Case 23 Drug Resistant epilepsy (mesial temporal abnormality)

Figure 23-1: MRI brain of the patient axial FLAIR, Coronal T2, Axial T2 and Coronal FLAIR.

Clinical presentation

• Female patient, 12 years old, complains of recurrent attacks of complex partial seizures that started at the age of 2.
• The attacks start with an aura, including sensations of fear and vertigo, followed by staring with no response to conversation. The condition is associated with automatisms such as involuntary purposeless acts like lip-smacking and eye blinking.
• There is no neurological deficit.
• The patient is on Tiratam, Tegretol, Lamictal, and Conviban.
• Ictal EEG shows right frontal spikes that spread to the right hemisphere and then become diffuse.

• Q1: What is meant by drug-resistant epilepsy (DRE)? Is a 2-year period mandatory before considering extra-medical intervention?
• Failure of an adequate trial of two tolerated, appropriately chosen, and correctly used anti-epileptic drug (AED) schedules to achieve seizure freedom, typically for 2 years, but there is no lower limit for surgically suitable candidates. This means that when resistance to AEDs occurs in the presence of surgical lesions that coincide with seizures, there is no reason to wait for two years in the case of DRE.

• Q2: Could DRE be suspected early in the disease?

It can be suspected if the following occur:

• Low efficacy with the appropriately chosen first drug.
• Ineffective outcome with two appropriate and adequate drugs; a third drug will benefit less than 5%.
• When two drugs fail to adequately control epilepsy, an investigation of refractory epilepsy should be initiated. We are losing neurons; time is neurons.

• Q3: What are the findings in the MRI?
• Marked asymmetry of the hippocampal heads with an atrophic right side. Additionally, the right hippocampus demonstrates a high signal on FLAIR. There is also an abnormality in the cortex and white matter architecture in the right temporal lobe compared to the left side, particularly in the anterior part of the temporal lobe.

Figure 1-2: Coronal demonstration of the temporal lobe and surrounding structures.

Figure 1-3: Axial demonstration of the mesial temporal lobe and surrounding structures.

• Q4: How can you explain the right frontal spike despite the lesion’s location appearing in the MRI?
• When the origin of the focus is in the mesial temporal lobe, it can pass to the frontal lobe through the uncinate fasciculus. This can be detected in the surface EEG, appearing as if it arises from the frontal lobe, which is not the case. This can be more specifically detected by using a subdural grid or stereotactic EEG. Additionally, interictal hypometabolism can be detected using a PET scan.

• Q5: How is a decision made regarding epilepsy surgery in cases of DRE?

This is a simple way to think:

• Is there a focus?

Yes

• Can it be removed safely?

                Yes: Lesionectomy

                 No: Multiple Subpial Transection (MST)

No: Generalized

• If one hemisphere: Hemispherotomy
• If bilateral

                Corpus Callosotomy

                 Vagal Nerve Stimulation (VNS)

Figure 23-2: How to make a decision in DRE.