Neurological disorders of the myenteric plexus: a review

The myenteric plexus is the neuronal complex that regulates the motility of the gut; a brief review of its pathology is presented in this paper as well as a tentative etiopathogenetic classification. Disorders of gut innervation include congenital (e.g. Hirschsprung's disease) or acquired diseases; the latter can be idiopathic or related to a more general pathological involvement of the whole organism as in the case of bacterial toxins, diabetes mellitus, Riley-Day disease and primary orthostatic hypotension. In view of the fundamental similarity of the myenteric plexus to the central nervous system, the study of this organ can be useful both for diagnosis of degenerative diseases of the central nervous system (i.e. via rectal biopsy) and for gaining a better etiopathogenetic insight into peripheral and central nervous system disease.     

L-dihydroxyphenylserine (Droxidopa): a new therapy for neurogenic orthostatic hypotension

Neurogenic orthostatic hypotension results from failure to release norepinephrine, the neurotransmitter of sympathetic postganglionic neurons, appropriately upon standing. In double blind, cross over, placebo controlled trials, administration of droxidopa, a synthetic amino acid that is decarboxylated to norepinephrine by the enzyme l-aromatic amino acid decarboxylase increases standing blood pressure, ameliorates symptoms of orthostatic hypotension and improves standing ability in patients with neurogenic orthostatic hypotension due to degenerative autonomic disorders. The pressor effect results from conversion of droxidopa to norepinephrine outside the central nervous system both in neural and non-neural tissue. This mechanism of action makes droxidopa effective in patients with central and peripheral autonomic disorders.     

The idiopathic orthostatic hypotension -- Shy-Drager syndrome (author's transl)]

The idiopathic orthostatic hypotension can be characterized as a presenile degenerative process with a liability to attack especially multiple systems. In the course of the disease clinically the autonomic functional failure stands in the beginning. It also determines the serious illness in the later stages, which is associated with an additional variable neurologic syndrome. By means of an own clinically and pathologically examined case it is given a survey of the present knowledge about the disease process. Especially it is declared on the localization of the lesions. Phaemacological tests point to a main disturbance of the preganglionic respectively central part of the sympathetic system. The analysis of the neuropathologically examined cases shows as the most regular finding a neuronal loss in the nucleus intermediolateralis, which certainly is hold responsible for a great part of the functional failure. But it is to assume, that lesions in other structures cooperate in the genesis of the syndrome, which morphologically are not yet recorded.     

Study of autonomic functions in primary orthostatic hypotension

A case of primary orthostatic hypotension with associated genitourinary tract disturbances but no major neurological signs of central nervous system involvement is reported. Some investigations designed to assess the functional status of the autonomic nervous system at various levels of its organisation are described together with the results. The nosological position of primary orthostatic hypotension and its relationship with the Shy-Drager syndrome are discussed. The effectiveness of indomethacin therapy in reducing orthostatic hypotension was confirmed.

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Sommario Gli Autori riportano un caso di ipotensione ortostatica idiopatica associato disturbi del sistema urogenitale, che non presenta importanti segni neurologici di deficit a carico del sistema nervoso centrale. Lo studio di questo caso ha dato lo spunto per descrivere alcune indagini, riportandone i risultati, atte a valutare lo stato funzionale del sistema nervoso vegetativo ai diversi livelli della sua organizzazione. Si discute inoltre il problema della posizione nosologica della ipotensione ortostatica idioptica e le sue correlazioni colla malattia di Shy-Drager. L'approccio terapeutico con indometacina ha confermato la sua efficacia nel ridurre l'ipotensione ortostatica.

     

Orthostatic hypotension and cognitive impairment in Parkinson's disease: Causation or association?

