Horizontal nystagmus: vestibular neuritis or lateral canal BPPV?
Reviewed by Victor Osei-Lah

A horizontal nystagmus due to lateral canal (LSC) BPPV that is present in the upright position, that changes direction with head turn in the horizontal plane has been termed ‘pseudo-spontaneous nystagmus’ (PSN) because it mimics that of vestibular neuritis. The key features of PSN seen during the head pitch test (HPT) are defined as, “The PSN beats toward the healthy side in geotropic LSC BPPV and toward the affected side in apogeotropic LSC BPPV. It increases with the head bent 30◦ backward, disappearing when the head is bent 30◦ forward (neutral position), and reverses its direction when the head is additionally inclined forward to 60◦”. The aim of the study was to determine the incidence of LSC BPPV in 273 patients diagnosed with vestibular neuritis at the emergency department. The HPT was positive in 56 patients (37 geotropic and 19 apogeotropic). Further positioning tests, seated supine position and head roll while supine tests, confirmed the diagnosis of LSC BPPV in all 56 patients. What is more, all responded to appropriate particle repositioning manoeuvres! It is interesting how a simple test such as the HPT can confirm LSC BPPV, timely effective treatment and the avoidance of expensive investigations and hospital admission. 

Lateral canal BPPV with pseudo-spontaneous nystagmus masquerading as vestibular neuritis in acute vertigo: a series of 273 cases.
Asprella-Libonati G.
JOURNAL OF VESTIBULAR RESEARCH
2014; 24:342-349.