Courtney Holmes

Cardiac Sympathetic Denervation in Parkinson Disease

Orthostatic hypotension is common in Parkinson disease (1). Although earlier studies implicated L-dopa treatment as the cause (2), more recent studies have shown that orthostatic hypotension may result from deficient cardiovascular reflexes that depend on release of the sympathetic neurotransmitter norepinephrine in the heart and blood vessels (3-5). We call this phenomenon sympathetic neurocirculatory failure. Several recent studies have reported decreased myocardial concentrations of radioactivity after injection of the sympathoneural imaging agent 123I-metaiodobenzylguanidine (123I-MIBG) in patients with Parkinson disease (6-13). This finding is consistent with but does not prove cardiac sympathetic denervation. In addition, studies have not specifically considered the possible association between cardiac sympathetic denervation and sympathetic neurocirculatory failure in Parkinson disease. Measures of autonomic function have included blood pressure during tilt-table testing (abnormalities of which can have several causes), heart rate responses to the Valsalva maneuver (which are determined mainly by changes in parasympathetic cholinergic outflow to the heart), or skin conductance or sweating responses (which are determined mainly by alterations in sympathetic cholinergic outflow to the skin). These measures may not allow assessment of sympathetic noradrenergic function. One way to detect sympathetic neurocirculatory failure in a patient with orthostatic hypotension is by analyzing beat-to-beat blood pressure associated with performance of the Valsalva maneuver (Figure 1). In patients with sympathetic neurocirculatory failure, blood pressure decreases progressively during phase II of the maneuver, whereas normally blood pressure plateaus or increases at the end of phase II (phase II-L). In patients with sympathetic neurocirculatory failure, phase IV blood pressure increases slowly back to baseline after release of the maneuver, whereas normally blood pressure overshoots. These abnormalities are a direct result of deficient cardiovascular reflexes that depend on sympathetically mediated release of norepinephrine. In our study, we defined sympathetic neurocirculatory failure as chronic, reproducible orthostatic hypotension associated with abnormal blood pressure responses in both phase II-L and phase IV of the Valsalva maneuver. Figure 1. Heart rate and blood pressure responses to the Valsalva maneuver in a control patient with a history of neurocardiogenic syncope ( left ) and a patient with Parkinson disease and orthostatic hypotension ( right ). Previous studies also have not independently confirmed that a low myocardial concentration of 123I-MIBGderived radioactivity actually reflects cardiac sympathetic denervation in Parkinson disease. Neurochemical findings indicating decreased norepinephrine release, neuronal uptake, turnover, and synthesis in the heart could provide such confirmation. In humans, 6-[18F]fluorodopamine can be used to visualize cardiac sympathetic innervation by positron emission tomographic (PET) scanning (14), which provides excellent spatial and temporal resolution. Since 6-[18F]fluorodopamine is a catecholamine handled in the heart in a manner similar to the way in which norepinephrine is handled (15), PET scanning may allow functional and anatomic assessments of sympathetic cardiac innervation (16). We used PET scanning after injection of 6-[18F]fluorodopamine and neurochemical measurements during cardiac catheterization to answer the following questions: 1) What proportions of patients with Parkinson disease, with or without sympathetic neurocirculatory failure, have decreased myocardial 6-[18F]fluorodopaminederived radioactivity? 2) Does decreased myocardial 6-[18F]fluorodopaminederived radioactivity in Parkinson disease actually reflect cardiac sympathetic denervation, as identified by indices of cardiac norepinephrine release, neuronal uptake, turnover, and synthesis? 3) Does the frequency of cardiac sympathetic denervation differ between groups of patients with Parkinson disease who have sympathetic neurocirculatory failure and those who do not? 4) Does cardiac sympathetic denervation also occur in patients with multiple-system atrophy, a progressive neurodegenerative disease of adults that features autonomic dysfunction and has parkinsonian, cerebellar, or mixed forms (17)? [The diagnosis of multiple-system atrophy is clinical and, except for a typically poor response to L-dopa treatment, can be difficult to distinguish from Parkinson disease.] 