Landers, Merrill DPT, OCS; Adams, Melissa DPT, ATC, CSCS; Acosta, Keri DPT; Fox, Andrew DPT
Olivopontocerebellar atrophy (OPCA) is a rare neurodegenerative disease of unknown cause that has received little attention in the physical therapy literature. It belongs to a rare group of degenerative cerebellar ataxias that are characterized by a selective loss of cells in the pontine nuclei, the inferior olivary nuclei, and the cerebellum.1–4 OPCA exists in two basic forms, inherited and sporadic. This is a report of a single case of the latter form.
Currently, the nosologic characterization of sporadic OPCA, also known as Dejerine-Thomas syndrome, is not well understood because there seems to be some overlap with idiopathic late-onset cerebellar ataxia and cerebellar predominant multiple-system atrophy.5 Some consider sporadic OPCA as a subgroup of multiple-system atrophy.1,6,7 However, Berciano et al5 in a review article on the subject suggest that the assumption that multiple-system atrophy and sporadic OPCA are the same disease is no longer tenable. Thus, they appear to be separate and distinct pathologies. Additionally, the confused nosology is compounded by the fact that OPCA is the usual pathologic substrate of a few spinocerebellar atrophy subtypes,5 which are sometimes referred to synonymously. Not surprisingly, some of this confusion has made the diagnosis of individuals with sporadic OPCA a difficult process. In addition, the clinical presentation is often complicated by several different clinical pictures, which suggests that OPCA represents an overarching diagnosis of many separate, as yet undefined, disease processes. However, based on current knowledge, the clinical presentation is usually idiopathic cerebellar ataxia and dysarthria with or without parkinsonism, autonomic disturbances, and/or ophthalmoplegia.8 This clinical presentation coupled with atrophy of the characteristic structures (ie, pons, inferior olivary nuclei, and cerebellum) using diagnostic imaging is consistent with the diagnosis.
Progressive cerebellar ataxia, usually gait ataxia and dysarthria, is the typical early presentation of sporadic OPCA.9–11 This gait ataxia is often characterized by veering from midline, wide-based stance, and sudden unexpected falls in the absence of any paralysis or weakness.12 It progresses such that the individual is often confined to a bed, chair, or wheelchair within a few years.12 Tiredness, especially of the legs, is also a common early symptom.2 These signs are followed later by severe disturbances in coordination of the upper extremities.13,14 The individual progressively loses fine motor skills and often develops an intention tremor.12 Like gait, speech is ataxic and is a constant symptom of the disease, beginning early and progressing to a point where the speech may become unintelligible.2 This ataxic dysarthria has been described as typical cerebellar speech (scanning), drunken, bulbar or pseudobulbar, slow and monotonous, or as a mixture.2,12
The involvement of other systems varies widely from individual to individual14; however, cerebellar disturbances predominate throughout the course of the disease.2 Extrapyramidal symptomatology, such as parkinsonian symptoms, can also occur in combination with the cerebellar symptoms, oftentimes lessening or masking it.2 Pyramidal signs are not only less common but are also known to occur. Dementia is relatively common (11.1%) and can occur in any phase of the disease process; however, it usually occurs in the middle to late stages.2 Autonomic dysfunction, usually in the form of urinary incontinence, is also a prominent feature in some individuals.12 Other symptoms that may be present include postural hypotension, oculomotor disturbances (eg, gaze-evoked nystagmus, saccade dysmetria, prolonged saccade reaction times, and slow saccades),15 ophthalmoplegia, and dysphagia.
Because the cause of sporadic OPCA is unknown, management has focused on problematic symptoms. Because there are very few published data regarding physical therapy for individuals with OPCA, most therapists rely on rehabilitation strategies from related pathologies. For instance, Gill-Body et al16 demonstrated modest improvements in the gait of two individuals with cerebellar dysfunction by challenging balance in different positions and training eye-head coordination to improve gaze stabilization. A balance and coordination training program was also found to be effective in individuals with posterior fossa and cerebellopontine angle tumors.17 Additionally, treadmill training with18 and without19 body-weight support has been shown to be effective in improving ambulatory parameters in cases of individuals with cerebellar ataxia. Taken together, these studies, from cerebellum-related pathologies with similar symptomatology, offer supporting evidence of similar gains in OPCA.