Orthostatic hypotension and cognitive impairment are common in Parkinson's disease (PD) and significantly impair quality of life. Orthostatic hypotension and cognitive impairment appear to be interrelated. Whether the relationship is causative or associative remains unclear. The vascular hypothesis proposes that recurrent episodic hypotension results in cerebral hypoperfusion, in turn causing anoxic damage to vulnerable areas of the brain and impaired cognitive function. Support for this hypothesis has come from brain MRI studies showing an association between white matter hyperintensities and a postural drop in blood pressure among PD patients. Alternatively, the association between orthostatic hypotension and cognitive decline in PD may reflect shared underlying synuclein‐related pathology affecting common neuroanatomical and neurochemical substrates. Cardiac imaging studies demonstrate noradrenergic denervation early in PD, and cardiac denervation has been associated with poorer cognition. Neurogenic orthostatic hypotension occurs as a result of defective norepinephrine release from sympathetic terminals upon standing. Neuropathological studies have also demonstrated Lewy body pathology in the locus coeruleus; the main source of noradrenaline in the brain. Locus coeruleus norepinephrine levels are reduced in PD patients with dementia when compared with PD patients without. In this review, we examine the evidence for an association between orthostatic hypotension and cognitive impairment in PD. We evaluate the literature supporting the hypothesis that progressive noradrenergic denervation underlies both orthostatic hypotension and cognitive impairment, and we examine studies suggesting that recurrent cerebral hypoperfusion results in cognitive decline in PD. Finally, we explore how modulation of blood pressure and the noradrenergic nervous system may improve cognition in PD. © 2016 International Parkinson and Movement Disorder Society     

Acetylcholinesterase inhibition: a novel approach in the treatment of neurogenic orthostatic hypotension

BACKGROUND: Pharmacological treatment of orthostatic hypotension is often limited because of troublesome supine hypertension. OBJECTIVE: To investigate a novel approach to treatment using acetylcholinesterase inhibition, based on the theory that enhanced sympathetic ganglion transmission increases systemic resistance in proportion to orthostatic needs. DESIGN: Prospective open label single dose trial. MATERIAL: 15 patients with neurogenic orthostatic hypotension caused by: multiple system atrophy (n = 7), Parkinson's disease (n = 3), diabetic neuropathy (n = 1), amyloid neuropathy (n = 1), and idiopathic autonomic neuropathy (n = 3). METHODS: Heart rate, blood pressure, peripheral resistance index (PRI), cardiac index, stroke index, and end diastolic index were monitored continuously during supine rest and head up tilt before and one hour after an oral dose of 60 mg pyridostigmine. RESULTS: There was only a modest non-significant increase in supine blood pressure and PRI. In contrast, acetylcholinesterase inhibition significantly increased orthostatic blood pressure and PRI and reduced the fall in blood pressure during head up tilt. Orthostatic heart rate was reduced after the treatment. The improvement in orthostatic blood pressure was associated with a significant improvement in orthostatic symptoms. CONCLUSIONS: Acetylcholinesterase inhibition appears effective in the treatment of neurogenic orthostatic hypotension. Orthostatic symptoms and orthostatic blood pressure are improved, with only modest effects in the supine position. This novel approach may form an alternative or supplemental tool in the treatment of orthostatic hypotension, specially for patients with a high supine blood pressure.     

The treatment of orthostatic hypotension with dihydroxyphenylserine

Neurogenic orthostatic hypotension is an incapacitating symptom of central and peripheral autonomic nervous system degeneration. It occurs in such clinical conditions as multiple system atrophy, pure autonomic failure, and small-fiber peripheral neuropathies. Although many treatments are available, their effects are inconsistent, unsustained, and complicated by side effects. 3,4-Dihydroxyphenylserine is a synthetic, unnatural amino acid that is an immediate norepinephrine precursor. There is theoretical and clinical evidence supporting the use of this agent in the treatment of neurogenic orthostatic hypotension in patients with peripheral and central autonomic nervous system dysfunction. We review the biochemistry, pharmacokinetics, and possible mechanisms of action and clinical utility of this agent in the treatment of neurogenic orthostatic hypotension.     

屈昔多巴的临床应用进展

屈昔多巴是一种人工合成的去甲肾上腺素前体药物,当交感神经系统受损时,屈昔多巴在L-芳香族氨基酸脱羧酶的作用下,在外周和中枢神经通过脱羧作用转化为去甲肾上腺素,从而使神经系统去甲肾上腺素水平升高。1989年,日本便将屈昔多巴运用在神经源性体位性低血压的治疗中,但是其未在欧洲或美国使用,直到2014年美国FDA批准屈昔多巴治疗有症状的直立性低血压,其次是原发性自主神经病变、多巴胺-β-羟化酶缺乏症或非糖尿病自主神经病变。2012年1月,中国重庆圣华曦药业股份有限公司3.1类新药屈昔多巴胶囊(商品名:善为)获批上市,是屈昔多巴在国内的首次应用。屈昔多巴在治疗体位性低血压、步态障碍以及透析性低血压的疗效确切,安全性良好。文中就屈昔多巴的药动学特性、作用机制、临床效果以及耐受性研究进行综述。     

