NPH assessment in a cognitive-first service: a retrospective analysis of alternative diagnoses and shunting outcomes

<h3>Introduction</h3> Idiopathic Normal Pressure Hydrocephalus (iNPH) is an underdiagnosed cause of impaired gait, cognition and urinary function in older adults that is often managed by non- neurodegenerative specialists. We present a retrospective analysis of a cognitive-first NPH service including alternative diagnoses, responses to tap-tests and shunting and comparison with US-NPH Shunt Registry data. <h3>Methods</h3> We reviewed all symptomatic NPH referrals to Imperial College NPH and memory clinics between April 2019 and December 2023; each record was analysed for variables including final diagnosis, tap-testing and shunting outcomes. <h3>Results</h3> 42/86 (49%) cases received a non-NPH diagnosis after investigation. 71% of the non-NPH group were given neurodegenerative/vascular diagnoses (36% of all referrals). 85% of probable iNPH patients underwent tap-testing and 49% had a positive response. 75% of responders were referred for shunt-surgery, with 35% of responders receiving a shunt to date (median wait 207.5 days) and 80% of shunted patients demonstrating improvement. <h3>Conclusions</h3> tap-testing (85% vs 74%) and shunt referral rates (38% vs 34%) compared well with the US-NPH Shunt Registry, although lower overall shunt rate (23% vs 34%) was attributed to long wait times. Primary neurodegenerative disorders often present to NPH clinic, highlighting the critical role for cognitive neurologists in this setting.