Local plantar vibration for the treatment of diabetic neuropathy: a case report

Abstract

Purpose

One of the most common and debilitating complications of diabetes is peripheral neuropathy. Physical modalities such as whole-body vibration are used to treat diabetic peripheral neuropathy (DPN), but there are limted studies on the effectiveness of local vibration for the treatment of PDN. In this study, we aimed to evaluate the effectiveness of local vibration in treating a patient with DPN.

Methods

The local vibration was applied on the plantar side of both feet. The patient received 10 min of local vibration with 62.5 Hz frequency for five sessions. We used brief BESTest for balance evaluation, Numerical Pain Rating Scale (NPRS) for pain assessment, monofilament examination score for protective sensation evaluation, vibration threshold, and skin temperature to evaluate the effects of local vibration, which were measured before the treatment, after one session  of treatment, and after 5th session of treatment.

Results

There was a 62.5% reduction in pain severity after five sessions of treatment. Vibration threshold of both patient’s feet and protective sensation of right foot returned to normal after treatment. Skin temperature was increased in all evaluated points of both patient’s feet, brief BESTest score increased by six points after five treatment sessions, indicating improvements in the blood flow of feet and balance, respectively.

Conclusions

Local plantar vibration was effective in improving the symptoms of DPN.

Introduction

Type 2 diabetes is a chronic metabolic condition that affects 415 million adults, especially those 65 or older, worldwide, and is projected to increase to 642 million by 2040 [1]. Diabetes is also prevalent in Iran, with 7.7% of adults aged 25 to 64 years are affected by diabetes [2]. The prevalence of diabetic neuropathy in diabetic patients is up to 50%, and it is one of the most common complications of diabetes [3]. The most common type of peripheral neuropathy in these patients is distal symmetric polyneuropathy of limbs that can be sensory or motor and involves small fibers, large fibers, or both [4].

The symptoms of diabetic neuropathy include reduced sensation, numbness, burning sensation, and pain, especially in the lower extremities due to nerve damage [5, 6]. Reduction of protective sensation, such as vibration, pressure, and pain, in patients with diabetic neuropathy may change the pattern of pressure distribution on the foot’s plantar side, leading to gait variability, disturbing balance control, and increasing the risk of diabetic foot ulcers [7]. Tactile sensation and proprioception of the foot are important in postural control as they provide feedback and feedforward information and play an important role in balance and walking [8, 9].

The most effective strategy to prevent complications of diabetic neuropathy is to control blood glucose [10], but medications are also available for the treatment of diabetic neuropathy [11]. The FDA approves pregabalin and Duloxetine to treat diabetic neuropathy [11], but their use may be limited by side effects and interaction with other medications [12].

Physical modalities, including electrical stimulation and exercise, can be used to manage the symptoms in patients with diabetic neuropathy [13, 14]. One of the physical modalities used in neuropathic patients is the vibration in both the whole body and local vibration. Whole-body vibration effects are well studied in patients with diabetic neuropathy, which is shown to have positive effects on balance, muscle strength, and neuropathic pain [15–17].

Local vibration is an available and inexpensive intervention used to treat chronic pain [18], but there are limited studies on the effects of local vibration on diabetic peripheral neuropathy (DPN). In a study, Stambolieva et al. found that eight weeks of plantar vibration has positive effects on pain relief and postural stability in patients with DPN [19].

To summarize, peripheral neuropathy is one of the common complications of diabetes, and pharmacological agents and physical modalities are used for its management. Local vibration is one of the physical modalities used to treat DPN but studies on its effectiveness are limited. In this case report, we reported the positive effects of plantar vibration on DPN symptoms.

Methods

Design

This was a single case study to evaluate the effects of local plantar vibration in a diabetic patient with DPN.

Subject

The patient was a 50-years old female with a 10–years history of type 2 diabetes. The patient was taking Metformin tablets to control blood glucose. HbA1c level was 9% in the patient, suggesting poor blood glucose control [20], putting her at a higher risk for diabetes complications, including diabetic neuropathy [10].

She reported numbness, burning pain, tenderness, and cramping in her legs and feet, worsening at night. She had used gabapentin and other medications for her pain, but none were effective. The patient had no wound on the foot surface and was able to walk independently. The patient’s both feet were dry and callous was formed in both feet. Also, ankle reflex did not exist. Distal symmetrical peripheral neuropathy) DSPN) confirmed by the electromyography (EMG), and Nerve Conduction Study (NCS) (Table 1). The sural nerve activity was absent in both feet.

Table 1.

EMG and NCS report

Nerve(Site)	Latency,ms	Amplitude, μv	NCV, m/s
Peroneal left (Ankle)	6.3	0.54	35.2
Peroneal right (Ankle)	5.3	0.57	32.2
Tibial left (Ankle)	5.4	1.8	30.2
Tibial right (Ankle)	5.6	2.2	34

The patient’s neuropathy score was 7 out of 10 based on the Michigan Neuropathy Screening Instrument (MNSI), and the score of the history section of MNSI was 8 out of 13.

Intervention

Before starting the treatment, we explained the procedure to the patient, and informed consent was obtained. The patient was positioned in a crook lying on the bed with a pillow under the knees. The patient wore no shoes and socks. The room temperature was set to 25 °C. A local vibration with a frequency of 62.5 Hz for 10 min was applied to the plantar side of both feet. The device was placed on a footstool, out of bed. The patient was treated for five sessions every other day. The patient did not receive any medication for the treatment of neuropathy during the treatment sessions.

Assessments

The balance was assessed by the Persian version of the brief Balance Evaluation Systems Test (Brief BESTest) [21–23]. This test has eight items in six sections evaluating systems attributing to balance. Items are scored from 0 to 3, with higher scores are dedicated to better performances. The total score is the sum of all item scores, ranging from 0 to 24 [21–23].