Brain hypoperfusion in a girl with systemic lupus erythematosus

We describe an adolescent girl with systemic lupus erythematosus, presenting with severe cardiovascular autonomic dysfunction and incapacitating orthostatic hypotension to a degree not previously reported. Further evaluation of cerebral blood flow velocity, using transcranial Doppler testing, demonstrated an abnormal hypercapnic cerebrovascular response. Both the orthostatic hypotension and the abnormal cerebrovascular hypercapnic response improved with intensive medical treatment of her systemic lupus erythematosus. Additional studies are necessary to elucidate the pathogenesis of these cerebrovascular and autonomic abnormalities, especially considering the potential consequences they may exert on cerebral perfusion, which may be subtle, underrecognized, and capable of affecting cognition.     

Multiple system atrophy. Clinical aspects, pathophysiology, and treatment

Progressive autonomic failure is a clinical syndrome of autonomic dysfunction that may occur in isolation as in idiopathic orthostatic hypotension (IOH) or in association with a central neurologic disorder, multiple system atrophy (MSA). MSA and IOH can be distinguished on the basis of biochemical and pharmacologic tests. Plasma norepinephrine levels are low in IOH and normal in MSA; neither group increases the plasma norepinephrine level adequately in response to postural change. Both MSA and IOH manifest an exaggerated pressor response to administered norepinephrine. However, only patients with IOH have true adrenergic receptor supersensitivity. The autonomic dysfunction in IOH primarily involves the peripheral autonomic neurons whereas the defect in MSA is the failure to activate appropriately an intact distal sympathetic nervous system. Neuropathologic studies reveal a multisystem degeneration in MSA; the few postmortem examinations of the central nervous system in IOH reveal lesions confined to the intermediolateral columns of the spinal cord. Orthostatic hypotension may be treated with a number of medications although supine hypertension limits the usefulness of these drugs. Further development and testing of a sympathetic neural prosthesis may help to resolve this therapeutic dilemma. Only the parkinsonian features in MSA respond to treatment with anticholinergic drugs.     

Neuroepidemiology of acquired immune deficiency syndrome

Neuroepidemiology is that branch of chronic disease epidemiology dealing with disorders that affect the nervous system. The potential for neurological involvement in the diagnosis and pathogenesis of Acquired Immune Deficiency Syndrome (AIDS) has recently been noted. The following review outlines the spectrum of neurological conditions seen in AIDS patients to date. These conditions include: infectious central nervous system complications of viral, bacterial, fungal or protozoan origin; noninfectious central nervous system complications such as neoplasms or cerebral vascular accidents, and cranial and peripheral neuropathy. The incidence of neurological abnormalities among AIDS cases may be seriously underestimated due to a delay in the presentation of an overt neurological syndrome and/or the overlooking of subtle neurological signs and symptoms in such an overwhelming systemic disease.     

Assessment of autonomic nerve function in myotonic dystrophy

The function of the autonomic nervous system was studied in 23 patients with myotonic dystrophy, from a defined population in northern Sweden with an extremely high prevalence of this disease. Heart rate variability tests showed only minor signs of parasympathetic dysfunction. Blood pressure and plasma noradrenaline measurements in recumbent and upright positions showed no signs of sympathetic neuropathy. Increased plasma levels of noradrenaline was an unexpected finding. Our study does not support the hypothesis that cardiac arrhythmias, orthostatic hypotension, gastrointestinal motility disturbances and urinary bladder dysfunction in myotonic dystrophy are caused by autonomic neuropathy, and we believe that these symptoms should rather be ascribed to a defective function of the target organs.     

