Generality
Horner's syndrome, also known as Bernard Horner syndrome, is a procession of symptoms and signs sustained by damage, or a malfunction, of the sympathetic nerves in the trunk.
Figure: person with Horner syndrome. From the site: wikipedia.org
The sympathetic trunk is a collection of neurons that emerge to the right and to the left of the spinal cord, cross the thorax and rise, bilaterally, up to the neck and face.
The causes of Horner syndrome are numerous; their identification is very important to establish the most correct therapy (causal therapy).
The most characteristic signs of Horner syndrome are: ptosis, miosis and anhidrosis. However, they are also very frequent: anisocoria, slowed pupil dilation and blood-injected conjunctiva.
For a correct diagnosis, the following are essential: the physical examination, the evaluation of the medical history, some eye tests and some diagnostic imaging tests.
Short reference to the sympathetic nervous system
The sympathetic nervous system constitutes, together with the parasympathetic nervous system, the so-called autonomous or vegetative nervous system ( SNA ), which carries out a control action on involuntary bodily functions.
Originating in the spinal cord, the sympathetic nervous system (or more simply the sympathetic system) has an exciting, stimulating and contracting function. As can be appreciated from the figure below, he presides over the attack and escape adaptation system, thus preparing the body to face a danger.
Its start up and the resulting answers are quick and immediate. In fact, in a few moments, it is able to: increase the strength and contractile frequency of the heart, dilate the bronchial tubes, dilate the pupils, increase the caliber of the coronary arteries, inhibit the digestive system, relax the bladder, prepare the organism to physical activity etc.
The nerves of the sympathetic nervous system are distributed to the blood vessels, to the sweat glands, to the salivary glands, to the heart, to the lungs, to the intestine and to numerous other organs.
What is Horner's syndrome
Horner's syndrome - also known as Bernard Horner syndrome or oculosympathetic paralysis - is a set of symptoms and signs, resulting from the damage or malfunction of a particular group of nerves in the sympathetic nervous system. This particular group of nerves is the so-called sympathetic or sympathetic chain .
TRUNK OF THE PLEASANT
The nerves that make up the sympathetic trunk emerge from the spinal cord, cross the thorax and, from here, rise up to the neck and face.
The nervous emergency is bilateral, therefore the right section and the left section of the body each have their own innervation.
CONGENITAL OR ACQUIRED CONDITION?
Horner's syndrome may be either an acquired condition, that is, developed over a lifetime after a given event, or a congenital condition, that is, present since birth.
Between the acquired form and the congenital form, the most common one is the first, with 95% of clinical cases.
Epidemiology
The congenital type of Horner syndrome has a frequency of one case for every 6, 250 newborns.
The spread of the acquired type of Horner syndrome is not known: doctors, in this regard, only state that it is an uncommon condition.
Causes
The cause of Horner's syndrome is an interruption of nerve signaling that crosses the nerves of the so-called sympathetic trunk. As was said in the previous chapter, it can be a nerve damage or malfunction that determines this interruption.
But what can damage or decree the malfunctioning of the nerve endings that make up the sympathetic trunk?
Before answering this question, it is important to point out that the sympathetic chain includes different types of nerves, placed in series and called "first order neurons", "second order neurons" and "third order neurons".
Damage or malfunction that triggers Horner's syndrome can affect one of three types of nerves.
CAUSES THAT MAY ACT AT THE LEVEL OF NEURONS OF THE FIRST ORDER
The first-order neurons of the sympathetic trunk extend from the hypothalamus to the spinal cord (hypothalamus-spinal tract), passing through the brainstem.
To alter the functioning or damage these nerve cells of the sympathetic trunk, then causing Horner's syndrome, may be:
- A stroke event
- A brain tumor
- A neck injury
- The presence of syringomyelia . Syringomyelia is a neurological disease characterized by the formation of fluid-filled cysts in the spinal cord.