One relatively novel approach to the conservative management of the individual with neurologic involvement, like cerebellar pathology, is the principle of challenge-oriented gait and balance training. This approach, which is based on motor-learning principles, has been shown to drive neuroplasticity in rodent models of cerebellar pathology.20–25 These researchers have found that complex motor skill learning or acquisition, in contrast to simple repetitive motor tasks, was associated with structural plasticity in the cerebellum.21,22,24,26 Additionally, because there is considerable evidence that the cerebellum plays a critical role in practice-dependent motor learning, a high frequency and long duration of treatment would be an important component of this treatment approach.27 Thus, the goal of challenge-oriented gait and balance rehabilitation was to continually provide a challenging learning environment by focusing on the repetition of complex motor skills. This treatment approach was the underlying treatment construct in this case study.
The purpose of this case study was to provide evidence of a successful gait and balance treatment strategy for OPCA in the rehabilitation literature. It is hoped that this relatively novel treatment approach will serve as a foundation for physical therapists seeking to improve gait and balance parameters in individuals with sporadic OPCA or other similar disease processes. The treatment in this case study builds on previous treatment principles for cerebellar dysfunction16 by emphasizing regular challenge to the individual through high frequency and high repetition of complex motor coordinative tasks. The principal goal of this intervention was the amelioration of the problematic gait abnormalities, namely, functional ambulation and the reduction of falls. To our knowledge, this intervention rationale/strategy has not been reported in the literature for OPCA or other types of cerebellar dysfunction.
Shortly after experiencing a 24-hour influenza-like sickness with a little dizziness, the individual, an otherwise healthy 16-year-old at the time, began to report difficulty in walking and being unable to run (Fig. 1). However, the difficulty in walking was not immediately apparent to family and friends. Approximately two months later, her gait became noticeably dysmetric. She was initially diagnosed incorrectly with multiple sclerosis and then subsequently referred to a neurologist who found no physical reason for her inability to walk normally. She was subsequently referred to a psychiatrist.
Six months later and with worsening gait, she became constantly tired and vertiginous. She was unable to ambulate independently. An otolaryngologist noticed a profound, spontaneous left beating nystagmus. Canalith repositioning techniques and four months of vestibular rehabilitation yielded no improvements. Subsequently, an electronystagmography test battery indicated a moderate left positional nystagmus (15 degrees per second) with normal optokinesis and horizontal pursuit. A normal fixation index response was also noted for both eyes open and closed. An acute peripheral vestibular weakness on the right was suspected because of a high directional preponderance (left beating response: 51% stronger), unilateral weakness (right ear response: 32% weaker), and nonresponsive right warm caloric response. In an effort to address this asymmetry and to decrease her vertigo, intratympanic gentamicin treatment28 was administered to her relatively hyperactive left vestibular system. Because gentamicin is vestibulotoxic, it selectively damages the hair cells of the vestibular system. The auditory hair cells, which are less prone to gentamicin insult, remain relatively unaffected. However, Smith et al28 reported hearing deterioration in approximately one third of subjects one month after treatment, half of whom subsequently improved. No positive benefit was noted from the intratympanic gentamicin treatment and the vertigo persisted. There was no perceptible change in her hearing. Because the vertigo persisted, it is likely that a more central mechanism may have been the source of the nystagmus. In either case, this gentamicin treatment to the left ear, coupled with the nonresponsive warm caloric test on the right ear, may have resulted in bilateral vestibular weakness. However, because we have no direct measure of vestibular hypofunction, this should be interpreted with some caution.
Eleven months after the initial symptoms, atrophy of the cerebellum was noted on magnetic resonance imaging. Based on this finding, her blood and urine were analyzed for heavy metals, and an ataxia profile was ordered. All results were within normal limits. She continued to have severe, constant vertigo and chronic fatigue. Upper extremity ataxia was now becoming more severe, and her handwriting became barely legible. In addition, she developed mild short-term memory loss, depression, and dysarthria. She gave up her driver’s license.