5) Is cardiac sympathetic denervation in patients with Parkinson disease related to L-dopa treatment or to disease duration or severity? Methods The Intramural Research Board of the National Institute of Neurological Disorders and Stroke approved the study protocol. All participants provided written informed consent. Participants We included patients with Parkinson disease or multiple-system atrophy who were studied at the National Institutes of Health Clinical Center in Bethesda, Maryland. Twenty-nine patients had Parkinson disease, including 10 who were not receiving or had never received L-dopa. Twenty-four patients had multiple-system atrophy, including 8 who were taking L-dopa at the time of evaluation. For comparison, we used 6-[18F]fluorodopamine PET scan data and, in most cases, cardiac neurochemical data from 7 patients with pure autonomic failure (5 men, 2 women [mean age SE, 60 6 years]) and 33 controls. Of these 33 controls, 22 had a history of neurocardiogenic syncope (4 men, 18 women [mean age, 35 3 years]) and 11 had a history of postural tachycardia syndrome (1 man, 10 women [mean age, 42 4 years]). 6-[18F]fluorodopamine PET scan data were also obtained from 19 normal volunteers. All patients with Parkinson disease were referred by neurologists or movement disorder clinics and fulfilled accepted clinical criteria (18). Parkinson disease was staged by using the HoehnYahr classification. All affected patients had bradykinesia, cogwheel rigidity, and one or more additional parkinsonian features (pill-roll tremor, stooped posture, festinating gait, difficulty initiating movement, masklike face, micrographia, or marked improvement in motor function during treatment with L-dopa). Patients with multiple-system atrophy had at least two parkinsonian features but were not classified in terms of cerebellar, parkinsonian, or mixed subtypes (17). All had gradually progressive parasympathetic failure (manifested by impotence in men, urinary retention or incontinence, constipation, or constant pulse rate) and had one or more additional features of multiple-system atrophy (heat or cold intolerance and decreased sweating, intention tremor or other evidence of cerebellar dysfunction, slurred speech or a history of aspiration, or no or only slight improvement during an adequate trial of L-dopa treatment). Sympathetic neurocirculatory failure was defined as reproducible, chronic orthostatic hypotension (decrease in diastolic pressure of at least 10 mm Hg and in systolic pressure of at least 20 mm of Hg after 3 to 5 minutes of standing), coupled with abnormal responses of beat-to-beat blood pressure associated with the Valsalva maneuver (19). As noted previously, patients with sympathetic neurocirculatory failure usually exhibit a progressive decrease in blood pressure in phase II-L of the maneuver and an absence of a pressure overshoot in phase IV after release of the maneuver. Valsalva Maneuver For the Valsalva maneuver, the patient lay supine with his or her head on a pillow and blew into a plastic or rubber tube connected to a sphygmomanometer, keeping a pressure of 30 mm Hg for 10 to 12 seconds. The response of beat-to-beat blood pressure during phase II-L of the Valsalva maneuver was considered to be normal if the diastolic and mean arterial pressure increased before the end of the straining and abnormal if they decreased. The response during phase IV was considered to be normal if the systolic blood pressure increased progressively to a value exceeding the baseline (measured just before the patient inhaled and then began straining) and abnormal if the systolic pressure did not exceed the baseline. Sympathetic Neuroimaging Patients were positioned in a GE Advance scanner (General Electric, Milwaukee, Wisconsin), with their thoraxes in the gantry. 6-[18F]fluorodopamine (specific activity, 7.4 to 37 MBq/mmol; dose in most cases, 0.037 MBq) was dissolved in approximately 10 mL of normal saline and infused intravenously at a constant rate for 3 minutes. Thoracic PET scanning was performed for up to 3 hours. The tomographic data were divided into intervals of 5 to 30 minutes. Data acquisition was not gated to the electrocardiogram. In most patients, PET scanning was also used to delineate the left ventricular myocardium and assess myocardial perfusion after administration of the perfusion imaging agent 13 N-ammonia. Intravenously injected 13 N-ammonia exits the bloodstream rapidly and enters cells nonspecifically. A few minutes after the injection, the concentration of 13 N-ammoniaderived radioactivity in the left ventricular myocardium exceeds that in the left ventricular chamber, enabling visualization of the myocardium. Myocardial tissue concentrations of 13 N-ammoniaderived radioactivity depend on local perfusion (20). Neurochemical Testing Patients underwent right-heart catheterization for measurements of norepinephrine spillover into coronary sinus plasma and of venousarterial differences in plasma levels of dihydroxyphenylglycol (DHPG) and L-dopa. After placement of arm and right internal jugular venous catheters (the latter advanced into the coronary sinus), a tracer amount of [3H]norepinephrine (levo- [2, 5, 6] [3H]norepinephrine, New England Nuclear, Boston, Massachusetts) was infused intravenously. Coronary sinus blood flow was measured by thermodilution, and arterial and great cardiac venous or coronary sinus blood was sampled

Sympathetic cardioneuropathy in dysautonomias.

