Clinical signs of dysautonomia (2023)


Dysautonomia does not lead to clear symptoms. Individual patient complaints may be part of a different disease process. It is the set of symptoms that indicate that there is a dysautonomous condition. Therefore, in capturing history, three tasks must be accomplished. The doctor must:

  1. Develop sufficient information to determine if a dysautonomic syndrome is indeed present.

  2. Distinguish secondary dysautonomia, including drug side effects, many of which improve or resolve when the underlying problem is treated, from primary dysautonomia, in which only symptomatic relief occurs.

  3. Distinguish between the different forms of primary dysautonomia, as they have different physical course and prognosis.

The symptoms of primary dysautonomia are listed inTable 76.2. Apart from postural syncope, symptoms are often mild or subtle and may only become apparent after a careful and detailed review of the systems.

Table 76.2

Dysautonomia symptoms.

Postural dizziness or syncopeis the most obvious symptom of dysautonomia. It is the most frequently reported and is usually of such concern that it becomes a major complaint or problem. Note that the symptoms evident in the patient are postural dizziness, syncope, or any other of the manifestations of cerebrovascular ischemia listed inTable 76.2. These symptoms are due to orthostatic (rectal) hypotension, but the latter is a sign to be elicited on physical examination and, strictly speaking, is not part of the historical database.

In addition to primary dysautonomia, there are many causes of orthostatic syncope due to orthostatic hypotension. These are listed inTable 76.3. The conditionsniceAndunsympathetichave been coined to describe situations in which the autonomic nervous system is normal (the former) and situations in which there is a dysautonomic state (the latter). An important point of differentiation between these two groups of problems is that when the autonomic response system is functioning normally (sympathotonic state), assuming standing is accompanied by an increase in heart rate. This can be felt and referred to as palpitations. In the unsympathetic state, the heart rate response is usually impaired along with other impairments in autonomic function.

Table 76.3

Causes of orthostatic hypotension.

The patient presenting with the postural symptoms associated with postural hypotension describes dizziness or transient weakness when rising from a supine position. This is especially evident when the movement is abrupt. The feeling is often described as a "wave" of helplessness that has swept over the person. The symptom is not accompanied by shortness of breath or chest pain. Palpitations are not present in the dysautonomous patient. Orthostatic syncope resolves rapidly once the head is lowered, and the symptom can sometimes be avoided by allowing the patient to stand slowly enough to allow the circulatory system to adjust. However, when the syndrome is fully developed, adaptation does not occur and severe symptoms of syncope can only be controlled by the use of supportive clothing and blood volume expansion therapy.

As mentioned earlier, these symptoms reflect a sudden decrease in blood supply to the brain and may have all the characteristics of transient cerebral ischemia. For example, some patients experience slurred speech or poor vision instead of the more commonly reported dizziness. In other individuals, particularly those with certain secondary drug-related dysautonomia, symptoms manifest as syncope or weakness after exercise and are not unique to postural changes.

Postural vertigo sometimes occurs in a normal person (eg on a hot day, after a hot bath, or when drinking socially). The historian must determine whether the postural symptoms are common, the circumstances under which they occur, whether the events are increasing in severity or frequency, and what other symptoms are associated with them in order to effectively distinguish between the many and varied causes.

urinary system dysfunctiondescribed by nearly two-thirds of patients with primary dysautonomia. These symptoms are also common in people with secondary dysautonomia, particularly in people with diabetes. Bladder symptoms are very non-specific. For example, nocturnal frequency may be part of a symptom complex due to heart failure, urinary tract infection, or bladder outlet obstruction, which are more common than dysautonomia. It could also be due to osmotic rigidity, which is more common in diabetics than severe dysautonomia. For these reasons, the historian must carefully assess each symptom in its overall context.

A point of variable importance in the history of bladder function is that dysautonomia, particularly primary syndromes, may be associated with loss of bladder sensation and motor dysfunction. Therefore, the dysautonomous patient may not be aware of the distended bladder.

