**5. Comparison with other DPN evaluation techniques**

In this section, we first describe the diagnostic criteria for DPN and give an outline of representative evaluation methods. Next, we roughly classify these nerve conduction studies as qualitative or quantitative and compare them. Finally, we discuss the difference between these quantitative tests and our proposed method.

#### **5.1. Diagnostic criteria and representative examination methods for diabetic neuropathy**

No specific tests for DPN currently exist and nor are diagnostic criteria reflecting an internationally established consensus available. It is therefore necessary to base comprehensive diagnoses of neuropathy on neurological symptoms and the results of examinations. The diagnostic criteria (**Table 4**) [16] of the A DA are used in daily clinical practice.

The tests used include the pain sensation test, vibration sensation test, 10-g monofilament test, and Achilles tendon reflex assessment. By regular application of these tests, it is possible to evaluate the onset and development of neuropathy. They are also effective in the early diagnosis of asymptomatic DPN. Being relatively easy to implement, the tests are useful when applied by a proficient practitioner. However, the results are qualitative.

To confirm the diagnosis, quantitative nerve conduction tests are necessary. These are not widely available, however, as they are time-consuming and require the use of expensive equipment.


**Table 4.** Definitions of minimal criteria for DSPN [16].

control groups were 20.1 ± 4.9, 11.7 ± 5.1, 19.4 ± 4.5, 15.7 ± 6.9, and 6.5 ± 5.7, respectively. This gave P values of 0.00 for DPN, 0.198 for non-DPN, 0.002 for symptomatic, and 0.025 for

The results confirmed that our novel device provides simple quantitative evaluation of tactile

In this section, we first describe the diagnostic criteria for DPN and give an outline of representative evaluation methods. Next, we roughly classify these nerve conduction studies as qualitative or quantitative and compare them. Finally, we discuss the difference between

No specific tests for DPN currently exist and nor are diagnostic criteria reflecting an internationally established consensus available. It is therefore necessary to base comprehensive diagnoses of neuropathy on neurological symptoms and the results of examinations. The

The tests used include the pain sensation test, vibration sensation test, 10-g monofilament test, and Achilles tendon reflex assessment. By regular application of these tests, it is possible to evaluate the onset and development of neuropathy. They are also effective in the early diagnosis of asymptomatic DPN. Being relatively easy to implement, the tests are useful when

To confirm the diagnosis, quantitative nerve conduction tests are necessary. These are not widely available, however, as they are time-consuming and require the use of expensive

sensation in diabetic patients, facilitating the early detection of asymptomatic DPN.

**5.1. Diagnostic criteria and representative examination methods for diabetic** 

diagnostic criteria (**Table 4**) [16] of the A DA are used in daily clinical practice.

applied by a proficient practitioner. However, the results are qualitative.

**5. Comparison with other DPN evaluation techniques**

**Figure 9.** Severity and classification of DPN. DPN = diabetic neuropathy.

these quantitative tests and our proposed method.

asymptomatic.

122 Actuators

**neuropathy**

equipment.

#### **5.2. Comparison of qualitative methods and the quantitative method**

The pain sensation test, made with a sharp object such as a pin, is used to test for hyperalgesia and weakness.

In the vibration sensation test, sensitivity to vibration is investigated by applying a 128 Hz tuning fork to the ankle or the toe of the foot. The ability to sense vibration is compared with that of a healthy person.

In patients with DPN, the Achilles tendon reflex is often attenuated or absent, providing an excellent test that can be performed in a short time if the examiner is proficient.

In the 10-g monofilament test, a thin thread of monofilament nylon is placed on the foot. It is used to investigate the function of the nerve that senses tactile and pressure. In DPN patients, the sensations are dulled.

These tests are representative qualitative examination techniques that can be performed in a short time.

In NCS, the stimulation conductivity of the peripheral nerve is measured. In patients who have developed neuropathy, the speed with which the stimulus is transmitted becomes slower. NCS is able to produce a quantitative measurement of the speed of the peripheral nerves of the human body [21, 22]. However, it requires the patient to be subjected to painful electric shocks. NCS also requires the use of expensive equipment. The examination time is lengthy, and if multiple peripheral nerves on both the left and right side are examined, the procedure may take several hours. NCS is therefore only available at large specialized hospitals.

#### **5.3. Comparison of NCS and quantitative tactile examination methods**

The proposed finger method is superior to NCS in some respects. First, the inspection time is short, taking a maximum of approximately 3 min. Second, the patient experiences no pain, as no electric current is applied to the nerve of the patient. The sensation is experienced only in the nerve being investigated. Third, while medical examination is normally performed by an expert, it is possible for the subject himself/herself to perform the test. This allows the test to be run at a place and time chosen by the patient. If tactile sensation reduces over time, poor glycemic control may be indicated. The test can detect such haptic loss. By making patients aware that their sense of touch is declining, the test may encourage them to seek treatment.

medication may also add unnecessarily to medical expenses. Our tactile test technique may

Quantitative Tactile Examination Using Shape Memory Alloy Actuators for the Early Detection…

http://dx.doi.org/10.5772/intechopen.75084

125

By promoting early detection and treatment of asymptomatic peripheral neuropathy, this novel technology may reduce the medical and social resources needed when complications arise or the severity of the condition is unknown. By promoting the use of this technology, the

A quantitative tactile examination technique using shape memory alloy actuators was developed. The painless, simple, and quantitative tactile examination technology that can be performed in a short time is an ideal examination technology. A notable feature of this technology is that it succeeded in miniaturization and power saving. This was demonstrated to allow early detection of DPN. Large-scale clinical trials should be conducted, to confirm the effectiveness of this novel technology, which may have applications in the identification of a wider range

This work was partly supported by the Grants-in-Aid for Scientific Research, the Japan Society for the Promotion of Science (no. 24500548 and 17 K17925), and by endowments from MSD

Keiji Uchida holds a patent on the quantitative tactile examination device. The other authors

, Keiji Uchida3

and Yu Nakamura1

, Hideyuki Sawada2

provide a useful tool for distinguishing between nociceptive and neuropathic pain.

authors hope to make a social contribution.

