Unilateral loss of peripheral vestibular function in patients: degree of compensation and factors causing decompensation

Vestibular Decompensation Following COVID-19 Infection in a Person With Compensated Unilateral Vestibular Loss: A Rehabilitation Case Study

BACKGROUND AND PURPOSE

Surgical removal of a vestibular schwannoma (vestibular schwannoma resection; VSR) results in a unilateral vestibular hypofunction with complaints of dizziness and imbalance. Although the anatomic lesion is permanent, recovery of balance and diminution of dizziness occurs through central neurophysiologic compensation. Compensation of the system is maintained through daily activity. Unfortunately, interruption of stimulus, such as decreased activities due to illness, can cause decompensation. Decompensation is described as the return of symptoms consistent with that experienced during the initial insult/injury (eg, dizziness, oscillopsia, balance difficulty). This case study describes a reoccurrence of vestibular dysfunction in a person with a history of VSR following hospitalization and protracted recovery from a COVID-19 infection. It further documents her recovery that may be a result of vestibular rehabilitation.

CASE DESCRIPTION

A 49-year-old woman (M.W.) with a surgical history of VSR (10 years prior) and a medical history of significant COVID-19 infection, resulting in an intensive care unit stay and prolonged use of supplemental oxygen, presented to physical therapy with persistent dizziness and imbalance. The video head impulse test confirmed unilateral vestibular hypofunction.

INTERVENTION

M.W. attended biweekly vestibular rehabilitation for 6 weeks and completed daily home exercises.

OUTCOMES

At discharge, M.W. demonstrated improvements in patient-reported outcomes (Dizziness Handicap Inventory), functional testing (MiniBEST, 2-Minute Walk Test), and gaze stability measures (video head impulse testing, dynamic visual acuity).

DISCUSSION

Vestibular decompensation preluded by a COVID-19 infection caused a significant decrease in functional mobility. Vestibular rehabilitation targeted at gaze and postural stability effectively reduced symptoms and facilitated recovery to M.W.'s pre-COVID-19 level of function. Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A458 ).

Factors affecting the outcome of vestibular rehabilitation in patients with peripheral vestibular disorders

OBJECTIVE

Previous studies have reported that developmental, environmental, medical, psychological, visual, and other sensory-related factors can influence the outcome of vestibular rehabilitation. However, only a few studies have used patient's daily lives as the main outcome. In addition, in some studies, rehabilitation was not supervised by a physical therapist. This study aimed to determine the factors associated with the outcome of physical-therapist-supervised vestibular rehabilitation in patients with peripheral vestibular disorders, with the impact of dizziness on quality of life as the main outcome.

METHODS

This retrospective cohort study included 47 patients with peripheral vestibular disorders. A physical therapist provided 40 min of vestibular rehabilitation once a week for 4 weeks. Age, sex, disease duration, Dizziness Handicap Inventory (DHI), Timed Up-and-Go test (TUG), Dynamic Gait Index (DGI), Functional Gait Assessment (FGA), Activity-Specific Balance Confidence Scale (ABC scale), and Hospital Anxiety and Depression Scale (HADS) were investigated. Multiple regression analysis was performed, with the DHI rate of change before and after the intervention as the objective variable.

RESULTS

Vestibular rehabilitation improved all outcomes. In the multiple regression analysis, the ABC scale was identified as a factor that significantly influenced the DHI rate of change (β = -0.428, p < 0.01).

CONCLUSION

A higher ABC scale score was associated with a lower DHI rate of change (i.e., better improvement). Therefore, it may be important to assess psychological aspects, especially confidence in balance, when implementing vestibular rehabilitation in patients with peripheral vestibular disorders.

Decompensated labyrinthine weakness presenting as de novo peripheral vertigo: a discrete clinical entity?

OBJECTIVE

A distinct subgroup of patients, presenting with apparently spontaneous onset of vertigo, is described.

RESULTS

Although vestibular evaluation revealed caloric weakness, the proximate cause of vertigo was not labyrinthine dysfunction, but rather the loss of vestibular compensation for an older and previously compensated labyrinthine injury.

CONCLUSION

Instead of addressing the vestibular weakness, effective management needs to focus on the condition that has caused the loss of compensation.

