Causes Although congenital Horner syndrome can be passed down in families, no associated genes have been identified. Horner syndrome that appears after the newborn period acquired Horner syndrome and most cases of congenital Horner syndrome result from damage to nerves called the cervical sympathetics. These nerves belong to the part of the nervous system that controls involuntary functions the autonomic nervous system. Within the autonomic nervous system, the nerves are part of a subdivision called the sympathetic nervous system. The cervical sympathetic nerves control several functions in the eye and face such as dilation of the pupil and sweating.
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Inability to open eye fully on the affected side. Loss of sweating on the affected side. Facial flushing if preganglionic lesion. Constricted pupil on the affected side, more apparent in a darkened room: Shine a torch in the eye to make the pupil constrict. Remove the torch and watch the pupil dilate.
Do the same on the other side and compare the response. The affected pupil lags behind the other in dilation as it lacks sympathetic tone but the test may need to be repeated several times to detect it. Then run them laterally over the forehead to just lateral to the eyebrows. On the affected side there may be more friction as the skin is drier because there is no sweating on that side. A lesion in the common carotid artery area causes loss of sweating that involves the entire side of the face.
Lesions distal to the carotid bifurcation produce lack of sweating on the medial aspect of the forehead and the side of the nose. Ipsilateral partial ptosis drooping of the upper eyelid with possible paradoxical contralateral eyelid retraction. There may be apparent mild enophthalmos due to the sagging lid. There is increased amplitude of accommodation. Pigmentation of the iris is under sympathetic control and is usually complete by the age of 2 years.
Examine for the presence of lymphadenopathy see table, below. Other signs depend on underlying cause see table, below.
Horner syndrome signs Open pop-up dialog box Close Horner syndrome signs Decreased eye pupil size is a key sign of Horner syndrome. Horner syndrome is a combination of signs and symptoms caused by the disruption of a nerve pathway from the brain to the face and eye on one side of the body. Typically, Horner syndrome results in a decreased pupil size, a drooping eyelid and decreased sweating on the affected side of your face. Horner syndrome is the result of another medical problem, such as a stroke, tumor or spinal cord injury. In some cases, no underlying cause can be found.
Pathophysiology[ edit ] Horner syndrome is due to a deficiency of sympathetic activity. The site of lesion to the sympathetic outflow is on the ipsilateral side of the symptoms. Second-order neuron disorder: Preganglionic lesions e. Third-order neuron disorder: Postganglionic lesions at the level of the internal carotid artery e. Three tests are useful in confirming the presence and severity of Horner syndrome: Cocaine drop test: Cocaine eyedrops block the reuptake of post-ganglionic norepinephrine resulting in the dilation of a normal pupil from retention of norepinephrine in the synapse. If the third order neuron the last of three neurons in the pathway which ultimately discharges norepinephrine into the synaptic cleft is intact, then the amphetamine causes neurotransmitter vesicle release, thus releasing norepinephrine into the synaptic cleft and resulting in robust mydriasis of the affected pupil.