Overview

It is important to get accurate diagnoses of conditions like epilepsy so that they can be treated properly. Luckily, with temporal lobe epilepsy, diagnosis is easy and laid out. By gathering information about seizure experiences and neuroimaging techniques, we can diagnose and locate the issue, which can lead to accurate epilepsy treatment. It is best to see specialists on this matter to prevent misdiagnosis.

Temporal Lobe Epilepsy¹

Temporal lobe epilepsy is a chronic seizure disorder that causes epileptic seizures of all kinds to occur. There are two types of temporal lobe epilepsy:

Mesial Temporal Lobe Epilepsy (MTLE)

Affecting the more central inner structures of the temporal lobe, such as the hippocampus, parahippocampal gyrus, and the amygdala. This is the most common form of the two and is usually caused by hippocampal sclerosis, although it can have other pathologies, such as tumours, infections, injuries, and others.

Hippocampal sclerosis is neuronal loss and changes to the structure and network beyond the hippocampal area. It is the most common cause of drug-resistant epilepsy in adults.

Lateral Temporal Lobe Epilepsy (LTLE) (aka neocortical temporal lobe seizures)

This form is very rare and most likely caused by lesions to the outer temporal lobe or genetic factors affecting lateral areas of the temporal lobe. Often, people with LTLE will have auditory hallucinations before seizures.

Epilepsy is typically the result of overstimulation of the neurons within an area, causing a seizure. This is understood to be a defence mechanism against potential neuronal damage by releasing the neurons of this energy.

Temporal lobe epilepsy is the most common form of seizure disorder worldwide, affecting ~50 million people.

~60% of forms of epilepsy, temporal or not, are focused on one area and about half of those cases are bilateral (one on each side). If epileptic seizures occur for over a year, anti-epileptic drugs are suggested to alleviate the risk of seizures.

Clinical symptoms¹

Presented symptoms of temporal lobe epilepsy involve seizures lasting 1-2 minutes, having recurring seizures and not a single instance. Seizures can manifest as:

1. Focal aware seizures: The person experiencing this seizure is conscious and aware of what is occurring. They will experience feelings, movements and sensations that they cannot control. These sensations can be any one or multiple of the senses. It may also be feelings of déjà vu or a feeling of revelation. Emotions like fear or anxiety may also occur beyond their control. There are a whole host of experiences due to the complexity of the brain²

From someone with temporal epilepsy: “The whole world suddenly seems more real at first. It's as though everything becomes crystal clear. Then I feel as if I'm here but not here, kind of like being in a dream. It's as if I've lived through this exact moment many times before. I hear what people say, but they don't make sense. I know not to talk during the episode, since I just say foolish things. Sometimes I think I'm talking, but later people tell me that I didn't say anything. The whole thing lasts a minute or two” – Temporal Lobe Epilepsy (TLE), Epilepsy Foundation, 2019.³

2. Focal impaired awareness seizures: Aware seizures may sometimes become impaired awareness seizures, meaning a loss of consciousness, meaning they are unaware of what is occurring. During this transition, the person may have a blank, motionless stare, dilated pupils, and perform movements they are unaware of
3. Focal seizures, as above, may extend to involve both of the brain's cerebral hemispheres. This most likely manifests with bilateral tonic-clonic convulsions

In both impaired awareness seizures and tonic-clonic seizures, there may be a ‘postictal period’, which may manifest with confusion, aphasia, and/or amnesia.

Patients, often with hippocampal sclerosis, have cognitive difficulties in association to the location of the seizure network. For example, those within the language areas struggle with remembering language. Mental illness is also higher within these individuals.²

Diagnostic criteria¹

Usually diagnosed within the first two decades of life, epilepsy is easy to diagnose if the findings of medical history, characteristics, EEG and MRI are typical. Prior medical events and history suggest and suspect epileptic diagnosis, but MRIs are the preferred method to be certain of the diagnosis, and an EEG to locate the seizure network.

