Introduction: Vertebrobasilar insufficiency (VBI) is difficult to diagnose because its symptoms are varied and nonspecific. Brain CT and MRI may be normal until parenchymal damage develops and treatment may be delayed.

Clinical history: An 82 year-old gentleman presented with several years’ history of increasing exertional dizziness and imbalance, on occasion associated with syncope. Brain CT and MRI with angiography demonstrated moderate microvascular changes in the posterior circulation territory without significant vascular pathology in the brainstem.

Method: Rest and stress cerebral perfusion imaging using Technetium 99m-labelled HMPAO was performed with SPECT acquisition on a triple-head gamma-camera with fan-beam collimators. In the stress study, 1gm of IV acetazolamide was administered 20 minutes before tracer injection. Analysis was performed by mapping the cerebral perfusion scan to a standard brain atlas and comparing this to an age-matched normal database, using the Neurostat program.

Results: The resting HMPAO study demonstrated mild perfusion defects in the left temporo-occipital cortex which were more extensive and severe on the stress HMPAO study. In addition, there were stress-induced perfusion defects in the mid-brain. The findings were consistent with reduced cerebral perfusion reserve in the posterior cerebral circulation.

Conclusion: The perfusion scan confirmed VBI as the cause of the patient’s symptoms and allowed targeted treatment. The literature suggests that cerebral perfusion SPECT detects cerebral ischaemia earlier than anatomic imaging such as MRI. However there is little data concerning its use in diagnosing VBI. Our case report highlights the value of cerebral perfusion SPECT as a sensitive diagnostic modality for VBI.