Ultrasound-Guided Approach to the Distal Tarsal Tunnel: Implications for Healthcare Research on the Medial Plantar Nerve, Lateral Plantar Nerve and Inferior Calcaneal Nerve (Baxter's Nerve).

BACKGROUND/OBJECTIVES: The tibial nerve, commonly misnamed the "posterior tibial nerve", branches into four key nerves: the medial plantar, lateral plantar, inferior calcaneal (Baxter's nerve), and medial calcaneal branches. These nerves are integral to both the sensory and motor functions of the foot. Approximately 15% of adults with foot issues experience heel pain, frequently stemming from neural origins, such as tarsal tunnel syndrome (TTS). TTS diagnosis remains challenging due to a high false negative rate in neurophysiological studies. This study aims to improve the understanding and diagnosis of distal tarsal tunnel pathology to enable more effective treatments, including platelet-rich plasma, hydrodissections, radiofrequencies, and prolotherapy. METHODS: Ultrasound-guided techniques were employed to examine the distal tarsal tunnel using the Heimkes triangle for optimal probe placement. RESULTS: The results indicate that the tunnel consists of two chambers separated by the interfascicular septum, housing the medial, lateral plantar, and inferior calcaneal nerves. Successful interventions depend on precise visualization and patient positioning. This study emphasizes the importance of avoiding the calcaneus periosteum to reduce discomfort. CONCLUSIONS: Standardizing nerve involvement classification in TTS is difficult without robust neurophysiological studies. The accurate targeting of nerve branches is essential for effective treatment.

Anatomical Exploration of the KI1 Acupoint: Implications for Medial and Lateral Plantar Nerve Stimulation.

Background and Objectives: This study aims to identify the precise anatomical location and therapeutic mechanisms of the KI1 acupoint (Yongquan) in relation to foot muscles and nerves, known for treating neurological disorders and pain. Materials and Methods: Dissection of six cadavers at Chungnam National University College of Medicine examined KI1's relation to the foot's four-layer structure. Results: The KI1 acupoint was located in the superficial and deep layers of the plantar foot, adjacent to significant nerves like the medial and lateral plantar nerves. Differences in the acupoint's exact location between genders were noted, reflecting variances in foot morphology. KI1 acupuncture was found to stimulate the muscle spindles and nerve fibers essential for balance and bipedal locomotion. This stimulation may enhance sensory feedback, potentially improving cognitive functions and balance control. Conclusions: This anatomical insight into KI1 acupuncture underpins its potential in neurological therapies and pain management.

An anatomical approach to the tarsal tunnel syndrome: what can ankle's medial side anatomy reveal to us?

BACKGROUND: The heel is a complex anatomical region and is very often the source of pain complaints. The medial heel contains a number of structures, capable of compressing the main nerves of the region and knowing its anatomical topography is mandatory. The purpose of this work is to evaluate if tibial nerve (TN) and its main branches relate to the main anatomical landmarks of the ankle's medial side and if so, do they have a regular path after emerging from TN. METHODS: The distal part of the legs, ankles and feet of 12 Thiel embalmed cadavers were dissected. The pattern of the branches of the TN was registered and the measurements were performed according to the Dellon-McKinnon malleolar-calcaneal line (DML) and the Heimkes Triangle (HT). RESULTS: The TN divided proximal to DML in 87.5%, on top of the DML in 12,5% and distal in none of the feet. The Baxter's nerve (BN) originated proximally in 50%, on top of the DML in 12,5% and distally in 37.5% of the cases. There was a strong and significant correlation between the length of DML and the distance from the center of the medial malleolus (MM) to the lateral plantar nerve (LPN), medial plantar (MPN) nerve, BN and Medial Calcaneal Nerve (MCN) (ρ: 0.910, 0.866, 0.970 and 0.762 respectively, p <  0.001). CONCLUSIONS: In our sample the TN divides distal to DML in none of the cases. We also report a strong association between ankle size and the distribution of the MPN, LPN, BN and MCN. We hypothesize that location of these branches on the medial side of the ankle could be more predictable if we take into consideration the distance between the MM and the medial process of the calcaneal tuberosity.

Neuromodulation of spinal reflex pathway for the treatment of detrusor overactivity by medial plantar nerve stimulation at surface of sole of foot in patients with spinal cord injury.