Semmes Weinstein 5.07 Monofilament (North Coast Medical Inc, USA) was used on 9 points on the plantar side of both feet, including the plantar surface of the first, third, and fifth metatarsophalangeal joints, first, third and fifth toes, the base of the first and fifth metatarsus and the heel and another one on the dorsal aspect of the foot to evaluate protective sensation. The monofilament was applied until it buckled and held for 1 s. Examiner demonstrated the monofilament sensation on one of the patient’s hands before examining the feet. The patient closed her eyes and said yes if she sensed the monofilament on her feet. An examiner recorded the patient’s test results, correct or incorrect, for each site on a diagram of the two feet and recorded each foot’s total correct score.

Vibrating sensation and threshold were assessed by a 128 Hz tuning fork (Rydal Seifer, Germany) on the dorsal side of the hallux’s interphalangeal joint and was graded from 0 (no sense) to 8 (normal sensation). Examiner demonstrated the sensation of vibration on the patient’s sternum before examining the feet. Examiner was instructed to gently strike the tuning fork against the palm so that vibration could be felt for 10 to 15 s. When the patient had no longer felt the vibration, the examiner recorded the score.

The feet’ temperature was measured using a handheld digital thermometer (Beurer company of Germany) in three plantar sides of the first and second metatarsal head and heel.

The patient scored pain or any unpleasant sensation in the feet using the Numerical Pain Rating Scale (NPRS) from 0 (no pain) to 10 (most possible pain).

The examiner evaluated the patient using the mentioned tests before the treatment.

Results

After five sessions of treatment, the vibration threshold of both feet was improved to the highest score. Also, pain severity was reduced by 62.5% in both feet, based on NPRS. The number of sensitive points in both feet improved by five points. Also, the protective sensation of the right foot became normal at the end of treatment. The patient’s brief BESTest score increased from 10 to 16 after five sessions of treatment. The temperature of all assessed points was increased after five sessions of treatment. Table 2 summarizes the outcomes.

Table 2.

Results of the evaluations of the patient before and after the treatment

	Before treatment	After the first session of treatment	After the fifth session of treatment
NPRS
Right foot	8	8	3
Left foot	8	8	3
Vibration threshold
Right foot	4	5	8
Left foot	5	6	8
Protective sensation
Right foot	5	8	10
Left foot	1	5	6
Brief BESTest	10	13	16
Temperature
First metatarsal head (right)	33.6	34.7	34.3
First metatarsal head (left)	32	32.8	33.1
Second metatarsal head (right)	33.5	34.7	34.2
Second metatarsal head (left)	32.4	33	33.5
Right heal	34.2	34.6	34.5
Left heal	34.1	33.6	35

Discussion

In this case report, we reported the successful use of plantar vibration in the treatment of DPN, improving vibration and protective sensation, balance, feet’s temperature, and relieving pain. Whole-body vibration was used to treat DPN [15–17], but local vibration is not well studied in this regard yet.

In previous studies, whole-body vibration was found to be effective in increasing blood flow of lower extremities in healthy adults and patients with diabetes [24, 25]. We evaluated the foot skin temperature as an indicator of blood flow [26]. Skin temperature was increased in both patients’ feet, indicating an improvement in the blood flow. An increase in the blood flow after vibration may be due to Nitric Oxide (NO) production [27], which has vasodilatory effects [28], in response to the shear force at vascular endothelium after the application of vibration [29]. However, production of NO is lower in diabetic patients compared to healthy adults [24, 27], and other mechanisms may also play a role.

Although we did not find any acute relief in neuropathic pain after one treatment session, after five sessions, the patient reported a 62.5% decrease in foot pain. This finding is in line with Stambolieva et al. study, as they reported a significant decrease in diabetic patients’ feet pain, tingling, and weakness after eight weeks of plantar vibration training [19]. Whole-body vibration also positively affects acute and chronic pain in patients with DPN [15]. Pain relief may be due to simultaneous stimulation of nerves with pain and vibration, as stimulation of large diameter sensory neurons with vibration reduces pain signals transmission, as described by Melzack in gate control theory [30, 31].

Sense of vibration in patient’s both feet returned to normal after the treatment. Also, protective sensation improved in both patient’s feet. Stambolieva et al. found that plantar vibration training can improve the NCV results of Peroneal and Sural nerves in patients with DPN [19]. Improvement in the blood flow following the vibration may be the reason for the improvement in nerves’ sensory function, as microangiopathy is one of the factors responsible for neuropathy progression [32]. Sensory deficits also lead to balance impairment [33], and improved somatosensory function enhances the balance [34], which may be why our patient had better balance function after treatment. Brief BESTest evaluated the systems responsible for maintaining the balance, including biomechanical constraints, stability limits, transitional-anticipatory postural adjustments, reactive postural responses, sensory orientation, and gait stability [23]. Improvement in brief BESTest score may indicate an overall improvement in the patient’s balance and related systems.

Conclusion

Plantar local vibration is a promising modality for the treatment of pateitns with DPN. We found an overall improvement in the patient’s sensory function, balance, and pain relief after five treatment sessions. Future clinical trials with longer follow-up are suggested for better evalution of local vibration effects in patients with PDN.

Authors’ contributions

SN, MS, and HRF contributed in the patient’s care. All authors contributed in preparing the manuscript.

Data availability

All relevant data are reported in the manuscript.

Declarations

Consent to participate

The patient provided a written informed consent to participate in the study.

Consent for publication

We obtained a written consent from the patients to prepare and publish this manuscript.

Conflict of interest

Authors have no conflict of interest to declare.