[Language impairment in amyotrophic lateral sclerosis]

For a long time, amyotrophic lateral sclerosis (ALS) was thought to be a neuro-degenerative disease with selective involvement of the motor neuron system. However, it has recently been established that ALS is a multisystem disorder that not only involve the motor system but also affects cognition. A typical cognitive impairment in ALS is frontotemporal dementia: a clinical subtype of frontotemporal lobar degeneration (FTLD). Furthermore, language impairment, including progressive non-fluent aphasia (PA) and semantic dementia (SD), which are also FTLD subtypes, have been linked to bulbar-onset ALS. Beside recent studies a Japanese paper published in 1893 gives an account of aphasia in bulbar-onset ALS. Interestingly, this was the first account of aphasia in Japan. Thus, language-related problems in ALS may have been overlooked, because evaluation of aphasic problems in ALS patients is difficult, mainly because of progressive bulbar or pseudo-bulbar palsy that results in and dysarthria. From a clinical point of view, progressing bulbar symptoms and medical interventions, such artificial ventilation make it difficult to evaluate language functions in ALS. However, we do observe frequent omission and paragraphia of kana letters, and syntactic errors in writing. Interestingly, some patients make exhibit errors exclusively in the case of kanji characters. Thus, evaluation of writing samples is important if order to identify language problems in ALS patients. The findings may also provide additional information such as dissociation between errors made in kana and kanji characters. The characteristic features of writing errors are thought to reflect the nature of aphasia including PA and SD, that are easily masked by dysarthria. In addition, writing errors can appear as "isolated agraphia" without aphasia and dementia. Pathologically, writing errors should indicate the brain regions involved by ALS, e.g., hemispheric dominance and frontal or temporal lobe involvement. In addition, selective involvement of Exner's writing center in the frontal lobe may be responsible for "isolated agraphia". Hence, further studies are required to determine the clinical significance of writing errors in ALS patients and their pathological correlation.