Background The classification of dysautonomias has been confusing, and the pathophysiology obscure. We examined sympathetic innervation of the heart in patients with acquired, idiopathic dysautonomias using thoracic positron-emission tomography and assessments of the entry rate of the sympathetic neurotransmitter norepinephrine into the cardiac venous drainage (cardiac norepinephrine spillover). We related the laboratory findings to signs of sympathetic neurocirculatory failure (orthostatic hypotension and abnormal blood-pressure responses associated with the Valsalva maneuver), central neural degeneration, and responsiveness to treatment with levodopa–carbidopa (Sinemet). Methods Cardiac scans were obtained after intravenous administration of 6-[18F]fluorodopamine in 26 patients with dysautonomia. Fourteen had sympathetic neurocirculatory failure — three with no signs of central neurodegeneration (pure autonomic failure), two with parkinsonism responsive to treatment with levodopa–carbidopa, and nine wit...

Improved assay for plasma dihydroxyphenylacetic acid and other catechols using high-performance liquid chromatography with electrochemical detection

Several modifications of an HPLC-electrochemical assay method for plasma levels of norepinephrine (NE), epinephrine (EPI), dopamine (DA), dihydroxyphenylglycol (DHPG), dihydroxyphenylalanine (DOPA) and dihydroxyphenylacetic acid (DOPAC) that improve the accuracy and reliability of DHPG, DOPA, and DOPAC measurements are described. In batch alumina extractions, increasing the amount of alumina decreased analytical recoveries of DHPG, DOPA, and especially DOPAC, and increasing the strength of the eluting acid increased recoveries of these catechols, without affecting recoveries of the amines NE, EPI and DA. Refrigeration (4 degrees C) until injection stabilized DOPAC in aqueous solution and therefore improved the reproducibility of plasma DOPAC measurements. Circulation of chilled water (15 degrees C) around the column using a water jacket decreased variability in retention times of the catechols and thereby facilitated identification of peaks, while enhancing separation of DHPG from the solvent front. Use of 6-fluoro-DOPA and 6-fluoro-DOPAC as internal standards did not improve inter-assay reliability. We recommend that in assays of plasma catechols including DOPAC, small (5 mg), precisely measured amounts of alumina be used, with a relatively strong eluting solution (e.g. 0.04 M phosphoric acid-0.2 M acetic acid, 20:80, v/v), and that the samples be refrigerated until injection, with column temperature held constant at less than 20 degrees C.

Occipital horn syndrome and a mild Menkes phenotype associated with splice site mutations at the MNK locus

We have found mutations in the Menkes disease gene (MNK) which impair, but do not abolish, correct mRNA splicing in patients with less severe clinical phenotypes. In one family, four males aged 2–36 years with a distinctive Menkes variant have a mutation at the +3 position of a splice donor site near the 3′ end of the Menkes coding sequence that is associated with exon skipping and a stable mutant transcript. In an unrelated 15-year-old male with typical occipital horn syndrome, a point mutation at the −2 exonic position of a splice donor site in the middle of the gene causes exon-skipping and activation of a cryptic splice acceptor site. In both mutations, maintenance of some normal splicing is demonstrable by RT-PCR, cDNA sequencing and ribonuclease protection.

Orthostatic hypotension from sympathetic denervation in Parkinson's disease

Background Patients with PD often have signs or symptoms of autonomic failure, including orthostatic hypotension. Cardiac sympathetic denervation occurs frequently in PD, but this has been thought to occur independently of autonomic failure. Methods Forty-one patients with PD (18 with and 23 without orthostatic hypotension) and 16 age-matched healthy volunteers underwent PET scanning to visualize sympathetic innervation after injection of 6-[18F]fluorodopamine. Beat-to-beat blood pressure responses to the Valsalva maneuver were used to identify sympathetic neurocirculatory failure and plasma norepinephrine to indicate overall sympathetic innervation. Results All patients with PD and orthostatic hypotension had abnormal blood pressure responses to the Valsalva maneuver and septal and lateral ventricular myocardial concentrations of 6-[18F]fluorodopamine-derived radioactivity >2 SD below the normal mean. In contrast, only 6 of the 23 patients without orthostatic hypotension had abnormal Valsalva responses (p < 0.0001 compared with patients with orthostatic hypotension), and only 11 had diffusely decreased 6-[18F]fluorodopamine-derived radioactivity in the left ventricular myocardium (p = 0.0004). Of the 12 remaining patients without orthostatic hypotension, 7 had locally decreased myocardial radioactivity. Supine plasma norepinephrine was lower in patients with than in those without orthostatic hypotension (1.40 ± 0.15 vs 2.32 ± 0.26 nmol/L, p = 0.005). 6-[18F]fluorodopamine-derived radioactivity was less not only in the myocardium but also in the thyroid and renal cortex of patients with PD than in healthy control subjects. Conclusions In PD, orthostatic hypotension reflects sympathetic neurocirculatory failure from generalized sympathetic denervation.