Syncope - a systematic overview of classification, pathogenesis, diagnosis and management

Syncope is defined as a temporary interruption of cerebral perfusion with a sudden and transient loss of consciousness and spontaneous recovery. Approximately one third of the population experiences syncope at least once during a lifetime. Presyncopal signs and symptoms, including weakness, headache, blurred vision, diaphoresis, nausea, and vomiting are sometimes present for seconds or minutes prior to loss of consciousness. After syncope, the patients may present with persisting drowsiness, headache, dizziness, nausea, but not usually confusion. Causes of syncope have been categorized as cardiovascular, non-cardiovascular, and unexplained. Cardiovascular causes can be subdivided into structural heart disease, coronary heart disease, and arrhythmia. Non-cardiovascular causes include neurological, metabolic, psychiatric and other disorders.Orthostatic hypotension - one of the most frequent causes of syncope - has manifold etiologies comprising various neurological and internal diseases. Orthostatic hypotension usually can be attributed to an impairment of peripheral vasoconstriction or to a reduction of the intravascular volume. Signs and symptoms, including the above prodromi are often present just after rising from a supine or sitting position. Frequently, blood pressure decreases significantly without an increase in heart rate. Autonomic cardiovascular modulation is often reduced. Many of the patients with "unexplained" syncope experience neurally mediated (i. e. neurocardiogenic or vasovagal) syncope. In these patients, cardiovascular control may be stable for an extended period of time during orthostatic stress, then there is a sudden decrease in blood pressure and heart rate. Neurocardiogenic or neurally mediated syncope can be associated with painful or emotionally stressful situations such as anxiety or fear, with prolonged standing or specific trigger situations such as micturition, defecation, coughing or sneezing, visceral or carotid sinus stimulation, or with trigeminal or glossopharyngeal neuralgia. So far, the mechanisms of neurocardiogenic syncope are not completely understood. The passive 60 degrees to 70 degrees head-up tilt test is useful for the diagnosis of orthostatic and neurally mediated syncope. The sensitivity of the test can be improved by additional pharmacological provocation, e. g. by isoproterenol, or by increased orthostatic stress using lower body negative pressure stimulation. For the treatment of syncope one should first consider non-pharmacological options. Patients with orthostatic hypotension should avoid rapid changes of the body position from supine to standing, as well as high room temperature or other situations inducing peripheral vasodilatation. An increased intake of sodium and fluids, mild physical exercise or so-called postural counter-maneuvers can improve orthostatic tolerance. Among the drugs recommended for pharmacologic treatment are mineralocorticoids (e. g. fludrocortisone), vasoconstrictor agents (e. g. ephedrine, midodrine), adenosine receptor blockers (theophylline) and beta2-blockers (propanolol), anticholinergic agents, e. g. scopolamine or disopyramide, and negative cardiac inotropes, e. g. beta1-adrenergic blockers or disopyramide. Serotonin reuptake inhibitors (e. g. fluoxetine, sertraline), alpha2-adrenergic agonists (clonidine), central nervous system stimulants such as methylphenidate or phentermine are thought to be beneficial in specific cases. Cardiac pacemakers often seem to be recommended without adequate indication. The antidiuretic, V2-receptor specific, vasopressin analogue desmopressin increases the intravascular volume. Erythropoietin improves anemia and red blood cell decrease and augments blood pressure and cerebral oxygenation. In postprandial hypotension, octreotide, a somatostatin analogue, prostaglandin inhibitors such as indomethacin or ibuprofen, as well as metoclopramide or two cups of coffee per day might be beneficial.     

帕金森病直立性低血压的研究进展

帕金森病(PD)是一种常见的神经系统变性疾病。PD患者除表现为典型的运动症状外,还具有一些非运动症状,如认知、情绪和睡眠等方面的改变。大部分PD患者在病程中会出现自主神经功能障碍,如便秘、排尿异常、性功能障碍、多汗、直立性低血压等。直立性低血压在PD患者中有较高的发生率,影响患者生活质量,文中就PD患者直立性低血压的诊断、病理生理机制及相关研究做一综述。     

Neurogenic orthostatic hypotension of Parkinson's disease: What exploration for what treatment?