This sensory abnormality may help distinguish the causes of urinary frequency, as osmotic diuresis and the frequency of congestive insufficiency are associated with an apparent sense of urgency. Similarly, the absence of cystic inflammation in dysautonomous patients results in frequency without dysuria, allowing differentiation from urinary tract infection. The lack of emotion, along with the motor dysfunctions of the syndrome, also makes dysautonomia (especially women) vulnerable to stress or overflow incontinence.

sexual dysfunction,is common in dysautonomia but can also be caused by a variety of other disorders (Table 76.4). For many years it was dismissed as almost exclusively psychogenic in origin. More recently, however, an organic or pharmacological cause has been identified in 80% of impotent men, and more than 50 organic causes of impotence have been identified.

Table 76.4

Organic causes of impotence.

A problem of particular concern is iatrogenic sexual dysfunction, which is caused by drug side effects on the autonomic nervous system. The drugs involved, especially those that lower blood pressure, are needed for life-long treatment of a major cardiovascular risk factor. The occurrence of side effects such as sexual dysfunction often leads to non-adherence to the prescription and can seriously affect a treatment plan. Therefore, if a patient is known to be receiving a drug that may cause this side effect, the possibility should be explored through careful and sensitive questioning for evidence of sexual performance difficulties. If these are discovered, the treatment regimen should be changed.

Certain historical points tend to indicate dysautonomia or some other organic cause of sexual dysfunction. In the evaluation of impotence, the presence or absence of morning erection is the main clue. Morning erection is a common phenomenon in men. The incidence tends to decrease with age, but still occurs in older men. It is a manifestation of sympathetic nervous system activity during the REM sleep cycle. As such, it is a true measure of autonomic nervous system capacity. The history taker should determine whether the patient has morning erections, how often they occur, and whether there are changes in their character (ie, a less tense erection). If the history is unclear, it is possible to check this phenomenon by objective methods (nocturnal swelling of the penis).

Another clue to the distinction between organic and psychogenic sexual dysfunction is the relationship of arousal and power with specific sexual partners. Psychogenic sexual disorders are often limited to a specific partner. It may be an expression of guilt over extramarital sexual activity, fear of possibly transmitting an STD, or performance anxiety. Organic problems manifest in all partners.

It is not easy to distinguish between the many causes of organic impotence. In inflammatory diseases, the presence of pain can be a clue. Most other causes must be distinguished by evaluating this symptom in the context of the overall history.

bowel dysfunctionappears to be a symptomatic bothersome problem less often in dysautonomous patients. This may be because small changes in stool consistency or frequency are not considered abnormal or noticeable by most patients. Since dysautonomias most often have the characteristics of sympathetic dysfunction, the patient will have frequent and less solid bowel movements. If the condition worsens, it can cause explosive diarrhea. The patient may also have uncontrolled bloating. As sphincter control is lost, the extremely embarrassing condition of sudden fecal incontinence can occur.

Nocturnal diarrhea is common. This provides a good historical point of differentiation between organic and functional bowel syndromes (not seen in psychogenic or functional diarrhea). Nocturnal diarrhea is particularly common in diabetic dysautonomia, but is not unique to this syndrome.

Abnormalities of sweatingreported by only a small number of patients with dysautonomia. Most of the time, the lower extremities are more affected by sweating than the trunk or arms. In diabetics, the distribution of non-sweating areas can be very irregular.

Failure to report this symptom does not mean that loss of sweating is a rare event in dysautonomia. It indicates that most functions of the autonomic nervous system are beyond conscious awareness. Therefore, the failure of these functions does not result in symptoms at the ordinary level of consciousness. Only those aspects of activity where the dysfunction causes either very dramatic symptoms (orthostatic blood pressure control) or where the dysfunction is very obvious (bowel, bladder, and sexual activity) are symptoms that are alarming enough to report.

Confirmation of the diagnosis is based on physical findings, many of which have no historical equivalent, and the performance of certain objective tests of autonomic function. These are described inChapter 79, Autonomous System Laboratory Evaluation.

basic science

The autonomic nervous system innervates every tissue and organ in the body. Most of the functions it performs are outside the normal range of consciousness. It is the guardian of the "milieu interieur". Many of its activities require a balanced interaction between the sympathetic and parasympathetic nervous systems. The system also operates through fast-acting reflexes that control a variety of physiological functions. In the case of dysautonomy, the system no longer works in a balanced way or fast enough. This combination of imbalance and loss of responsiveness leads to the appearance of the symptoms that characterize dysautonomic syndromes. As mentioned earlier, many activities of the autonomic system never lead to symptoms because, even when functioning abnormally, they never manifest themselves at the patient's level of consciousness.

