202 Acta Neurologica Taiwanica Vol 20 No 3 September 2011 From the Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan. Received July 26, 2010. Revised September 7, 2010. Accepted January 20, 2011. Correspondence to: Jen-Jen Su, MD. Department of Neurology, National Taiwan University Hospital, Chung-Shan Southern Road, Taipei 100, Taiwan. E-mail: jjsneuro@yahoo.com.jp Frontotemporal Dementia and Motor Neuron Disease: Report of 3 Cases in Taiwan and Literature Review Kai-Hsiang Chen, Ming-Jang Chiu, Ting-Wen Cheng, Jen-Jen Su Abstract- Purpose: Case reports and a review of literature of the coexistence of motor neuron disease (MND) and frontotemporal dementia (FTD). Case Report: All three patients demonstrated generalized lower motor neuron signs and very few upper motor neuron signs. In the level of patterns of cognitive impairments, neuropsychological studies do not distinguish between patients with onset of weakness from bulbar palsy and patients with onset of weak- ness from limbs. All patients of FTD had their onset of MND or amyotrophic lateral sclerosis symp- toms within a two-year interval which is similar to previous reports. FTD combined with MND may shorten the survival to less than three years shorter than cases with FTD only. Respiratory failure occurred one to two years after onset of the behavioral symptoms in all patients. Conclusion: We reported three patients of FTD with MND to remind clinicians that these two disorders may occur together on the same patient and that these two disorders may belong to one broad spectrum neurodegenerative disease. Key Words: motor neuron disease, amyotrophic lateral sclerosis, frontotemporal dementia, frontotemporal lobar degeneration Acta Neurol Taiwan 2011;20:202-208 INTRODUCTION Motor neuron disease (MND) comprises a group of conditions with progressive motor neuron loss. Clinically, MND produces progressive weakness, mus- cle wasting, fasciculation, spasticity, dysarthria and ven- tilation problem with a survival of 3 to 5 years in 50% of the patients. Amyotrophic lateral sclerosis (ALS) is the most common form of presentation, and is charac- terized by the progressive loss of both upper (UMN) and lower motor neurons (LMN). Other variants include progressive muscular atrophy, primary lateral sclerosis and progressive bulbar palsy (1) . However, a clear patho- physiology of the disease is still not known. Frontotemporal dementia (FTD) is a focal, non- Alzheimer form dementia, characterized by behavioral or language dysfunctions with a high clinical, genetic, and neuropathological heterogeneity (2) . In 1994, the