Discuss the advantages and disadvantages of different brain imaging techniques in the investigation of epilepsy
Epilepsy is a neurological disorder which is characterised by epileptic seizures. Seizures occur when there is an abnormal excess of synchronous neuronal activity in the brain (Fisher R S et al., 2005). Seizures are recurrent occurrences that can occur for a brief period of time often being undetectable or lasting for long periods characterised by vigorous shaking (WHO., 2012). The incidence of epilepsy is 50 per 100 000, with an estimated prevalence of 5-10 cases per 1000 in the UK (Nunes V D et al., 2012). Epilepsy occurs due to a number of factors such as trauma, vascular disorders, tumours, infections, metabolic dysfunction and genetic predisposition (Conn P M., 2003). Other factors that may play a role in the onset of epilepsy are genetic and environmental factors. As there are up to 25 gene mutations linked to epilepsy hypothesising that it may be due the change in protein ion channel subunits, proteins involved in synaptic transmissions and synaptic receptors (Conn P M., 2003). One other cause may be altered cortical development (Conn P M., 2003).
Classification of seizures are classified as partial and generalised based upon their clinical and electrographic data (Engel Jr J., 2006). Partial seizures generally affect only one hemisphere of the brain (Daroff R B et al., 2012); the type of seizures can then be divided into simple and complex partial (Nunes V D et al., 2012) lasting for approximately 30 seconds to 2 minutes. Generalised seizures impairs consciousness and disrupts normal function of the whole brain; affecting both cerebral hemispheres. Generalised seizures are divided into absence, myoclonic, atonic, tonic and tonic-clonic (Nunes V D et al., 2012), they can occur for a short period of time or for a longer period of time. Of the epileptic population 66% of people with epilepsy have it controlled with antiepileptic drugs; another way of controlling epilepsy is with surgery (Nunes V D et al., 2012).
The area of epilepsy within the brain can be located using a number of neuroimaging techniques. It may be via MRI, nuclear imaging such as PET and SPECT and Multimodal imaging. Functional MRI is a non-invasive technique which can map the physiological or metabolic consequences of changed electrical activity (Kesavadas C et al., 2008). PET and SPECT are both used ictally in epilepsy where radioisotopes are injected into the person eventually reaching the brain (Howes O D et al., 2009); once it reaches the tissue of interest it is detected via radioactive emissions, producing an image of brain activity. Multimodal imaging is a combination of imaging techniques in which both MRI and EEG are used to measure blood flow to compare with one another.
A systematic review was conducted to explore the advantages and disadvantages of the different imaging techniques used in epilepsy. Databases used were PsychINFO, Medline and Google...