Differential Diagnosis for Bilateral Pinpoint Pupils
Single Most Likely Diagnosis
- Opioid intoxication: This is the most common cause of bilateral pinpoint pupils due to the opioid's effect on the parasympathetic nervous system, leading to pupillary constriction.
Other Likely Diagnoses
- Pontine stroke: A stroke affecting the pons in the brainstem can cause damage to the pupillary constriction pathways, resulting in pinpoint pupils.
- Neurosyphilis: This condition can affect the brainstem and lead to pupillary abnormalities, including pinpoint pupils.
- Argyll Robertson pupils: A condition characterized by bilateral small pupils that constrict when focusing on a near object but do not react to light, often associated with neurosyphilis.
Do Not Miss Diagnoses
- Subarachnoid hemorrhage: Although less common, a subarachnoid hemorrhage can cause pinpoint pupils due to increased intracranial pressure and brainstem compression.
- Pituitary apoplexy: A medical emergency where the pituitary gland suddenly hemorrhages, potentially compressing the brainstem and causing pupillary abnormalities.
- Medullary thyroid carcinoma: In rare cases, this type of cancer can produce substances that mimic opioid effects, leading to pinpoint pupils.
Rare Diagnoses
- Familial amyloid polyneuropathy: A rare genetic disorder that can affect the autonomic nervous system, leading to pupillary abnormalities.
- Holmes-Adie syndrome: A rare neurological disorder characterized by a tonic pupil (a pupil that reacts slowly to light) on one side, but in some cases, it can present bilaterally with small pupils.
- Diphtheria: A bacterial infection that can cause neurotoxic effects, including pupillary abnormalities, although this is extremely rare in areas with widespread vaccination.