Blood pressure control, orthostatic hypotension and orthostatic syncope

Autonomic nervous system reflexes provide a rapid-acting mechanism for momentary control of blood pressure. These reflexes are critical to maintaining an adequate blood supply to the brain when a person is upright. Although the brain's vasculature is capable of self-regulating and dilating when blood pressure falls, this ability is limited. If blood pressure drops sufficiently, cerebral perfusion also drops. For example, orthostatic hypotension, the drop in blood pressure when standing, is accompanied by syncope or dizziness, the most obvious symptoms of dysautonomia.

The baroreceptor/pacemaker pressor reflex is the autonomic mechanism responsible for this aspect of blood pressure control. The reflex arc consists of several components: sensory receptors, the site of integration, the efferent system, and the effector organ.

The sensory receptors

Arterial baroreceptors are specialized stretch receptors found in the walls of highly elastic large vessels. The most commonly reported sites of these receptors are the carotid sinus and aortic arch, although such sensory receptors are likely to be widespread in the walls of the major arteries of the head and neck. These sensory organs respond to the stretch exerted by the pulsating column of blood on the elastic vessel wall and translate the stretch created by the energy in the pulse wave into an analog signal. This travels to the brain in sensory fibers of the vagus nerve.

The place of inclusion

The "vasomotor center" is located in the pontomedullary portion of the hindbrain in an area containing nuclei closely connected to the reticular activating system. This impulse integration area receives input from arterial baroreceptors and stimuli from a variety of other sources. These sources include higher neurological areas such as the thalamus, hypothalamus, and cortex, as well as additional peripheral sensory receptors located on the venous side of the circulatory system, the heart itself, and other organs and tissues. Signals from all these sources are continuously received, provide an instantaneous description of the physiological state of the individual, are integrated into the "vasomotor center" and ultimately control the tonic level of pulse activity in the autonomic system. Because this system is continuously active, the continuous modulation of neuronal traffic allows immediate response to the changing environment.

Arterial baroreceptor input has an inhibitory effect on the tonic level of autonomic cardiovascular activity. If the blood pressure increases, the baroreceptors are stretched more and more and more nerve impulses are transmitted. The effect of this increased inflow to the vasomotor center is twofold: There is an effectelevatedparasympathetic output to the heart – this slows the heart rate. There arereducedActivity in the sympathetic nervous system – this also tends to slow the heart rate and, more importantly, allows the blood vessels to relax the arterial resistance and reduce the contraction intensity of the heart muscles. All these effects lead to a drop in blood pressure with the baroreceptors restoring their 'set point'.

If, on the other hand, blood pressure drops, the baroreceptors send fewer signals. parasympathetic activitydecreases,which can increase the heart rate. More important is the activity of sympathetic neural impulsesincreasesThis leads to stimulation of heart rate and contractility, and constriction of arterial and venous blood vessels. All of these effects serve to reverse the drop in blood pressure.

The abductive system

The autonomic nervous system has classically been described as a "two-neuron" efferent system. Information from the integration centers is transmitted into the central nervous system via a "first neuron" that exits the CNS to reach a ganglion where a synaptic event takes place. In fact, several neurons (intercalated neurons) are involved in the transmission process within the central nervous system. The cell bodies of some of these intervening neurons are located in the intermediate lateral columns of the spine and are the cells where the degeneration occursMultiple system atrophy with autonomic failure.

The axons of the last intervening cells of the sympathetic division migrate to the ganglia after exiting the spinal cord. With this division, the exit points of the spinal cord are located in the thoracic-lumbar region, and the ganglia are located in a chain near the spine. Ganglionic synaptic transmission does not occur from one neuron to another. It involves extensive reentry of nerve impulses through multiple synaptic events, in which single presynaptic axons excite many postsynaptic cell bodies and individual postsynaptic cells are excited by many presynaptic transmitter axons.

