Pathology of the Week – Horner’s Syndrome

Horner’s Syndrome: Medicalese: named after Swiss ophthalmologist Johann Friedrich Horner in 1869.

This disorder is an interesting one to study as it involves some of the more complex cranial and autonomic nervous pathways. Horner’s syndrome is a grouping of four autonomic symptoms that arise from a loss of autonomic sympathetic nervous system input. These four symptoms are ocular ptosis, ocular miosis, facial anhydrosis and facial hyperaemia. All just big scary medicalese terms which I will detail below. I will reference the Merck Manual’s quick review, Jeff Mann MD’s guide, as well as an excellent neuroimaging article Lee et al, 2007 (article is free access).

Courtesy of OD Palace

Signs and Symptoms

Many features of the human face are actively initiated and maintained by the sympathetic branch of the autonomic nervous system. The four symptoms of Horner’s syndrome represent a loss of sympathetic input. Note that Horner’s syndrome generally presents on one side, or ipsilaterally. This patient is exhibiting both ocular ptosis and, to some degree, ocular miosis. Ocular ptosis is a drooping of the eyelid caused by a loss of sympathetic innervation. One interesting point is that a specific droop of 2mm (as seen above) is common. This is because the first 2mm of motion is a result of Müller’s muscle (the superior tarsal muscle). Ocular miosis is an unequal constriction of the pupil. The size of the pupil is a result of competing sympathetic and parasympathetic nervous system inputs. If the pupil loses its sympathetic input the parasympathetic input is uncontested and the pupil becomes constricted. Facial anhidrosis is medicalese for the inability to sweat. Hyperaemia is flushed skin on the affected side.

Courtesy: Ryo Sakai


The causes of Horner’s syndrome can best be considered within three categories based on their anatomical location along the autonomic nervous system pathway: central, pre-ganglionic and post-ganglionic. Recall most of these autonomic nervous pathways are duplicated, one on each side of the body.

Central causes are the most rare of of the three and, anatomically, represent a tract from the brainstem to the C7/T1 level of the spinal cord. These areas are subject to all the usual brain/spinal cord pathologies such as ischaemia/infarctions, tumors, herniation, demyelination and trauma. As you can imagine this patient would most likely also present with other nervous system symptoms.

Pre-ganglionic causes arrise from the nerve that runs from the spinal column to the superior cervical ganglion (SVG). These so called second-order nerves depart the spinal column at T1, arch around the apex of the lung and synapse with the SVG located near the carotid artery. Pre-ganglionic Horner’s syndrome is most often caused by trauma or tumors. Interestingly an often cause of pre-ganglionic Horner’s secondary to trauma is iatrogenic – a fancy way of saying the person was injured during a medical procedure.

Post-ganglionic causes are located on the third-order nerves that depart from the SVG and synapse at various areas of the face and eyes. Pathologies in this area that can cause Horner’s are again tumors and trauma, also carotid artery dissection, aneurisms and inflammation.

Management and Treatment

Horner’s syndrome is a cluster of symptoms. Treatment involves localizing the original disorder in secondary Horner’s and treating. Primary Horner’s syndrome has no current treatment.

Implications for Prehospital Care

The four Horner’s syndrome symptoms may present during an initial patient assessment. As afore mentioned these may accompany a, potentially acute, life threatening disorder. A better understanding of the mechanisms behind neurological features such as ipsilateral ocular ptosis/ miosis can also aide in other acute diagnoses.

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