dystonia as the first, frequently transient, symptom of Parkinson's disease in humans. The association of striatal dopamine deficiency with dystonia and parkinsonism implies that other factors influence clinical manifestations.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1997

Septuagenarian Sydenham's with secondary hypomania.

A 74-year-old man with a remote history of Sydenham's chorea but no personal or family history of mood disorder had simultaneous onset of severe, generalized chorea and a mild manic syndrome in clear consciousness. Both chorea and hypomania improved after treatment with sodium valproate and clonazepam. Agitated delirium or mood lability have been described in Sydenham's, but this case is the first report of criteria-based secondary mania with probable Sydenham's chorea, as well as the longest reported remission between symptomatic Sydenham's episodes. The parallel course of this patient's hypomania and chorea supports current pathophysiologic theories of idiopathic mania.

Aged↗