In the second part of our series, we started to describe the many different types of dementia. Below, we’ll finish describing the other types of dementia.
Vascular dementia is an umbrella term that describes impairments in cognitive function caused by problems in the blood vessels that feed the brain. In some cases, a blood vessel may be completely blocked, causing a stroke. Some strokes result in dementia while others don’t. It depends on the severity of the stroke and the portion of the brain that’s affected. Vascular dementia also can occur when blood vessels in the brain become narrowed, reducing the amount of blood flow to those sections of the brain.
Nerve cells in the front and side regions of the brain are especially affected. Typical symptoms include changes in personality and behavior and difficulty with language. No distinguishing microscopic abnormality is linked to all cases. Pick’s disease, characterized by Pick’s bodies (nerve cells containing an abnormal accumulation of fibers made of the protein tau), is one type of frontotemporal dementia.
This is a rapidly fatal disorder that impairs memory and coordination and causes behavior changes. It is caused by the mis-folding of prion protein throughout the brain. Variant Creutzfeldt-Jakob disease (vCJD) is believed to be caused by consumption of products from cattle affected by mad cow disease, and is not related to classic CJD.
Normal pressure hydrocephalus
As with other manifestations of hydrocephalus, this dementia is caused by the buildup of fluid in the brain. Symptoms include difficulty walking, memory loss, and inability to control urination. The condition can sometimes be corrected with surgical installation of a shunt in the brain to drain excess fluid.
Alzheimer’s disease (AD) is the most common and most studied cause of dementia. Significant advances have been made since the first set of clinical criteria for AD were put forth in 1984 that are now captured in the new criteria for AD published in 2011. Key features in the updated criteria include recognition of a broad AD spectrum (from preclinical to mild cognitive impairment to AD dementia) and requirement of AD biomarkers for diagnosis. Correctly diagnosing dementia type is increasingly important in an era when potential disease-modifying agents are already or are soon to be marketed. The typical AD dementia syndrome has, at its core, an amnestic syndrome of the hippocampal type, followed by associated deficits in word-finding, spatial cognition, executive functions, and neuropsychiatric changes. Atypical presentations of AD have also been identified that are presumed to have a different disease course. It can be difficult to distinguish between the various dementia syndromes given the overlap in many common clinical features across the dementias. The clinical difficulty in diagnosis may reflect the underlying pathology, as AD often co-occurs with other pathologies at autopsy, such as cerebrovascular disease or Lewy bodies. Neuropsychological evaluation has provided clinicians and researchers with profiles of cognitive strengths and weaknesses that help to define the dementias. There is yet no single behavioral marker that can reliably distinguish AD from the other dementias. The combined investigation of cognitive and neurobehavioral symptoms coupled with imaging markers could provide a more accurate approach in the future for differentiating between AD and other major dementia syndromes.