Posterior cortical atrophy
Posterior cortical atrophy (also known as the Benson syndrome or visual variant of Alzheimer's disease) is a rare neurodegenerative disease which shares pathological and imaging features with Alzheimer disease.
No specific demographic has been identified as being particularly at risk and no genetic linkages have been established 1. As with Alzheimer's disease, patients are typically elderly.
Posterior cortical atrophy is clinically dominated by disruption of normal higher order visual processes, and as such patients eventually behave essentially like individuals who are blind. Patients typically present with 1:
- visual agnosia : early and pronounced feature
- apraxia: early and pronounced feature
- optic ataxia
- oculomotor apraxia
- environmental disorientation
Although mild memory impairment is often present early in the disease, it is clinically different from that seen in Alzheimer's disease 1.
Neuritic plaques and neurofibrillary tangles are present, especially in parieto-occipital and temporo-occipital areas, and less commonly in the primary visual cortex 1. As such, posterior cortical atrophy shares features with Alzheimer's disease, so much so that some authors believe it to be a variant of the later, and refer to it as visual variant of Alzheimer's disease. Indeed pathologically the conditions are essentially indistinguishable, other than the distribution of pathological changes.
MRI is the modality of choice for assessing patients with neurodegenerative diseases, although CT may allow gross volume changes to be appreciated. Nuclear medicine functional studies are also of benefit.
Typical features include 1:
- bilateral, but often more pronounced right sided, parieto-occipital and temporo-occipital atrophy
SPECT and PET demonstrates hypometabolism in the same areas affected by atrophy 1.
Treatment and prognosis
As is the case with most neurodegenerative diseases, no cure is available. Management it medical and centers on behavioural techniques targeted at overcoming visual disabilities as well as antidepressants 1.
The disease is gradually progressive with patients usually succumbing within 8 - 12 years from the time of symptom onset 1.
Posterior cortical atrophy was first described by Franck Benson in 1988, and thus is also known as Benson syndrome 1.
The primary differential diagnosis includes:
- clinically very different, with memory is a more pronounced and early feature
- mesial temporal lobes are spared 1
Creutzfeldt-Jakob disease (CJD)
- clinically CJD has a more rapid time course
Neurodegenerative diseases are legion and their classification just as protean. A useful approach is to divide them according to underlying pathological process, although even using this schema, there is much overlap and thus resulting confusion.
- progressive supranuclear palsy (PSP)
fronto-temporal lobar degeneration (FTLD)
- behavioural variant fronto-temporal dementia (bvFTLD)
- language variant fronto-temporal dementia (lvFTLD), (aka primary progressive aphasia (PPA)
- corticobasal degeneration
- typical / classical Alzheimer's disease
- variant (e.g. posterior cortical atrophy)
- cerebral amyloid angiopathy (CAA)
- transthyretine-associated cerebral amyloidoses
- human prion diseases (not always included as neurodegenerative)
- neuronal intranuclear hyaline inclusion disease (NIHID)
- Alzheimer disease
- spinocerebellar ataxias
- Huntington disease
- hereditary spastic paraplegia
- amyotrophic lateral sclerosis (ALS)
- 1. Bernard Croisile "Benson's syndrome or Posterior Cortical Atrophy" September 2004, Orphanet full text pdf
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Posterior cortical degeneration||✗|
|Visual variant of Alzheimer's disease||✓|