Introduction:
Harlequin syndrome causes symptoms like skin flushing on one side of the face, arms, and chest, no sweating, and no pupil reaction to stimuli. In addition, the affected side of the face looks pale in color. This sign is typical of the Harlequin syndrome. A few tests, like quantitative pseudo motor axon reflex testing and thermoregulatory tests, are done, and specific imaging studies are also done to rule out the causes of this condition. There is no particular treatment for this condition. However, treating the underlying causes contributes to managing the Harlequin syndrome.
What Is a Harlequin Syndrome?
Harlequin syndrome is a rare neurologic condition that affects the autonomic nervous system. The autonomic nervous system is a part of the peripheral nervous system that manages involuntary physiologic functions like breathing, heart rate, digestion, blood pressure, etc.
What Causes Harlequin Syndrome?
The causes of these syndromes are unclear. However, an injury, compression, or occlusion in the sympathetic nerve fibers to the face can result in Harlequin syndrome. Single-side blockage of the nerve that carries sudomotor (part of the autonomic nervous system that manages the sweat gland to environmental factors) and vasomotor (part of the autonomic nervous system that manages or maintains the width of the blood vessels) supply to the face results in hemifacial (one half of the face) discoloration of the face. In addition, the color of one-half of the body becomes red, and there is an absence of sweating on one side of the body.
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Idiopathic Harlequin Syndrome: When the reasons are unknown for the cause of the Harlequin sign, it is called idiopathic Harlequin syndrome.
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Secondary Harlequin Syndrome: When the causes are due to underlying lesions or surgical procedures, it is called secondary Harlequin syndrome.
A few lesions cause Harlequin syndrome like,
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Pancoast Tumor: Pancoast tumor is a type of abnormally formed patch of tissue in the apex of the lung, mostly involving the chest wall structure rather than the lung tissue.
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Cervical Sympathetic Tumors: Cervical sympathetic tumors are rare benign nerve tumors. It often occurs on the neck and is asymptomatic (it does not cause any symptoms).
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Thoracic Syrinx: It is a fluid-filled mass inside the spinal cord.
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Medullary Infarction: Medullary infarction results from reduced or no blood supply to the medulla oblongata's lateral part (the brain's bottom portion). The reduced blood supply may be due to a blockage in the blood vessel that supplies the brain due to a blood clot or any obstruction.
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Thalamic Hemorrhage: It is a type of intracerebral hemorrhage (bleeding inside the brain) that results due to uncontrolled long-term hypertension (high blood pressure)
A few post-anesthetic procedures cause Harlequin signs like,
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Thoracic Epidural: The area around the spinal cord is called the epidural space. A medication is injected into the epidural space to relieve back pain.
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Paravertebral Blocks: In this technique, a local anesthetic is injected into the thoracic vertebra near where the spinal nerves emerge.
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Multilevel Intercostal Nerve Block: It is the injection of a medication to relieve pain in the chest area that results after a herpes zoster infection or surgery.
A few surgical procedures like,
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Thyroidectomy: It is the removal of the thyroid gland through surgical procedures.
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Neck Schwannoma Excision: Schwannomas are benign tumors that arise in the peripheral nerve sheath (a layer of connective tissue that surrounds and protects the nerve fibers). The surgical removal of these benign tumors in the nerve fibers in the neck region also causes the Harlequin syndrome.
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Venoarterial Extracorporeal Membrane Oxygenation (VA ECMO): It is temporary mechanical support that provides extracorporeal gas exchange in acute cardiorespiratory failure cases.
What Are the Symptoms of Harlequin Syndrome?
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Flushing or paleness of one side of the body, especially on the face, arms, and chest.
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Absence of sweat on one side of the body.
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The skin is cold on touching.
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One side of the body sweats when the person is exercising or in an emotional state, while the other side of the body does not sweat, and flushing is seen.
These signs are called Harlequin signs. These symptoms occur when the person with this condition exercises, the body becomes warm or is under some intense emotional state.
What Are the Tests to Find Harlequin Syndrome?
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Physical Examination: The Harlequin sign is typical of this condition. The doctors look for the Harlequin sign for the diagnosis.
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Stress Test: A stress test is done while the person is asked to walk on a treadmill for 5 to 15 minutes. This is done to check for Harlequin signs. In other cases, it is also done to check how well the heart works. It is also called an exercise test.
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Quantitative Sudomotor Axon Reflex Test (QSART): Quantitative sudomotor axon reflex test measures the nerves that manage the sweat glands. It is done to stimulate the sweat glands through mild electrical stimulation. This causes the naturally occurring chemical called acetylcholine to stimulate the sweat glands.
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Thermoregulatory Sweat Test (TST): Thermoregulatory sweat test is done to evaluate the stability of the central and peripheral sympathetic sudomotor pathways from the central nervous system to the sweat glands. It is done by making the patient lie on a bed and sprinkled with a powdered substance that changes its color while sweating from yellow to bright purple.
How Is Harlequin Syndrome Treated?
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There is no specific treatment for Harlequin syndrome. The Harlequin signs resolve on their own once the triggering factor subsidies in a few minutes.
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Suppose the Harlequin face is due to a local anesthetic agent (a medication that causes numbness and temporary loss of sensation). In that case, the sign will resolve once the effects of the anesthetic agent wear off.
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Harlequin's face due to retraction or compression injury while performing neck surgeries may last for a few days to a few weeks. However, if specific injuries lead to the total transection of T2-T4 fibers (thoracic part of sympathetic nerve fibers), there will be permanent facial discoloration.
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In some instances, stellate ganglion blocks are considered in patients responsive to this treatment. It involves injecting a medication into the nerves that help improve the blood circulation in the head, neck, upper arms, and upper chest.
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Botulinum toxin is also injected to achieve temporary muscle paralysis in a particular area. Botulinum is a purified form obtained from bacteria. It is used to block the nerve signals to the muscles.
What Is the Prognosis of Harlequin Syndrome?
The prognosis is good by treating the underlying condition causing the Harlequin syndrome. Harlequin syndrome is a benign condition that resolves over time. However, recurrence is common.
Conclusion:
Harlequin syndrome is a neurologic condition that causes faults in the functioning of the autonomic nervous system. It leads to unilateral flushing of the face, arms, and chest. Also, it leads to the absence of sweating on one side of the body. These signs usually occur when the affected person exercises, the body is warm or is emotional. Diagnostic tests like stress tests and thermoregulatory stress tests are helpful. There is no treatment as such for this condition, as the causes are unknown. If the condition is due to an underlying lesion, treating the lesion will help the condition resolve. However, the signs resolve on their own over time or once the triggering factor subsides. Treating the underlying condition that results in Harlequin syndrome will improve the patient's quality of life.
