Unveiling The Mask Of Horner’s Syndrome

Unveiling The Mask Of Horner’s Syndrome

July 10, 2021

Horner syndrome is a relatively rare disorder characterized by a constricted pupil (miosis), drooping of the upper eyelid (ptosis), absence of sweating of the face (anhidrosis), and sinking of the eyeball into the bony cavity that protects the eye (enophthalmos).

These are the four classic signs of the disorder. The congenital, and more rare, form of Horner syndrome is present at birth but the cause is not known.

Most often, Horner syndrome is acquired as a result of some kind of interference with the sympathetic nerves serving the eyes.

The underlying causes can vary enormously, from a snake or insect bite to a neck trauma made by a blunt instrument.

There are many potential causes of Horner’s syndrome. It can be caused by any interruption in function of the sympathetic nerve fibers, which start in the hypothalamus and run via the upper spinal cord, near the carotid artery, to the face.

Nerve function may be impaired due to factors such as injury, compression, or a disease process.

Horner’s syndrome is characterised by ipsilateral ptosis, miosis and anhidrosis that result from a lesion affecting the oculosympathetic pathway.

The syndrome can be benign if idiopathic or iatrogenic, however, it can also be predictive of a life-threatening event such as demyelinating inflammatory, infectious, vascular or neoplastic problems.

It is important to promptly and accurately diagnose the cause; ophthalmologists are likely to be on the front lines.

According to Dr Aaron M. Fairbanks, a senior ophthalmology resident at Mayo Clinic, Rochester, Minnesota, United States, no definitive information is available about the pathologies associated with Horner’s syndrome and the incidence rate in US adults is unknown.

Because no US population-based studies of the syndrome had been undertaken, Dr Fairbanks and his colleagues set out to determine its population-based incidence in adults, evaluate the underlying causes and disease manifestations, and investigate the value of imaging in patients with a neurologically isolated Horner’s syndrome.

Retrospective Review

The investigators conducted a retrospective chart review of all adults diagnosed with Horner’s syndrome in Olmsted County, Minnesota, using the Rochester Epidemiology Project database, between 1 January 2000 and 31 December 2018.

According to Dr Fairbanks, the team of investigators reviewed the charts for the correct diagnoses, and recorded the patient demographic data, presenting signs and symptoms, imaging results and aetiologies, and analysed all the results.

Of the 736 patients identified in the review of cases, 78 confirmed cases were included in the study; the rest were excluded because of their non-resident status, disease onset outside the study time frame, or miscoded or incorrect diagnoses.

According to the team of investigators, the causes varied widely from those that were benign, including idiopathic and surgical causes, cluster headache and goitre, to neurologically or systemically dangerous causes including carotid artery dissection; stroke; neoplastic and traumatic causes; varicella zoster; arteriovenous fistula; and fibromuscular dysplasia.


The median patient age was 57 years and all patients were white. The age- and sex-adjusted incidence of Horner’s syndrome during the study period was 4.24/100,000/year with no difference in sex or over time.

“We did find a significant [P < 0.001] difference across age groups, with older patients having a higher incidence of Horner’s syndrome,” Dr Fairbanks pointed out.

Three-quarters of cases were diagnosed by neurologists and ophthalmologists, with most diagnosed clinically. “Interestingly,” Dr Fairbanks said, “idiopathic cases were more likely to be confirmed with cocaine or apraclonidine eyedrop testing (P = 0.002), and stroke, surgical and dangerous causes were more often diagnosed clinically (P = 0.008).”

The most common aetiologies were idiopathic (20 patients, 25.6%), followed by internal carotidartery (ICA) dissection (15 patients, 19.2%), stroke (12 patients, 15.4%), surgical (12 patients, 15.4%) and neoplastic (11.5%). Analysis of the aetiologies indicated that about 56% of cases had a dangerous neurological or systemic origin, according to investigators.

Compared with other aetiologies, the patients with ICA dissections—which were more likely to be diagnosed in younger individuals with a mean age of 49 years (P = 0.02)—were more likely to have pain (P < 0.001), facial paraesthesia (P = 0.007), blurred vision (P = 0.04) and photophobia (P < 0.004). Most of the cases with a stroke had a lateral medullary infarction.

Neoplastic causes

Neoplastic causes included four Pancoast tumours that affected the oculosympathetic pathway at the lung apex. It was noted that the most common neoplasm was lung cancer.

Moreover, as Dr Fairbanks explained, the investigators found that neuroimaging results were surprising in that almost 40% of patients with a neurologically isolated Horner’s syndrome had a positive finding on computed tomography (CT) or magnetic resonance imaging (MRI).

Dr Fairbanks went on to note that in isolated Horner’s syndrome cases, pain suggested both a dangerous aetiology and a positive imaging result, which was driven primarily by patients found to have an ICA dissection.

In this first US population-based study of the incidence of Horner’s syndrome, the primary take-home point is that 56.4% of cases resulted from a dangerous cause; in previous reports the percentages ranged from 8% to 78%.

Another finding useful in diagnosis is that about 40% of patients with an isolated Horner’s syndrome had positive CT or MRI findings, which is almost double the percentage reported previously.

Finally, investigators noted that pain reported by patients suggested a dangerous aetiology and positive imaging, which in this study was most likely to be secondary to an ICA dissection.

Ophthalmologists should keep in mind that ICA dissections are likely to occur in younger patients, may look like an isolated syndrome or present with neurological disease and stroke, are painful, and may cause facial paraesthesia, blurred vision or photophobia, compared with other causes.

“We recommend imaging of the oculosympathetic pathway in all cases of Horner’s syndrome without a clear aetiology, even in neurologically isolated cases, particularly when pain is present,” Dr Fairbanks emphasised.