Vestibular neuronitis in pilots: follow-up results and implications for flight safety

OBJECTIVES To report our experience over the past 12 years with the evaluation and follow-up of pilots with vestibular neuronitis and to discuss points relevant to flight safety and the resumption of flying duties. STUDY DESIGN A retrospective, consecutive case series.METHODS Eighteen military pilots with vestibular neuronitis were examined and followed up. A complete otoneurological workup was performed, including both physical examination and laboratory evaluation. The latter included electro-oculography (EOG) and a rotatory chair test using the smooth harmonic acceleration protocol. RESULTS The mean patient age was 35 +/- 6 years (range, 23 to 42 y), and the average follow-up period was 20.5 +/- 12.8 months (mean +/- standard deviation [SD]; (range, 11 to 48 mo). Electro-oculography caloric test on presentation documented significant unilateral hypofunction in all patients. Thirteen of the 18 patients (72%) had abnormal smooth harmonic acceleration test results. None of the pilots reported any symptoms on follow-up. However, five (28%) had positive otoneurological examination findings, and eight (44%) still had significant caloric lateralization (>25%). The average caloric hypofunction was reduced from 67.8% +/- 29.3% at onset to 40% +/- 16% (mean +/- SD, <.05, paired test). Seven of the patients (39%) had additional electro-oculography findings beyond caloric hypofunction. These included spontaneous, positional, and positioning nystagmus. Smooth harmonic acceleration disease on follow-up was documented in eight patients (44%), five of whom had canal paresis. Eleven patients (61%) demonstrated residual vestibular damage on follow-up. In 6 of these 11 cases (55%), the laboratory evaluation revealed vestibular deficits otherwise undiagnosed by the bedside test battery. CONCLUSIONS The vestibular system plays a central role in orientation awareness and is often challenged by flying conditions. The finding that approximately 60% of pilots who have had vestibular neuronitis continue to show signs of vestibular malfunction, despite apparent clinical recovery, emphasizes the need for a complete vestibular evaluation, including specific bedside testing and laboratory examinations, before flying duties can be resumed.

Head shaking nystagmus in the follow-up of patients with vestibular diseases

We examined 420 patients with vestibular diseases of different origin; 273 with peripheral vestibular disease and 147 with both peripheral and central vestibular disease. Recurrent vestibulopathy like Menière's disease, or benign paroxysmal positional vertigo, were not included. Patients were evaluated initially and 6 months after pharmacological and/or rehabilitation therapy. At the initial assessment, the head-shaking test was specific for the side of the lesion in both groups, even if spontaneous nystagmus was no longer present. Thus, head-shaking nystagmus is a physical sign that can be easily evoked and gives useful information about the presence of vestibulo-ocular reflex asymmetry. At the follow-up at 6 months, many changes in the head-shaking nystagmus were noted: in some cases it appeared, in some others it changed direction and more often it disappeared. There is actually no acceptable explanation for the disappearance of the head-shaking nystagmus, despite some evidence that vestibular compensation could play a role. It is definitely proved that sensitivity of the head-shaking test is really poor, especially in the course of time and, therefore, it should not be used alone in the follow-up of patients with vestibular disease.

Deficits and recovery of head and trunk orientation and stabilization after unilateral vestibular loss

The aim of the study was to analyse changes in the orientation and stabilization of the head and trunk and their recovery after complete unilateral loss of vestibular information in humans. The ability of nine Ménière's patients to orient and stabilize their heads and trunks in space was investigated during a simple dynamic task of knee-bends and compared with the performance of 10 healthy subjects. Patients' performance was recorded before unilateral vestibular neurotomy (UVN) and during the time-course of recovery (1 week, 1 month, 3 months). Experiments were performed both in eyes open (EO) and eyes closed (EC) conditions to evaluate the role of visual cues in the recovery process. Head and trunk mean angular position (orientation) and mean maximal angular rotation (stabilization) in the roll plane and the yaw plane were recorded using a video motion analysis system. The results indicate that, in the acute stage after UVN (1 week), patients exhibit marked impairments in head and trunk orientation in both visual conditions. In the EC condition, head and trunk were deviated towards the operated side in the roll plane and the yaw plane. Head and trunk stabilization in space was impaired in the roll plane and associated with increased stabilization of the head on the shoulders. Interestingly, vision caused a complete inversion of the orientation pattern, with head and trunk rotations towards the intact side in the roll plane and the yaw plane. Relative to darkness, vision also reduced head and trunk oscillations. Recovery from abnormal head orientation in the light and impaired head stability in both visual conditions was achieved within 1 month and 3 months after UVN, respectively. However, head and trunk orientation in the dark and trunk stabilization in the roll plane remained uncompensated 3 months post-lesion. These results suggest that unilateral vestibular loss leads to a postural syndrome similar to that described previously for various animal species. They confirm the necessity of vestibular inputs for properly stabilizing head and trunk during self-generated displacements in healthy subjects. They also support the notion that vestibular compensation relies on visual cues whose substitution role gradually decreases after UVN.

