Abstract
The purpose of this exploratory pilot study was to assess balance confidence in adults with CMT. Charts of individuals with CMT followed in the peripheral neuropathy clinic were reviewed. Information abstracted included demographic, assistive device use, falls, pain, strength, Activities-specific Balance Confidence score, Lower Extremity Functional Scale, 30’ Go, and the Five Times Sit to Stand Test. Balance confidence was found to be decreased in individuals with CMT and was associated with patient report of falls and functional mobility tests. Further investigation of balance confidence and its relationship to falls and quality of life is warranted in a population with CMT.
Abbreviations
Charcot-Marie-Tooth disease Activities-specific Balance Confidence Scale Manual Muscle Testing Lower Extremity Functional Scale Five Times Sit to Stand Test Numeric Rating Scale
INTRODUCTION
Charcot-Marie-Tooth (CMT) disease is a family of inherited peripheral neuropathies that affects approximately 1 in 2500 individuals. CMT is a heterogeneous progressive condition that results from one of over 70 known genetic causes. While genetically diverse, patients with CMT typically exhibit peripheral motor and sensory nervous system dysfunction with distally accentuated weakness, sensory loss, and foot deformities [1]. Motor and sensory dysfunction in CMT causes various impairments and functional limitations, including gait difficulties and falls, and impacts quality of life [2, 3]. Currently there are no pharmacological treatments available to slow or arrest progression of the disease, and therefore symptom management is vital to maintaining safety, mobility and participation in daily activities.
Individuals with CMT often report instability and falls during functional activities [4]. Both lower extremity weakness and sensory impairment have been associated with instability and falls in CMT and in other neuromuscular conditions [5–7]. Gait instability can in turn contribute to a fear of falling. Fear of falling, often measured as balance confidence, has been associated with an increased risk for falls, self-restricted activity levels and decreased quality of life in older adults and individuals with neurologic conditions [8–10]. There is evidence that instability can be improved in individuals with hereditaryneuropathy, such as CMT [11]. Additionally, interventions to address balance confidence specifically have been shown to be beneficial in older adults [12].
Balance confidence is unexplored in CMT, and it is unknown how individuals with CMT perceive their balance abilities and how this concept relates to measures of impairment or function in these individuals. The Activities-specific Balance Confidence Scale (ABC) [13] is a patient reported measure that has been utilized in neurological disorders including multiple sclerosis and Parkinsons disease, but has hitherto not been utilized as part of the assessment of patients with CMT. The purpose of this exploratory pilot study was to assess balance confidence as reflected by the ABC in adults with CMT, and examine the relationships between the balance confidence, clinical measures of lower limb function and falls in individuals with CMT.
METHODS
Patients seen in the outpatient peripheral neuropathy clinic by one of the investigators or co investigators between 3/12/2007 and 3/12/2012 for CMT were identified from neuromuscular outpatient clinic medical records under an Institutional Review Board approved protocol. Charts were assessed for inclusion in this study. All individuals between the ages of 18–69, diagnosed with CMT, and who participated in a formal balance assessment were included in this study. Individual with co-morbid neurological conditions were excluded from the study. The neuromuscular clinic records of those patients meeting eligibility requirements were reviewed. Information abstracted from the medical record included, age, gender, diagnosis (CMT type classification), use of assistive devices, fall frequency, pain, strength (using Manual Muscle Testing, MMT) Activities-specific Balance Confidence (ABC) score, the Lower Extremity Functional Scale (LEFS), 30’ Go, and the Five Times Sit to Stand Test (FTSST).
MEASURES
Measures at the impairment level, the functional level and the patient-reported level were assessed during clinic visits. Impairment level measures included lower extremity strength, sensation and pain. Lower extremity strength was assessed using standard manual muscle testing procedures which have demonstrated good inter-rater reliability [14, 15]. The muscle groups that were assessed include hip flexion, extension, and abduction, knee flexion and extension, and ankle dorsi flexion and plantar flexion. Sensation, including vibration, sharp (pin) and proprioception at the great toe, was assessed using standard neurologic exam procedures. Pain was assessed using the numeric rating scale (NRS) [16].
