Caloric and search-coil head-impulse testing in patients after vestibular neuritis

The objective of this study was to compare results of quantitative head-imp ulse testing using search coils with eye-movement responses to caloric irri gation in patients with unilateral vestibular hypofunction after vestibular neuritis. The study population consisted of an acute group (<3 days; N = 1 0; 5 male, 5 female; 26-89 years old) and a chronic group (>2 months; N = 1 4; 8 male, 6 female; 26-78 years old) of patients with unilateral vestibula r hypofunction after vestibular neuritis. The testing battery included: (1) simultaneous measurement of eye and head rotations with search coils in a magnetic coil frame during passive Halmagyi-Curthoys head-impulse testing a nd (2) electronystagmography during bilateral monaural 44 degreesC warm and 30 degreesC-cold caloric irrigation. The main outcome measures were (1) th e gain of the horizontal vestibulo-ocular reflex during search-coil head im pulse testing and (2) the amount of canal paresis during caloric irrigation . All acute and chronic patients had a unilateral gain reduction during sea rch-coil head-impulse testing. A pathological canal paresis factor was pres ent in 100% of the acute patients but in only 64% of the chronic patients. The clinically suspected unilateral vestibular hypofunction resulting from vestibular neuritis was validated in all acute patients by both search-coil head-impulse and caloric testing. Hence, either of these tests is sufficie nt for diagnosis in the acute phase of vestibular neuritis. Chronic patient s, however, were reliably identified only by search-coil head-impulse testi ng, which suggests that the low-frequency function of the labyrinths often becomes symmetrical, leading to a normal canal paresis factor.