The primary aim of this study was to determine if balance is impaired in early WFS as compared to typically developing age-matched controls. Our findings indicate not only an overall difference in balance between individuals with WFS and typically developing age- matched individuals, but more specifically deficits in the anticipatory transitions, postural responses and sensory orientation subcomponents. Dynamic gait was not significantly impacted in the WFS group.
In this investigation, the mini-BESTest was used to assess balance as it can be administered in the clinic, requires less than fifteen minutes, does not necessitate expensive equipment [21
] and, as demonstrated here, can be used to assess children. In typically developing individuals, studies attempting to characterize “normal” developmental trends in balance have assessed postural sway on a force platform [23
]. While informative, these studies are laborious, expensive and require analysis beyond that which is easily done in a clinical setting.
In addition to the comparison of total and subcomponent scores from the mini-BESTest, the WFS group took more time to complete both the TUG and SOO, but not the DT-TUG. Our data do not allow for a clear explanation of why dynamic gait and DT-TUG are not affected at the level of the other components, however, one could speculate that learned compensatory strategies would confound these measures more than the others due to the complexity of dynamic gait and the DT-TUG. As individuals with WFS exhibit atypical balance at a very early stage of development (e.g. 6 years of age) but also continue to walk unassisted, compensatory strategies may be incorporated to maintain balance during gait. These compensatory strategies may confound less sensitive measures of complex balance tasks and may have contributed to the generalize description of “ataxia” provided in previous reports. It should be noted that the DT-TUG task could not be performed as described in the original description of the mini-BESTest [21
]. Specifically the dual task was altered from a subtraction task to a random number naming task as per the original full BESTest [25
]. This modification was made to allow for all participants to complete the same task. While a dual task paradigm has been shown to produce measureable decrements in young (5–6 yrs) and older (7–16 yrs) typically developing individuals, the typically developing group did not differ in age to the WFS group and thus it is unlikely the nature of the task influenced our findings.
As expected, balance in typically developing young individuals correlated with age, indicating a developmentally driven change in mini-BESTest scores. This correlation was not present in the WFS group; rather, mini-BESTest scores for the WFS group were related to overall motor involvement. To our knowledge, this study is the first to quantify this or any neurological deficit related to WFS. This finding supports the idea that balance deficits are present early in the disease process and relate to overall motor involvement of the individual with WFS, independent of age. This suggests that a younger individual with more severe WFS may have more significant balance deficits than an older individual with less advanced WFS, thus the level of impairment and possible intervention strategies cannot be generalized by age but rather require careful assessment of each affected individual.
Recently, increased attention has been given to neurologic complications and neuroanatomical abnormalities associated with WFS. In a retrospective clinical study of medical records and physician reports of 59 individuals with WFS, Chaussenot and colleagues [7
] found that 31(53%) of the individuals reported neurological complications at a median age of 15 years. These symptoms included a wide range of clinically described manifestations such as cerebellar ataxia (14 of 31 individuals), peripheral neuropathy (12 of 31 individuals) and cognitive impairment (10 of 31 individuals). This is in contrast to a previous report that found reported onset of neurological symptoms in the late third or fourth decade of life [2
]. However, neither study directly evaluated the patients, or used quantified, objective measures. In addition, many reports have cited the lack of relationship between neuroanatomical findings of brain abnormalities in the WFS population and clinical symptom presentation [7
]. Here we report measureable differences in balance between typically developing individuals and individuals with WFS across a wide age range (6 to 25 years of age). The early presence of a measureable neurological deficit in our study may indicate that: 1) measures of balance impairment may provide a more sensitive metric of neurologic involvement than have been previously explored and 2) balance deficits may precede the onset of ataxia.
Future studies focused on quantifying the neurological complications of WFS, particularly in young individuals, are needed. As this investigation is the first to measure balance deficits in this population, future work focused on gait tasks and dynamic balance would be a logical progression. Quantification of gait and motor deficits would allow for clinical interventions to be developed and tested in this population. Additionally, longitudinal data are needed on progression of the neurological symptoms associated with WFS.
Currently, no cure has been found for WFS and no standard of care for treatment has been established. Unfortunately, specific treatment strategies are beyond the scope of this investigation as we are only now becoming aware of the early presentation of balance deficits. A multidisciplinary management approach is necessary given the vast number and variable severity of symptoms. Physical therapy may provide a useful venue to address impaired balance and may be able to use tests such as the mini-BESTest to hone a treatment strategy useful to the WFS population. Given the progressive nature of WFS, and the level of deficit present, the goal of any treatment plan may be to maintain the current level of balance function over a longer portion of the individual’s lifespan. Future studies will be needed to examine the usefulness of such strategies.
A limitation of the current study is that individuals with WFS present with various individual symptoms that should be considered when investigating balance impairments. Of particular interest are the effects of any form of diabetes which may include peripheral neuropathy, visual impairments, or cochlear implants on an age-matched population. As proprioceptive, tactile, visual and vestibular sensation and perception are related to balance, these components warrant further investigation and could be explored in future work. Additionally, these data are focused on individuals early in the progression of WFS and do not address individuals at later chronological ages or individuals further along in the disease progression. Caution should be used in generalizing these findings to individuals beyond the age ranges and disease severity levels presented herein.