Case Study

A 62 year old man lived alone. He had treated hypertension, hypercholesterol-emia but was otherwise in good health. His daughter reported a 2 year history of memory problems that led to forced retirement at work. He was referred to Neurology and underwent an uneventful evaluation with normal MRI, EEG, and laboratory testing. He was diagnosed with dementia of the Alzheimer type and was treated with donepezil. Memory problems continued and fluctuated with significant deficits evident primarily in recent memory despite treatment. Neuropsychological testing demonstrated a moderate cognitive impairment of the amnestic type. A 2nd sleep-deprived EEG and paraneoplastic profile were normal. A definitive procedure was performed.

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Figure: Computer-assisted ambulatory EEG demonstrating (A) left sharp-and-slow-wave in (black arrow) and (B) focal seizure without awareness (red arrow). Seizure detection software recovery was without clinical report. EEG parameters include a bipolar montage, sensitivity of 7 uv/mm, and filters of 1-70 Hz.

What was ultimately wrong with the patient?

Temporal lobe seizures (TLS) may transiently impair cognitive and memory function and result in fluctuating memory loss to reflect the ictal-post-ictal continuum. In Alzheimer's disease, toxic accumulations of A-beta peptides underlies the memory disorder triggering synaptic degeneration, circuit remodeling, and abnormal synchronization within the same hippocampal networks to lead to progressive memory loss1. The neuronal hyperexcitability that is associated with seizures augments the synaptic release of A-beta and may further compound the cognitive deficits in compromised patients such as those with AD. While AD and epilepsy are felt to reflect independent disorders, progressive cognitive and memory deficits are known to occur in patients with TLS associated with hippocampal sclerosis. Furthermore, seizures are a common comorbidity in those with early onset AD. When seizures are subtle, nocturnal, or occur in seniors that expect memory loss, the diagnosis may be elusive. If memory loss fluctuates, subtle TLS without awareness should be considered. In our patient living alone, prolonged EEG had a greater yield than repeated EEG2.

References

  1. Noebels J. A perfect storm: Converging paths of epilepsy and Alzheimer's dementia intersect in the hippocampal formation. Epilepsia 2011;52(Suppl. 1):39-46.
  2. Tatum WO IV, Ross J, Cole AJ. Epileptic pseudodementia. Neurology 1998;60:1137-1152.
Authored By: 
William O. Tatum DO
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Authored Date: 
04/2011