Head-shaking nystagmus (HSN): the theoretical explanation and the experimental proof

Head-shaking nystagmus (HSN) is induced by oscillating the head at high frequency in the horizontal plane. This test is used in the clinic to detect the presence of a unilateral loss of vestibular function. HSN has been described as monophasic with fast-phase direction towards either side, or biphasic with the direction of fast phases reversing after a few seconds. Loss of vestibular function amplifies existing non-linearities in the vestibular system, so that imposed sinusoids can induce biases which are the source of HSN. Fifty-one patients suffering from loss of peripheral vestibular function (43 partial, 11 total unilateral tests) were exposed to whole-body sinusoidal stimulation, with increasing head velocities (90-220 degrees/s) at 1/6Hz, to explore the consistency of per-rotatory induced biases. A bias was induced in all cases, but it wandered on either side, healthy or pathologic, unless test head velocities were larger than approximately 180 degrees/s. Given this condition, the slow-phase bias was located towards the pathologic side for all patients with significant bias ( > 5 degrees/s). These observations demonstrate that the sign and amplitude of the bias is variable and is not correlated with the lesioned side, unless high head velocities are imposed. This explains why the direction of the initial phase of HSN in the clinic seems so labile. Subsequent monophasic or biphasic characteristics of HSN are simply the reflection of interactions between two main time constants associated with "velocity storage" and "gaze holding" in the vestibular central processes.

An approach to imaging the dizzy patient

Disease of the vestibular system involves a lengthy differential diagnosis, from the relatively trivial to potentially life-threatening conditions. As a definitive specific diagnosis is often difficult to make, imaging may be used simply to "rule out" serious pathology. In this context, suboptimal imaging choices may be unnecessarily expensive and may fail to document the pathology. In contrast, an orderly investigation includes appropriate audiometric and vestibular tests, which when reviewed in the clinical context, indicate the most pertinent imaging modalities. This enables the clinician to plan a cost-effective, definitive imaging strategy. This review considers the role of imaging in an integrated approach to investigating the dizzy patient. A discussion of vestibular pathology is presented to assist in the review, and several cases are provided as examples.

Cochleosacculotomy for the treatment of Menière's disease in the elderly patient

Cochleosacculotomy is a surgical option for the treatment of incapacitating vertigo in elderly patients with Menière's disease. This procedure was performed in nine patients (mean age: 73 years) for control of vertigo and/or drop attacks. The average follow-up period was 29 months. Vertigo was controlled in eight of nine patients, but hearing worsened in all but one patient. No patient developed a transient increase in vertigo in the postoperative period. Cochleosacculotomy should be considered in elderly patients with recurrent vertigo and severe non-fluctuating sensorineural hearing loss who would otherwise be candidates for labyrinthectomy.

Vestibulo-ocular reflex (VOR) biases in normal subjects and patients with compensated vestibular loss

The properties of the vestibulo-ocular reflex (VOR) were examined during sinusoidal passive head rotation in the dark at 1/6 Hz, in 9 normal subjects and 14 unilateral vestibular patients. Rotation speeds ranged from 90 to 180 degrees/s. The bias (offset of slow-phase velocity from zero) and gain in the VOR were estimated by using a polynomial (cubic) fit between head and slow-phase eye velocity, thereby allowing for possible non-linearities in the reflex. The gain in the VOR in this context refers to the linear components of the fit, and so predicts sensitivity only at low head velocities. The aim of the study was to verify previous theoretical predictions that VOR bias could vary with the rotation parameters, that this bias could be used to detect the side of a vestibular lesion even at low frequency rotation, and make non-linearities more obvious. Confirming these predictions, the VOR bias in a given test is never equal to any spontaneous nystagmus, even if present before rotation. The range of values for the gain in the VOR (as defined above) in normals and compensated unilateral vestibular patients overlap, so that they cannot be statistically separated into two response sets.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery from unilateral vestibular nerve section in human subjects evaluated by physiological, psychological and questionnaire assessments

