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Overview:
- Temporal lobe epilepsy was traditionally considered an acquired condition.
- Causes include lesions such as:
- Hippocampal sclerosis
- Tumours
- Trauma
- Vascular malformations
- Malformations of cortical development
- Recent research has highlighted the genetic involvement in some forms of temporal lobe epilepsy.
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Inheritance:
- Familial temporal lobe epilepsy is inherited in an autosomal dominant manner.
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Types:
- Mesial Familial Temporal Lobe Epilepsy (MFTLE):
- Characterised by seizure symptomatology typical of mesial temporal lobe epilepsy.
- Symptoms include:
- Déjà vu
- Autonomic phenomena
- Lateral Familial Temporal Lobe Epilepsy (LFTLE):
- Also known as partial epilepsy with auditory symptoms.
- Characterised by subjective ictal symptoms.
- Symptoms include:
- Auditory hallucinations originating from the lateral temporal lobe.
- Mesial Familial Temporal Lobe Epilepsy (MFTLE):
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Onset and Nature:
- Both MFTLE and LFTLE typically begin in adolescence or adult life.
- These forms of epilepsy are usually considered benign epilepsy syndromes.
Mesial Familial Temporal Lobe Epilepsy (MFTLE)
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Overview:
- MFTLE is an autosomal dominant epileptic disease.
- Onset typically occurs in teenage or early adult life.
- Median onset is in the middle of the third decade of life.
- No cases have been identified in children under 10 years.
- Women may be affected more than men (58%).
- Epidemiology is unknown, but it may be a common condition.
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Clinical Manifestations:
- Seizures are generally mild, infrequent, and well controlled with antiepileptic drugs (AEDs).
- Seizure Types:
- Simple focal seizures (90%) are more common than complex focal seizures (66%).
- Simple focal seizures may be the only seizure type (18%).
- Ictal Symptoms:
- Déjà vu
- Experiential phenomena and hallucinations
- Autonomic disturbances
- Emotional symptoms (fear and panic)
- Visual and auditory illusions
- Somatosensory sensations (diffuse numbness and tingling)
- Generalized Tonic-Clonic Seizures (GTCS):
- Occur in only two-thirds of patients.
- In 50% of cases, GTCS occur before appropriate treatment is initiated.
- Infrequent, with a worst-case scenario of one GTCS per year.
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Aetiology:
- Autosomal dominant inheritance with reduced penetrance (60%).
- The responsible gene has not yet been identified.
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Diagnostic Procedures:
- MRI:
- Often normal but may show hippocampal atrophy in severe cases.
- Minor, non-specific abnormalities (diffuse, small, high signal areas on T2-weighted images).
- Interictal FDG-PET:
- May show ipsilateral temporal hypometabolism in patients with active seizures.
- EEG:
- Interictal EEG is usually normal (50% of cases).
- May show mild, focal, slow waves (28%) or sparse, unilateral sharp and slow wave complexes (22%).
- Sleep may occasionally activate epileptiform abnormalities.
- MRI:
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Differential Diagnosis:
- Differentiating from normal phenomena in cases with mild and infrequent seizures of predominantly déjà vu can be challenging.
- Main differentiating features from hippocampal epilepsy:
- Onset in teens or early adult life
- No febrile convulsions or other antecedent factors
- No ictal symptoms of rising epigastric aura
- Mild and infrequent seizures that may remit
- Usually normal MRI
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Prognosis:
- Generally good prognosis.
- One-sixth of cases with mild simple partial seizures alone might be unaware of their condition if not for affected family members.
- Complex focal seizures and GTCS are infrequent and respond well to AEDs.
- Rare for seizures to persist after drug treatment (10-20% of cases).
- Long remissions, with or without therapy, are common.
- More severe clinical spectrum observed in patients considering surgical treatment.
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Management:
- Seizures are usually easily controlled with carbamazepine or phenytoin.
- Patients with refractory MFTLE have a good surgical outcome when unilateral or clearly asymmetric hippocampal atrophy is identified.
- Preoperative investigation should be the same as for patients with sporadic refractory MFTLE.
Cite this: ICNApedia contributors.Familial (Autosomal Dominant) Focal Epilepsies. ICNApedia, The Child Neurology Knowledge Environment. 09 November 2024. Available at: https://icnapedia.org/knowledgebase/articles/familial-autosomal-dominant-focal-epilepsies Accessed 09 November 2024.