Fifteen months after the initial symptoms, she had been given a vague diagnosis of cerebellar ataxia. She was referred to physical therapy for strength and gait training with the goal of independent ambulation with a four-point cane. Speech and occupational therapy was also ordered. Eighteen months after the initial symptoms, a new neurologist re-examined the case and reordered previous tests. Positive oligoclonal bands in her cerebrospinal fluid suggested an autoimmune problem, so prednisone was prescribed. All genetic and paraneoplastic test results were negative and other neurologic diseases (eg, spinocerebellar atrophy [types 1, 2, 3, 6, 7, 8, 10, and 17], Friedreich’s ataxia, Wilson’s disease, dentatorubral-pallidoluysian atrophy) were ruled out. She was subsequently diagnosed as having OPCA. After three months of physical, occupational, and speech therapy, minimal improvements were noted. Efforts to improve independence with gait using a cane were unsuccessful secondary to upper extremity ataxia and safety concerns. She did not agree to use a walker, so she began using a wheelchair and/or walked with arm-in-arm assistance with a family member. Three additional months of physical therapy treatment yielded no important gains. The lack of improvement from rehabilitation up to this point may have had more to do with disease progression than a lack of treatment efficacy.
She was discharged and asked to follow a home exercise program (ie, treadmill walking while holding on to the railing, and various sitting and standing exercises to promote strength and endurance), and she exercised faithfully for the next 15 months, now three years from the initial symptoms. There had been no changes, good or bad, in her condition for approximately two years; therefore, it was determined that her condition had stabilized.
This individual referred herself to a university-based gait and balance research laboratory housed in the Department of Physical Therapy at the University of Nevada, Las Vegas, NV. On initial presentation to the gait and balance laboratory, this pleasant 19-year-old woman was alert and oriented. She had difficulty with smooth pursuits and exhibited a profound left beating nystagmus that accentuated with upward and left lateral gaze. Extraocular movements were full, and her pupils were large but reactive. She had ∼30% hearing loss bilaterally, which was a result of a surgical repair for a diaphragmatic hernia when she was a newborn.29 Her speech was somewhat dysarthric with a scanning quality, and she had speech articulation consistent with hearing loss. She had normal and symmetrical facial somatosensation. Her tongue and facial muscle movements were symmetrical bilaterally. Olfaction, taste, salivation, and swallowing were reported to be normal. Vestibular nerve assessment through gaze stabilization was not assessed. Deep tendon reflexes were symmetrical but reduced bilaterally (1 on a scale of 0 to 4). Motor examination revealed 5/5 manual muscle strength bilaterally in the upper and lower extremities. She had mildly reduced axial and extremity tone. She had no pain or paresthesias and had normal cutaneous sensation throughout. Coordination testing revealed moderate bilateral dysmetria when performing finger-to-nose, finger-to-finger, and heel-to-shin tests. She had slow rapid finger movements and dysdiadochokinesia bilaterally. There was no tremor, myoclonus, dystonia, mirror movements, spasticity, dysphagia, or autonomic dysfunction.
She was independent with bed mobility. However, her independence with transitional movements and most activities of daily living (eg, dressing, grooming, toileting, eating, and bathing) was slow and required the supportive control of her arms on furniture or walls. Her gait was severely ataxic with significant deviation from midline, asymmetry in stride length, and wide stance. She lost her balance, which would have resulted in a fall if not guarded, approximately every three to five steps. However, she was able to walk around her home independently by supporting herself with her arms on the furniture or the walls. As she could not move very far before losing her balance, furniture was strategically placed throughout the house so that her gait was never totally independent of the furniture and wall support. Despite these adaptations, she still fell (defined as an unexpected fall to the ground) regularly (approximately one time per day). She used a standard wheelchair for mobility but was not independent in its use because her severe upper extremity ataxia made its use slow and laborious; however, she usually walked arm-in-arm with moderate assistance from a family member to prevent a fall.
She engaged in typical age-related activities (eg, movies, shopping, eating out, and e-mailing) with friends and family. However, her level of participation was limited by her slowness with tasks. During the duration of the study, she was also a successful college student, taking most of her courses online. However, her severe ataxia made typing and writing very difficult and slow.
