Differential Diagnosis for Anisocoria in Neonates

When considering the causes of anisocoria (unequal pupil sizes) in neonates, it's crucial to approach the diagnosis systematically to ensure that no critical conditions are overlooked. The following categories help in organizing the differential diagnoses:

• Single Most Likely Diagnosis

  • Physiological anisocoria: This condition is relatively common and benign, where there is a small, normal variation in pupil size. It is often seen in healthy individuals, including neonates, and does not indicate any underlying pathology.

• Other Likely Diagnoses

  • Congenital ptosis: This condition involves a drooping eyelid from birth, which can give the appearance of anisocoria due to the uneven exposure of the pupils.
  • Congenital Horner's syndrome: A condition that affects the nerves of the face and eye, leading to ptosis, miosis (small pupil), and anhidrosis (lack of sweating) on the affected side of the face.
  • Iris coloboma: A hole in the iris that can affect the pupil's shape and size, leading to anisocoria.

• Do Not Miss Diagnoses

  • Brain tumors or masses: Although rare, any mass effect within the brain can cause compression of the nerves controlling pupil size, leading to anisocoria. Early detection is crucial for treatment and prognosis.
  • Hydrocephalus: Accumulation of cerebrospinal fluid in the brain can lead to increased intracranial pressure, potentially affecting cranial nerves and causing anisocoria.
  • Intracranial hemorrhage: Bleeding within the brain can compress or damage nerves, leading to anisocoria among other symptoms.

• Rare Diagnoses

  • Congenital syphilis: A condition that can cause a variety of ocular abnormalities, including anisocoria, though it is relatively rare in areas with access to prenatal care.
  • Botulism: A rare but serious illness caused by a toxin that can affect the nerves, leading to symptoms including anisocoria.
  • Ocular or orbital trauma: Though less common in neonates, any trauma to the eye or orbit can result in anisocoria due to direct injury to the iris or nerves controlling pupil size.

Each of these diagnoses has a different level of urgency and potential impact on the neonate's health, emphasizing the importance of a thorough evaluation to determine the underlying cause of anisocoria.