Posterior Cortical Atrophy: Clinical Characteristics and Differences Compared to Alzheimer’s Disease

Abstract

Background: Predominant and progressive complex visual disorders are often due to posterior cortical atrophy (PCA), a rare early-onset dementing syndrome presenting with visual complaints. In clinicopathological studies, PCA is most commonly considered a form of Alzheimer’s disease (AD); no prior study has evaluated clinical differences between PCA and AD. Methods: This study identified 15 patients who presented with progressive complex visual disorders and predominant occipitoparietal hypoperfusion on SPECT. These patients were retrospectively compared on clinical variables with 30 patients with clinically probable AD matched for gender, age and duration of illness. Results: The PCA patients presented with alexia, elements of Balint’s syndrome, apperceptive visual agnosia, dressing apraxia and environmental disorientation along with elements of Gerstmann’s syndrome. Compared to the AD patients, the 15 PCA patients (mean age of onset 58 years, range 51–64) had significantly better verbal fluency, less memory difficulty, more depression and greater insight into their illness but similar familial and apolipoprotein E risk factors. In the PCA patients, MRI often showed occipitoparietal atrophy without detectable mesiotemporal atrophy. Conclusions: PCA is a distinct clinical syndrome and not just AD with prominent visual deficits. Compared to AD controls, PCA patients have better language and memory but more insight and depression and more posterior atrophy on MRI. These results indicate clinical criteria for the diagnosis of PCA and recommend specific interventions such as visual aids and antidepressant medications. Similar risk factors and course suggest that PCA is most commonly an early-onset posteriorly shifted AD variant.

Imaging correlates of posterior cortical atrophy

“…The clinical features of these 38 PCA patients were typical of other described cases and case series of PCA [4,19,39,43,48]. In all our patients the clinical features were characterized by predominant visuospatial, visuoperceptual deficits, and visual agnosia, as well as problems with reading and writing and environmental disorientation.…”

“…While parietal lobe atrophy was also present in the patients with typical AD, it was much less severe than that observed in the PCA patients, and in contrast it seemed to affect the left parietal lobe greater than the right. Features such as agraphia, acalculia and apraxia typically result from left parietal lobe damage, and are relatively common findings in patients with typical AD [12,39,51].…”

“…In fact the typical AD subjects had significantly greater atrophy of the left medial temporal lobe (particularly the hippocampus) and inferior and middle temporal gyri than the PCA patients, reflecting the deficits in episodic memory that are found in patients with typical AD. This is perhaps unsurprising since patients were excluded from a diagnosis of PCA if they had significant and early episodic memory impairment, and AD patients perform worse on tests of episodic memory than PCA patients [39,43].…”

“…Inclusion criteria were as follows: 1) insidious onset of symptoms; 2) a chief complaint of at least two prominent symptoms referable to the occipital, parietal or posterior temporal lobes that has been liked to PCA; 3) no primary ocular disease accounting for the compliant after ophthalmologic evaluation by an ophthalmologist, 4) an evaluation by at least one behavioral neurologist and 5) progression of symptoms. The list of prominent symptoms linked to PCA include visuospatial deficit, visual perceptual deficit, visual agnosia, environmental disorientation, prosopagnosia, body schema distortion, or any feature suggestive of the Balint's or Gerstmann syndromes [4,39,48]. Patients were excluded if there was early loss of insight, or prominent cognitive impairment affecting language fluency, behavior, or episodic memory that preceded the onset of visual impairment, or exceeded the severity of the visual complaint at onset.…”

“…Visual assessments of MRI have been reported in cases of PCA and have typically shown a pattern of bilateral posterior cerebral atrophy, predominantly affecting the occipital, parietal, and the temporal lobes [1,4,21,24,32,39,41,43]. However, a number of recent automated image analysis techniques have been applied to study patterns of cerebral atrophy on MRI.…”