Neonatal Diagnosis and Treatment of Menkes Disease

BACKGROUND Menkes disease is a fatal neurodegenerative disorder of infancy caused by diverse mutations in a copper-transport gene, ATP7A. Early treatment with copper injections may prevent death and illness, but presymptomatic detection is hindered by the inadequate sensitivity and specificity of diagnostic tests. Exploiting the deficiency of a copper enzyme, dopamine-beta-hydroxylase, we prospectively evaluated the diagnostic usefulness of plasma neurochemical levels, assessed the clinical effect of early detection, and investigated the molecular bases for treatment outcomes. METHODS Between May 1997 and July 2005, we measured plasma dopamine, norepinephrine, dihydroxyphenylacetic acid, and dihydroxyphenylglycol in 81 infants at risk. In 12 newborns who met the eligibility criteria and began copper-replacement therapy within 22 days after birth, we tracked survival and neurodevelopment longitudinally for 1.5 to 8 years. We characterized ATP7A mutations using yeast complementation, reverse-transcriptase-polymerase-chain-reaction analysis, and immunohistochemical analysis. RESULTS Of 81 infants at risk, 46 had abnormal neurochemical findings indicating low dopamine-beta-hydroxylase activity. On the basis of longitudinal follow-up, patients were classified as affected or unaffected by Menkes disease, and the neurochemical profiles were shown to have high sensitivity and specificity for detecting disease. Among 12 newborns with positive screening tests who were treated early with copper, survival at a median follow-up of 4.6 years was 92%, as compared with 13% at a median follow-up of 1.8 years for a historical control group of 15 late-diagnosis and late-treatment patients. Two of the 12 patients had normal neurodevelopment and brain myelination; 1 of these patients had a mutation that complemented a Saccharomyces cerevisiae copper-transport mutation, indicating partial ATPase activity, and the other had a mutation that allowed some correct ATP7A splicing. CONCLUSIONS Neonatal diagnosis of Menkes disease by plasma neurochemical measurements and early treatment with copper may improve clinical outcomes. Affected newborns who have mutations that do not completely abrogate ATP7A function may be especially responsive to early copper treatment. (ClinicalTrials.gov number, NCT00001262.)

SYMPATHETIC CARDIONEUROPATHY IN DYSAUTONOMIAS

Background The classification of dysautonomias has been confusing, and the pathophysiology obscure. We examined sympathetic innervation of the heart in patients with acquired, idiopathic dysautonomias using thoracic positron-emission tomography and assessments of the entry rate of the sympathetic neurotransmitter norepinephrine into the cardiac venous drainage (cardiac norepinephrine spillover). We related the laboratory findings to signs of sympathetic neurocirculatory failure (orthostatic hypotension and abnormal blood-pressure responses associated with the Valsalva maneuver), central neural degeneration, and responsiveness to treatment with levodopa–carbidopa (Sinemet). Methods Cardiac scans were obtained after intravenous administration of 6-[18F]fluorodopamine in 26 patients with dysautonomia. Fourteen had sympathetic neurocirculatory failure — three with no signs of central neurodegeneration (pure autonomic failure), two with parkinsonism responsive to treatment with levodopa–carbidopa, and nine wit...

Association Between Supine Hypertension and Orthostatic Hypotension in Autonomic Failure