In the parasympathetic system, the exit points of the central nervous system are divided into two units. Most part activity, especially the control of the heart and visceral organs, occurs through the cranial nerves, especially the vagus nerve (cranial nerve X). A second area for impulse output from the CNS is in the sacral portions of the spinal cord. This area manages the parasympathetic impulses that control the colon, bladder and sexual function. During the parasympathetic division, axon fibers emerging from the CNS migrate to the effector organ before making synaptic contact with the “second neuron”. Synaptic interactions take place in the neural plexus and not in unitary ganglia. Acetylcholine is the synaptic neurotransmitter in both the sympathetic ganglia and the parasympathetic plexus.

The executive body

For autonomic cardiovascular reflexes, the active organ is the entire cardiovascular system. The different parts of the cardiovascular system each respond in characteristic ways to sympathetic stimulation. The sum of these individual answers gives the complete answer:

  • The venous circuit:Sympathetic stimulation of veins causes constriction. This reduces the storage capacity for blood volume and the immediate consequence is that an increased blood volume flows back to the heart. This increase in "preload" results in increased cardiac output (CO).

  • Arterial circulation:Arteriolar sympathetic stimulation causes smooth muscle contraction and leads to an increase in peripheral vascular resistance (PVR). The most sensitive arterial layers are found in visceral organs and skin. The narrowing of these vascular beds results in a shift of blood flow to the heart and brain, organs in which the vessels tend to respond less or not at all to arterial sphincter stimuli. As a result of these effects, not only does blood pressure rise, but there is also a redistribution of blood volume, which maintains blood flow to the most vital organs. Arterial constriction is mediated by the alpha-postsynaptic membrane receptor. This reaction predominates in the vessels of the skin and intestines. However, in striated muscle, arterioles have a relatively higher concentration of beta-postsynaptic receptors. These cause a vasodilator response when stimulated by norepinephrine, the neurotransmitter of the sympathetic 'second neuron'. Exercise also produces a direct vasodilator effect through the autoregulatory mechanism. When the balance between sympathetic vasoconstriction and combined neuronal and autoregulatory vasodilation is lost, as can occur in dysautonomia or as an adverse effect of certain drugs, syncope may occur during exercise or exercise. This symptom should be investigated in the medical history, especially in people taking guanethidine or drugs that block alpha receptors.

  • The heart:Sympathetic stimulation of the heart leads to an increase in both heart rate and the force of ventricular contraction. Both effects are beta-receptor mediated responses and increase cardiac output.

The effects of increased sympathetic stimulation on blood pressure can be predicted using the following equation:

Clinical signs of dysautonomia (4)

Reflex actions that increase either cardiac output (CO) or peripheral vascular resistance (PVR) increase blood pressure. When both CO and PVR are elevated, there is a synergistic effect that has an even greater effect on blood pressure.

The effects of changing posture (assuming standing) can therefore be described as follows: When standing, there is a temporary pooling of blood in the legs and visceral vein of venous blood due to the effect of gravity on the column. There is a sudden drop in the volume of blood returning to the heart, and this sudden decrease in preload results in a transient drop in cardiac output and blood pressure. All this happens in a single heartbeat and is immediately felt by the baroreceptors. The built-in autonomic response constricts the veins and restores pretension. increases heart rate and contractility, thereby increasing cardiac output. and constricts arterioles, increases blood pressure, and redistributes arterial blood flow to maintain blood flow to the heart and brain.

After compensatory events, when the reflex is functioning normally, systolic blood pressure tends to remain slightly reduced (because it is highly sensitive to the effects of reduced preload) and diastolic blood pressure tends to increase (because it reflects the increase in PVR). ). There are no absolutely agreed upon "normal" limits to these changes. A drop in systolic pressure of 10 mm Hg is common, and up to 25 mm Hg may be acceptable in the absence of symptoms. Similarly, diastolic pressure may increase by 5 mm Hg, may not change, or even drop by 5 to 10 mm Hg. The response is still considered "normal" if the patient remains asymptomatic.

Reflex-mediated compensatory responses do not occur in dysautonomia patients. When the patient is standing, blood pressure falls below tolerable limits and there is no redistribution of blood flow. Blood supply to the brain decreases and postural syncope occurs.

