Routine clinical features may aid BVFTD diagnostic accuracy

By Eleanor McDermid, Senior medwireNews Reporter

Researchers have identified clinical features that can help determine which patients assessed for behavioural variant frontotemporal dementia (BVFTD) are most likely to actually have the condition.

Emma Devenney (Neuroscience Research Australia, Sydney, New South Wales) and team found a family history of neurological disorders and the results of cognitive testing to be most informative.

“Our results indicate that the likelihood of progression may be determined during a routine neurologic consultation by means of a detailed clinical interview and examination and a brief test of global cognition”, they write in JAMA Neurology.

Of the 58 patients studied, 38 initially satisfied criteria for probable BVFTD. Two of these patients proved to have Alzheimer’s disease pathology at autopsy, but the other 36 either converted to definite BVFTD or continued to satisfy the criteria for probable BVFTD, “suggesting that a probable BVFTD diagnosis in the clinic is accurate”, according to the team.

The other 20 patients were categorised as having possible BVFTD, failing to meet probable status because they had no abnormalities on brain imaging. During an average follow-up of 3.1 years, these patients divided into 11 who changed their status to probable or definite BVFTD and nine who remained in the possible category.

Eight of the patients who changed category did so because genetic testing identified the C9orf72 expansion, and another three developed brain atrophy.

All but one of the patients with the C9orf72 expansion had a family history of neurodegenerative disorders or psychiatric disease. Conversely, none of the patients who remained in the possible BVFTD category had a family history of neurological disorders.

The team therefore suggests that family medical history “may guide clinicians to appropriately identify patients for referral to genetic services.”

Another “striking” difference between patients who did and did not change category was their episodic memory. Despite “relative sparing of episodic memory” being stipulated in current diagnostic criteria for BVFTD, patients who changed from possible to probable BVFTD had significantly poorer baseline performance for visual, verbal and recognition memory than those who remained in the possible category.

“Contrary to current recommendations, this study and numerous others have found that memory deficits in BVFTD are often present and constitute an important component of the phenotype”, say the researchers.

“Given that pathology-based pharmaceutical treatments are on the horizon, the differentiation of FTLD from the pathological features of Alzheimer disease seems to be imperative.”

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