Evaluation, Diagnosis, and Prognosis
After examining the individual (approximately three years from her initial symptoms and approximately two years of no significant changes in her symptoms), our initial impression was that the greatest factor impeding her progress was severe dyscoordination and her confidence with independent balance-related tasks. Her main goal was to walk normally without an assistive device. It was thought that her prognosis was good because of her young age, stable condition, strong motivation, and good family support. However, slow progress was anticipated with modest overall improvement secondary to the nature and severity of the underlying disorder.
Based on her symptoms, our evaluation, and evidence from magnetic resonance imaging, her diagnosis was consistent with OPCA. Because there was no family history, it was assumed that her case was sporadic OPCA, although a recessive inheritance could not be fully ruled out. Her case was, however, somewhat unique in that the onset of sporadic OPCA is generally later (mean = 49.2 years old, SEM = 1.6 years).2 Because her neurologist and family believed that her condition had not progressed during the past two years, it was reasonable to assume that any neurodegenerative changes had slowed significantly or plateaued. Unfortunately, we do not have any physical measures to confirm this. This plateau is also a unique presentation for OPCA because most individuals with OPCA characteristically decline over time.
University-Based Physical Therapy Intervention
Based on her goals and our clinical impressions, we designed an intervention program to stimulate the atrophied brain structures by providing a challenge-oriented treatment program to improve her balance and gait. The focus of the present intervention was twofold: to provide a high level of repetitive training intensity and to provide consistent, recalibrated challenge or task novelty during gait and balance tasks. The idea of the challenge-oriented treatment was that if a task was not challenging for the individual, it would not sufficiently drive any changes. Thus, the individual in this case study was asked to perform balance tasks that were progressively more challenging as she gained more confidence and ability. In general, when a task became easy to perform, it was made more challenging. The principle of coupling high levels of repetition with task challenge and/or novelty to drive motor skill acquisition and concomitant neuroplastic changes was the theoretical basis behind the treatment design.21–24 The rate of progression was entirely dependent on her ability to acquire the new motor skills. Mastery of a task was the criterion for progression to a more challenging task.
This individual participated in a 12-week gait and balance training program, which consisted of 1.5 to 2 hours of various challenging static and dynamic balance tasks five times per week. The duration of this program was arbitrarily determined but was based on the notion that procedural learning, which is often impaired in those with cerebellar lesions,30–32 would be enhanced by high repetition and long duration.33,34 This treatment approach emphasized the selective promotion of somatosensation to compensate for weakened vestibular function from the intratympanic gentamicin therapy. This approach was based on work by Brown et al,35 who reported benefit of selectively promoting somatosensation in individuals with bilateral vestibular loss. Although the main emphasis was the promotion of somatosensation, some gait and balance activities that would promote vestibular and visual adaptation were also included. The daily treatment program consisted of the following:
1. Approximately 30-45 minutes of dynamic gait tasks (eg, obstacle course negotiation [ie, stepping over and around obstacles, balance beam], gait with head turns, quick turning and stopping, carioca walking, sidestepping, ascending and descending steps, and walking on compliant surfaces);
2. Approximately 30-45 minutes of static balance tasks with eyes opened and closed (eg, single leg stance, tandem stance, static standing on compliant surfaces, balance boards and wobble boards, squats and lunging, and various computerized dynamic posturography tasks such as weight shifting and tracking);
3. Approximately 20-30 minutes of static and dynamic balance tasks with external perturbation on various surfaces (eg, upper extremity tasks such as reaching with the upper extremity, throwing and catching weighted balls, therapist-induced physical displacements of the center of gravity, treadmill walking without arm support).
An overground harness system was used initially for the first 8 weeks. It allowed her to challenge her balance over a 30-foot long track system without experiencing a fall to the ground and without any deweighting. It should be noted that this overground harness system did not provide any support to her during the treatment. There was enough slack in the wires that she could experience a fall but not enough that she would hit the ground. In addition, she was not allowed to use her arms to stabilize herself on any external structures including the harness wires. In addition to the regular workouts, she received a home exercise program to perform under the supervision of a family member six days per week. The intention of the home exercise program was to allow her more repetition to increase learning. The home exercise program consisted of gait, balance, and coordination activities similar to those performed during treatment sessions. She also had access to a pool at home and was instructed in aquatic exercises. At the eight-week point of her treatment, she was weaned from the overground harness and progressed to gait and balance tasks with minimal to moderate assistance using a gait belt. As her safety and skill level improved, she was given progressively more challenging tasks.
