Early Dropped Head Syndrome Is More Prevalent in C9orf72 and FUS/TLS ALS

Dropped head syndrome (DHS) is common in advanced stages of amyotrophic lateral sclerosis (ALS), but infrequently reported among the early symptoms. We explored the frequency of DHS in a genetic ALS cohort harboring pathogenic variants to determine whether DHS is a prognostic factor for survival, particularly when appearing at an early stage.

We collected the following variables to investigate a phenotype/genotype correlation: pathogenic variant (PV), sex, age at clinical ALS onset, time between ALS onset and DHS onset, and between DHS onset and death. DHS appearing within 12 months of clinical onset was classified as early DHS (EDHS); otherwise, as late DHS (LDHS).

We observed DHS in 62 of 93 patients with genetic ALS, with a median of 26.5 months between ALS clinical onset and identification of DHS. DHS was present in 72.1% of the 43 patients with C9orf72 expansions, 52.9% of the 34 with SOD1 , 100% of the 10 with FUS/TLS, and 50% of the 6 with other ALS gene PVs. EDHS appeared in 16 patients. Ten EDHS patients were C9orf72, and six were FUS/TLS . DHS was a significant factor for survival in the age-adjusted Cox regression model. The hazard ratio was 11.63 times higher for patients with DHS, with age as a concomitant variable.

Our results suggest that DHS is more prevalent in patients with C9orf72 and FUS/TLS than in those with SOD1 and other ALS-linked genes, and a risk factor for short survival, especially when appearing within 12 months of ALS onset.