Functional measures used during the clinical assessment were timed functional tests; FTSST and the 30’ Go. The FTSST assesses the time it takes an individual to move from sit to stand 5 consecutive times. This measure has been used as an assessment of lower extremity strength and has also been found to be reliable and valid in patients with balance disorders [17–19]. The 30’ Go assesses the time it takes the subject to traverse 30’. It has been shown to be a reliable functional assessment in individuals with neuromuscular conditions [15].
Patient reported measures including the ABC and the LEFS, were also collected during the clinic visit. The ABC is a self-report measure of balance confidence [20]. Subjects were asked to rate on a scale of 1–100 how confident they are that they will not lose their balance while performing 16 different activities. The ABC has been shown to be a reliable and valid measure [21, 22]. The LEFS is a reliable self-report measurement that assesses the functional limitations of the lower extremities [23].
Statistical analyses
Correlational analysis was performed to determine the relationship between the ABC, falls, lower extremity impairment measures and functional outcomes. A two– tailed test with a p value <0.05 was considered significant in this exploratory study.
RESULTS
Twenty-eight individuals (13 female, 15 male) with CMT underwent a balance assessment including completion of the ABC. Hereditary neuropathy diagnoses included CMT type 1a (PMP22 gene duplication (39%), CMT 1x (4%) CMT Type 2 (39%), and hereditary neuropathy with liability to pressure palsies (4%). The mean age of the cohort was 52.1 (20–78) years. Seven (28%) individuals wore orthotic braces and 5 (23%) utilized an assistive device (either a cane or walker). Falls were reported by 14 (50%) individuals. The mean overall ABC score was 56%. The mean ABC score for individuals who had sustained a fall was 50% and 63% for those who had not. The ABC correlated with patient report of falls (ρ= – 0.43; p = 0.024), lower extremity functional scale (LEFS) (ρ= 0.88; p = 0.0001; n = 14), the 30’ Go (ρ= – 0.670; p = 0.0001; n = 27) and the Five Times Sit to Stand (FTSST) (ρ= – 0.46; p = 0.028; n = 23) (Table 1). Falls were also significantly associated with the 30’ Go (ρ= 0.47; p = 0.01; n = 27). No significant associations were found between sensation, pain and lower extremity strength and balance confidence.
DISCUSSION
Falls and imbalance are important health concerns for individuals with CMT. These concerns along with decreased balance confidence may contribute to decreased health related quality of life [2]. Balance confidence, as measured by the ABC, was found to be decreased in our sample of adults with CMT and correlated with measures of functional mobility and falls. Evaluation of balance confidence has not been traditionally incorporated in the assessment of patients with CMT. The findings of this study suggest that inquiry regarding balance confidence may provide additional insights regarding function and fall risk in CMT, and deserves further study as a potentially modifiable risk factor in the prevention of falls in CMT.
While strength and sensation have been documented to contribute to balance in individuals with neuromuscular conditions, we did not find significant relationships between strength, as assessed by MMT, and sensation and balance confidence and falls in this sample. The reason for the lack of association between lower limb MMT, balance confidence or falls in the present study is uncertain. It may reflect that weakness which is mainly distal in patients with CMT is partly compensated for by use of ankle foot orthotics or gait assistive devices. In addition, the sensory assessments used in the clinical setting may have been suboptimal to differentiate levels of impairment that may contribute to balance confidence. Proprioception as an example is only grossly assessed on bedside testing at larger joints such as the ankle. Future prospective studies on modifiers of balance confidence should incorporate more quantifiable sensory assessments.
The Five Times Sit to Stand Test (FTSST) was, in contrast to MMT, associated with decreased balance confidence. While this functional movement requires adequate lower extremity strength, sit to stand has historically had only moderate correlations with lower extremity strength. Sensory input, balance, and psychological status also contribute to this functional task and may support the relationship between balance confidence and sit to stand seen in our study.
Given the findings of this study, and the negative impact that falls and decreased balance confidence have on an individual, a larger prospective study of balance confidence and its impact on falls is warranted in a population with CMT.
CONFLICT OF INTEREST
The authors have no conflict to report.