Sympathetic control of urogenital function

Understanding the distribution and function of the sympathetic nerve innervation of the bladder also helps in understanding the symptoms of dysautonomia. Sympathetic motor fibers travel to the body of the bladder, where they relax the muscle (beta-receptor mediated), and to the bladder outlet sphincter, where they stimulate contraction (alpha-receptor mediated). A failure of the entire system would therefore lead to spontaneous constriction of the bladder wall muscles and relaxation of the sphincter. Small bladder with poor sphincter tone shows rapid filling and reduced reservoir capacity. Frequency and incontinence are the consequences of this chain of events.

Sympathetic innervation is also important for sexual performance. There are many events in the sexual experience, all of which depend in some way on a normally functioning sympathetic nervous system.

  • Excitement:Visual stimuli, imagination, and other cortical events integrated with thalamic and hypothalamic stimuli all appear to be important for sexual interest (libido) and arousal. The integrated output of these higher neurological centers appears to affect the sympathetic system, as many drugs that inhibit aspects of CNS sympathetic function decrease libido. and in an experimental study, a sympathetic CNS stimulant, yohimbine, appears to be an aphrodisiac in rats.

  • Swelling:Actual perfusion of the genital structures with blood is mediated by sympathetic outflow from both central nervous system centers and spinal reflexes. In men, this is the power - penile erection. In women, the swelling manifests itself in the form of an erection of the clitoris and swelling of the labia.

  • RECRUITMENT:Secretions from the testes, seminal vesicles, and prostate are mobilized by the motor activity of the smooth muscles of the elastic structures, all of which are richly innervated and responsive to sympathetic stimuli. The process of moistening with secretions from the glandular structures of the labia and vagina probably represents the analogous process in women.

  • Ejaculation:This is a reflex event mediated in the sacral part of the spinal cord by a parasympathetic loop and is rarely if ever inhibited in dysautonomia or by drugs. However, normal advanced ejaculation depends on adequate closure of the bladder sphincter. As previously mentioned, this is a sympathetic motor function and is impaired in some dysautonomic syndromes, particularly diabetes, and by some drugs.

    If sympathetic stimulation does not result in closure of the bladder sphincter during the parasympathetic reflex event of ejaculation, retrograde ejaculation will occur. Even if the feeling of ejaculation is present, the lack of ejaculation is an annoying symptom. It can be so painful for the patient that compliance with the prescription is seriously compromised.

    The event associated with ejaculation in women is unknown. The muscle contractions of the vagina and uterus that occur at the moment of climax may be caused by the parasympathetic reflex system, but this has not been proven.

  • Climax:Autonomic events associated with the peak of sexual arousal have the characteristics of a generalized sympathetic nervous system discharge. Blood pressure increases, heart rate increases, erection occurs, etc. Individual patients, both male and female, have reported that certain medications that block sympathetic outflow delay or reduce the sensation of climax. These accounts are anecdotal and have not been studied in a systematic or controlled manner.

Given these multiple effects of the sympathetic nervous system on sexual performance, and given that dysautonomia is rarely complete, there are many different ways in which sexual function could be disrupted in dysautonomia syndromes. The literature usually does not differentiate between these effects. Most of the time it is just a failure of potency or loss of libido. As shown inTable 76.5, detailing the effects of certain antihypertensive drugs on sexual performance, it is possible to distinguish different aspects of sexual failure depending on the likely location of autonomic inhibition.

Table 76.5

Effects of some antihypertensive drugs on sexual performance have been reported.

This approach to analyzing the effects of antihypertensive drugs makes it clear that damage to the central site of sympathetic integration results in inhibition of potency and libido, with limited effect on ejaculation. Inhibition of neurotransmission at peripheral sites (ganglion or nerve endings) results in reduced potency and ejaculation, but has no effect on libido. It is noteworthy that beta-blockers, whose action is limited to the peripheral nervous system, have no sexual effects, while propranolol, a drug of this class that enters the CNS, has a similar effect on sexual performance as other central ones. - active drugs.

Information on these effects is incomplete for most drugs, even antihypertensives, which are probably the most extensively studied, because these topics are not systematically studied in most drug evaluation protocols. However, some characteristic side effects are predictable depending on a drug's site of action. For example, the histamine receptor antagonist cimetidine has been shown to have a site of action in the central nervous system. The drug inhibits libido and potency. This pattern of adverse effects is exactly what would be expected given the drug's receptor-blocking mechanism and central nervous system site of action.

