Conference Coverage

What Are the Top Missed Imaging Diagnoses in Epilepsy?

Focal cortical dysplasia, bilateral hippocampal sclerosis, and temporal encephalocele are subtle lesions that can be easy to overlook.


 

WASHINGTON, DC—Neuroimaging is a core competency for epileptologists, according to an overview presented at the 71st Annual Meeting of the American Epilepsy Society. Neurologists trained in this subspecialty must bring “value-added” skills to the routine reports that radiologists provide—ensuring that both a proper diagnostic protocol and a quality-assurance mindset are in place so that when images are used, they are of sufficient quality to exclude wrong diagnoses.

Ultimately, it is the role of the epileptologist to review these images in the context of other localizing data and to work with radiologists in an integrative way, said Graeme Jackson, MD, Senior Deputy Director of the Florey Institute of Neuroscience and Mental Health in Melbourne.

Graeme Jackson, MD

“Finding a focal abnormality can truly change the path that patients move forward on, and it can change whether we have implantations, whether we have regional resections or focal resections…. It is critically important for good imaging to be a part of the path these patients travel on,” he said. Hippocampal sclerosis and bottom-of-sulcus dysplasia (BOSD) are entities that epileptologists “can’t miss,” he added.

What Is the Protocol?

In a presentation comprised largely of imaging studies in cases across the lifespan—infant, young child, teenager, adult, and senior citizen—Dr. Jackson discussed the diagnostic information essential for all patients with epilepsy: a clinical history for context, an EEG for function, and structural MRI with an epilepsy protocol for structure.

To map out the proper protocol, clinicians have to contend with many choices for MRI studies. Eventually, the process results in images. One pathway leads to a report from the radiologist, and another pathway leads to the epileptologist’s review.

Epileptologists are responsible for obtaining images that are adequate—not just taking what they get, said Dr. Jackson. “The radiologist is sitting there—[with] probably 2,000 images … a couple of minutes and a lot of cases.” As the “epileptologist, you have the advantage of having other information. You have the focus [and] the hypotheses.… It is critical that they be reviewed and iterated, particularly in difficult cases.”

Four “Can’t Miss” Imaging Diagnoses

The top four missed imaging diagnoses in epilepsy are obvious abnormalities, hippocampal sclerosis, malformations of cortical development, and a diagnosis of nothing, in which the clinician must be confident because the implicit observation is that the brain is completely structurally normal. Clinicians sometimes miss subtle things that can only be identified by looking correctly in the proper location, said Dr. Jackson.

In contrast to the four “can’t miss” diagnoses, focal cortical dysplasia, bilateral hippocampal sclerosis, temporal encephalocele, and parahippocampal dysplasia are among the many subtle lesions that clinicians can easily miss.

Examining a Case Study

Dr. Jackson assessed the case of Rachel, age 17, who has BOSD. This form of dysplasia encompasses localized seizures and can present at any time from infancy to adulthood. Although these entities are often intractable, 90% of patients who undergo resection of the cortical BOSD remain seizure-free.

Rachel had her first seizure at age 15. It lasted a few seconds and caused her to drop her ice cream. Her facial appearance was blank and she was pointing her right index finger, said Dr. Jackson. Her condition evolved into intractable tonic-clonic seizures at night, resulting in multiple medication use and side effects. After imaging revealed that Rachel—a left-dominant-language individual with aspirations to be a teacher—had a tiny abnormality at the base of the sulci, she underwent surgery.

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