The proband was a 54-year-old French male patient with a personal history of dyslipidaemia and tuberculosis in childhood. From the age of 41 years, he slowly developed progressive weakness and atrophy of proximal upper-limb muscles and later (at 46 years of age) involvement of the lower limbs, associated with axial weakness. At that time, the walking test was unlimited, whereas at 50 years of age, he was only able to walk 50 m using a cane for support.
Then, the proband developed acute behavioural changes including irritability, severe anxiety and major depression, which led to him being hospitalised in a psychiatric hospital at 53 years of age. He developed gradual cognitive decline characterised by impairment of executive functions. The deterioration of upper- and lower-limb weakness and cognitive functions accelerated. The patient was eventually unable to walk and was confined to a wheelchair. His cognitive dysfunctions consisted of impaired frontal lobe functions, dominated by major behavioural changes (such as changes in affects, decline in social interpersonal conduct and perseveration) and aphasia (phonemic and semantic paraphasia). His score on the Frontotemporal Behavioural Scale was abnormal (3 items out of 4 were pathological). However, his memory was not impaired: the Mini-Mental State Examination (MMSE) was normal (29 out of 30 points).
An electromyography (EMG) (fig. 1) showed fibrillation potentials and positive sharp waves at rest, and myopathic or neurogenic features according to the muscles examined: polyphasic small-amplitude short-duration motor unit potentials and polyphasic long-duration with slow-frequency motor unit potentials were found together in the EMG study. These results suggested inclusion body myopathy, which was confirmed by a muscle biopsy revealing histopathological changes consisting of rimmed vacuoles. Plasma creatine kinase levels were mildly increased (262 IU/l, normal values 20-220 IU/l). Nerve conduction studies were normal.
Cerebral magnetic resonance imaging (MRI) was performed at 54 years of age and revealed frontal and internal temporal atrophy (fig. 2). Fluorodeoxyglucose (FDG) positron emission tomography (PET) scan showed severe bilateral hypometabolism, involving especially the frontal and temporal lobes (fig. 3). The occipital lobe, basal ganglia and cerebellar metabolism were normal. Behavioural-type frontotemporal dementia was therefore diagnosed based on the clinical frontal lobe dysfunction and the results of the cerebral MRI and PET scan.