Supplement Table 1. Admission diagnosis of the patients (N=1262) Admission* N % Peripheral vestibular disorder 842 67.5 Acute vestibular neuritis 381 30.1 Benign paroxysmal positional vertigo 202 16.0 Meniere disease** 105 8.3 Other inner ear diseases 35 2.8 Unclassified peripheral vestibular syndrome 119 9.4 Unclassified 242 18.2 Central vestibular disorder 102 8.3 Stroke 44 3.5 Tumor 5 0.4 Head injury 8 0.6 Migraine 5 0.4 Other brain diseases 8 0.6 Unclassified central vestibular disorder 32 2.5 Cardiovascular syndrome 72 5.6 Vertebrogenic syndrome*** 3 0.2 Somatoform syndrome 1 0.1 *The ICD-Codes (ICD-10-GM) behind these diagnosis categories were: R42 (vertigo and dizziness), H81.0 (Meniere disease), H81.1 (benign paroxysmal positional vertigo), H81.2 (acute vestibular neuritis), H81.3 (other types of peripheral vestibular disorders), H81.4 (central vestibular disorder), H81.8 (other vestibular disorders), H81.9 (vestibular disorders, not specified), H82* (vertigo syndromes, otherwise not classified), H83.0 (labyrinthitis), H83.2 (hypofunction of the labyrinth). The descriptions of the codes are translations by the authors as the German modification (GM) was used. The ICD-codes sometimes did not allow a direct allocation to the diagnosis groups. The allocation is explained in Supplement Methods 1. **admission because of acute exacerbation or first episode of Meniere disease ***This category is controversial, but was upheld, as it was used as initial diagnosis in 3 cases. This category was not used for final diagnosis. 1 Supplement Table 2. Symptoms of the patients (N=1262) Symptom N % Onset of vertigo/dizziness episodes 1 day ago 661 52.4 >1 day ago 333 26.4 Weeks ago 113 9.0 Months ago 77 6.1 Years ago 67 5.3 Not documented 11 0.9 Duration of the vertigo/dizziness episodes Seconds 69 5.5 Minutes 135 10.7 Hours 471 37.3 Days 63 5.0 Continuous 275 21.8 Not documented 244 19.3 Character of the vertigo episodes Rotary vertigo 1136 90.0 Non-spinning vertigo 203 16.1 Other symptoms Nausea/vomiting 953 75.5 Hearing loss 196 15.5 Tinnitus 207 16.4 Focal neurological symptoms 48 3.8 Headache 211 16.7 Ataxia/Dysdiadochokinesis 26 2.1 Pathological spontaneous nystagmus Yes 638 50.6 No 624 49.4 Lateralization of the disease* Left side 440 34.9 Right side 449 35.6 Both sides 24 1.9 No lateralization 349 27.7 *An allocation of the affected side was only possible for peripheral vestibular syndrome 1 Supplement Table 3. Further extended diagnostic diagnostic investigations of all patients (N=1262) Investigation* Result N % Vestibular tests Head impulse test normal 163 12.9 pathologic 173 13.7 not performed 926 73.4 Video head impulse test normal 169 13.4 pathologic 116 9.2 not performed 977 77.4 Head impulse test w/o video normal 268 21.2 pathologic 255 20.2 not performed 739 58.6 Caloric test normal 486 38.5 pathologic 536 42.5 not performed 240 19.0 Romberg’s test normal 420 33.3 pathologic 193 15.3 not performed 649 51.4 Unterberger’s test normal 229 18.1 pathologic 221 17.5 not performed 812 64.3 Dix-Hallpike test normal 217 17.2 pathologic 431 34.2 not performed 614 48.7 Posturography normal 6 0.5 pathologic 18 1.4 not performed 1238 98.1 Rotating chair test normal 20 1.6 pathologic 33 2.6 not performed 1209 95.8 Neck rotation test normal 6 0.5 pathologic 29 2.3 not performed 1227 97.2 cVEMP normal 57 4.5 pathologic 62 4.9 not performed 1143 90.6 Glycerol/furosemide test normal 10 0.7 pathologic 15 1.1 not performed 1324 98.2 Hearing tests Pure tone audiometry normal 313 24.8 pathologic 650 51.5 not performed 299 23.7 Tympanometry normal 573 45.4 pathologic 56 4.4 not performed 633 50.2 TEOAE normal 23 1.8 1 pathologic 22 1.7 not performed 1217 96.4 BERA normal 82 6.5 pathologic 14 1.1 not performed 1166 92.4 Imaging cCT normal 444 35.2 pathologic 32 2.5 not performed 786 62.3 cMRI normal 521 41.3 pathologic 61 4.8 not performed 680 53.9 Color duplex sonography normal 247 19.6 pathologic 48 3.8 not performed 967 76.6 Other imaging (X-ray) normal 11 0.9 pathologic 38 3.0 not performed 1213 96.1 Other investigations Serology normal 514 40.7 pathologic 118 9.4 not performed 629 49.8 CSF test normal 46 3.6 pathologic 6 0.5 not performed 1210 95.9 Mean±SD Median, range Number of all instrumental investigations per 9.8±6.6 9, 0-50 inpatient stay Number of vestibular investigations per inpatient 5.2±3.7 5, 0-34 stay cCT = cranial computed tomography; CSF =cerebrospinal fluid; cMRI = cranial magnetic resonance imaging; cVEMP = cervical vestibular-evoked myogenic potentials; TEOAE = transient evoked otoacoustic emissions; BERA = brainstem evoked response audiometry. *Definition of pathologic values for the different vestibular test and the hearing tests: