Neuroimaging to Evaluate for Structural Brain Lesions in Central Sleep Apnea
In a patient with five or more central sleep apnea episodes per hour, brain MRI should be performed to evaluate for structural lesions affecting respiratory control centers, particularly in the brainstem and cerebellum.
Diagnostic Rationale
The presence of significant central sleep apnea (CSA) warrants investigation for underlying neurological causes, as structural brain lesions can disrupt respiratory control mechanisms 1, 2.
When to Pursue Neuroimaging
Polysomnography must first confirm the diagnosis of CSA by demonstrating:
- Central apneas without respiratory effort (distinguishing from obstructive events) 1, 2
- Apnea-hypopnea index (AHI) ≥5 events/hour with central events predominating 1
- Absence of rib cage and abdominal movement during apneic episodes 1
Key Clinical Scenarios Requiring Brain Imaging
Neurological disorders are a recognized cause of CSA, and the following presentations should prompt neuroimaging 1:
- History of stroke or transient ischemic attack
- Suspected neurodegenerative disease
- Unexplained CSA without heart failure, medication use, or other clear etiology
- Presence of other neurological symptoms or signs
Specific Imaging Approach
MRI as the Preferred Modality
Brain MRI at 3.0 Tesla with advanced sequences is the optimal imaging test for evaluating CSA-related lesions 3, 4:
- Standard structural MRI sequences to identify gross lesions and white matter changes 3
- Diffusion tensor imaging (DTI) is more sensitive than conventional MRI for detecting subtle microstructural changes in the brainstem that correlate with CSA severity 3
- Focus on specific anatomical regions: brainstem (particularly medulla and pons), middle cingulate gyrus, and bilateral cerebellar posterior lobes 3, 4
Anatomical Targets
Lesions causing CSA localize to a common brain network involving 4:
- Middle cingulate gyrus
- Bilateral cerebellar posterior lobes
- Brainstem respiratory control centers
Microstructural changes in the brainstem show the strongest correlation with CSA severity, even when conventional imaging appears normal 3.
Important Clinical Considerations
Differential Diagnosis Context
Before attributing CSA to structural brain lesions, exclude more common etiologies 1:
- Heart failure (most common cause)
- Atrial fibrillation (shorter cycle length <45 seconds)
- Chronic opioid or sedative use
- Renal failure
- Treatment-emergent CSA from CPAP therapy
Common Pitfall to Avoid
Do not assume all apneas are obstructive - polysomnography with assessment of respiratory effort is mandatory to distinguish central from obstructive events before pursuing neuroimaging 1. In patients with marked respiratory muscle weakness, true obstructive events may be misscored as "central" on external sensors, requiring esophageal pressure monitoring 5.
When Neuroimaging is Lower Yield
Brain imaging may be deferred initially if CSA occurs in the context of 1:
- Known severe heart failure with typical Cheyne-Stokes respiration pattern (cycle length 45-75 seconds)
- Recent initiation or dose increase of opioids or sedatives
- End-stage renal disease on dialysis
In these cases, treat the underlying condition first and reassess CSA persistence before pursuing neuroimaging 1.