- Multiple sclerosis and all those pathologies that determine the progressive loss, by myelinated nerve cells, of the myelin sheath.
- An encephalitis
- Lateral marrow syndrome (or Wallenburg syndrome )
CAUSES THAT MAY ACT AT THE LEVEL OF NEURONS OF THE SECOND ORDER
The second-order sympathetic neurons of the sympathetic trunk extend from the spinal cord, cross the highest part of the thorax and end at the level of the neck.
To alter them to the point of causing Horner's syndrome, it may be:
- The presence of a lung tumor . The tumor mass causes a compression of sympathetic nerves, which no longer work properly. Doctors call the set of symptoms caused by the presence of the tumor mass with the technical term "mass effect".
- A schwannoma . Schwannomas are benign tumors that originate from the Schwann cells of the peripheral nervous system. Schwann cells belong to the so-called glia cells, which provide stability and support for the many nerves present in the human body.
- Damage to one of the main blood vessels that connect to the heart (eg the aorta)
- A chest cavity surgery
- Thyroidectomy surgery
- A traumatic injury, suffered at the base of the neck
- Klumpke's paralysis . It is a possible consequence of a trauma. At its origin there is an involvement of the brachial plexus.
- The presence of a thyroid tumor, due to the aforementioned "mass effect".
- The presence of goiter . The enlargement of the thyroid gland causes a nerve compression, similar in consequence to that created by the tumoral masses.
CAUSES THAT MAY ACT AT THE LEVEL OF NEURONS OF THE THIRD ORDER
The third-order neurons of the sympathetic trunk extend from the neck and end at the level of the facial skin and the muscles of the iris and eyelids.
To alter them to the point that they are responsible for Horner's syndrome, it may be:
- Damage to the carotid artery, in a section that passes through the neck.
- Damage to the jugular vein, in a section that passes through the neck
- A tumor at the base of the skull, due to "mass effect"
- An infectious disease that affects a tissue at the base of the skull . Among the possible infectious diseases, ear infections are also included.
- The presence of migraine
- The presence of cavernous sinus thrombosis
- The presence of cluster headaches
MAIN CAUSES IN CHILDREN
In infants and children, the main causes of Horner syndrome are:
- Injuries to the neck or shoulders, which take place during childbirth. For example, it is the case of the so-called Klumpke paralysis.
- Congenital defects of the aorta. These are conditions that affect the second-order neurons of the sympathetic chain.
- Some tumors of the nervous system, such as neuroblastoma.
IDIOPATHIC HORNER SYNDROME
A percentage of cases of Horner syndrome is idiopathic . In medicine, the term idiopathic, associated with a pathology, indicates that the latter has made its appearance without obvious and demonstrable reasons.
Symptoms and Complications
To learn more: Symptoms Horner's syndrome
The most characteristic signs of Horner syndrome are:
- Persistent miosis . It is the condition for which the pupil remains of a narrow diameter even in the absence of light.
- Ptosis . It consists of a partial or complete lowering of the upper or lower eyelids. This condition is also known as "drooping eyelids".
- Anhidrosis . It is the term by which doctors indicate the complete reduction or absence of sweating. In the case of Horner's syndrome, anhidrosis affects the face or only part of it.
These signs are often added:
- Anisocoria . It is the medical term used to indicate a different width of the eye pupils, even when both eyes are subjected to the same illumination.
- Slow dilation of the pupil in the presence of dim light.
- Loss of the cilio-spinal reflex . The cilio-spinal reflex is connected to the homonymous nervous center, located on the neck, whose stimulation determines the dilation of the pupil.
- Conjunctiva injected with blood
- Heterochromatic iris . It means that an individual has irises of different colors. This sign is found only in congenital forms of Horner's syndrome.
- Straight hair on one side only of the head . Like the heterochromatic iris, this clinical sign is also exclusive to congenital forms of Horner's syndrome.