The aim of this short review is to illustrate, using orthostatic hypotension as an example, the clinical problems related to autonomic features in Parkinson's disease. Orthostatic hypotension is frequently encountered in Parkinson's disease and its diagnosis remains manometric (a fall of at least 20 and/or 10 mmHg in standing blood pressure). It is often associated with supine hypertension to be taken into account before prescribing. To distinguish between the role of disease and of drugs (not only antiparkinsonian drugs), a simple clinical test of autonomic nervous system activity (deep breathing test and standing test with measurement of 30/15 ratio) can be used. When diagnosis with multisystem atrophy is discussed, cardiac [¹²³I]-metaiodobenzylguanidine (MIBG) scintigraphy is of value showing in Parkinson's disease a decreased uptake of the radiopharmaceutical indicating postganglionic sympathetic denervation. Concerning treatment, nonpharmacological methods have to be systematically used since no drug has been specifically evaluated for the treatment of orthostatic hypotension of Parkinson's disease.     

Neuropathology of autonomic dysfunction in synucleinopathies

The synucleinopathies—Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, and pure autonomic failure—result from distinct patterns of abnormal α‐synuclein aggregation throughout the nervous system. Autonomic dysfunction in these disorders results from variable involvement of the central and peripheral autonomic networks. The major pathologic hallmark of Parkinson's disease and dementia with Lewy bodies is Lewy bodies and Lewy neurites; of multiple system atrophy, oligodendroglial cytoplasmic inclusions; and of pure autonomic failure, peripheral neuronal cytoplasmic inclusions. Clinical manifestations include orthostatic hypotension, thermoregulatory dysfunction, gastrointestinal dysmotility, and urogenital dysfunction with neurogenic bladder and sexual dysfunction. Strong evidence supports isolated idiopathic rapid eye movement sleep disorder as a significant risk factor for the eventual development of synucleinopathies with autonomic and/or motor involvement. In contrast, some neurologically normal elderly individuals have Lewy‐related pathology. Future work may reveal protective or vulnerability factors that allow some patients to harbor Lewy pathology without overt autonomic dysfunction. © 2018 International Parkinson and Movement Disorder Society     

Insulin-induced hypotension and neurogenic orthostatic hypotension

Insulin-induced hypoglycemia induced a fall in blood pressure (BP) in patients with idiopathic orthostatic hypotension (IOH) and multiple system atrophy (MSA), but not in control subjects. Only in IOH was there a correlation between plasma norepinephrine (NE) levels and maintenance of BP during the test. The hypotension was not affected by pretreatment with propranolol. Hypotension during insulin-induced hypoglycemia is manifested in patients who lack an adequate NE response. The hypotension, however, may be due to a central action of insulin because not all MSA patients with impaired NE release become hypotensive.     

Primary neurogenic orthostatic hypotension

Eight further cases of neurogenic orthostatic hypotension are described together with a necropsy study on one case. Three cases showed evidence of autonomic dysfunction in isolation, while in five cases this was accompanied by evidence of more diffuse central nervous system degeneration. (Parkinsonism, cerebellar ataxia, dementia, pyramidal signs, bulbar weakness, and muscular wasting were all seen in varying proportions.)     

Beta-endorphin, ACTH, and catecholamine responses in chronic autonomic failure

Plasma epinephrine (EPI), norepinephrine (NE), beta-endorphin, and corticotropin (ACTH) responses were measured during insulin-induced hypoglycemia in normal subjects and in patients with either multiple system atrophy (MSA) or idiopathic orthostatic hypotension (IOH). In normal subjects, there was a striking rise in EPI, NE, beta-endorphin, and ACTH following the nadir of hypoglycemia. Both beta-endorphin and ACTH responses were significantly lower than normal in patients with MSA, in contrast to normal levels in IOH patients. No correlation was observed between the degree of adrenergic insufficiency and the beta-endorphin and ACTH responses. The normal peptide responses in IOH are consistent with involvement limited to the peripheral sympathetic nervous system, whereas lesions in the central nervous system in MSA interfere with release of beta-endorphin and ACTH in response to hypoglycemia. The strong correlation between beta-endorphin and ACTH levels is consistent with their common origin. Peripheral adrenergic activity is not essential for beta-endorphin and ACTH release in humans.     

Orthostatic hypotension and the Holmes-Adie syndrome: A study of two patients with afferent baroreceptor block

Two patients who presented with symptoms due to orthostatic hypotension were found on examination to have the Holmes-Adie syndrome. Physiological investigation suggested that they both had an afferent block from baroreceptors in contrast to the efferent autonomic block found in most other cases of idiopathic orthostatic hypotension, including the cases of multisystem disease, now often called the Shy-Drager syndrome.