Self-reported cold sensitivity in normal subjects and in patients with traumatic hand injuries or hand-arm vibration syndrome

Cold sensitivity, described as "an exaggerated or abnormal reaction to cold exposure of the injured part, causing discomfort or the avoidance of cold", is a common complaint following hand injuries [1, 2]. A variety of symptoms, such as pain, aching, numbness, weakness, stiffness and change in skin colour may be elicited by exposure to cold [3] but individual variations limit a symptom-based definition [4]. Post-traumatic cold sensitivity develops within the first few months and does not generally improve over time [2, 5]. The pathophysiology behind the complex phenomenon of cold sensitivity remains unclear, thus a multifactor aetiology, including bony, vascular and neural components is suggested [6]. Cold sensitivity can occur in connection with a variety of injuries and conditions. It is frequently reported after traumatic hand injuries [7‐12], after surgically treated Dupuytren's contracture [13] and in patients with hand-arm vibration syndrome (HAVS) [14, 15].

Cold sensitivity may have a profound effect on health-related quality of life as well as upper extremity disability, as described in patients with specific hand injuries [16, 17] and as indicated in a group of patients with digital replantation or amputation where 65% considered cold intolerance the main reason for their disability [18]. However, the impact on disability and health-related quality of life in patients with HAVS compared to patients with a traumatic hand injury and to normal subjects has not previously been considered. For a proper comparison of patient groups, validated self-report questionnaires, such as the Cold Intolerance Symptom Severity (CISS) questionnaire [3, 19], are important for defining the individual patient's symptoms and signs and clarifying the impact cold sensitivity may have on daily life. Our aim, therefore was to describe the self-reported consequences of cold sensitivity and its association with self-reported disability and health-related quality of life in patients with hand injuries or HAVS and in normal subjects.

The characteristics of the subjects and patients are described in Table 1. The patients with traumatic hand injury had a median HISS score of 75 (5-305). Twenty-five out of 30 patients with HAVS had according to the Stockholm Workshop scale vibration-induced white fingers, 27 of 30 had sensorineural symptoms and 22 of 30 had both white fingers and sensorineural symptoms (Table 1). Twenty-six of the 30 patients had an impaired vibrotactile sense, while the remaining four patients, in addition to the other criteria for HAVS had affected vibration threshold values at high frequencies. Six out of 30 patients with HAVS were operated with carpal tunnel release; however, there was no significant difference in CISS score between operated and non-operated patients (p = 0.64).

There was an internal dropout for the CISS questionnaire (normal population, n = 13, traumatic hand injury, n = 2, HAVS, n = 2), in that not everyone answered all included questions.

Our results show that abnormal self-reported cold sensitivity was not only observed in patients with a traumatic hand injury, but was particularly common among patients with hand-arm vibration syndrome (HAVS) as compared to normal subjects. In addition, the severity and occurrence of symptoms and the relief of cold-induced symptoms after returning to a warm environment, the influence on daily life, disability and health-related quality of life were most apparent in patients with a diagnosis of HAVS. Among our patients this diagnosis was based on a history of regular exposure to hand-held vibrating tools with white fingers on exposure to cold and/or sensorineural symptoms, an impaired vibrotactile sense and neurophysiological findings supporting HAVS but excluding other causes of neuropathy.

A novel finding in this study was the significant relationship between abnormal self-reported cold sensitivity and health-related quality of life in our patients, indicating the severe impact of cold sensitivity for the individual patient. The association was particularly apparent for subscales in the SF-36 focusing on how the magnitude and interference of bodily pain affects work performance or questions concerning satisfaction and performance at work or during other daily activities (Role Physical). In addition, abnormal cold sensitivity was also associated with greater disability, as measured using the DASH questionnaire. A more severe cold sensitivity, associated with more functional limitations and reduced health-related quality of life, has previously been reported in patients with upper extremity injuries [16]. Consequences and adaptations in daily life may also result in changed life roles and a struggle to maintain self-image [24]. A majority of vibration-exposed patients consider cold sensitivity as severe or as a problem that hinders their functioning [15]. Furthermore, they report a poorer quality of life and difficulties in the activities of daily living [25]. It is important to include an assessment of cold sensitivity for vibration-exposed patients since it may be an early neurological symptom of vibration-induced injury [14, 26].

Both groups of patients had an underlying nerve injury or neuropathy. Structural changes in nerve trunks occur after a traumatic hand injury, but may also be present in HAVS [14] although possibly differing in character [27, 28]. Complex structural alterations occur in nerve trunks in HAVS with demyelination, degeneration of nerve fibres of different diameter, receptor dysfunction and even a central component has recently been suggested [29, 30]. Thus, the structural changes in HAVS may be even more complex, located at multiple levels, but profound changes also take place after a traumatic hand injury with nerve involvement. However, several non-neuronal factors may be predictors of cold sensitivity [6]. A difference between the two groups of patients were that patients with HAVS were older and had a history of long-time vibration exposure compared to the patients with traumatic hand injuries who were relatively recently injured. Even a short exposure time to vibrating tools may induce cold sensitivity and reduce sensitivity to temperature [31]. However, we have previously described that age peer se has no impact on cold sensitivity in neither normal's nor hand injured patients; thus, ruling out the possibility that age may explain the difference in symptoms between the groups [6]. The complex pathophysiology in HAVS may contribute to the severe self-reported cold sensitivity in this group. In addition, there was no significant difference in CISS scores between our patients with an amputation and those with a pure nerve lesion, which may indicate that nerve regeneration per se has no impact on cold sensitivity.

All patients ranked weakness, stiffness, numbness and skin-colour change as the most troublesome symptoms on exposure to cold, while pain and aching were only ranked as equally troublesome in patients with HAVS. There are some inconsistencies in previous studies concerning exactly what symptoms patients experience when exposed to cold [4, 5, 32]. Such inconsistencies may be explained by variations in the study population or whether the severity or presence of symptoms was evaluated. Our patients experienced cold-induced symptoms frequently with a significant difference in the time it took for patients, compared to the normal subjects, to experience relief of symptoms on return to a warm environment. Activities, such as holding a package from the freezer or washing in cold water, are problematic and cold sensitivity has a clear impact on leisure activities in a majority of patients with abnormal self-reported cold sensitivity. This is in keeping with earlier findings [24, 33]. Cold, wintry weather was, as expected, very troublesome for the majority of patients. Not only temperature, but also rain, high humidity and windy weather trigger cold-induced symptoms. Patients with severe cold sensitivity may therefore also have problems during other seasons. Interestingly, seasonal variation is not included as a variable in the CISS questionnaire. One strength of our study is that we investigated the patients at a defined time-point during the cold season.

The frequent exposure to cold, as shown by high scores on the PWES, put hand-injured patients in an exposed position and forced them to change their work. Patients who had changed employment had significantly higher CISS scores than those who remained in their jobs, indicating the impact cold sensitivity may have.

In conclusion, abnormal cold sensitivity is seen in 75% of patients with HAVS and in 45% of patients with a traumatic hand injury. The predominant problems are weakness, numbness, stiffness, skin colour change and pain/aching, on exposure to cold. One important finding was a significant difference in time taken for symptoms to be relieved on return to a warm environment between both patient groups and compared to the normal population. Cold sensitivity among patients with traumatic hand injuries, such as nerveinjuries and amputations, and HAVS may have a profound impact on performance at work, in leisure pursuits and in other activities in daily life. It is apparent that there is an association between self-reported cold sensitivity and disability and health-related quality of life.