Epilepsy is a neurological condition marked by recurrent, unprovoked seizures, which are sudden bursts of abnormal electrical activity in the brain. These episodes can cause a range of symptoms, from brief staring spells to full-body convulsions. The brain’s hippocampus, a seahorse-shaped structure deep within the temporal lobe, plays a significant role in certain types of epilepsy. Hippocampus epilepsy refers to a specific form of this disorder where seizures originate in or are strongly linked to this particular brain region.
Understanding Hippocampus Epilepsy
The hippocampus, a small, curved structure deep within each temporal lobe, is part of the limbic system, involved in emotion, motivation, and memory. Its primary function is processing memory, particularly forming new declarative memories like facts and locations. It also plays a role in transferring short-term memories into long-term storage and in spatial navigation.
Dysfunction in the hippocampus can lead to seizures, making it a common site for seizure activity. Hippocampus epilepsy is often called Mesial Temporal Lobe Epilepsy (MTLE) because it involves the medial temporal lobe, where the hippocampus is located. This area is susceptible to epileptic activity due to its neuronal firing patterns and hyperexcitability. In many MTLE cases, structural changes like hippocampal sclerosis, a scarring of the tissue, are observed.
Common Symptoms
Individuals with hippocampus epilepsy often experience characteristic symptoms related to the hippocampus’s functions in memory and emotion. Seizures originating in this region are typically focal onset seizures, meaning they begin in one area of the brain. These can manifest as focal aware seizures, where the person remains conscious, or focal impaired awareness seizures, where awareness is reduced or lost.
Auras are common initial symptoms of these seizures, acting as a warning sign. These sensory or emotional experiences can include feelings of déjà vu, a sense of unprovoked fear or anxiety, or unusual smells or tastes. During focal impaired awareness seizures, individuals may exhibit automatisms, which are repetitive, non-purposeful movements such as lip smacking, fumbling with fingers, or chewing. After a seizure, a period of post-ictal confusion or memory issues, like difficulty recalling recent events, is also common.
Underlying Causes and Risk Factors
Various factors can contribute to the development of hippocampus epilepsy. A common cause is a history of complicated febrile seizures in childhood, particularly those lasting longer than 30 minutes and associated with high fevers. These prolonged seizures can lead to scarring of the hippocampus, known as hippocampal sclerosis. Head injuries, especially those causing significant brain trauma, are another potential risk factor.
Brain infections such as encephalitis or meningitis can also damage the hippocampus and increase the likelihood of developing epilepsy. Strokes or brain tumors in or near the temporal lobe can disrupt normal brain function and lead to seizure activity. While not fully understood, genetic predispositions can also play a role, with familial mesial temporal epilepsy being a recognized syndrome.
Diagnosis and Treatment Strategies
Diagnosing hippocampus epilepsy involves a comprehensive evaluation to identify the seizure origin and any underlying brain abnormalities. A neurological examination is a first step, assessing overall brain function. Electroencephalogram (EEG) recordings are then used to detect abnormal electrical activity in the brain, helping to pinpoint the seizure’s starting point. Magnetic Resonance Imaging (MRI) is also a routine diagnostic tool, capable of identifying structural changes in the brain, such as hippocampal sclerosis, which often appears as atrophy or scarring in the hippocampus.
Treatment for hippocampus epilepsy typically begins with anti-seizure medications (ASMs). These medications work to control the abnormal electrical activity in the brain and reduce seizure frequency. For individuals whose seizures are resistant to medication, which occurs in about one-third of cases, surgical options may be considered. Procedures such as temporal lobectomy, which involves removing a portion of the temporal lobe including the hippocampus, or a more focused selective amygdalohippocampectomy, can significantly improve seizure control. Approximately 70% to 90% of patients undergoing these resections achieve seizure freedom. Other potential therapies include vagus nerve stimulation (VNS), a device implanted to send electrical pulses to the vagus nerve, and dietary changes like the ketogenic diet.