Objectives: Suprasacral spinal cord lesions are prone to have neurogenic detrusor overactivity leading to urinary incontinence. Current medical management has known side-effects and often surgical managements are irreversible. Electrical stimulation to modulate spinal reflex pathway having same nerve root as urinary bladder is reported in the literature. This study aimed to reduce detrusor overactivity in patients with spinal cord injury (SCI) using surface electrical stimulation of medial plantar nerve at the sole of foot. Materials and Methods: Twenty adults with SCI having episode of at least 1 leak/day due to detrusor overactivity as diagnosed by cystometrogram (CMG), were on clean intermittent catheterization and ankle jerk was present consented for the study. Participants were asked to maintain bladder diary a week before and during 2 weeks of treatment. CMG was done on day-0 and day-14. cmcUroModul@tor®, an inhouse developed electrical stimulator was used for ½ h daily for period of 2 weeks. Patient satisfaction feedback questionnaire was taken on completion of treatment. CMG data were analyzed using Wilcoxon signed-ranked test while bladder diary was analyzed using binomial distribution. P < 0.05 was considered as statistically significant. Institutional Review Board (IRB) and ethics committee of Christian Medical College, Vellore, approved the study (CMC/IRB/11061). Results: Statistical significant improvement in maximum detrusor pressure (P = 0.03) and cystometric capacity (P = 0.04) was observed. Of 20 subjects, 18 showed improvement in bladder diary. Conclusion: Neuromodulation of medial plantar nerve at sole of foot by surface electrical stimulation is non-invasive, cost-effective, and alternative simple treatment modality for urinary incontinence due to detrusor overactivity.

Transcutaneous medial plantar nerve stimulation in women with idiopathic overactive bladder.

PURPOSE: To define transcutaneous medial plantar nerve stimulation (T-MPNS) as a new neuromodulation method and assess the efficacy of T-MPNS on quality of life (QoL) and clinical parameters associated with incontinence in women with idiopathic overactive bladder (OAB). MATERIALS AND METHODS: Twenty-one women were included in this study. All women received T-MPNS. Two self-adhesive surface electrodes were positioned with the negative electrode near the metatarsal-phalangeal joint of the great toe on the medial aspect of the foot and the positive electrode 2 cm inferior-posterior of the medial malleolus (in front of the medio-malleolar-calcaneal axis). T-MPNS was performed 2 days a week, 30 minutes a day, for a total of 12 sessions for 6 weeks. Women were evaluated for incontinence severity (24-h pad test), 3-day voiding diary, symptom severity (Overactive Bladder Questionnaire [OAB-V8]), QoL (Quality of Life-Incontinence Impact Questionnaire [IIQ-7]), positive response and cure-improvement rates, and treatment satisfaction at baseline and at the 6th week. RESULTS: Statistically significant improvement was found in the severity of incontinence, frequency of voiding, incontinence episodes, nocturia, number of pads, symptom severity, and QoL parameters at the 6th week compared with baseline. Treatment satisfaction, treatment success, and cure or improvement rates were found to be high at the 6th week. CONCLUSIONS: T-MPNS was first described in the literature as a new neuromodulation method. We conclude that T-MPNS is effective on both clinical parameters and QoL associated with incontinence in women with idiopathic OAB. Randomized controlled multicenter studies are needed to validate the effectiveness of T-MPNS.

Segmental Schwannomatosis of the Lower Extremity - A Case Series.

Segmental schwannomatosis involving a nerve in single limb is uncommon. Schwannomatosis is used to describe a distinct clinicopathological disease of multiple schwannomas without manifestations of neurofibromatosis, and it is termed segmental when a single extremity is involved. Surgery is indicated when there is progressive clinical deterioration or progressive increase in size of the tumors. We present a case series of segmental schwannomatosis involving the lower limb.

Which combined nerve conduction study scores are best suited for polyneuropathy in diabetic patients?

