A small study found that memory persisted over time in people with primary progressive aphasia (PAP) with Alzheimer’s disease.
Episodic memory was retained on initial testing and did not decline after 2.35 years, while PPA symptoms were present for 6.26 years, although language skills declined significantly, said M. Marcel Mesulam, M.D., of the School of Medicine. Feinberg at Northwestern University in Chicago. , and coauthors in Neurology.
“Although we knew that the memory of people with PAP was not initially affected, we didn’t know if they kept their memory functioning for many years,” Mesulam said in a statement. “It was difficult to determine because most memory tests rely on verbal skills that these people have lost or are losing.”
PPA is a neurodegenerative condition characterized by severe language problems that worsen over time. About 40% of patients with PAD have atypical manifestations of Alzheimer’s disease, often with logopenic PAD.
The study included 17 patients with PAD with Alzheimer’s disease, who were compared with 14 people with typical Alzheimer’s disease. Participants with PPA came from the Northwestern PPA Research Program and had autopsy or biomarkers suggestive of Alzheimer’s disease and at least two consecutive visits with language and memory assessments. Alzheimer’s pathology was based on autopsy in eight participants, cerebrospinal fluid biomarkers in three, and amyloid PET in six. Ten of the participants were male, 11 had logopenic PAD. The age at onset of symptoms ranged from 47 to 74 years, with an average of 59 years.
The typical Alzheimer’s group included eight men and six women from the Northwest Alzheimer’s Center, in whom Alzheimer’s was the primary neuropathological diagnosis at autopsy. The average age at onset of symptoms was 66 years. In this group, verbal memory and speech functions deteriorated over time with the same severity.
Imaging performed in the PPA group only showed asymmetric left-sided mediotemporal atrophy. Autopsy in both groups revealed bilateral hippocampal-entorhinal neurofibrillary degeneration. Compared to the typical Alzheimer group, the PPA group had a lower incidence of TDP-43 mediotemporal pathology and a lower incidence APOE4 genotype.
“Perhaps the most intriguing finding is that memory retention in the PPA-Alzheimer’s group is observed despite equally widespread abnormalities in the structures of the medial temporal lobes in both groups,” said Seyed Ahmad Sajjadi, MD, Ph.D. University of California, Irvine. , and co-authors in an accompanying editorial. “Therefore, the medial structures of the temporal lobes in patients with PPA-Alzheimer’s disease can be considered resistant, rather than resistant to Alzheimer’s pathology.”
The lack of atrophy of the right medial temporal lobe in the PPA group supports this idea: “This implies a separation of neurodegeneration and pathology in people with PPA-Alzheimer’s,” the editors wrote.
“Combined with the more common cortical atrophy of the left hemisphere in the PPA group, it seems reasonable to conclude that neurodegeneration, and not just the presence of pathology, is what correlates with the clinical presentation in these patients,” they added. “This is an important concept in an era of targeted therapies that increasingly target people with or with minimal cognitive impairment.”
Research limitations include the relatively small sample size. Autopsies were not performed for all PPA cases. In addition, episodic memory was assessed using different tests in two groups.
Neither study authors nor editors reported disclosures.