Case Study

A 55 year old RHWF with refractory localization-related epilepsy was referred for surgical evaluation after a change in her “provider”. She had a history of febrile convulsions with weekly focal seizures with and without impaired consciousness on 5 AEDs. An aura of déjà vu occurred prior to staring, lip smacking, and impaired responsiveness for periods of 30 seconds. Rare focal seizures evolving to convulsions were noted in addition to daily independent auras. MRI demonstrated left >> right MTS. Scalp EEG recorded left > right bitemporal spikes (80% left) and 3 left hemisphere-onset seizures. Neuropsychological testing demonstrated impaired executive function and severe verbal memory deficits. Wada results were 5/8 left injection and 6/8 right injection. She underwent iEEG with B/L occipital-temporal depth electrodes…

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Figure: Depth iEEG (top), EKG, and scalp EEG (bottom) demonstrating a subclinical seizure from the left depth. Note the absence of scalp correlate. 23 sbuclinical seizures were recorded in 24 hours. Recording parameters include longitudinal bipolar montage, sensitivity 7 uv, and filters of 1-70. Hz.

What did the EEG Reveal?

Disturbances of memory are among the most common complaints in TLE. Epilepsy surgery may be curative but can compromise memory function. Patients undergoing left temporal lobe surgery often have memory deficits before surgery and postoperative worsening of both verbal learning and memory1. Memory function is most impaired in people with bilateral anatomic or functional hippocampal lesions. Operations within the dominant temporal lobe have the strongest association with predicting post-operative memory decline, pre-operative immediate verbal memory the weakest, and delayed worsening that may become noted over the subsequent 2 year course2. Mechanisms for apparent interictal memory dysfunction includes injury to the mesial temporal lobe, impairment from AEDs, and possibly frequent epileptiform discharges that transiently disrupt cognitive processing. Our patient underwent a selective amygdalohippocampectomy after iEEG recorded frequent subclinical seizures. She has been seizure free for > 6 months and is on 2 AEDs. Working memory acquisition and consolidation problems “greatly improved” following dominant temporal lobe surgery.

References

  1. Alpherts WC, Vermeulen J, van Rijen PC, da Silva FH, van Veelen CW, Dutch Collaborative Epilepsy Surgery Program. Verbal memory decline after epilepsy surgery?: A 6-year multiple assessments follow-up study. Neurology 2006;67(4):626-631.
  2. Stroup E, Langfitt J, Berg M, McDermott M, Pilcher W, Como P. Predicting verbal memory decline following anterior temporal lobectomy. Neurology 2003;60(8):1266-1273.
Authored By: 
William O. Tatum DO
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Authored Date: 
10/2011