Pattern recognition and pathological imaging vital in dementia diagnosis
Good history taking coupled with pattern recognition to identify specific subtypes of dementia, along with prudent use of functional and pathological imaging, are vital in the diagnostic approach for dementia.
“It is very important to take a good history coupled with subtyping using pattern recognition to approach patients suspected of having cognitive impairment. Early-onset dementia also requires detailed family history taking,” said Dr Yat-Fung Shea from the Division of Geriatrics, Queen Mary Hospital (QMH), Hong Kong.
“Patterns that point to specific subtypes of dementia include episodic memory impairment in Alzheimer’s disease [AD]; Parkinsonism, visual hallucinations and autonomic dysfunction in Lewy body dementia; cognitive symptoms after a year of motor features in Parkinson’s disease dementia; gait problems, urinary incontinence and dementia in normal pressure hydrocephalus; and rapidly progressive dementia occurring over weeks to months in Creutzfeldt-Jakob disease [CJD],” explained Shea.
“A detailed family history is also necessary for early-onset dementia. Our group recently identified a novel mutation in a Chinese family with early-onset AD,” added Shea. [Neurobiol Aging 2017;50:168e9-168e11]
Plain CT scans in patients with AD would reveal medial temporal lobe atrophy. MRI will, however, provide better resolution to classify the degree (grade) of AD. [Neurology 2008;71:1986-1992]
Rapid cognitive decline with weakness followed by ataxia would point to CJD and will manifest in MRI as hypointense signals in the basal ganglia. Cerebrospinal fluid (CSF) examination will reveal elevated tau proteins. [J Am Geriatr Soc 2014;62:1609-1610]
“Nowadays, disease-modifying agents can be useful only at a patient’s asymptomatic stage of disease. Hence, we need to rely heavily on the use of CSF or radiologic markers to identify patients in the preclinical stage,” explained Shea.
A study performed between January 2007 and December 2014 at QMH on dementia patients (n=102) who underwent PET scanning with or without 11C-P1B tracer for amyloid plaques showed that the diagnosis was subsequently changed in 36.3 percent of patients, signifying the impact of functional imaging in diagnosis. [Hong Kong Med J 2016;22:327-333]
“Progress in the use of blood biomarkers for amyloid-beta are taking place using methods such as immunoprecipitation coupled with mass spectrometry and peptide fractionation plus super computers and machine learning, as demonstrated in two recent studies which provided good predictive power in the diagnosis of preclinical AD,” said Shea. [Nature 2018;554:249-254; Sci Adv 2019;5:eaau7220]
“Good history taking and the use of blood tests and structural imaging are useful in the diagnosis of dementia. For more difficult cases, functional and molecular imaging must be performed. Hopefully in the future, we will have molecular imaging available for tau proteins, alpha-synuclein and TAR DNA binding proteins. We are also hopeful with the emergence of blood tests for amyloid-beta and, more importantly, disease-modifying treatment for preclinical stages of disease,” Shea concluded.