Quantitative MR may provide expert eye in epilepsy imaging
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Current imaging practices suffice for detecting gross HA among patients with epilepsy, but can be inadequate in the detection of subtle HA. Other challenges include a lack of experience with such interpretation in practices that don’t include a radiologist with expertise in epilepsy. Hippocampal volumetry can fill the void, but is difficult to integrate into clinical practice. Thus, automated software may fill the gap.
Nikdokht Farid, MD, from the department of radiology at University of California, San Diego, and colleagues enrolled 37 patients with TLE and 116 healthy control subjects in a study to analyze the ability of volumetric MR analysis software to depict HA and help correctly lateralize seizure focus.
The quantitative MR analysis compared each patient’s regional brain volumes with a normative database, corrected for sex, head size and age. The researchers used the healthy control subjects to reinforce the database, which had been targeted to a population with Alzheimer’s disease.
The clinical images were interpreted by board-certified neuroradiologists to more closely reflect clinical practice. Volumetric MR images were interpreted by academic neuroradiologists with expertise in epilepsy. The quantitative analysis was compared with the MRI estimates.
The software matched or outperformed visual review. Farid and colleagues reported that at least one of the volumetric MR reviewers missed hippocampal asymmetry in three of 34 cases. “In four cases, hippocampal asymmetry was missed on visual inspection but was detected at quantitative MR imaging.” Among the 12 patients who underwent surgical resection, there were no cases in which visual inspection detected histologically confirmed HA that was missed by quantitative MR imaging.
The researchers wrote that MR hippocampal volumetry can aid expert review in four situations:
- Cases of subtle volume loss;
- Cases of bilateral volume loss, resulting in little or no asymmetry;
- When the head is tilted in the MR scanner; and
- When centers lack an expert in epilepsy imaging.
They noted that missed HA may delay referral to epilepsy surgical centers, which could compromise care for some patients who are surgical candidates. In addition, some surgeons are reluctant to treat patients when imaging findings don’t correlate with other data. Thus, the use of quantitative analysis could improve care at both community and tertiary epilepsy centers, according to Farid et al.
Finally, they noted that the format not only improves radiologic interpretation in clinical scenarios but also may derive clinical values for use in clinical trials that require MRI analysis.