Differential Diagnosis for Near Syncope, Vertigo, and Chiari Malformation

Single Most Likely Diagnosis

• Chiari Malformation Type I: This condition is characterized by the herniation of the cerebellar tonsils into the foramen magnum, which can lead to symptoms such as near syncope, vertigo, and headaches due to the compression of the brainstem and the obstruction of cerebrospinal fluid (CSF) flow.

Other Likely Diagnoses

• Vestibular Migraine: This condition can cause vertigo, headaches, and sensitivity to light and sound, which may also lead to near syncope due to the intense discomfort and potential for triggering vasovagal responses.
• Orthostatic Hypotension: A drop in blood pressure upon standing can cause near syncope and may be exacerbated by dehydration, certain medications, or autonomic nervous system dysfunction, which could be related to or worsened by the Chiari malformation.
• Benign Paroxysmal Positional Vertigo (BPPV): Although typically not associated directly with near syncope, the intense vertigo episodes can potentially lead to falls or near-syncopal episodes due to the sudden onset of severe vertigo.

Do Not Miss Diagnoses

• Brainstem Stroke or Transient Ischemic Attack (TIA): Given the proximity of the Chiari malformation to the brainstem, any compromise of blood flow in this area could lead to severe and potentially life-threatening symptoms, including sudden onset vertigo, near syncope, and neurological deficits.
• Subarachnoid Hemorrhage: Although less directly related to Chiari malformation, a sudden and severe headache (often described as "the worst headache of my life") accompanied by vertigo or near syncope could indicate a subarachnoid hemorrhage, which is a medical emergency.
• Cervical Spine Instability: In the context of a Chiari malformation, instability of the cervical spine could lead to spinal cord compression or injury, presenting with a range of symptoms including vertigo, near syncope, and neurological deficits.

Rare Diagnoses

• Ehlers-Danlos Syndrome: This genetic disorder can lead to tissue fragility and is associated with an increased risk of Chiari malformation, as well as orthostatic intolerance, which could explain near syncope and vertigo.
• Pseudotumor Cerebri (Idiopathic Intracranial Hypertension): Although more commonly associated with headache and visual disturbances, pseudotumor cerebri can occasionally present with vertigo and, in rare cases, near syncope due to increased intracranial pressure.