Neurosurgery notes/Functional/Seizure/Seizure classification/Temporal lobe epilepsy

Temporal lobe epilepsy

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Seizure classification

Mesial temporal (hippocampal) sclerosis causing mesial temporal lobe epilepsy

General

  • Most common cause of intractable temporal lobe epilepsy.
  • Most well defined epilepsy syndrome responsive to structural intervention

History

  • Higher incidence of complicated febrile seizures than in other types of epilepsy
  • Common family history of epilepsy
  • Onset in latter half of first decade of life
  • Auras in isolation are common
  • Infrequent secondarily generalized seizures
  • Seizures often remit for several years until adolescence or early adulthood
  • Seizures often become medically refractory
  • Common interictal behavioral disturbances (especially depression)

Clinical features

  • Most have aura (especially epigastric, emotional, olfactory or gustatory) × several secs
  • Complex partial seizures (CPS) often begin with arrest & stare
  • Oroalimentary & complex automatisms are common.
  • Posturing of contralateral arm may occur.
  • Seizure usually lasts 1–2mins
  • Postictal disorientation, recent-memory deficit, amnesia of ictus and (in dominant hemisphere) aphasia usually lasts several mins

Neurologic and laboratory features

  • Neuro exam
    • Normal except memory deficit
  • MRI
    • Hippocampal atrophy and signal alteration
    • Ipsilateral dilatation of temporal horn of lateral ventricle
  • EEG
    • Unilateral or bilateral independent anterior temporal EEG spikes with maximal amplitude in basal electrodes
    • External ictal EEG activity only with CPS, usually initial or delayed focal rhythmic onset pattern of 5–7 Hz, maximal in 1 basal temporal derivation
  • Interictal fluorodeoxyglucose PET scan
    • Hypometabolism
      • Temporal lobe
      • Possibly ipsilateral thalamus and basal ganglia
  • Neuropsychological testing
    • Memory dysfunction specific to involved temporal lobe
  • Wada test
    • Amnesia with contralateral amobarbital injection

Origin

  • Hippocampal sclerosis
    • Cell loss in Ammon’s horn of the hippocampus on one side.
      • Microscopically, neuronal loss mainly occurs in the CA1 region, more so than the CA4, CA3, and CA2 regions and the dentate gyrus
      • See anatomy
    • Gliosis occurring

Treatment

  • Detected on MRI 90%
  • Surgery has very good outcome
    • Surgical resection:
      • Wiebe 2001
        • 58% in the surgical group and 8 percent in the medical group
            • notion image
    • Radiosurgery

Uncinate seizures

  • Aka: Obsolete term: “uncal fits.”
  • Origin: Inferior medial temporal lobe, usually in the hippocampal region.
  • Olfactory hallucinations (kakosmia or cacosmia: the perception of bad odors where none exist).