INTRODUCTION/AIMS: Nerve conduction studies (NCS) are widely used in diagnosing diabetic polyneuropathy. Combining the Z scores of several measures (Z-compounds) may improve diagnostics by grading abnormality. We aimed to determine which combination of nerves and measures is best suited for studies of diabetic polyneuropathy. METHODS: Sixty-eight patients with type 1 diabetes and 35 controls were included in this study. NCS measurements were taken from commonly investigated nerves in one arm and both legs. Different Z-compounds were calculated and compared with reference material to assess abnormality. A sensitivity proxy, the accuracy index (AI), and Cohen's d were calculated. RESULTS: Z-compounds with the highest AI consisted of the tibial and peroneal motor, and the sural, superficial peroneal, and tibial medial plantar sensory nerves in one or two legs. All Z-compounds were able to discriminate between diabetic subjects and nondiabetic controls (mean Cohen's d = 1.42 [range, 1.03-1.63]). The association between AI and number of measures was best explained logarithmically (R2  = 0.401), with diminishing returns above approximately 14 or 15 measures. F-wave inclusion may increase the AI of the Z compounds. Although often clinically useful among the non-elderly, the additional inclusion of medial plantar NCS into Z-compounds in general did not improve AI. DISCUSSION: Performing unilateral NCS in several motor and sensory lower extremity nerves is suited for the evaluation of polyneuropathy in diabetic patients. The use of Z-compounds may improve diagnostic accuracy in diabetic polyneuropathy and may be particularly useful for follow-up research studies as single summary measures of NCS abnormality development over time.

Predictive Outcome Modeling of Preoperative Clinical Symptoms and Electrodiagnostic Data in Tarsal Tunnel Surgery.

Background The relationship between tarsal tunnel syndrome (TTS), electrodiagnostic (Edx) findings, and surgical outcome is unknown. Analysis of TTS surgical release outcome patient satisfaction and comparison to Edx nerve conduction studies (NCSs) is important to improve outcome prediction when deciding who would benefit from TTS release. Methods Retrospective study of 90 patients over 7 years that had tarsal tunnel (TT) release surgery with outcome rating and preoperative tibial NCS. Overall, 64 patients met study inclusion criteria with enough NCS data to be classified into one of the following three groups: (1) probable TTS, (2) peripheral polyneuropathy, or (3) normal. Most patients had preoperative clinical provocative testing including diagnostic tibial nerve injection, tibial Phalen's sign, and/or Tinel's sign and complaints of plantar tibial neuropathic symptoms. Outcome measure was percentage of patient improvement report at surgical follow-up visit. Results Patient-reported improvement was 92% in the probable TTS group ( n = 41) and 77% of the non-TTS group ( n = 23). Multivariate modeling revealed that three out of eight variables predicted improvement from surgical release, NCS consistent with TTS ( p = 0.04), neuropathic symptoms ( p = 0.045), and absent Phalen's test ( p = 0.001). The R 2 was 0.21 which is a robust result for this outcome measurement process. Conclusion The best predictors of improvement in patients with TTS release were found in patients that had preoperative Edx evidence of tibial neuropathy in the TT and tibial nerve plantar symptoms. Determining what factors predict surgical outcome will require prospective evaluation and evaluation of patients with other nonsurgical modalities.

Ultrasound-guided topographic anatomy of the medial calcaneal branches of the tibial nerve.

BACKGROUND: The purpose of this study was to evaluate the topographic anatomy of the tibial nerve and its medial calcaneal branches in relation to the tip of the medial malleolus and to the posterior superior tip of the calcaneal tuberosity using the ultrasound examination and to verify its preoperative usefulness in surgical treatment. MATERIALS AND METHODS: Bilateral ultrasound examination was performed on 30 volunteers and the location of the tibial nerve bifurcation and medial calcaneal branches origin were measured. Medial calcaneal branches were analysed in reference to the amount and their respective nerves of origin. RESULTS: In 77% of cases, tibial nerve bifurcation occurred below the tip of the medial malleolus with the average distance of 5.9 mm and in 48% of cases above the posterior superior tip of the calcaneal tuberosity with the average distance of 2.7 mm. In 73% of cases medial calcaneal branches occurred as a single branch originating from the tibial nerve (60%). The average distance of the first, second and third medial calcaneal branch was accordingly 9.3 mm above, 9.5 mm below and 11.6 mm below the tip of the medial malleolus and 17.7 mm above, 1.6 mm below and 4 mm below the posterior superior tip of the calcaneal tuberosity. CONCLUSIONS: As the tibial nerve and its branches present a huge variability in the medial ankle area, in order to prevent the iatrogenic injuries, the preoperative or intraoperative ultrasound assessment (sonosurgery) of its localisation should be introduced into the clinic.

