1 | INTRODUCTION AND BACKGROUND
Alzheimer’s disease (AD) is the most common neurodegenerative disease
accompanied by dementia, which is considered due to the deposition of
pathologic amyloid β and successive pathologic tau protein. The main
clinical features of AD are an amnestic presentation, which includes
learning impairment and problems recalling recently learned information,
as well as nonamnestic impairments.1 Regional atrophy
and hypoperfusion are typically observed in the medial temporal lobes,
as shown by magnetic resonance (MR) imaging
and [123I]
iodoamphetamine single-photon emission computed tomography (IMP-SPECT),
respectively. Mild cognitive impairment (MCI) is defined as the
prodromal stage of dementia, with amnestic MCI considered that due to AD
and supported by pathophysiological evidence.2
Sleep apnea syndrome (SAS) can cause cognitive impairment, which can be
improved through continuous positive airway pressure (CPAP)
treatment.3 Additionally, cancer in non-central
nervous system malignancies can cause cancer-related cognitive
impairment.4
We present a case of a right-handed 64-year-old Japanese man who visited
our clinic with his wife, complaining of memory impairment. The patient
was suspected of early-stage MCI due to AD based on IMP-SPECT findings.
Pathologic amyloid β and tau protein deposition in the brain was also
shown using 11C-Pittsburgh compound-B (PiB)
positron emission tomography (PET)
and 18F-THK5351 (THK5351)-PET,
respectively.1 During the observation, the patient was
diagnosed with SAS and treated successfully, although his cognitive
impairment progressed. Eighteen months after the baseline visit, the
patient might be diagnosed with early-stage AD. Nineteen months after
the baseline visit, the patient was diagnosed with lung cancer without
metastasis and underwent surgery. Several months after the surgery (2
years after the baseline visit), his cognitive ability as evaluated by
neurocognitive testing showed significant improvement.
The cognitive impairment in our current case can therefore be considered
to have been caused by carcinogenesis derived from the patient’s lung
cancer. When diagnosing AD, it is important to collectively consider the
patient’s physical illness rather than based solely on the results of
neurocognitive tests and pathophysiological findings.