The primary dysautonomias

In the 19th century literature there are a number of case reports describing patients with symptoms indicative of dysautonomia. They emphasize orthostatic hypotensive symptoms. Relevant basic research has focused on the factors responsible for blood pressure control. Clinical interest was sparked by the 1925 report of three patients with the following characteristics:

Orthostatic hypotension


Steady heart rate

Nocturnal polyuria


loss of libido

Chronic diarrhea


cures intolerance

Minimal signs of neurological disease

youthful appearance


Low metabolism

Increased blood urea nitrogen

This syndrome was called "idiopathic orthostatic hypotension" by its describers, Bradbury and Eggleston. However, the symptom complex suggests that some form of dysautonomia was present in the patients. More recently the termprogressive autonomic failurehas been suggested as a more appropriate name for the syndrome.

Despite the many abnormalities in patients with this syndrome, attention has focused on orthostatic syncope and orthostatic hypotension. This interest culminated in Wagner's publication of a seminal review on the subject in 1959. Although the focus of this research was orthostatic blood pressure variation, the list of causes he identified includes all the most common dysautonomic disorders, both primary as well as secondary ones.

A year later, Shy and Drager published the description of a syndrome that bears their name. It is also characterized by the presence of orthostatic hypotension, but additional aspects of neurological dysfunction were very evident and emphasized. The patients, men in their fifth to seventh decades of life, presented with the following symptoms and signs:

Orthostatic hypotension

atonic bladder

urinary incontinence


Loss of rectal sphincter tone

rectal incontinence

loss of sweating


External paralysis of the eyes



Lack of movement associated with walking


Atrophy of peripheral muscles

Abnormal EMGs

Neuropathic Muscle Injury

The authors described pathological changes in the mediolateral columns of the spinal cord. The subsequent confirmation of these pathologic findings and the link between spinal cord pathology and autonomic symptoms led to a shift in the focus of assessment and treatment from simple blood pressure to broader aspects of the entire disease process.

Familial dysautonomia(Riley-Day syndrome), a completely different type of primary dysautonomia, was first described in 1949. This syndrome has been considered a pediatric problem, although with improved treatment there are now several patients who have survived into young adulthood. The disease is genetic and is inherited in an autosomal recessive manner. It occurs almost exclusively in Ashkenazi (Northern European) Jews.

A very specific feature of this disease is the almost complete absence of somatosensory function in affected individuals. Both the autonomic and sensory nervous systems have a reduced number of peripheral fibers and this appears to be a 'peripheral' rather than a 'central' nervous system disorder. The main characteristics of the syndrome are as follows:

Orthostatic hypotension

lack of tears

Missing taste buds



abdominal distension




overflow incontinence

Abnormal gait (wide gait)

Suppressed reflexes

Although this syndrome shares some of the features of other dysautonomias, it is an entirely different disease because of the extent and distribution of additional neurologic damage, the genetic nature of transmission, and the congenital presentation. Interestingly, two of the female victims who reached childbearing age were fertile and gave birth to normal children.

Clinical significance

The primary dysautonomias

Syndromes of primary neurologic disease with autonomic failure require very careful evaluation and differentiation.

With progressive autonomic failure(Bradbury-Eggleston Syndrome or Idiopathic Orthostatic Hypotension) Symptoms of autonomic failure are an early manifestation. The history at the time of the patient's first treatment suggests postural syncope. This may also include genitourinary or intestinal symptoms, but these are usually revealed on examination of the systems and are not offered spontaneously by the patient. Although this syndrome is progressive, it develops slowly. Once effective blood pressure control is achieved, the patient can live relatively comfortably for many years.

The reverse is theShy - dragonThe syndrome is a more rapidly developing disease and much more difficult to treat. Dysautonomic symptoms usually follow the appearance of signs of other aspects of neurologic degeneration. The Parkinson's-like symptoms that often occur with this syndrome are particularly difficult to treat and can even complicate the treatment of postural vertigo. Druglarge-Dopa, for example, may be useful in controlling stiffness, but may cause orthostatic hypotension.

