Differential Diagnosis for Pinpoint Pupils
Single Most Likely Diagnosis
- Opioid intoxication: This is the most common cause of pinpoint pupils due to the stimulation of opioid receptors in the brain, which leads to pupillary constriction. Opioids, including prescription medications and illicit drugs like heroin, can cause this effect.
Other Likely Diagnoses
- Pontine stroke: A stroke affecting the pons in the brainstem can damage the pupillary constriction centers, leading to pinpoint pupils. This condition is a medical emergency.
- Horner's syndrome: This neurological disorder affects the nerves to the face and eye, causing ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the same side of the face.
- Cholinergic toxicity: Exposure to cholinesterase inhibitors (e.g., organophosphate pesticides or certain medications) can lead to an overactivation of acetylcholine receptors, causing pinpoint pupils among other symptoms.
Do Not Miss Diagnoses
- Subarachnoid hemorrhage: Although less common, a subarachnoid hemorrhage can cause pinpoint pupils due to increased intracranial pressure and brainstem compression. This is a life-threatening condition requiring immediate medical attention.
- Status epilepticus: Prolonged or recurrent seizures can lead to various neurological symptoms, including changes in pupil size. Recognizing and treating status epilepticus is crucial to prevent long-term brain damage.
- Serotonin syndrome: This potentially life-threatening condition, caused by an excess of serotonin in the body, can result from the use of certain medications. Symptoms include altered mental status, neuromuscular abnormalities, and autonomic dysfunction, which may include pupillary changes.
Rare Diagnoses
- Argyll Robertson pupils: A condition characterized by bilateral small pupils that constrict when focusing on a near object but do not react to light. It is often associated with neurosyphilis but can be seen in other conditions affecting the brainstem.
- Diphtheria: This bacterial infection can cause neurological complications, including cranial nerve palsies that might affect pupil size.
- Familial amyloid polyneuropathy: A rare genetic disorder that can lead to autonomic dysfunction, including pupillary abnormalities.