1. Eye movements were recorded in four rhesus monkeys, before and after bilateral ablations of the flocculi and portions of the paraflocculi (“flocculectomy”). Animals were trained to fixate and follow targets so that pursuit, saccades, and vestibular and optokinetic nystagmus could be quantitated. 2. The vestibuloocular reflex (VOR) was mildly affected by flocculectomy. In darkness the VOR gain (eye velocity/head velocity) for steps of head velocity (normal range, 0.84-0.96) increased postoperatively in one monkey to 1.17, decreased in another to 0.62, and did not change significantly in the other two (0.96, 0.94). VOR phase lead at 0.05-Hz oscillation in darkness (normal range, O,O--LOO) increased in two monkeys by 12 and 9.5 O but did not change significantly in the others. 3. Visual suppression of inappropriate vestibular nystagmus was impaired. During oscillation at 0.25 Hz with a head-fixed visual scene, the average amount of attenuation of the VOR decreased from 5 1% preoperatively to 20% postoperatively. Visual suppression of caloric nystagmus was comparably affected. 4. Smooth tracking of small targets moving in space was impaired either with the head still (smooth pursuit) or moving (cancellation of the VOR by fixating a target rotating with the head). The average gain (gaze velocity/target velocity) in either case was about 0.65 (normal, 0.95-0.98). The pursuit deficit was less than that reported after total cerebellectomy, suggesting other cerebellar structures also participate in smooth tracking. 5. Optokinetic nystagmus (OKN) was present postoperatively but, in response to a constant-velocity stimulus, the initial slowphase velocity decreased by 50% and the rise time to a steady state nearly doubled. For stimuli belowr 6O”/s the average steady-state gain was only mildly diminished to 0.86 (normal, 0.98) and the time course of optokinetic afternystagmus (OKAN) in darkness was normal. The response to higher velocity optokinetic stimuli was impaired. These abnormalities can largely be attributed to the coexisting pursuit deficit although the protracted rise to a steady state suggests a change in the ability of the brain stem optokinetic system to handle large amounts of retinal slip. 6. Flocculectomized monkeys showed horizontally, gaze-paretic nystagmus with exponentially decaying centripetal drift (time constant, 1.56 s) and vertically, downbeat nystagmus with exponentially decaying (in three monkeys) or exponentially increasing (in one monkey) slow phases. All animals showed rebound nystagmus. These results implicate the flocculus and possibly the paraflocculus in the control of the time constant and stability of the brain stem oculomotor integrators. 7. Saccadic velocities and accuracy were normal but flocculectomized monkeys showed brief (40150 ms duration), approximately exponential, postsaccadic drift with amplitudes up to 15% of the size of the saccade. The eyes usually drifted in the same direction as the saccade but each monkey showed an idiosyncratic pattern depending on saccade direction and eye position. Postsaccadic drift may reflect a mismatch between the phasic (pulse) and tonic (step) innervational changes that create saccades.

Effects of ablation of flocculus and paraflocculus of eye movements in primate

Objectives: To examine the prevalence and incidence, clinical presentation, societal impact and comorbid conditions of benign paroxysmal positional vertigo (BPPV) in the general population. Methods: Cross-sectional, nationally representative neurotological survey of the general adult population in Germany with a two stage sampling design: screening of 4869 participants from the German National Telephone Health Interview Survey 2003 (response rate 52%) for moderate or severe dizziness or vertigo, followed by validated neurotological interviews (n = 1003; response rate 87%). Diagnostic criteria for BPPV were at least five attacks of vestibular vertigo lasting Results: BPPV accounted for 8% of individuals with moderate or severe dizziness/vertigo. The lifetime prevalence of BPPV was 2.4%, the 1 year prevalence was 1.6% and the 1 year incidence was 0.6%. The median duration of an episode was 2 weeks. In 86% of affected individuals, BPPV led to medical consultation, interruption of daily activities or sick leave. In total, only 8% of affected participants received effective treatment. On multivariate analysis, age, migraine, hypertension, hyperlipidaemia and stroke were independently associated with BPPV. Conclusion: BPPV is a common vestibular disorder leading to significant morbidity, psychosocial impact and medical costs.

https://jnnp.bmj.com/content/jnnp/78/7/710.full.pdf

Epidemiology of benign paroxysmal positional vertigo. A population-based study

A CENTRAL PROBLEM in vestibular physiology has been the elucidation of the dynamics of the peripheral vestibular apparatus. Following the development of the torsion-pendulum model by Steinhausen (24, 25), many efforts have been directed toward the determination of the time constants of the model. That the model, itself, might not adequately describe the transfer characteristics of the peripheral system has seldom been questioned. Further, the procedures employed to estimate the time constants have had their drawbacks. The dynamics of the system have sometimes been deduced from hydrodynamic principles (5, 6, 15, 17, 22, 23). Such an analysis permits the inference of only some of the relevant variables. In the torsionpendulum model, it will be recalled, the angular deflection of the cupula g(t) is related to the angular acceleration a(t) by the equation

Physiology of peripheral neurons innervating semicircular canals of the squirrel monkey. II. Response to sinusoidal stimulation and dynamics of peripheral vestibular system.

