Aspiration and silent aspiration in Niemann-Pick disease type C1: longitudinal findings from the NIH natural history study.

BACKGROUND

Niemann-Pick disease type C1 (NPC1) is a rare neurodegenerative disorder in which dysphagia is common and aspiration pneumonia is a leading cause of mortality. Aspiration may be clinically apparent or silent, reflecting impaired airway sensation and protective reflexes. We aimed to characterize aspiration and silent aspiration in the National Institutes of Health (NIH) NPC1 Natural History Study (NCT00344331). We analyzed 130 participants with NPC1 enrolled between 2006 and 2024 who underwent speech-language pathology swallowing evaluations, including clinically indicated videofluoroscopic swallow studies (VFSS). Aspiration risk was rated using the NIH Penetration-Aspiration Scale (NIH-PAS). Silent aspiration was defined as aspiration on VFSS without cough, throat clearing, or wet vocal quality. Longitudinal models examined the presence of silent aspiration alone or (2) a NIH-PAS score > 1 (moderate-profound aspiration) or silent aspiration. Covariates included demographics, neurologic disease onset and duration, body weight/BMI, reflux and seizure medications, miglustat use, NPC Neurological Severity Score (NSS) 5-domain total and subscores (including swallow and respiratory), and the Annualized Severity Increment Score (ASIS).

RESULTS

Silent aspiration occurred in 24/130 (18.4%) participants. Among these, 50% demonstrated recurrent silent aspiration at subsequent visits, and 58.3% exhibited intermittent silent aspiration on follow-up. Considering aspiration risk, 27/130 (20.8%) had NIH-PAS > 1, including all silent aspirators. Silent aspiratiors alone had worse NIH-PAS, higher total NSS with poorer swallow, speech, ambulation, and fine-motor subscores, and higher ASIS. Patients with silent aspiration or NIH-PAS > 1 had an increased aspiration risk with longer neurologic symptom duration, seizure history, higher NSS, higher ASIS, and in children with lower weight percentile. Miglustat use was protective in the overall cohort, but not in the pediatric subgroup (< 20 years-old). Mean time to silent aspiration was ~ 10 years from neurologic symptom onset, with no difference by neurological disease onset.

CONCLUSION

Silent aspiration is common in NPC1 and closely linked to advancing neurologic disease severity than to age-of-onset phenotype. Bedside clinical evaluations may underestimate silent aspiration; proactive longitudinal swallowing surveillance is warranted in individuals with higher NSS/ASIS scores, seizure history, pediatric weight decline, or evolving motor-speech impairment. These findings support incorporating overt and silent aspiration alongside swallowing function, into routine care and therapeutic trials.