Abstract—Supine hypertension occurs commonly in primary chronic autonomic failure. This study explored whether supine hypertension in this setting is associated with orthostatic hypotension (OH), and if so, what mechanisms might underlie this association. Supine and upright blood pressures, hemodynamic responses to the Valsalva maneuver, baroreflex-cardiovagal gain, and plasma norepinephrine (NE) levels were measured in pure autonomic failure (PAF), multiple-system atrophy (MSA) with or without OH, and Parkinson’s disease (PD) with or without OH. Controls included age-matched, healthy volunteers and patients with essential hypertension or those referred for dysautonomia. Baroreflex-cardiovagal gain was calculated from the relation between the interbeat interval and systolic pressure during the Valsalva maneuver. PAF, MSA with OH, and PD with OH all featured supine hypertension, which was equivalent in severity to that in essential hypertension, regardless of fludrocortisone treatment. Among patients with PD or MSA, those with OH had higher mean arterial pressure during supine rest (109±3 mm Hg) than did those lacking OH (96±3 mm Hg, P =0.002). Baroreflex-cardiovagal gain and orthostatic increments in plasma NE levels were markedly decreased in all 3 groups with OH. Among patients with PD or MSA, those with OH had much lower mean baroreflex-cardiovagal gain (0.74±0.10 ms/mm Hg) than did those lacking OH (3.13±0.72 ms/mm Hg, P =0.0002). In PAF, supine hypertension is linked to both OH and low baroreflex-cardiovagal gain. The finding of lower plasma NE levels in patients with than without supine hypertension suggests involvement of pressor mechanisms independent of the sympathetic nervous system.

Norepinephrine Precursor Therapy in Neurogenic Orthostatic Hypotension

Background—In patients with neurogenic orthostatic hypotension (NOH), the availability of the sympathetic neurotransmitter norepinephrine (NE) in the synaptic cleft is insufficient to maintain blood pressure while in the standing posture. Methods and Results—We determined the effect of oral administration of the synthetic amino acid L-threo-3,4-dihydroxyphenylserine (L-DOPS), which is decarboxylated to NE by the enzyme L–aromatic amino acid decarboxylase (L-AADC) in neural and nonneural tissue, on blood pressure and orthostatic tolerance in 19 patients with severe NOH (8 with pure autonomic failure and 11 with multiple-system atrophy). A single-blind dose-titration study determined the most appropriate dose for each patient. Patients were then enrolled in a double-blind, placebo-controlled, crossover trial. L-DOPS significantly raised mean blood pressure both supine (from 101±4 to 141±5 mm Hg) and standing (from 60±4 to 100±6 mm Hg) for several hours and improved orthostatic tolerance in all patients. After L-DOPS, blood pressure increases were closely associated with increases in plasma NE levels. Oral administration of carbidopa, which inhibits L-AADC outside the blood-brain barrier, blunted both the increase in plasma NE and the pressor response to L-DOPS in all patients Conclusions—Acute administration of L-DOPS increases blood pressure and improves orthostatic tolerance in patients with NOH. The pressor effect results from conversion of L-DOPS to NE outside the central nervous system.

Neurocirculatory Abnormalities in Parkinson Disease With Orthostatic Hypotension: Independence From Levodopa Treatment

Patients with Parkinson disease often have orthostatic hypotension. Neurocirculatory abnormalities underlying orthostatic hypotension might reflect levodopa treatment. Sixty-six Parkinson disease patients (36 with orthostatic hypotension, 15 off and 21 on levodopa; 30 without orthostatic hypotension) had tests of reflexive cardiovagal gain (decrease in interbeat interval per unit decrease in systolic pressure during the Valsalva maneuver; orthostatic increase in heart rate per unit decrease in pressure); reflexive sympathoneural function (decrease in pressure during the Valsalva maneuver; orthostatic increment in plasma norepinephrine); and cardiac and extracardiac noradrenergic innervation (septal myocardial 6-[18F]fluorodopamine-derived radioactivity; supine plasma norepinephrine). Severity of orthostatic hypotension did not differ between the levodopa-untreated and levodopa-treated groups with Parkinson disease and orthostatic hypotension (−52±6 [SEM] versus −49±5 mm Hg systolic). The 2 groups had similarly low reflexive cardiovagal gain (0.84±0.23 versus 1.33±0.35 ms/mm Hg during Valsalva; 0.43±0.09 versus 0.27±0.06 bpm/mm Hg during orthostasis); and had similarly attenuated reflexive sympathoneural responses (97±29 versus 71±23 pg/mL during orthostasis; −82±10 versus −73±8 mm Hg during Valsalva). In patients off levodopa, plasma norepinephrine was lower in those with (193±19 pg/mL) than without (348±46 pg/mL) orthostatic hypotension. Low values for reflexive cardiovagal gain, sympathoneural responses, and noradrenergic innervation were strongly related to orthostatic hypotension. Parkinson disease with orthostatic hypotension features reflexive cardiovagal and sympathoneural failure and cardiac and partial extracardiac sympathetic denervation, independent of levodopa treatment.