Is frontal gait a myth in normal pressure hydrocephalus?

Background: Patients with idiopathic normal pressure hydrocephalus (iNPH) are considered to present a magnetic, slow, wide-based gait, also called frontal gait. However, this gait profile is not specific for iNPH and encountered in patients with other neurological conditions mimicking iNPH (i.e. iNPH mimics), such as vascular dementia. We aimed to characterize the gait profiles in iNPH and their mimics and to compare the prevalence of clinical gait abnormalities between both groups. Methods: This retrospective study included 140 patients suspected of iNPH (76.3 +/- 6.8 yo; 30.7% female). Eighty patients (57.1%) were diagnosed with iNPH according to the NPH consensus guidelines criteria; the remaining sixty patients were classified as mimics (23 neurodegenerative conditions, 12 multifactorial conditions, 9 vascular dementia, 7 mixed dementias, 6 toxic conditions, 2 psychiatric conditions, and 1 stroke). Two independent diagnosis-blinded clinicians (kappa, 0.73) evaluated gait according to four categories: frontal gait, parkinsonian gait, other clinical gait abnormalities, and normal gait. Results: iNPH patients and mimics shared similar clinical characteristics. Frontal gait occurred in only 26% of patients (with a similar prevalence for the mimics). Parkinsonian gait was significantly more prevalent among the mimics (32% versus 15%; p-value: 0.032). This association between parkinsonian gait and mimics remained significant after adjusting for age, gender, comorbidities and white matter changes (OR: 2.404; 95% CI: [1.03-5.64]; p value: 0.044). Conclusion: Frontal gait is not the most prevalent gait abnormality in iNPH and does not discriminate iNPH from its mimics. Parkinsonian gait is more prevalent among the mimics.