**8. Conclusions**

of neuropathies.

**Acknowledgements**

**Conflict of interest**

**Author details**

3 SCA Corporation, Japan

Junichi Danjo<sup>1</sup>

and Takeda Pharmaceutical Company.

declare that they have no competing interests.

\*, Sonoko Danjo1

\*Address all correspondence to: jdanjo@med.kagawa-u.ac.jp 1 Department of Neuropsychiatry, Kagawa University, Japan 2 Department of Applied Physics, Waseda University, Japan

#### **6. Discussion**

#### **6.1. Strengths and significance of this device**

A key strength of this device is that it can be used by patients themselves, producing quantitative results within minutes. It may be applied not only to DPN but to all forms of peripheral neuropathy. We are currently developing a device for assessing the lower limbs. Applications to diseases other than DPN are also being investigated.

#### **6.2. Limitations**

The cross-sectional studies reported here involved outpatients, and the sample sizes were limited. To confirm the effectiveness of the technology, future studies should use larger samples and a wider range of patients.

#### **7. Future work**

The tactile test quantification technology introduced in this chapter has a wide range of potential applications. In future studies, we will apply it to other types of peripheral neuropathy.

One such current study is applying the tactile test equipment to the feet. The equipment has already developed to a point where practical application is possible. We plan to conduct further clinical studies of patients with DPN, quantitatively measuring the tactile sensations in the feet as well as the fingers. This will be useful in identifying DPN in different areas of the body.

In further developments, we will use the technology to visualize the severity of peripheral neuropathy in a manner that will be easily understandable by both healthcare professionals and patients. This may prove useful for monitoring the severity of peripheral neuropathy induced by anticancer drugs such as paclitaxel. It may also encourage patients with peripheral neuropathy to seek early treatment.

No currently available examination method can distinguish clearly between nociceptive pain and neuropathic pain, which are treated with standard pain medications and expensive analgesics, respectively. Patients who are misdiagnosed may be prescribed inappropriate analgesics and experience pain over a long period. The prescription of inappropriate pain medication may also add unnecessarily to medical expenses. Our tactile test technique may provide a useful tool for distinguishing between nociceptive and neuropathic pain.

By promoting early detection and treatment of asymptomatic peripheral neuropathy, this novel technology may reduce the medical and social resources needed when complications arise or the severity of the condition is unknown. By promoting the use of this technology, the authors hope to make a social contribution.

## **8. Conclusions**

pain, as no electric current is applied to the nerve of the patient. The sensation is experienced only in the nerve being investigated. Third, while medical examination is normally performed by an expert, it is possible for the subject himself/herself to perform the test. This allows the test to be run at a place and time chosen by the patient. If tactile sensation reduces over time, poor glycemic control may be indicated. The test can detect such haptic loss. By making patients aware that their sense of touch is declining, the test may encourage them

A key strength of this device is that it can be used by patients themselves, producing quantitative results within minutes. It may be applied not only to DPN but to all forms of peripheral neuropathy. We are currently developing a device for assessing the lower limbs. Applications

The cross-sectional studies reported here involved outpatients, and the sample sizes were limited. To confirm the effectiveness of the technology, future studies should use larger sam-

The tactile test quantification technology introduced in this chapter has a wide range of potential applications. In future studies, we will apply it to other types of peripheral neuropathy. One such current study is applying the tactile test equipment to the feet. The equipment has already developed to a point where practical application is possible. We plan to conduct further clinical studies of patients with DPN, quantitatively measuring the tactile sensations in the feet as well as the fingers. This will be useful in identifying DPN in different areas of the body. In further developments, we will use the technology to visualize the severity of peripheral neuropathy in a manner that will be easily understandable by both healthcare professionals and patients. This may prove useful for monitoring the severity of peripheral neuropathy induced by anticancer drugs such as paclitaxel. It may also encourage patients with periph-

No currently available examination method can distinguish clearly between nociceptive pain and neuropathic pain, which are treated with standard pain medications and expensive analgesics, respectively. Patients who are misdiagnosed may be prescribed inappropriate analgesics and experience pain over a long period. The prescription of inappropriate pain

to seek treatment.

124 Actuators

**6. Discussion**

**6.2. Limitations**

**7. Future work**

ples and a wider range of patients.

eral neuropathy to seek early treatment.

**6.1. Strengths and significance of this device**

to diseases other than DPN are also being investigated.

A quantitative tactile examination technique using shape memory alloy actuators was developed. The painless, simple, and quantitative tactile examination technology that can be performed in a short time is an ideal examination technology. A notable feature of this technology is that it succeeded in miniaturization and power saving. This was demonstrated to allow early detection of DPN. Large-scale clinical trials should be conducted, to confirm the effectiveness of this novel technology, which may have applications in the identification of a wider range of neuropathies.