Objectives: To examine the prevalence and incidence, clinical presentation, societal impact and comorbid conditions of benign paroxysmal positional vertigo (BPPV) in the general population. Methods: Cross-sectional, nationally representative neurotological survey of the general adult population in Germany with a two stage sampling design: screening of 4869 participants from the German National Telephone Health Interview Survey 2003 (response rate 52%) for moderate or severe dizziness or vertigo, followed by validated neurotological interviews (n = 1003; response rate 87%). Diagnostic criteria for BPPV were at least five attacks of vestibular vertigo lasting < 1 min without concomitant neurological symptoms and invariably provoked by typical changes in head position. In a concurrent validation study (n = 61) conducted in two specialised dizziness clinics, BPPV was detected by our telephone interview with a specificity of 92% and a sensitivity of 88% (positive predictive value 88%, negative predictive value 92%). Results: BPPV accounted for 8% of individuals with moderate or severe dizziness/vertigo. The lifetime prevalence of BPPV was 2.4%, the 1 year prevalence was 1.6% and the 1 year incidence was 0.6%. The median duration of an episode was 2 weeks. In 86% of affected individuals, BPPV led to medical consultation, interruption of daily activities or sick leave. In total, only 8% of affected participants received effective treatment. On multivariate analysis, age, migraine, hypertension, hyperlipidaemia and stroke were independently associated with BPPV. Conclusion: BPPV is a common vestibular disorder leading to significant morbidity, psychosocial impact and medical costs.

Epidemiology of benign paroxysmal positional vertigo: a population based study. Editorial Commentary

This is a prospective in-depth study of patients with sudden idiopathic sensorineural hearing loss. We found that 65% recover completely to functional hearing levels spontaneously and independent of any type of medical treatment. The majority do so within 14 days and many within the first few days. Prognosis can be predicted according to the slope of the initial audiogram (low-frequency losses do better than high-frequency losses), hearing at 8 kHz, erythrocyte sedimentation rates, in some select instances spatial disorientation symptoms, and speech discrimination scores. There was a very poor correlation between hearing and vestibular test abnormalities, except hypoactive calories. There were no correlations with age (excepting the very elderly), with antecedent respiratory infections, hypertension, diabetes, or other chronic diseases. We conclude that there is a fundamental difference in the behavior of apical and basal cochlea losses, that hearing recovery is always better at low than at high frequencies, that because of the high spontaneous recovery rates, tympanotomies seeking peri-lymph fistulas should be delayed ten days unless there is a progressive hearing loss, and that none of the current recommended treatments, especially histamine, have any effect on the outcome.

Natural History of Sudden Sensorineural Hearing Loss

Using serially sectioned human temporal bones, the volumes of otoconia masses were compared between young children and elderly people The latter group had significantly less otoconia volume than the former group, both in the macula utriculi and macula sacculi The ratio between macula utriculi and macula sacculi was 100:70 in the young group, whereas it was 100:35 in the elderly group Thus, the macula sacculi in the elderly group showed the severest otoconia reduction

Otoconia in Young and Elderly Persons: A Temporal Bone Study

Pathological studies were performed on eight temporal bones, of which six were from in- dividuals with unilateral sudden deafness and two from one individual with bilateral sequential sudden deafness. The hearing losses were profound in four ears, severe in three ears and moderate in one ear. At the time of onset of the sudden deafness two reported having headcolds, one had acute pharyngitis, two had pneumonia and two complained of headache. Vertigo as an associated symptom was severe in one case and mild in two cases. The principal pathologi- cal changes consisted of atrophy, in varying com- binations and severity, of the organ of Corti, tec- torial membrane and stria vascularis. These patho- logical alterations were judged to be more like those occurring in labyrinthitis of known viral etiology than those following experimentally induced vascular lesions in animals. There are many known causes for deafness of sudden onset. A partial listing would in- clude: bacterial labyrinthitis, viral labyrinthi- tis (mumps, measles), ototoxic drugs, tem- poral bone fracture, inner ear concussion, noise, surgical injury, otitic barotrauma, in- ner ear hemorrhage (leukemia), macroglobu- hernia, occlusion of the posterior inferior cerebellar artery (lateral medullary syn- drome), multiple sclerosis, carcinomatous en- cephalomyelitis, glioma of the pons, metas- tatic neoplasms, vestibular schwannoma, Me- niere's disease and severe cochlear otosclero- sis. These causes for sudden deafness are abundantly documented in the literature. There are also many cases of sudden deaf- ness in which the etiology is not so obvious.

The pathology of sudden deafness.

• Three infants with cerebrospinal fluid otorrhea and recurrent meningitis due to Mondini dysplasia have been treated at Baylor College of Medicine, Houston, Tex; 39 other patients with this association have been described. This review highlights the characteristics and embryologic basis of the malformation. The clinical evaluation of an infant with recurrent meningitis is outlined, and the importance of brain-stem response audiometry and thincut computed tomography of the temporal bones is discussed. Surgical management depends on the functional status of the dysplastic ear; usually, a stapedectomy is performed and the vestibule is obliterated. Although the surgical failure rate is 30% after one procedure, early identification of the dysplasia and prompt surgical management diminish morbidity and mortality and permit early habilitation of the child with congenital hearing impairment. (Arch Otolaryngol Head Neck Surg. 1990;116:608-612)

Recurrent Meningitis and Mondini Dysplasia

Dimensional study of the vestibular apparatus

The maintenance of dynamic equilibrium in the squirrel monkey, measured by squirrel monkey rail test, was investigated after unilateral, bilateral simultaneous, and bilateral non-simultaneous labyr...

Makoto Igarashi

Papers

Otoconia in Young and Elderly Persons: A Temporal Bone Study

The pathology of sudden deafness.

Recurrent Meningitis and Mondini Dysplasia

Dimensional study of the vestibular apparatus

Dynamic equilibrium in squirrel monkeys after unilateral and bilateral labyrinthectomy.