The Drooping Eyelid No One Could Explain

Call 911 straight away for a droop that appears suddenly, or a droop that comes with facial weakness, slurred speech, loss of balance, or sudden vision loss. Those are stroke signs, and treatment is time-critical.

Also go to an emergency department immediately, not tomorrow, for a droop with double vision, a larger pupil on that side, a severe headache, or new neck or facial pain. Those patterns can mean an aneurysm pressing on the third cranial nerve, or a torn carotid artery. Both carry a stroke risk within hours.

A gradual droop with an unchanged pupil and no other symptoms can be reviewed at a routine appointment. A new droop with a smaller pupil on the same side should be assessed within days. It is fair to ask one specific question: does the imaging plan include the top of my lungs?

Most ptosis, the medical term for a drooping eyelid, is mechanical and benign. The most common cause by far is age-related stretching of the tendon that lifts the eyelid. It comes on slowly over years, often affects both eyes to different degrees, causes no pain, and leaves the pupils completely normal. Long-term contact lens wear, previous eye surgery, eyelid swelling from a stye or chalazion, and a lifelong droop present since birth account for most of the rest.

What makes a drooping eyelid worth a careful look is not the eyelid. It is the pupil underneath it, and what else is happening on the same side of the body.

Clinicians sort a new droop largely by pupil size.

• Droop with a larger pupil on the same side, often with double vision, a painful eye, or severe headache, suggests a third cranial nerve palsy. This can indicate an aneurysm and is treated as an emergency.
• Droop that comes and goes, worse late in the day or after using the eyes, with double vision and normal pupils, suggests myasthenia gravis, a neuromuscular condition.
• Droop with a smaller pupil on the same side suggests Horner syndrome. The classic triad is a mildly drooping lid, a constricted pupil, and reduced sweating on that side of the face.

For Horner syndrome, the difference between the pupils is more obvious in a dim room than a bright one. The affected pupil is slow to widen when the lights go down. Horner syndrome itself is not a disease. It is a sign that something has interrupted a nerve pathway running from the brain, down into the chest, up the neck alongside the carotid artery, and into the eye.

That pathway dips into the top of the chest, so a tumor at the apex of the lung can compress it. These are called Pancoast or superior sulcus tumors. They make up roughly 3% to 5% of lung cancers and behave unlike other lung cancers. Cough and coughing blood are often absent. The first symptom is usually pain in the shoulder, present in up to 96% of cases.

The full pattern to recognize is a quiet, slowly developing droop with a small pupil, along with any of these.

• Shoulder or shoulder-blade pain that no injury explains.
• Pain running down the inner arm.
• Numbness or tingling in the ring and little fingers.
• Weakness or wasting of the small muscles of the hand.
• Hoarseness.
• A smoking history.

Diagnostic delays of up to five to ten months are reported with these tumors, precisely because the parts get assessed separately.

Other causes along the same pathway include carotid artery dissection, which typically causes a painful Horner syndrome with neck or face pain and carries a stroke risk. Strokes, spinal lesions, or neck masses higher up can also cause it.

Assessment begins with photographs or observation of both pupils in bright and dim light. This checks for the dilation lag that suggests Horner syndrome. Pharmacological testing with apraclonidine eye drops can confirm it, though the test can be falsely negative in the acute phase, shortly after onset.

Confirmation is followed by imaging of the whole pathway, not just the head, because the lesion can be anywhere along it. That usually means MRI of the brain, neck, and spinal cord, MR or CT angiography of the carotid arteries, and CT of the chest with attention to the lung apices. A plain chest X-ray is not enough to rule out a tumor at the top of the lung. Overlying bone and soft tissue shadows make that region hard to read. Nerve conduction studies and a chest MRI may be added if hand weakness is present.

• EyeWiki (American Academy of Ophthalmology): Horner Syndrome.
• StatPearls: Pancoast Syndrome.
• NCI: Non-Small Cell Lung Cancer Treatment (PDQ).
• NICE NG12: recommendations organised by site of cancer.