Background
The temporal lobe is the most epileptogenic region of the brain. In fact, 90% of patients with temporal interictal epileptiform abnormalities on their electroencephalograms (EEGs) have a history of seizures.
Temporal lobe epilepsy was defined in 1985 by the International League Against Epilepsy (ILAE) as a condition characterized by recurrent, unprovoked seizures originating from the medial or lateral temporal lobe.
The seizures associated with temporal lobe epilepsy consist of simple partial seizures without loss of awareness and complex partial seizures (ie, with loss of awareness). The individual loses awareness during a complex partial seizure because the seizure spreads to involve both temporal lobes, which causes impairment of memory. The partial seizures may secondarily generalize. As humans have 2 temporal lobes, one side is domininant for language function, and, if there is marked aphasia, seizure focus may be lateralized to the left temporal lobe for most right-handed people.
Temporal lobe epilepsy was first recognized in 1881 by John Hughlings Jackson, who described "uncinate fits" seizures arising from the uncal part of temporal lobe and the "dreamy state."
In the 1940s, Gibbs et al introduced the term psychomotor epilepsy.[1] The international classification of epileptic seizures (1981) replaced the term psychomotor seizures with complex partial seizures. Complex means that there is some alteration of conciouness, versus a simple partial seizure, which means there is no alteration of conciouness. The ILAE classification of the epilepsies uses the term temporal lobe epilepsy and divides the etiologies into cryptogenic (presumed unidentified etiology), idiopathic (genetic), and symptomatic (cause known, eg, tumor).
For more information, see Epilepsy and Seizures.
Etiology
Hippocampal sclerosis
Approximately two thirds of patients with temporal lobe epilepsy treated surgically have hippocampal sclerosis as the pathologic substrate. Hippocampal sclerosis involves hippocampal cell loss in the CA1 and CA3 regions and the dentate hilus. The CA2 region is relatively spared.
Hippocampal sclerosis produces a clinical syndrome called mesial temporal lobe epilepsy (MTLE).
The clinical correlate of hippocampal sclerosis on neuroimaging on magnetic resonance imaging (MRI) is called mesial temporal lobe sclerosis (MTS), which is high-signal intensity on either T2-weighted or fluid-attenuated inversion recovery (FLAIR)–sequence MRIs and/or atrophy of the hippocampi.
The etiologies of temporal lobe epilepsy include the following:
- Infections, eg, herpes encephalitis, bacterial meningitis, neurocysticercosis
- Trauma producing contusion or hemorrhage that results in encephalomalacia or cortical scarring; difficult, traumatic delivery such as forceps deliveries
- Hamartomas
- Malignancies (eg, meningiomas, gliomas, gangliomas)
- Paraneoplastic (anti-Hu , NMDA-receptor antibodies)
- Vascular malformations (ie, arteriovenous malformation, cavernous angioma)
- Cryptogenic (a cause is presumed but has not been identified)
- Idiopathic (genetic)
The last of the above etiologies, idiopathic, is rare. Familial temporal lobe epilepsy was described by Berkovic and colleagues,[2] and partial epilepsy with auditory features was described by Scheffer and colleagues.
Febrile seizures
A subset of children with complex febrile convulsions appears to be at risk of developing temporal lobe epilepsy in later life. Complex febrile seizures are febrile seizures that last longer than 15 minutes, have focal features, or recur within 24 hours.
The association of simple febrile seizure with temporal lobe epilepsy has been controversial.
Go to Febrile Seizures for complete information on this topic.
Epidemiology
Approximately 50% of patients with epilepsy have partial epilepsy. Partial epilepsy is often of temporal lobe origin. However, the true prevalence of temporal lobe epilepsy is not known, since not all cases of presumed temporal lobe epilepsy are confirmed by video-electroencephalography and most cases are classified by clinical history and interictal electroencephalogram (EEG) findings alone.
Sex and age predilection
Temporal lobe epilepsy is not more common in one sex, but female patients may experience catamenial epilepsy, which is an increase in seizures during the menstrual period.
Epilepsy occurs in all age groups. Recently, a significant increase in new-onset seizures in elderly persons has been recognized.
Prognosis
In comparison with the general population, morbidity and mortality are increased in persons with temporal lobe epilepsy, due to increased accidents from the episodes of consciousness loss.
Mortality also results from sudden unexpected death in epilepsy (SUDEP). Patients with refractory temporal lobe epilepsy, especially those with secondarily generalized tonic clonic seizures, have a risk of sudden death that is 50 times greater than that in the general population.
Epilepsy surgery seems to modify the risk of SUDEP if the patient remains seizure free. In patients who have undergone surgery, the mortality rate becomes equivalent to that of the general age- and sex-matched population.
The presence of a seizure-free state 2 years after anterior temporal lobectomy is predictive of long-term seizure-free outcome for the patient.
About 47-60% of patients become seizure free with medical treatment. After 3 first-line antiepileptic drugs (AEDs) have failed, the chance for seizure freedom is 5-10%. The ILAE now has a formal definition of medically intractable/drug-resistant epilepsy, which defined as after a patient has had an adequate trial with 2 antiepileptic drugs and is still having seizures. Surgery in well-selected patients with refractory temporal lobe epilepsy yields a seizure-free outcome rate of 70-80%.
Patient Education
Fetal anomalies due to antiepileptic medications
Physicians should carefully document on the chart that they have explained to their female patients with epilepsy about the increased risk of fetal anomalies associated with antiepileptic medications, a 2-fold increase (4-6%), and the increased risk of neural tube defects with valproate (1.5-2.0%) and carbamazepine (0.5%).
Patients should be told that most women with epilepsy have healthy children (90-95%). They also should be told that the chance of a normal pregnancy outcome is increased with planned pregnancies, improved seizure control, folate supplementation (0.4-4 mg each day prior to pregnancy), minimizing the number of AEDs used, and never abruptly discontinuing AEDs without consulting the physician.
For patient education information, see the Brain and Nervous System Center, as well as Epilepsy.
Gibbs EL, Gibbs FA, Fuster B. Psychomotor epilepsy. Arch Neurol Psychiatry. 1948;60:331-339.
Berkovic SF, McIntosh A, Howell RA, Mitchell A, Sheffield LJ, Hopper JL. Familial temporal lobe epilepsy: a common disorder identified in twins. Ann Neurol. Aug 1996;40(2):227-35. [Medline].
Acharya V, Acharya J, Lüders H. Olfactory epileptic auras. Neurology. Jul 1998;51(1):56-61. [Medline].
Engel J Jr, McDermott MP, Wiebe S, Langfitt JT, Stern JM, Dewar S, et al. Early surgical therapy for drug-resistant temporal lobe epilepsy: a randomized trial. JAMA. Mar 7 2012;307(9):922-30. [Medline].
Semah F, Picot MC, Adam C, Broglin D, Arzimanoglou A, Bazin B, et al. Is the underlying cause of epilepsy a major prognostic factor for recurrence?. Neurology. Nov 1998;51(5):1256-62. [Medline].
Foldvary N, Nashold B, Mascha E, Thompson EA, Lee N, McNamara JO, et al. Seizure outcome after temporal lobectomy for temporal lobe epilepsy: a Kaplan-Meier survival analysis. Neurology. Feb 8 2000;54(3):630-4. [Medline].
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