To assess her progress, standardized gait and balance assessment tools were used at baseline and at four, eight, and 12 weeks. As there are no scales specifically designed to measure gait and/or balance in OPCA or other causes of cerebellar ataxia, it was thought that some well-established assessment tools were sufficiently generic enough to provide a valid and reliable assessment of her gait and balance function. The following outcome variables were measured each time: self-selected gait velocity (SSGV),36,37 Berg Balance Scale (BBS),38–40 Dynamic Gait Index (DGI),41–44 Activities-Specific Balance Confidence Scale (ABC),45 and computerized dynamic posturography.46,47
The SSGV has been used as a composite measurement of the temporal and distance variables of functional gait. It is considered to be a valid and reliable measurement of gait (intraclass correlation coefficient [ICC] for those with vestibular disorders = 0.95)48 and is calculated as the individual walks at his or her own pace over 10 m. In this study, we had the participant walk 20 m at a comfortable pace, but only measured her velocity in the middle half (ie, from the 5-m point to the 15-m point). The 95% minimal detectable change (MDC) and minimal clinically important difference for SSGV have been reported to be 0.08 m/sec (habitual speed, individual told to walk at their normal or comfortable pace) and 0.10 m/sec (fast speed, individual told to walk as quickly as possible without running).49
The BBS and DGI are standardized observation-assisted assessment tools with solid psychometric properties. In both of these tests, therapists rate the individual’s performance during various balance- and gait-related tasks. The BBS is highly reliable (ICCs >0.98)40,50 with scores ranging from 0 to 56; higher scores are indicative of higher balance-related function. The 90% MDC for the BBS has been reported to be six scale points.51 The DGI scores range from 0 to 24 with higher scores indicative of higher, dynamic gait-related functioning. It is also highly reliable (ICCs >0.983).41 The clinically significant change for the DGI is four scale points.52
The ABC is a self-reported assessment of balance confidence for 16 different functional tasks. Scores for each task are reported as a percentage of confidence, with a 100% score indicative of complete balance confidence in performing a particular task. The total ABC score is an average of all of the tasks. The total ABC score has been shown to be reliable (r = 0.92).45 The 95% MDC of the ABC is 14% points as calculated from the standard error of measurement of 5%.53
Computerized dynamic posturography was performed using the NeuroCom Smart Balance Master system (NeuroCom International, Inc., Clackamas, OR) to test sensory organization and limits of stability (LOS). The sensory organization test (SOT) quantifies how an individual uses the three main components of the sensory balance system (vision, vestibular information, and proprioception). There are six SOT conditions with each one selectively taxing a different component of the three sensory modalities of balance. The SOT scores are a measurement of postural sway and range from 0 to 100, with higher scores representing less postural sway. Reliability of the composite SOT score (weighted average of all six sensory conditions) is fair to good in noninstitutionalized older adults (ICC = 0.66)54 and healthy young adults (ICC = 0.67).55 The responsiveness (95% MDC) of the SOT composite score has been reported to be eight points55 and 14.4 points.56 The composite SOT score can be subdivided into individual sensory systems (ie, somatosensory, visual, and vestibular; Table 1). LOS testing measures one’s ability to move the body in and out of the base of support while keeping the feet stationary. The testing protocol requires the individual to shift his or her center of gravity toward eight successive targets each spaced 45 degrees apart circumferentially. LOS testing results in various subscores, including endpoint excursions, directional control, reaction time, and movement velocity (Table 2). LOS testing has good test-retest reliability for movement velocity and directional control (ICCs >0.824).50 Responsiveness values for the other LOS measurements have not been reported.
