Differential Diagnosis for Gait Instability and Dizziness

The patient presents with symptoms of gait instability, dizziness described as the room spinning, and mild vertical nystagmus, along with an ataxic gait and dysmetria. These symptoms suggest a problem affecting the balance and coordination centers in the brain or the inner ear. Given the acute onset and the specific combination of symptoms, the differential diagnosis can be organized as follows:

• Single Most Likely Diagnosis

  • Vertebrobasilar artery compromise: The symptoms of vertigo, ataxia, and nystagmus are highly suggestive of a problem in the posterior circulation, which is supplied by the vertebrobasilar arteries. These arteries supply blood to the brainstem, cerebellum, and the inner ear structures, and compromise can lead to the symptoms the patient is experiencing.

• Other Likely Diagnoses

  • Labyrinthine artery compromise: While less common, the labyrinthine artery supplies the inner ear, and its compromise can lead to vertigo and hearing loss. However, the presence of ataxia and nystagmus might suggest a more central cause.
  • Middle cerebral artery (MCA) stroke: Though less likely given the specific symptoms, an MCA stroke can occasionally present with ataxia if the stroke involves areas that project to the cerebellum. However, the primary symptoms of an MCA stroke usually include hemiparesis, aphasia, or neglect, which are not present in this case.

• Do Not Miss Diagnoses

  • Posterior Inferior Cerebellar Artery (PICA) stroke: A stroke in the PICA distribution can cause similar symptoms, including vertigo, ataxia, and nystagmus. It's a less common cause but critical to diagnose due to its implications for stroke treatment.
  • Basilar artery occlusion: This is a medical emergency that can present with a variety of symptoms including vertigo, ataxia, and cranial nerve deficits. Early recognition is crucial for timely intervention.

• Rare Diagnoses

  • Anterior cerebral artery (ACA) stroke: ACA strokes typically present with lower limb weakness, urinary incontinence, and sometimes cognitive changes, making it an unlikely cause for this patient's symptoms.
  • Carotid artery disease: While carotid disease can lead to stroke, the symptoms described are not typical for carotid artery compromise, which more commonly causes anterior circulation strokes affecting the MCA territory.
  • Other rare vascular causes: Such as vasculitis or moyamoya disease, which could potentially cause similar symptoms but are much less common and would typically be considered after more common causes have been ruled out.