Imaging of Epilepsy Ali Jassim Alhashli Year IV – Unit VIII (CNS) – Problem 6

Introduction 1% of population in the world suffer from epilepsy (so it is relatively common). 8% of population in the world will experience at least 1 seizure during their lifetime. Importance of imaging: Importance of imaging: – It is important to find the cause of seizure and remove it if possible so the patient will be treated (without referring to antiepileptics which might be taken for at least 2-3 years!). MRI was first applied (as an imaging procedure for seizures) in 1970’s. it has greater sensitivity than CT-scan. It provides structural, functional and biochemical information. – Note that biochemical information are detected by a technique known as MR-spectroscopy which is measuring the presence and concentration of various metabolic substances in parts of the brain so you can decide if there is an abnormality according to that).

Goals of Imaging Imaging allows us to see if there is structural abnormality. It helps us in defining the location of the lesion and its extent. Identify the relation of the lesion to activity of seizure. Identify important functional areas of the cortex.

Classification of Epilepsy Epilepsy Partial: affecting part of the body and there is a focal abnormal activity in the cortex Simple partial: in which the patient does not lose his consciousness Complex partial: in which the patient loses his consciousness (because electrical activity is reaching the diencephalon) Focal to generalized “tonic- clonic” seizure”: this occurs when abnormal electricity reaches thalamus and spreads from there to the whole brain Generalized: affecting the whole body and the abnormal electrical activity is spreading throughout the cortex

Imaging Modalities CT-scan: CT-scan: – It is useful to identify large lesions. – Suitable in emergency. – Suitable if there is recent onset of seizure. – Used if MRI is contraindicated or unavailable. – It is providing complementary ( مُكَمِّل ) information.

This image is for a child who is presented with seizure. It is showing a high density area which is appearing white in color and it is corresponding to a hemorrhage. Imaging Modalities

This image is showing hemorrhage which occurred due to venous thrombosis of the transverse sinus (indicated by arrows). Imaging Modalities

This image shows astrocytoma in a child Imaging Modalities

MRI: MRI: – It is the imaging modality of choice. – Mutliplanar. – Better soft tissue contrast. – Useful for surgical planning. Who to image (either by using CT-scan or MRI): – All patients with partial (focal) seizure (because there is a higher chance to find a lesion related to partial seizure than to a one which is related to a generalized seizure). – When there is partial seizure with secondary generalization. – When a patient has epilepsy which is not classified (unknown if it is partial/focal or generalized). – Imaging used with poorly controlled seizures. Imaging Modalities

Expected Pathology of Epilepsy MTS (Mesial Temporal Sclerosis): there is a strong relation between partial epilepsy and damage to the hippocampal pyramidal cells in mesial temporal lobe. – Note: a dual pathology is associated with MTS (which means that if you find MTS you will find another pathological lesion with it). Developmental disorders. Neoplasms. Brain injury. Note: these causes will be explained in more details in next slides.

Hippocampus (Anatomy) This is an MRI → the blue arrows indicate the hippocampus, notice that hippocampus is composed of a body and a tail.

Developmental disorders: – Neuronal migration disorders/ hamartoma: in which there is a normal grey matter in an abnormal location (neurons cannot migrate from the ventricles and reach the cortex-this is represented by the first image). The second image shows nodular heterotopia (nodules in ventricles which are representing neurons that don’t reach the cortex). – Vascular malformations: they are mostly arteriovenous malformation (seizures are seen in 70% of persons with this condition). Expected Pathology of Epilepsy

Neoplasms/ brain tumors: an example is ganglioglioma (see the first image). Infections: an example is herpes encephalitis affecting the temporal lobe (see the second image). Expected Pathology of Epilepsy

Infarcts: this happens in patients suffering from sickle cell disease (SCD) in which there will be multiple infarcts in frontal and occipital lobes. Expected Pathology of Epilepsy