On initial assessment, the participant required maximum assistance to walk 10 m at a habitual speed of 0.375 m/sec. During this initial 10-m walking test, she had two losses of balance that required moderate assistance to recover (Fig. 2). After 12 weeks of training, she improved her gait velocity to 0.526 m/sec, and she only required standby assistance with no loss of balance over the same distance. Before entering the study, she averaged a fall per day. During the initial stages of the study, she fell less regularly (approximately three to four times per week). By the end of the study, she was averaging one fall or less per week. Recently, she was contacted by phone, now three years from completion of the treatment, and she continues to report an average fall frequency of zero to one fall per week. In addition to the improvement in gait velocity, she also demonstrated improvement on the BBS, DGI, and ABC (Table 3).
Slow, large amplitude, anteroposterior sway patterns on all SOT conditions of the Balance Master were noted for each testing session. She exhibited a strong reliance on somatosensory information; however, she stabilized well with vision despite the profound nystagmus. Additionally, there was virtually no ability to use vestibulosensory input, as she fell repeatedly (11 of 12 trials) on condition 5 (absent visual and inaccurate somatosensory input) during the four testing sessions. This is consistent with profound vestibular weakness caused by the intratympanic gentamicin therapy and/or vestibulocerebellar atrophy. She demonstrated good improvement on the Balance Master for both the SOT and LOS. Before the balance and gait intervention, she had an SOT composite score of 31. After 12 weeks, her score was 47 (Fig. 3). For the LOS testing, her reaction time did not improve over the 12-week training period (0.29-0.63 seconds; Table 3); however, her directional control was more accurate, and she was able to move her center of gravity farther (ie, endpoint and maximum endpoint excursions) in the direction of each target during the 12-week training period (Table 3).
In this article, we report the outcomes of an individual with sporadic OPCA and vestibular weakness who participated in 12 weeks of intensive gait and balance training. Although it is difficult to draw definitive conclusions, these data suggest modest improvements in gait and balance outcomes during the 12-week intervention. In light of these improvements, we suggest that individuals with OPCA may be responsive to this type of treatment. These data provide first-line evidence that this type of intervention may be beneficial to individuals with OPCA. Further testing using a more rigorous design is warranted.
The overall trends of the outcomes in this study are consistent with another study, which found that intense gait and balance training was effective in improving gait, balance, and mobility in individuals with chronic stroke.58 We are most confident in the improvements in our study of the participant’s SSGV and DGI because both of these scores increased more than the clinically significant change and/or the MDC/minimal clinically important difference (Table 4). In addition to the improvements in gait velocity, she was safer, as she had no episodes of loss of balance during gait velocity testing (Fig. 2). This was a considerable improvement from her baseline measurement, when she had two episodes of loss of balance, each requiring maximum assistance to prevent a fall. Therefore, she was not only walking faster, but she was also having fewer falls in the laboratory during testing. Additionally, she fell less frequently at home. She reported a decrease in her fall frequency at home from one fall per day to zero to one fall per week at the completion of the study. Importantly, this relatively low-fall frequency (zero to one fall per week) has persisted for three years (recent communication) since the completion of the treatment.
Although her gait velocity (0.526 m/sec) improved during the 12 weeks (Table 4), it was still considerably ataxic and slow compared with normative comfortable walking values for women in their 20s (1.41 m/sec). (There were no normative data for subjects younger than 20 years. Because she was 19 years old at the time of this study, we believe that this is an appropriate approximation.)59 In addition, it is still well below the speed necessary (1.2 m/sec) to cross the street before the traffic light changes in urban settings.60,61 Her DGI score improvement of six scale points (from one to seven scale points) was beyond the clinically significant change of four scale points, suggesting positive benefit over the 12-week intervention (Tables 3 and 4). However, her final score of seven scale points on the DGI was still considerably less than the threshold of 19 scale points for fall risk.62,63
Her improvement on the BBS (five scale points) did not meet the MDC (six scale points) for the BBS; however, it was trending in the right direction (Tables 3 and 4). Although some improvement was observed, she is still at risk of falling because her BBS score was 39, which is lower than recommended cutoff scores of 4064 and 44.65
She also had a considerable improvement in her balance confidence (Table 3). Her initial ABC was a 50.6% but increased sharply at the four-week point (85.6%). At the 12-week measurement, her balance confidence remained high (85.1%). This improvement was well beyond the 95% MDC of 14.0 scale points (calculated from standard error of measurement; Table 4).53 Therefore, she felt much more confident in her balance compared with before training. This is consistent with her reported decrease in fall frequency.
