Temporal lobe epilepsy (TLE) may be simple focal seizures without loss of awareness (with or without aura) or focal dyscognitive seizures (with loss of awareness). Loss of awareness occurs during a focal dyscognitive seizure when the seizure spreads to involve both temporal lobes.
Focal epilepsy is often of temporal lobe origin but the true prevalence of TLE is not known.
- Aura occurs in the majority of temporal lobe seizures. Most auras and automatisms last a very short period - seconds or 1 to 2 minutes. Auras may cause sensory, autonomic or psychic symptoms:
- Somatosensory and special sensory phenomena:
- Olfactory, auditory and gustatory illusions and hallucinations may occur.
- Patients may report distortions of shape, size and distance of objects.
- These visual illusions differ from the visual hallucinations associated with occipital lobe seizure in that there is no formed visual image.
- Objects may appear smaller or larger than usual.
- Vertigo may occur with seizures in the posterior superior temporal gyrus.
- Psychic phenomena:
- Feeling of déjà vu (familiarity) or jamais vu (unfamiliarity).
- Depersonalisation (ie feeling of detachment from oneself) or derealisation (surroundings appear unreal).
- Fear or anxiety.
- May describe seeing their own body from outside.
- Autonomic phenomena: changes in heart rate and sweating. Patients may experience an epigastric fullness sensation or nausea.
- Somatosensory and special sensory phenomena:
- Following the aura, a temporal lobe focal dyscognitive seizure begins with a wide-eyed, motionless stare, dilated pupils and behavioural arrest.
- Lip-smacking, chewing and swallowing may be noted.
- Manual automatisms or unilateral dystonic posturing of a limb may also occur.
- A focal dyscognitive seizure may evolve to a generalised tonic-clonic (GTC) seizure.
- Patients usually experience a postictal period of confusion. The postictal phase may last for several minutes.
- Amnesia occurs during a focal dyscognitive seizure because of bilateral hemispheric involvement.
Possible underlying causes
- Past infections - eg, herpes encephalitis or bacterial meningitis.
- Head injury producing contusion or haemorrhage that results in encephalomalacia or cortical scarring.
- Vascular malformations (ie arteriovenous malformation, cavernous angioma).
- Cryptogenic: a cause is presumed but has not been identified.
- Idiopathic (rare).
- Hippocampal sclerosis produces a clinical syndrome called mesial temporal lobe epilepsy, which begins in late childhood, then remits but reappears in adolescence or early adulthood in a refractory form.
- Febrile seizures: some children with complex febrile convulsions appear to be at risk of developing TLE in later life.
- Absence seizures: have an abrupt onset with no aura, usually last for less than 30 seconds, have no postictal confusion and are not associated with complex automatisms. Focal dyscognitive seizures are usually preceded by a distinct aura, last longer than a minute, and have a period of postictal confusion.
- Frontal lobe focal dyscognitive seizures appear in clusters of brief seizures with abrupt onset and ending. There is minimal postictal state. May cause behavioural changes with vocalisations and complex motor and sexual automatisms. In differentiating from TLE, may need electroencephalograph (EEG) localisation.
- Excessive daytime somnolence - eg, due to a sleep apnoea or narcolepsy.
- Periodic limb movement disorder.
- Tardive dyskinesia.
- Panic attacks.
- Occipital lobe epilepsy: may spread to the temporal lobe and be clinically indistinguishable from a temporal lobe seizure.
- Psychogenic seizures: patients with psychogenic seizures may also have epileptic seizures.
- Interictal EEG: one third of patients with TLE have bilateral, independent, temporal interictal epileptiform abnormalities.
- MRI is the neuroimaging investigation of choice.
- Positron emission tomography (PET) using radioisotope fluorodeoxyglucose (18F) (FDG-PET) is useful when the MRI result is normal.
- Single-photon emission computed tomography (SPECT) is useful for candidates for surgical intervention.
- Video-EEG telemetry is used as part of the pre-surgical evaluation. It is also used if the diagnosis of TLE is still uncertain.
- Carbamazepine or lamotrigine are the drugs of choice for focal seizures. Levetiracetam, oxcarbazepine or sodium valproate should be considered if carbamazepine and lamotrigine are unsuitable or not tolerated.
- Adjunctive treatment: offer carbamazepine, clobazam, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, sodium valproate or topiramate as adjunctive treatment if first-line treatments are ineffective or not tolerated.
- Other anti-epileptic drugs (AEDs) that may be considered by the tertiary epilepsy specialist are eslicarbazepine acetate, lacosamide, phenobarbital, phenytoin, pregabalin, tiagabine, vigabatrin and zonisamide.
Treatments for refractory TLE
- Vagus nerve stimulation (VNS) with a high-frequency stimulation rate may be effective in reducing seizure frequency. A battery-operated stimulator device is implanted in the left vagus nerve in the neck.
- Anteromedial temporal resection is the most frequently performed operation for medial TLE.
- Patients with refractory TLE have an increased risk of sudden death.
- Seizure-free state two years after anterior temporal lobectomy is predictive of long-term seizure-free outcome.
- About half of patients become seizure-free with medical treatment.
- After three first-line AEDs have failed, the chance for seizure freedom is greatly reduced.
- Surgery in well-selected patients with refractory TLE leads to a seizure-free outcome rate of about 70.
- Patients with refractory TLE typically have deficits in memory function.
- Those patients with dominant TLE often have impaired language function.
Further reading and references
; NICE Evidence Services (UK access only)
; NICE CKS, December 2014 (UK access only)
; The Epilepsies: Seizures, Syndromes and Management. Chapter 12, Symptomatic and Probably Symptomatic Focal Epilepsies. 2005.
; Epilepsy associated tumors: Review article. World J Clin Cases. 2014 Nov 162(11):623-41. doi: 10.12998/wjcc.v2.i11.623.
; Scottish Intercollegiate Guidelines Network - SIGN (2015)
; NICE Clinical Guideline (January 2012)
; Epilepsy surgery for pharmacoresistant temporal lobe epilepsy: a decision analysis. JAMA. 2008 Dec 3300(21):2497-505.
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