From the Guidelines
Horner syndrome is caused by damage to the sympathetic nerve pathway, which can occur due to various factors including stroke, tumors, neck trauma or surgery, carotid artery dissection or aneurysm, and certain medications, as well as less common causes such as multiple sclerosis, syringomyelia, and cluster headaches, as identified in the most recent study 1. The causes of Horner syndrome can be diverse and complex, involving damage to the sympathetic nerve pathway at various points, including the brain stem, spinal cord, or neck.
- Common causes include:
- Stroke, particularly those affecting the brainstem or hypothalamus
- Tumors, such as lung cancer, especially Pancoast tumors at the lung apex
- Neck trauma or surgery
- Carotid artery dissection or aneurysm
- Certain medications
- Less common causes include:
- Multiple sclerosis
- Syringomyelia, a fluid-filled cavity in the spinal cord
- Cluster headaches In some cases, Horner syndrome may be congenital or idiopathic, without an identifiable cause. The interruption of sympathetic nerve signals results in the classic triad of symptoms: ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (reduced sweating) on the affected side of the face, as noted in 1. Identifying the specific cause is crucial for proper treatment, as Horner syndrome itself is not a disease but a manifestation of an underlying condition, as emphasized in 1 and 1. Understanding the path of the sympathetic nerve pathway and its potential points of damage is essential for diagnosis and treatment, as discussed in the most recent study 1.
From the Research
Causes of Horner Syndrome
The causes of Horner syndrome can be attributed to the disruption of the sympathetic innervation to the eye anywhere along its three-neuron circuit 2. Some of the specific causes include:
- Internal carotid dissection 2, 3
- Pancoast tumor 2
- Enlarged thyroid gland 2
- Stellate ganglionectomy 2
- Superior sulcus squamous cell carcinoma 4
- Lower lobe adenocarcinoma 4
- Occlusive carotid disease secondary to atherosclerosis 3
- T1-T2 disk herniation 5
- Arterial dissection, which is the most common pathology causing injury to the carotid artery 3
Anatomical Correlates
The sympathetic pathway to the eye has a long and circuitous course, beginning in the brain and traveling down the spinal cord to exit in the chest, then up the neck and into the orbit 6. This pathway is susceptible to disruption via various anatomical levels, including the hypothalamus, spinal cord, and sympathetic trunk 6, 5.
Disease Processes
Horner syndrome may be a manifestation of a life-threatening condition, and its diagnosis requires familiarity with the oculosympathetic pathway, its anatomical correlates, and the disease processes that may interrupt it 2, 6, 4. Imaging modalities such as PET, CT, and MRI are important components of the work-up for patients presenting with acquired Horner syndrome 4.