Improvements were noted in all the computerized dynamic posturography measurements except one. The improvement of 16 points on the SOT composite equilibrium score exceeded suggested MDC values of eight55 and 14.4 points (Table 4).56 A closer look at the sensory analysis (Fig. 3) reveals that improvements were noted in all three sensory areas (somatosensory, vestibular, and visual). According to the SOT scores, the greatest area of improvement was in visual adaptation, despite the fact that visual stabilization was not a large focus of the intervention. There were good gains in somatosensory adaptation as would be expected because it was the main focus of the intervention. The improvement was not as marked as visual adaptation, but this may be related to a ceiling effect. We did not expect any improvement in vestibular function secondary to the vestibular weakness from the underlying disease and the intratympanic gentamicin therapy. However, we suggest caution in these individual sensory analyses because these are only theoretical approximations and probably do not represent the true change in these systems. Because LOS responsiveness values have not been reported, we have no way of confidently assessing improvement; however, there were considerable improvements in endpoint excursion, maximum endpoint, and directional control (Tables 3 and 4). Reaction time did not improve during the course of treatment. However, she was more accurate in her displacement of her center of gravity toward the intended targets.
Additionally, because our participant had profound nystagmus, we anticipated her ability to stabilize visually would not be a successful treatment strategy. Her initial SOT was 13.9 of 100 for vision and 0 of 100 for the vestibular system (Fig. 3). Because these scores were so low, it supported our decision to focus on the somatosensory system. It was thought that a focus on visual and vestibular stabilization would not have produced meaningful changes because the severe nystagmus and presumed gentamicin-induced vestibular hair cell destruction would have rendered meaningful improvements unlikely. However, in retrospect, after having noticed the improvements in her ability to use visual and vestibular information (Fig. 3), these areas may have benefited from greater attention in the design of our treatment. In support of this notion is work by Hirvonen et al66 who demonstrated that intratympanic gentamicin treatment does not damage all the vestibular hair cells and may, in fact, spare “enough hair cell synaptic activity to drive the spontaneous activity of vestibular afferents.” In addition, Lin et al67 suggest the possibility that in some cases the intratympanic gentamicin treatment may be irritative rather than destructive. Taken together, these studies suggest that there may be viable and functioning vestibular hair cells even after intratympanic gentamicin treatment. From a clinical perspective, this would suggest that physical therapy treatment efforts on vestibular adaptation are warranted even after an ablative procedure such as intratympanic gentamicin.
Because it is well recognized that motor learning is impaired in individuals with cerebellar lesions, it is important to understand that procedural motor learning may have affected the intervention. However, procedural motor learning was not assessed at any point in the study. Future studies should use design strategies to determine what role, if any, procedural motor learning impairment affects recovery. Although the participant’s SOT scores on somatosensory analysis suggest near-normal functioning, no tests of kinesthesia were used. A clearer picture of her condition and progress would have been aided by this information. In addition, vestibular ocular reflex and gaze stabilization testing would have provided a more complete picture. It should also be noted that the psychometric properties (ie, reliability, validity, and responsiveness) of the assessment tools used in this study were determined in individual populations who did not have cerebellar dysfunction or ataxia and may not hold true for individuals with OPCA. Therefore, future studies using these assessment tools for OPCA or cerebellar dysfunction/ataxia would benefit from the establishment of these measurement characteristics in this population. Another concern is that practice or testing effects may have accounted for a portion of the improvements noted in our study. Finally, the frequency of treatment provided in the case study (five times per week) may not be practical in a traditional setting.
Current evidence of gait and balance rehabilitation for sporadic OPCA is lacking in the literature. Furthermore, there is very little information on any type of rehabilitation for this disease. This study offers preliminary evidence of the efficacy of an intensive gait and balance intervention for an individual with sporadic OPCA.
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