Muscle ultrasonography for detecting fasciculations in frontotemporal dementia

Ultrasound detection of muscle fasciculations was recently proposed for assessing lower motor neuron (LMN) dysfunction in ALS patients. Given the continuum between ALS and frontotemporal degeneration (FTD), the aim of the present study was to evaluate muscle ultrasound (MUS) in FTD both for feasibility and prevalence of fasciculations. Twenty-two FTD patients were examined (five muscles bilaterally: biceps brachii, first dorsalis interosseous, T10 paraspinalis, vastus lateralis, tibialis anterior) with a 7-MHz linear array transducer and a fasciculation score (FS) computed. Twenty-two matched cognitively-intact control subjects and six ALS patients were also included. Results showed that MUS was feasible, reliable and well tolerated in all subjects. Two FTD/MND patients displayed very high FS values, similar to those in ALS patients. The remaining 20 FTD patients displayed a mean FS value significantly higher than the control group with six patients (30%) having FS values out of the range of controls. Disease progression rate correlated with the FS. In conclusion, MUS can be easily applied to FTD patients and represents a non-invasive technique for defining LMN involvement in these patients. LMN dysfunction is a frequent condition in FTD and might identify a subset of patients with a different clinical course.