Patients undergoing vestibular nerve section for vertigo or acoustic neuroma surgery were compared pre- and post-operatively and during long-term follow-up using a range of tests including: nystagmography, impulsive rotational testing of the vestibulo-ocular reflex (VOR), ability to estimate and reproduce imposed rotational displacements, validated questionnaires rating vertigo, imbalance, autonomic reactivity and somatisation, and clinical and self-assessment scales of overall outcome in terms of symptoms and disability. Correlations were found between rating scale assessments, questionnaire scores and estimates of self-rotation. Neither nystagmography nor VOR tests correlated with the presence or severity of vertigo or imbalance. Post-operatively, vertigo patients reported that they had received significant relief, although they had higher incidences of residual complaints of imbalance and vertigo than patients after acoustic neuroma surgery. Factors impeding rehabilitation in patients with vertigo are discussed.

Vestibulo-ocular compensation following unilateral vestibular deafferentation

Vestibulo-ocular compensation following vestibular deafferentation was investigated in 26 acoustic neuroma patients following tumor removal and in 5 Menière's disease patients following vestibular nerve section by using sinusoidal harmonic acceleration testing. All three test parameters (phase lead, gain, and asymmetry), when averaged, shifted significantly on the first postoperative test (average 0.4 months after operation). A marked progression in central compensation with gain returning to the range of normal control values was seen in the tests performed 1 to 6 months (average 2.6 months) postoperatively. However, phase lead and asymmetry (especially at 0.01, 0.02, 0.04, and 0.08 Hz) remained outside the range of normal control values, and all three parameters failed to return to their preoperative level even when tested at more than 12 months (average 20.2 months) after operation. This finding indicates that the deficits of the vestibulo-ocular reflex to head acceleration are of long duration if not permanent.

Intratympanic gentamycin in severe Ménière's disease

From 1982 to 1987, 20 patients with disabling attacks of vertigo and severe hearing loss due to unilateral Ménière's disease were treated with local intratympanic gentamycin. In 18 patients control of vertiginous attacks was achieved. Hearing deteriorated in 8 patients. In spite of complete control of attacks a disabling ablation type of unsteadiness and dizziness affected 7 patients. Two patients required additional treatment after 5-8 months remission. Intratympanic gentamycin seems to be a less useful method of treating severe unilateral Ménière's disease than previously stated. It is, however, a possible alternative to surgical labyrinthectomy with a fair chance of residual hearing preservation.

Habituation therapy for chronic vestibular dysfunction: preliminary results

Chronic vestibular dysfunction is often a frustrating problem for both patient and physician. A program of customized vestibular habituation therapy is introduced and its efficacy in a group of 65 patients is evaluated. Preliminary findings suggest that 59% of patients will have a dramatic improvement, after which their vestibular symptoms no longer cause any restriction in their lifestyles. An additional 23% of patients note considerable improvement, but have persistent symptoms that continue to restrict their activities. Vestibular habituation therapy is a rational, multidisciplinary approach to the treatment of chronic vestibular dysfunction that is a significant alternative to traditional pharmacologic management. Failure of vestibular compensation after involvement in a disciplined program of habituation therapy constitutes a much stronger indication for vestibular surgery in patients with unilateral peripheral lesions.

Morphologic correlates of vestibular compensation in the cat

Vestibulo-ocular (VO) neurons in the superior vestibular nucleus (SVN) were labeled with horseradish peroxidase (HRP) and studied quantitatively in the electron microscope to determine the morphologic correlates of vestibular compensation. Eighteen cells from four normal cats were compared to 26 cells from four 8-week vestibular neurectomy animals and 29 cells from four 1-year neurectomy animals. There was a greater than 70% decrease in synaptic profiles (SP) on the VO soma in both experimental groups. Increased excitatory activity in the residual SP are indicated by (1) smaller synaptic vesicles (SV) with increasing survival after neurectomy, (2) the association of the SP with a higher ratio of asymmetric to symmetric synapses, and (3) a higher volume fraction of mitochondria in the SP. The experimental VO soma showed a 17% reduction in size (cytoplasm), and a decrease in rough endoplasmic reticulum and polyribosomes. The target cell also showed an increased number of somal spines associated with the remaining SP in the 1-year neurectomy group.