Vestibular tests Definition of a pathologic test result Formatted Table Head impulse test The head impulse test had to be performed at least two times in each direction. The bed side head impulse test was abnormal if a re-fixation saccade Formatted: English (U.S.) was detected by visual inspection. Video head impulse test The software algorithm had to capture and process at Formatted: English (U.S.) least 7 correctly done head impulses in each Formatted: English (U.S.) direction; A pathologic results was defined as a Formatted: English (U.S.) 2 vestibulo-ocular reflex (VOR) gain <0.7. Formatted: English (U.S.) Caloric test Each ear had to be irrigated alternately with a Formatted: English (U.S.) constant flow warm and cold water and for a constant Formatted: English (U.S.) period of time (60 sec). The maximum slow-phase Formatted: English (U.S.) velocity (SPV) of nystagmus was calculated following Formatted: English (U.S.) each irrigation, and Jongkees's formula was used to Formatted: English (U.S.) determine canal paresis (CP). It was considered abnormal if CP was ≥25%. Formatted: English (U.S.) Romberg’s test A significant increase of swaying or loss of balance when the patient had to close the eyes was defined as pathologic. Unterberger’s test A deviation of >45 degrees in rotation to one side Formatted: English (U.S.) during the step test was defined as pathologic. Dix-Hallpike test A positive maneuver was diagnostic for benign Formatted: English (U.S.) position vertigo, Characteristics of classical Formatted: English (U.S.) positioning nystagmus included geotropic torsional Formatted: English (U.S.) direction, brief latency (5 to 20 seconds), decline with repeated positioning, 30 seconds or less duration, and reversal upon arising. Atypical positioning nystagmus was a sign for either peripheral or central Formatted: English (U.S.) disease. Posturography Only computerized dynamic posturography with the Formatted: English (U.S.) Equitest® system using the sensory organization test (SOT) was analyzed. The SOT is automatically showing pathologies if the test results exceed the normal reference values. Rotating chair test Primarily, the horizontal canal vestibulo-ocular reflex Formatted: Don't adjust space between Latin (VOR) was analyzed. The sinusoidal harmonic and Asian text, Don't adjust space between Asian text and numbers acceleration (SHA) test was used. A reduced VOR Formatted: English (U.S.) gain, a phase shift, or an asymmetric response was pathologic. In some patients also the step test was Formatted: English (U.S.) used. Again, a reduced VOR gain, a phase shift, or Formatted: Font: 12 pt, Not Bold, Font color: Auto, English (U.S.) an asymmetric response was pathologic. Neck rotation test A directional nystagm during neck rotation was defined as pathologic. cVEMP No cVEMP during repeated measurement was pathologic. Glycerol/furosemide test An improvement of the PTA at three frequencies by 25 dB was a defined as a positive sign for Meniere disease. Hearing tests Pure tone audiometry (PTA) The PTA for air conduction thresholds at 500, 1000 and Formatted: English (U.S.) 2000 Hz was analyzed. A thresholf >25 dB was pathologic. Tympanometry A reduced height of the peak or a flat tympanogram was pathologic. TEOAE Absence of TEOAE was pathologic. BERA Absence of the brainstem response, prolonged waves I - V interaural latency differences, or an absolute Formatted: Font: Not Bold, English (U.S.) prolonged latency of wave V were pathologic Formatted: Font: Not Bold, English (U.S.) 3 Supplement Table 4. Overview of the therapy of the patients (N=1262) Therapy N % Drug treatment Yes 1166 86.4 No 183 13.6 Prednisolone, intravenous or oral 746 55.3 Antivertiginous drugs 910 67.5 Vestibular suppressant 776 57.5 Antiemetic drugs 127 9.4 Rheological/nootropic drugs 172 12.8 Acyclovir 49 3.6 Doxycycline 24 1.8 Dexamethasone, intratympanic 18 1.3 Gentamicin, intratympanic 6 0.4 Lidocaine, transtympanic 2 0.1 Repositioning procedures (Semont, Epley) 312 23.1 Physical therapy 1019 75.5 Tympanoscopy 11 0.8 Mean±SD Median, range Prednisolone therapy duration, days 8±4 10, 1-27 1 Supplement Table 5. Final diagnosis of the patients (N=1262) Admission* N % Peripheral vestibular disorder 940 74.5 Acute vestibular neuritis 358 28.4 Benign paroxysmal positional vertigo 272 21.6 Meniere disease 117 9.3 Other inner ear diseases 32 2.5 Unclassified peripheral vestibular syndrome 161 12.8 Unclassified 160 12.7 Central vestibular disorder 115 9.1 Stroke 20 1.6 Tumor 8 0.6 Head injury 7 0.6 Migraine 10 0.8 Unclassified central vestibular disorder 70 5.6 Cardiovascular syndrome 39 3.1 Somatoform syndrome 8 0.6 *for the related ICD-Codes, see Supplement Table 1.