Differential Diagnosis for Vertigo and Diplopia

Given the symptoms of vertigo and diplopia with normal CT and blood work, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Benign Paroxysmal Positional Vertigo (BPPV): This condition is characterized by brief, intense episodes of vertigo triggered by specific head movements. It is a common cause of vertigo and can sometimes be associated with diplopia due to the vestibular-ocular reflex. Normal CT and blood work do not rule out BPPV, as it is diagnosed clinically and with the Dix-Hallpike maneuver.

• Other Likely Diagnoses

  • Vestibular Migraine: This condition can cause vertigo, and while less common, it can also lead to transient visual symptoms including diplopia. Normal imaging and blood work are consistent with this diagnosis, as it is primarily clinical.
  • Labyrinthitis: An inner ear disorder that can cause vertigo and sometimes visual disturbances. It might not be evident on CT scans, especially if it's an early or mild case.
  • Meniere's Disease: Although it primarily causes vertigo, hearing loss, and tinnitus, in some cases, it might lead to visual disturbances due to the intense vertigo episodes affecting balance and vision.

• Do Not Miss Diagnoses

  • Stroke or Transient Ischemic Attack (TIA): Although less likely with normal CT, it's crucial not to miss a posterior circulation stroke, which can present with vertigo and diplopia. A high index of suspicion is required, especially in patients with risk factors. Further imaging like MRI might be necessary.
  • Multiple Sclerosis: Optic neuritis can cause diplopia, and vertigo can occur due to brainstem or cerebellar involvement. Normal initial blood work and CT do not rule out MS, which requires MRI for diagnosis.
  • Wernicke's Encephalopathy: This is a medical emergency that can present with ophthalmoplegia (leading to diplopia), ataxia, and confusion. It's caused by thiamine deficiency and requires immediate treatment.

• Rare Diagnoses

  • Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain, which can cause vertigo and, less commonly, diplopia due to its effects on nearby cranial nerves.
  • Chiari Malformation: A structural defect in the cerebellum that controls balance, which can cause vertigo and, in some cases, visual disturbances including diplopia due to compression of cranial nerves or the brainstem.