Figure: case of anisocoria: note the different diameter between the right and left pupil. From: wikipedia.org
It is important to point out that, in general, the aforementioned signs affect only one side of the face / head, in this case the one innervated by damaged / malfunctioning nerves. In practical terms, if the sympathetic trunk shows damage to the right nerves, the ptosis will be located on the right eye and so on.
Clinical manifestations can affect both sides when nerve damage / malfunction is bilateral (ie there is involvement of the right nerves and left nerves).
WHEN TO REFER TO THE DOCTOR?
Since among the causes of Horner syndrome there are also very life-threatening morbid conditions, it is advisable to consult the doctor (or go to the nearest hospital center) when the above signs appear. Only a thorough medical investigation is able to clarify the exact nature of the manifestations and their severity.
Diagnosis
To diagnose Horner syndrome and identify the triggering causes, the following are fundamental: the physical examination, the evaluation of the clinical history (NB: it is generally part of the physical examination), the practice of particular eye tests and, finally, some tests diagnostic imaging tools.
EXAMINATION OBJECTIVE AND CLINICAL HISTORY
A thorough physical examination requires the doctor to visit the patient and question him about the clinical signs present. The most common questions are:
- What are the clinical manifestations found?
- When did they appear?
- Did they arise after some particular event?
At the end of this series of questions (or similar), the evaluation of the clinical history begins. This consists of a conversation between doctor and patient (or doctor and family, if the patient is a child), during which the first asks the second:
- If you suffer from particular diseases.
- If you take medicines, especially eye drops.
- If you are a smoker
- If you suffer from migraine
- Etc
The aforementioned questions and the previous physical examination provide the doctor with excellent elements, to establish the pathological condition in place and the causes that trigger it.
The description of ptosis is very important
During the physical examination, the doctor evaluates the characteristics of the clinical signs.
This is fundamental to distinguish Horner's syndrome from similar pathologies in terms of symptoms.
For example, analyzing the peculiarities of ptosis (in particular severity) allows us to understand whether this clinical manifestation is due to Horner's syndrome or to a lesion of the oculomotor nerve.
EYE TESTS
The eye tests that are particularly useful for diagnostic purposes (especially when doubts remain) are:
- The cocaine eye drops test
- The test with hydroxiamfetamine eye drops
- The test for the assessment of pupillary dilation rate
IMAGE DIAGNOSTIC TEST
Diagnostic imaging tests - in this case nuclear magnetic resonance (NMR), CT (Computerized Axial Tomography) and X-rays - allow us to identify the exact site of nerve damage / malfunction. In other words, they serve to identify which order of neurons from the sympathetic trunk has undergone the pathological alteration.
Moreover, the aforementioned instrumental examinations provide very clear images of any tumors, lesions to the blood vessels, cysts in the spinal cord, etc.
Treatment
Premise: at present, doctors have not yet discovered an effective treatment method to restore the health of a damaged nerve. Therefore, when a nerve structure suffers damage, this is permanent and the function regulated by the nerves involved is irremediably compromised.
To date, there is no specific therapy for Horner syndrome.
However, excluding the cases in which there is damage to the nervous structures, acting on the triggering causes can represent a valid therapeutic solution, for the achievement of a complete recovery.
The aforementioned treatment method, focused on the factors of origin of the morbid condition, is called causal therapy .
SOME USEFUL EXAMPLES TO UNDERSTAND
To understand what was stated above, it is useful to give some examples.
When a tumor is caused by Horner syndrome, surgical removal of the tumor mass leads to the disappearance of clinical signs, as there is a restoration of nerve function (compromised due to the mass effect).
In the same way, when the origin of the pathology is due to damage to the aorta or carotid artery, surgery for the resolution of the aforementioned damage allows the restoration of the normal functions of the sympathetic trunk and resolves the symptoms.
Prognosis
Any prognosis related to the prognosis depends on the severity of the triggering causes: if the latter are treatable and have a high survival rate, Horner's syndrome has a positive course.
