Diagnosis, Pathology, and Treatment of bvFTD Pose Challenges

HILTON HEAD, SC—Behavioral variant frontotemporal dementia (bvFTD), a clinically and pathologically heterogenous condition, can be difficult to distinguish from other forms of dementia or frontotemporal disease. “Although clinical symptoms vary based on which part of the brain is affected, there is a significant amount of overlap, with different pathologies causing the same type of syndrome,” said Richard Ryan Darby, MD, Assistant Professor of Neurology at Vanderbilt University Medical School in Nashville. “In a large proportion of patients, behavioral changes can lead to criminal behavior.” Future research examining brain lesion networks may shed light on this condition, said Dr. Darby at the 41st Annual Contemporary Clinical Neurology Symposium.

Ryan Darby, MD

Clinical Features and Diagnosis

The incidence of bvFTD is equal to that of Alzheimer’s disease. However, patients with bvFTD tend to be younger: between the ages of 45 and 65. “Social and behavioral features predominate,” said Dr. Darby. “If a patient in this age range with no previous psychiatric history presents to you with a new psychiatric diagnosis such as schizophrenia or bipolar disease, this should raise your suspicion of bvFTD.” These psychiatric problems often cause considerable disruptions in patients’ lives. They often have problems at work and lose their source of income. “Patients often have no insight about their symptoms,” said Dr. Darby.

A differential diagnosis of bvFTD is possible in patients with three or more of the following six clinical features: socially inappropriate behavior (eg, eating from the trash or walking around naked at inappropriate times); lack of empathy; apathy; stereotyped or repetitive behavior (eg, saying things repeatedly, pacing); hyperorality (eg, eating uncontrollably, particularly sweet foods); and executive dysfunction, especially when memory is preserved.

“When you talk to caregivers, they often say, ‘This is not the person I married,’ or, ‘This is not my father. He seems like a different person,’” said Dr. Darby. An MRI or a PET scan showing changes in the frontotemporal lobes is a firm basis for a diagnosis of bvFTD, said Dr. Darby. Genetic testing for autosomal dominant mutation or pathology or an autopsy provides a definite diagnosis.

Pathology

Between 40% and 50% of patients with bvFTD have tau pathology, said Dr. Darby. This pathology includes the classic Pick body form of tau, tufted astrocytes (which are associated with clinical symptoms of progressive supranuclear palsy), and astrocytic plaques (which are associated with symptoms of corticobasal degeneration). Similarly, between 40% and 50% of patients with bvFTD have a TAR DNA-binding protein 43 (TDP-43) pathology. TDP-43 Type A pathology is associated with perirolandic seizures, Type B is associated with amyotrophic lateral sclerosis (ALS), and Type C is associated with semantic dementia. Between 5% and 10% of patients with bvFTD have fused-in sarcoma pathology, which is associated with ALS.

Mutations in C9orf72 occur in 13% to 50% of patients with bvFTD who have genetic mutations. ALS and parkinsonism are common clinical presentations in patients with this genetic mutation. MAPT and GRN mutations are present in 5% to 20% of cases, and each can present clinically as parkinsonism.