In addition, more than one form of neurodegenerative disease appears to be present in the group of patients diagnosed with Shy-Drager syndrome. While everyone eventually develops dysautonomia, some develop it only in association with Parkinsonian-like abnormalities associated with olio-ponto-cerebellar degeneration. Others may have a variable distribution of neurologic abnormalities, including sensory system abnormalities and voluntary motor dysfunction. Because this syndrome can lead to degeneration of various neurological systems, it is named after itMultisystems nutritionwas proposed. These patients do not develop dementia.

To further complicate the situation, autonomic dysfunction may occur in some patients with true Parkinson's disease. The disorders of the righting reflex that often occur with this disease make it difficult to stand up abruptly. They are often confused with true orthostatic blood pressure abnormalities and postural syncope. However, some patients develop signs of autonomic degeneration and orthostatic hypotension late in the course of the disease. Dementia is a manifestation of Parkinson's disease that is not present in Shy-Drager syndrome or progressive autonomic failure.

Because these primary syndromes have such different natural histories and ease of treatment, it is important to try to distinguish them. The points of difference are summarized inTable 76.6.

Table 76.6

Differential diagnosis of the most important primary dysautonomia.

Primary dysautonomic syndromes can be devastating conditions that seriously affect the patient's life due to their pattern of symptoms: inability to stand up, inability to control bowel and bladder, failure of normal sexual function. These symptoms may be accompanied by tremors, rigidity, and other symptoms and signs similar to Parkinson's disease when autonomic degeneration occurs in combination with multiple system atrophy. Fortunately, these are rare diseases. No treatment method can stop or cure it. While some symptoms, particularly postural syncope, can be controlled, this is often made difficult by the treatment required to control Parkinson's disease. There are no really effective treatments for the other aspects of primary dysautonomia.

Secondary and idiopathic dysautonomia

Diabetes mellitus is perhaps the most important systemic disease in which dysautonomia manifests. The diabetic may develop symptoms of autonomic dysfunction very early in the disease process, before significant changes in glucose tolerance develop. and the dysautonomic process can be particularly difficult to diagnose in diabetics because it often does not follow the classic pattern of presentation. For example, although the pressure component of the baroreceptor reflex may be inhibited, the pacemaker component often remains intact. The sympathetic character of postural hypotension in the diabetic will not be apparent since the heart rate response to postural changes remains.

The diabetic may also experience some of the effects of dysautonomia on visceral function before developing problems with orthostatic blood pressure control. This is why diabetics often experience nocturnal diarrhea or diarrhea alternating with constipation as an expression of dysautonomous bowel function. Impotence and retrograde ejaculation are also commonly reported.

The occurrence of orthostatic hypotension and orthostatic syncope is a significant problem with some drugs (Table 76.7). This side effect makes it impossible to continue using an agent in a treatment regimen, even if it produces the desired therapeutic effect, because of the risks to the patient and the patient's inability to tolerate this problem.

Table 76.7

Drugs that cause autonomic orthostatic hypotension.

The list of drugs that can cause postural syncope is long and varied. Some produce this effect through actions on the autonomic nervous system. Others do not impair autonomic function, but lead to a reduction in circulating blood volume. These drugs share the common property of reducing cardiac output and preload, either by causing symptoms of autonomic inhibition or reduced resting volume. Drugs that reduce only peripheral vascular resistance (eg, hydralazine, minoxidil)do not provokeorthostatic hypotension. This is an important consideration when planning a change in therapy to alleviate the side effect of postural syncope.

The most important consequence of these side effects is probably not postural syncope or impaired sexual performance per se, but the patient's lack of adherence to the treatment plan when a drug is identified as the cause of the condition. Mistrust of medicines is often transferred to other factors, and even minor illnesses are attributed to a medicine. Since medications are required for the lifelong management of most patients, this nonadherence and associated reluctance to trust a medication becomes an extremely important clinical management issue.

Other secondary dysautonomia are relatively rare. Moreover, the symptoms of autonomic failure are only part of the overall syndrome presented by the patient. Most of the time, the diagnosis of these diseases is suggested by these other symptoms. However, the complete differential diagnosis must be reconsidered, as secondary dysautonomic syndromes are often part of the correctable problems and improve with successful treatment or control of the underlying systemic disease.

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