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Tuberous Sclerosis Complex: Seizure localization by SISCOM

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This is a CT scan of the head in

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a 16-year-old boy with seizures.

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And we can see some calcified nodules along

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the lateral margin of the lateral ventricles.

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A tiny speck here on the superolateral margin

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of the right lateral ventricle,

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and a slightly larger but still overall small

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lesion on the lateral margin of the posterior

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body of the left lateral ventricle.

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We see another tiny area of mineralization

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adjacent to the right caudothalamic groove,

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which is the lateral margin of the anterior

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body of the right lateral ventricle,

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adjacent to the level of the foramen of Monroe.

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MRI confirms a diagnosis of tuberous sclerosis complex.

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You can see areas of dysplasia

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in both cerebral hemispheres.

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We can see here in the left,

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approximately the junction of the left

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parietal and occipital lobes.

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You can see the left frontal lobe.

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You can see the left temporal lobe.

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Here's the lesion in the left temporal lobe.

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It's in the left inferior temporal gyrus.

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Overall,

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there's a relatively mild tuber burden,

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but this patient still had profound seizures

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that were debilitating.

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Historically, it was said that tuberous sclerosis complex was

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not a great candidate for epilepsy surgery.

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Because you had multiple lesions,

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you don't know which one to resect,

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and you can't resect them all.

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Well,

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that's where modern imaging and multimodality

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evaluation can really help.

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Working with the epileptologists,

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these two images are from what's called Ciscom

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subtraction SISCOM interictal SPECT imaging,

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co-registered with MRI. What does that mean?

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It means we give a nuclear medicine,

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radio tracer that localizes to areas

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of blood flow and metabolism.

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It is an agent that can cross the blood

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brain barrier, and you give it once.

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When a patient is interictal,

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they haven't seized in a while.

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And what generally happens is areas where

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seizures originate between seizures have

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slightly lower metabolism and slightly lower

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blood flow than the rest of the brain.

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Then what you try and do is you monitor

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the patient with continuous EEG,

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and you have a nuclear medicine technologist

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sitting at the bedside,

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ready to inject the tracer.

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When the patient seizes,

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they inject the medicine right away.

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During a seizure,

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the area of seizure onset is highly

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metabolically active.

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Because it's highly metabolically active,

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it has a lot of blood flow.

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The radio tracer then localizes to this area,

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more so than areas of the brain.

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Well, we now have it where, during a seizure,

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ICTYL injection is slightly more blood

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flow than the rest of the brain,

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and the interictal has less blood flow.

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Most of the rest of the brain should have

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approximately similar blood flow in

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the ICTYL and interictal states.

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So with complex mathematics

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and computer formulas,

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it's possible to co-register the ictal and

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interictal images and subtract them.

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And you preferentially identify areas

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where the seizures are coming from.

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And this gives us a hint that possibly the

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left temporal pole is an area where seizures

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might be coming from if we remember this

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patient had an area of dysplasia

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in the left temporal lobe,

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and we know that the seizures likely are

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coming from there because this also

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matches what the EEG says.

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So now,

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even though the patient has other

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areas of cortical dysplasia,

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we now have reasons to think that the left

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temporal lobe is going to be the predominant

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cause of the seizures.

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So this patient underwent a

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left temporal lobectomy.

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The left temporal lobectomy allowed the left

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temporal pole to be resected with, hopefully,

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the site of seizure onset.

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You can see here that

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as we go inferiorly,

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their resection went more further posteriorly.

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Why is that helpful? Well,

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we thought the temporal pole was where

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the seizures were coming from,

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and that was confirmed on intraoperative

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electrocorticography.

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But we felt that it was possible,

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while we were there,

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to get this area of dysplasia in that region,

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which possibly was either the cause of the

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seizures or there was a seizure

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circuit where it was involved,

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and therefore both were able to be resected.

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Well, why not just take off everything?

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Well,

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the goal of this was to preserve as

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much brain parenchyma as possible,

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because we don't know if the patient,

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years down the road,

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may need a second resection somewhere else.

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Additionally,

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this is the left hemisphere in

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a right-handed individual.

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And this bump right here is the transverse

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temporal gyrus, or Heschel's gyrus.

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This is the region where,

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in the left hemisphere,

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you typically have receptive language.

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And this patient,

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functional MRI confirmed a left hemispheric

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language lateralization.

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So by performing the resection

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at an angle like this,

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they were able to avoid the language cortices.

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So this patient has tuberous sclerosis complex.

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And while there are several areas

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of cortical dysplasia,

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EEG confirmed with Ciscom ICTYL

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interictal subtraction.

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SPECT co-registered with MRI confirmed that

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the left temporal was likely the culprit

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with a multimodality workout.

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Up in collaboration with the epileptologist.

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It allowed a resection that

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removed both the presumed site of seizure onset

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and the adjacent

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area of dysplasia,

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which was likely either the

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source or involved.

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And the patient had improved seizure control.

Report

Description

Faculty

Asim F Choudhri, MD

Chief, Pediatric Neuroradiology

Le Bonheur Children's Hospital

Tags

Syndromes

Pediatrics

Neuroradiology

Neuro

MRI

CT

Brain

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