What type of MRI with or without contrast is recommended for evaluating headache, metallic smell, and nausea?

MRI for Headache with Metallic Smell and Nausea

For a patient presenting with headache, metallic smell, and nausea, an MRI of the head without IV contrast is the most appropriate initial imaging study.

Rationale for MRI Selection

Type of MRI

• MRI without contrast is the preferred initial neuroimaging choice for evaluating headache with associated symptoms like metallic smell and nausea 1, 2.
• Non-contrast MRI provides excellent visualization of brain parenchyma and can detect most significant intracranial pathologies without exposing the patient to the risks of gadolinium-based contrast agents 2.

When to Consider Contrast

• MRI with and without contrast should be added only if there is specific suspicion for:
  • Intracranial infection
  • Tumor or mass lesion
  • Inflammatory conditions
  • Vascular pathologies 1

Advantages of Non-Contrast MRI

• High sensitivity for detecting ischemia, small infarcts, and subtle cases of subarachnoid hemorrhage 1
• Excellent for evaluating brain parenchyma without radiation exposure 1
• Specialized sequences like FLAIR, diffusion-weighted imaging, and susceptibility-weighted imaging can detect various pathologies without contrast 2

Clinical Considerations for This Presentation

Significance of Symptoms

• The combination of headache with metallic smell (potential olfactory hallucination) and nausea raises concern for:
  • Possible temporal lobe pathology
  • Seizure-related phenomena
  • Migraine with aura

Imaging Protocol Recommendations

• Include these key sequences in the non-contrast MRI:
  • T1-weighted imaging
  • T2-weighted imaging
  • FLAIR (fluid-attenuated inversion recovery)
  • DWI (diffusion-weighted imaging)
  • SWI/GRE (susceptibility-weighted imaging/gradient-recalled echo) for hemorrhage detection 1, 2

When to Consider Adding Contrast

Add contrast only if the initial non-contrast MRI shows:

• Abnormal findings requiring further characterization
• Focal lesion requiring enhancement pattern assessment
• Suspected intracranial infection or inflammatory process 1

Cautions and Considerations

Contrast-Related Risks

• Gadolinium-based contrast agents carry risks including:
  • Nephrogenic systemic fibrosis in patients with renal impairment
  • Potential gadolinium deposition in brain tissue with repeated exposures 2, 3

Diagnostic Yield

• The diagnostic yield of neuroimaging in chronic headache without red flags or neurological deficits is relatively low (0.9-2.1%) 4, 5
• However, the presence of unusual symptoms like metallic smell warrants imaging to rule out secondary causes 1

Conclusion

Non-contrast MRI is the most appropriate initial imaging study for evaluating headache with metallic smell and nausea, providing excellent sensitivity for detecting significant intracranial pathologies while avoiding unnecessary contrast administration. Additional contrast-enhanced imaging should be performed only if the initial non-contrast study reveals abnormalities requiring further characterization.