What are the diagnostic criteria and treatment options for temporal lobe epilepsy?

Temporal Lobe Epilepsy: Diagnostic Criteria and Treatment Options

Temporal lobe epilepsy (TLE) is diagnosed through a combination of clinical history, electroencephalography (EEG), and neuroimaging, with treatment primarily consisting of antiepileptic drugs, and surgery for drug-resistant cases.

Diagnostic Criteria

Clinical History and Seizure Characteristics

• TLE seizures typically present with specific auras such as rising epigastric sensations, unusual unpleasant smells, or other recurring phenomena specific to the individual 1
• Key distinguishing features include:
  • Automatisms (chewing, lip smacking, or blinking) 1
  • Tonic-clonic movements that are prolonged with onset coinciding with loss of consciousness 1
  • Prolonged post-ictal confusion 1
  • Hemilateral clonic movements 1
  • Tongue biting (typically on lateral side of tongue) 1

Electroencephalography (EEG)

• EEG is essential for diagnosis, lateralization, and localization of temporal lobe seizures 2
• Characteristic findings include:
  • Irregular 2-5 Hz lateralized activity 2
  • 5-10 Hz sinusoidal waves or repetitive epileptiform discharges 2
  • Background attenuation and start-stop-start phenomenon 2
• Postictal delta waves can provide valuable lateralizing information, concordant with the seizure onset side in most patients 2

Neuroimaging

• MRI is the preferred imaging modality for TLE diagnosis 1
• High-resolution protocols should include:
  • Coronal T1-weighted (3 mm) imaging perpendicular to the hippocampal long axis 1
  • High-resolution volume (3-D) T1-weighted gradient echo with 1-mm isotropic voxels 1
  • Coronal T2 and coronal/axial fluid-attenuated inversion recovery (FLAIR) sequences 1
• These sequences are essential to assess for hippocampal sclerosis (the most common cause of TLE), signal abnormality, atrophy, and loss of internal structure 1, 3

Advanced Diagnostic Techniques

• FDG-PET can detect hypometabolism in the epileptogenic zone with 79-95% sensitivity and specificity in TLE 1
• PET is particularly valuable when MRI is negative, helping to detect subtle cortical dysplasia or other lesions missed on initial evaluation 1
• Video-EEG monitoring is crucial for capturing and characterizing events when diagnosis is uncertain 4
• Invasive EEG (stereoelectroencephalography) may be necessary for precise localization in surgical candidates 1, 2

Treatment Options

Pharmacological Management

• Antiepileptic drugs (AEDs) are the first-line treatment for TLE 5, 4
• Selection of appropriate AED depends on:
  • Seizure type and epilepsy syndrome 5
  • Individual drug characteristics including pharmacokinetics, side effects, dosing interval, and cost 5
• Most AEDs are effective as initial monotherapy for partial seizures, including those originating in the temporal lobe 5
• If trials of more than two AEDs fail to control seizures, referral to an epilepsy center is recommended 5

Surgical Management

• Epilepsy surgery should be considered in all patients with drug-resistant TLE 4
• Surgical treatment renders 60-70% of patients with TLE free of disabling seizures 5
• Accurate localization of seizure onset is required for successful surgical management 2
• Presurgical evaluation typically includes:
  • Video-EEG monitoring 4
  • High-resolution MRI 1
  • FDG-PET (especially in MRI-negative cases) 1
  • Invasive EEG when necessary 2

Alternative Therapies

• Vagus nerve stimulation may be considered for patients who are not surgical candidates or have failed surgical treatment 4

Clinical Pitfalls and Caveats

• TLE seizures can be easily confused with other conditions, particularly:
  • Syncope (differentiate by presence of prodromal symptoms, duration of unconsciousness, and post-event recovery) 1
  • Psychogenic non-epileptic seizures (look for eye fluttering, pelvic thrusting, and prolonged duration) 1
• Brief seizure activity can occur during syncope; when the history clearly indicates syncope, this type of seizure activity does not require neurologic investigation 1
• Inappropriate use of EEG in cases of clear syncope may lead to misdiagnosis 1
• Temporal lobe hypometabolic regions on PET often extend beyond the presumed epileptogenic zone, reflecting broader cerebral dysfunction 1
• Comorbid depression occurs in approximately one-third of TLE patients and should be addressed as part of comprehensive management 4