Mesial temporal sclerosis (MTS) is a neurological condition strongly associated with a severe form of epilepsy. MTS itself is a physical change in the brain tissue, not an immediate cause of death. The true danger stems from the resulting seizure disorder, which significantly increases the risk of mortality through associated complications. This condition is characterized by scarring of a memory-forming region, creating electrical instability in the brain. Management focuses on controlling seizures and mitigating the elevated risks they introduce.
Defining Mesial Temporal Sclerosis
Mesial temporal sclerosis (MTS) is defined by the abnormal hardening and shrinkage of tissue in the inner part of the temporal lobe. The primary structure affected is the hippocampus, an area fundamental for learning and memory formation. This damage involves the loss of neurons and gliosis, where glial cells proliferate to form scar tissue. Because of this focused damage, MTS and hippocampal sclerosis are often used interchangeably.
MTS is the most common cause of structural epilepsy in adults. The condition is typically understood to result from an initial injury to the brain early in life. Common risk factors include prolonged febrile seizures in childhood, head trauma, or infections like meningitis. This initial event causes damage that may lead to a silent progression before seizures begin years later.
The Primary Risk: Refractory Temporal Lobe Epilepsy
The principal danger associated with MTS is its tendency to cause refractory temporal lobe epilepsy (TLE), meaning the seizures are resistant to medication. Up to 70% of patients with MTS develop drug-resistant seizures, dramatically increasing health risks. These seizures originate from the scarred hippocampus and manifest as focal seizures, sometimes involving strange sensations, déjà vu, or automatisms. They can progress to generalized tonic-clonic seizures, causing convulsive movements and loss of consciousness.
Uncontrolled generalized tonic-clonic seizures are the largest risk factor for Sudden Unexpected Death in Epilepsy (SUDEP). SUDEP is defined as the sudden, unexpected death in a person with epilepsy where the cause is undetermined after examination. The risk of SUDEP is significantly higher in MTS patients, reaching up to 9.3 per 1,000 person-years in surgical candidates. The mechanism involves seizure-induced dysfunction in the cardiorespiratory system, such as central apnea following a seizure.
Secondary risks also contribute to the mortality associated with uncontrolled TLE. Patients risk accidental injury during a seizure, such as falls or burns, especially if they lose consciousness. Status epilepticus, a prolonged seizure or series of seizures without recovery, is a medical emergency that can lead to permanent brain damage or death. The overall mortality rate in people with drug-resistant epilepsy is increased two- to three-fold, emphasizing the need for effective seizure control.
Diagnosis and Management Approaches
Diagnosis relies on clinical history and advanced neuroimaging, particularly Magnetic Resonance Imaging (MRI). High-resolution MRI scans are the definitive tool, confirming hippocampal atrophy (shrinkage) and signal changes indicating scarring. Electroencephalography (EEG) is also used to record the brain’s electrical activity. This helps localize where the seizure activity originates in the temporal lobe.
Initial management involves treatment with antiepileptic drugs (AEDs) to reduce seizure frequency. However, because MTS is strongly associated with drug-resistant epilepsy, this first-line approach is often unsuccessful. When two or more AEDs fail to control seizures, the condition is deemed refractory. Patients are then typically referred for a surgical evaluation.
For patients with refractory TLE caused by unilateral MTS, surgical intervention is the most effective treatment option. The most common procedure is a temporal lobectomy, which removes the affected temporal lobe tissue, including the scarred hippocampus. Less invasive options, such as Laser Interstitial Thermal Therapy (LITT), use heat to destroy the scarred area. Surgery is highly effective, with 60% to 80% of selected patients achieving seizure freedom, significantly reducing the risk of SUDEP and accidents.
Long-Term Quality of Life and Prognosis
The long-term prognosis for MTS patients depends highly on achieving seizure freedom. Surgical treatment offers a far better outcome than relying solely on medication. Successful surgery results in a high likelihood of remaining seizure-free, substantially improving quality of life. Achieving seizure control also reduces the elevated mortality risks associated with uncontrolled epilepsy.
Even with seizure control, hippocampal damage can lead to persistent memory impairment, particularly in forming new memories. Patients may also face elevated rates of mood disorders, such as depression and anxiety, requiring ongoing management. When seizures are controlled, memory function can sometimes improve. Early and effective treatment, especially surgery for drug-resistant cases, offers the best chance for a favorable long-term prognosis.