Magnetic resonance images (MRIs) can image the brain accurately so that trained professionals can analyse the image to detect any abnormalities. Hippocampal sclerosis, one of the common causes of epilepsy, can often be detected through an MRI by assessing the structural change.³

Electroencephalograms (EEGs) detect electrical activity in the brain. Seizure networks have high levels of activity, so the sharp spikes of activity can be detected through the EEG.³

Often, seizures are refractory, suggesting repeated lesions to a particular area of the brain where the seizure network may be present. Additionally, listening to the description of the seizures from the individual themselves can give information about what kind of seizure it is. If they are unaware during their seizures, it's best to get an account from someone reliable and present for them.

Diagnostic techniques

Neuroimaging is the primary technique used in epilepsy diagnosis. Computerised tomography (CT) scans may be used at first to identify an issue, but aren’t sensitive enough when compared to MRIs, the primary method of detection. The most common finding on an MRI is scarring on the temporal lobe – indicative of hippocampal sclerosis – most often presenting in a way that the hippocampus on one or both sides has shrunk.

MRI evaluations are vital to pre-surgical assessment, identifying hippocampal sclerosis and reduction in hippocampal volume. Additionally, it locates the epileptic system and where it will be targeted surgically.

• When the MRI is abnormal, seizures tend not to stop with medication, and surgery is the optimal decision
• fMRIs have also become the norm for detecting post-operative outcomes, such as language-related outcomes

Bilateral hippocampal sclerosis can have difficulties in detection and diagnosis. Volumetric assays are necessary for further details.

Diagnostic accuracy relies on an EEG, which can localise epileptic locations and identify seizure networks. EEGs show a sharp spike or waves at the tip of the frontal lobe if a seizure network is present. When seizures occur more towards the middle of the temporal lobe, this is harder to diagnose.

Most importantly, accurate diagnosis relies on the experience and skill of the diagnostic team. MRI experienced teams can diagnose with better accuracy but also first time round, and get people started on appropriate treatment.

It is recommended that people contact epilepsy specialists or specialist epileptic clinics for an accurate diagnosis.^[3]

Further imaging techniques, such as PET and MRS scans, can also be used in unconfirmed cases. They are especially useful in the surgical analysis of the patient when MRI is proving unsuccessful.

Other diagnosis¹

While epilepsy is easy to diagnose, there are often still instances of misdiagnosis with other conditions.

Other forms of focal onset epilepsy (i.e., absence, frontal lobe, parietal lobe)

Temporal lobe epilepsy is not the only form of epilepsy, as these seizure networks can be located in various different areas. The focal points where it is located will most likely be revealed throughout the diagnostic process and will manifest differently than temporal lobe epilepsy. Treatment outcomes for each may differ so it is important to get an accurate diagnosis.

Migraine⁴

Some symptoms, mechanisms, and therapies of migraines and epilepsy can overlap, such as overactivity of neurons and loss of consciousness. Both epilepsy and migraines are episodic disorders. Additionally, some migraines can have a similar EEG reading to epilepsy.

Psychiatric disorders (i.e. panic disorder, psychotic disorders)

With panic attacks or psychotic episodes, people can misinterpret the symptoms and associate the episode with symptoms of seizures. It is important to see a professional and receive an accurate diagnosis and proper testing to determine the correct cause so that the help received is the help required.²

Nonepileptic seizures

Everyone may end up experiencing a seizure in their life. A seizure does not mean epilepsy. It is important to identify the cause of the seizure, especially if it is recurring, but there are a variety of causes of a seizure, and not all indicate epilepsy.

Syncope

Passing out or losing consciousness and quickly recovering may be attributed to impaired awareness seizures. This may not be true, and it is important to confirm the cause.

Summary

The diagnosis of temporal lobe epilepsy is clear-cut, and you should ask to see an expert if you are concerned. Epilepsy manifests as aware, unaware, or tonic-clonic seizures, and can have a variety of minor secondary symptoms. The diagnostic process involves an extensive history of the seizures, and will have an MRI and EEG as the primary tools for detecting epilepsy. While there are some challenges due to improvements in technology and specialisation, it is relatively easy to receive a diagnosis. Misdiagnosis can occur, but it should be resolved if going through the proper channels.