Preliminary Diagnosis: Tuberous sclerosis
I. What imaging technique is first-line for this diagnosis
- MRI with contrast
- MR spectroscopy can be performed for accurately diagnosing associated cortical tubers and subependymal nodules
II. Describe the advantages and disadvantages of this technique for diagnosis of tuberous sclerosis.
Advantages
- Often diagnostic in the appropriate clinical setting.
- Useful as a surveillance imaging technique in young children and adolescents in monitoring for development of subependymal giant cell astrocytoma (SEGA)
- Able to localize anatomically and define the extent of disease better than any other imaging modality
- Does not utilize ionizing radiation
Disadvantages
- Expensive
- Time-consuming
- Prone to motion artifact
- Unable to differentiate quiescent tubers from active tubers that are associated with a seizure focus
- MR with contrast can be used only in patients with adequate renal function (i.e., GFR >30)
III. What are the contraindications for the first-line imaging technique?
- Patients with non-MR compatible metallic hardware and certain foreign bodies
IV. What alternative imaging techniques are available?
- Contrast enhanced and non-contrast enhanced CT
- PET/SPECT nuclear medicine imaging
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of tuberous sclerosis.
Contrast enhanced and non-contrast CT
Advantages
- Able to detect enhancing subependymal nodules (SEN) characteristic in tuberous sclerosis
- Can be used to follow enlarging SEN worrisome for developing SEGA
- Can be used to detect calcified SEN and cortical/subcortical tubers to better effect than MRI
- Faster than MRI and less susceptible to motion artifact
Disadvantages
- Lacks anatomic resolution of MRI
- Not as sensitive or specific as MRI in the detection of cranial lesions associated with tuberous sclerosis
- Exposes the patient to ionizing radiation
PET/SPECT nuclear medicine imaging
Advantages
- Able to differentiate active from non-active cortical/subcortical tubers, which in turn helps surgical planning if necessary
- Able to differentiate epileptogenic foci in tuberous sclerosis
- Able to differentiate SEGA from SEN
Disadvantages
- Lacks anatomic resolution compared with both CT and MR
- Easily misses lesions under 1.5 cm in size
- Exposes the patient to ionizing radiation
VI. What are the contraindications for the alternative imaging techniques?
Contrast enhanced and non-contrast CT
- Contraindicated in pregnant patients, especially during the first two trimesters.
- CT with contrast is contraindicated in patients with end-stage renal disease who are not on dialysis.
PET/SPECT nuclear medicine imaging
- Contraindicated in pregnant patients
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