Differential Diagnosis for 30 yo Male Patient with Nausea, Dizziness, and Anisocoria (Different Pupil Sizes, Non-Reactive)

• Single Most Likely Diagnosis
  • Third Cranial Nerve (Oculomotor Nerve) Palsy: This condition often presents with anisocoria (pupil size difference), particularly if the pupil is dilated and non-reactive on the affected side. Nausea and dizziness can accompany if there's an associated increase in intracranial pressure or if the palsy is part of a larger neurological issue. The third cranial nerve controls several eye muscles and the constriction of the pupil, making it a prime suspect for these symptoms.
• Other Likely Diagnoses
  • Migraine: Sometimes, migraines can cause neurological symptoms including nausea, dizziness, and visual disturbances. While less common, some migraines can lead to transient anisocoria.
  • Vestibular Disorders: Conditions affecting the vestibular system, such as labyrinthitis or vestibular neuritis, can cause dizziness and nausea. Though anisocoria is less commonly associated, it could potentially occur in complex cases or those with additional neurological involvement.
• Do Not Miss Diagnoses
  • Subarachnoid Hemorrhage: A life-threatening condition that can present with sudden onset of severe headache, nausea, vomiting, and sometimes anisocoria if the third cranial nerve is compressed by blood. It's crucial to consider this diagnosis due to its high mortality rate if untreated.
  • Brain Tumor or Cyst: Space-occupying lesions in the brain can cause increased intracranial pressure, leading to nausea, dizziness, and potentially anisocoria if they compress or invade cranial nerves.
  • Stroke or Transient Ischemic Attack (TIA): Though less commonly associated with anisocoria, strokes or TIAs in certain brainstem locations could potentially cause these symptoms. Given the high risk of permanent neurological damage or death, these conditions must be ruled out promptly.
• Rare Diagnoses
  • Adie Syndrome: A rare neurological disorder characterized by a tonic pupil (which reacts poorly to light) that can cause anisocoria. It's often accompanied by decreased or absent deep tendon reflexes.
  • Syphilis: In its tertiary stage, syphilis can cause a range of neurological symptoms, including pupillary abnormalities like Argyll Robertson pupils (bilateral small pupils that constrict when focusing on a near object but do not react to light). While rare, it's an important consideration in patients with risk factors for sexually transmitted infections.