A 67-year-old man presents with a recurrent episode of syncope. He states that this has happened to him multiple times, particularly when he changes body position from sitting to standing, exerts himself, or turns his head quickly. He says that he notes numbness, vertigo, and sometimes even trouble with speaking immediately prior to fainting. The episodes usually last 1-5 minutes. When he wakes up, he is mildly confused but typically returns to baseline within a minute. The patient has a past medical history of diabetes, dyslipidemia, and hypertension. His temperature is 98.5°F (36.9°C), blood pressure is 153/89 mmHg, pulse is 90/min, respirations are 11/min, and oxygen saturation is 97% on room air. The patient's neurological exam is unremarkable. However, when he is asked to stand up and start walking, he experiences the same numbness and tingling and feels like he may faint. Which of the following is the most likely diagnosis?
Vagal event
Seizure
Blood vessel narrowing
Stroke
Blood vessel narrowing
This elderly patient with risk factors for vascular disease (diabetes, dyslipidemia, hypertension) is presenting with episodes of dizziness, vertigo, numbness/tingling, dysarthria, and syncope, which seem to be provoked by standing rapidly and changing head position. This is concerning for vertebrobasilar syndrome, caused by blood vessel narrowing.

Vertebrobasilar syndrome is caused by narrowing (via causes such as atherosclerosis, dissection, or congenital narrowing among others) of the vertebrobasilar vascular system. It is a common cause of syncope that may be worsened by changes in head position or standing rapidly. Other unique features include numbness/tingling, a sensation of vertigo, nausea, vomiting, dysphagia, and dysarthria. Note the episodes of syncope in this condition are intermittent and specifically provoked and do not have lasting/permanent neurological deficits in contrast to a stroke. Management is first centered on vascular imaging which may include a CTA head/neck or an MRA head/neck. Further care depends on the symptoms present but typically involves smoking cessation, glycemic control, blood pressure control, aspirin, and a statin.

Xuan-Ting et al. review posterior circulation strokes which occur more frequently in patients with atherosclerosis of the vertebrobasilar system. They note that MRI is one of the most accurate tests for assessing posterior circulation strokes which may present with dizziness and syncope. It is far superior to CT imaging. For this reason, they recommend that CT imaging alone cannot definitively rule out a posterior circulation stroke.

Incorrect Answers:
Answer B: Cardiac dysrhythmias such as ventricular tachycardia can cause sudden onset and offset syncope without prodromal symptoms. The differentiating feature of this form of syncope is the rapid onset and offset in a high-risk patient. The diagnosis can be confirmed with an ECG; however, many patients will require prolonged observation on telemetry.

Answer C: Seizure presents with impaired consciousness, tonic-clonic activity, and a post-ictal state which gradually improves over hours. The lactate may be elevated after a seizure, and the prolactin level is a more specific indicator of a seizure. However, the diagnosis is most appropriately made based on history, exam, and EEG.

Answer D: Stroke involving the vertebrobasilar system may cause syncope in addition to ongoing dizziness and vertigo with ataxia. However, this patient's symptoms seem to be positional and have entirely resolved; thus, a stroke is unlikely. He is at higher risk of stroke given his vertebrobasilar insufficiency and an MRI should still be performed in this patient.

Answer E: Vagal event presents with a warm prodrome with palpitations, flushing, and syncope. Muscle twitching (but no tonic-clonic activity) may be seen. Patients may wake up slightly confused but return to baseline within seconds.

Bullet Summary:
Vertebrobasilar insufficiency may present with positional episodes of syncope caused by insufficient blood flow through the vertebrobasilar blood vessels.