MRI appearance of jogger's foot.

OBJECTIVE: To characterize the MRI findings present in patients with clinically proven or suspected jogger's foot. MATERIALS AND METHODS: Ten years of medical charts in patients clinically suspected of having jogger's foot and who had MRI studies completed were identified utilizing a computer database search. Six study cases were identified. The MRI examinations of the study cases and an age- and gender-matched control group were reviewed in a blinded fashion by two musculoskeletal radiologists. Size and signal intensity of the medial plantar nerve were measured and characterized. The medial foot musculature was assessed for acute or chronic denervation changes. RESULTS: The medial plantar nerve was found to have moderately increased T2 signal compared with normal skeletal muscle in 3/6 study group cases and markedly increased T2 signal in the remaining 3/6 cases. In all control cases, the nerve was reported to have T2 signal equal or minimally higher than normal skeletal muscle. The mean total size of the medial plantar nerve was significantly larger in the study group when compared with that in the control group at all measured locations (p < 0.04). CONCLUSIONS: Abnormal thickness and T2 hyperintensity of the medial plantar nerve centered at the master knot of Henry are characteristic MRI findings in patients with jogger's foot when compared with control subjects. Muscular denervation changes may also be seen, most commonly in the flexor hallucis brevis muscle.

Results of ultrasound-guided release of tarsal tunnel syndrome: a review of 81 cases with a minimum follow-up of 18 months.

BACKGROUND: This study aims to analyse the clinical results of ultrasound-guided surgery for the decompression of the tibial nerve, including its distal medial and lateral branches, to treat tarsal tunnel syndrome. These structures are the complete flexor retinaculum and the deep fascia of the abductor hallucis muscle, including individualised release of the medial and lateral plantar nerve tunnels. METHOD: This is a retrospective review of 81 patients (36 men and 45 women) with an average age of 41 years old (32-62) and an average clinical course of 31 months (8-96) compatible with idiopathic tarsal tunnel syndrome, who underwent ultrasound-guided decompression of the proximal and distal tarsal tunnel between February 2015 and November 2017 (both months included), with a minimum follow-up of 18 months. RESULTS: Based on the Takakura et al. scale for the 81 patients, 76.54% obtained excellent results, 13.58% good results, and 9.87% poor results. The patients with the longest course of symptoms displayed the worst results. CONCLUSION: Although 9% of patients did not improve, ultrasound-guided tarsal tunnel release might be a viable alternative to conventional open approaches.

Superficial course of the medial plantar nerve: case report.

The medial and lateral plantar nerves are branched from the tibial nerve and move to the tip of the toes. A variation of medial plantar nerve was found on the left side of a 78-year-old Korean male cadaver. The tibial nerve was divided into the lateral and medial plantar nerves beneath the plantar flexor. The medial plantar nerve passed deep to plantar aponeurosis and superficial to the flexor digitorum brevis. It gave off a common plantar digital nerve and then divided into three proper plantar digital nerves near the metatarsal bases. In this article, we report a superficial course of the medial plantar nerve and describe its unique morphology and discuss the clinical significance of this variation.

Interfascicular septum of the calcaneal tunnel and its relationship with the plantar nerves: A cadaveric study.

The relationship between the plantar nerves and internal fascial structure of the calcaneal tunnel is clinically important to alleviate pain of the sole. The study aimed to investigate the three-dimensional (3D) anatomy of the calcaneal tunnel and its internal fascial septal structure by using microcomputed tomography (mCT) with a phosphotungstic acid preparation, histologic examination, and ultrasound-guided simulation. Twenty-one fixed cadavers and three fresh-frozen cadavers (13 men and 11 women, mean age 82.1 years at death) were used in this study. The 3D images of the calcaneal tunnel harvested by mCT were analyzed in detail. Modified Masson trichrome staining and serial sectional dissection after ultrasound-guided injection were conducted to verify the 3D anatomy. Within the calcaneal tunnel, the interfascicular septum (IFS) commenced proximal to the malleolar-calcaneal line and distal to the bifurcation of the tibial nerve into the plantar nerves. The medial and lateral plantar nerves were separated by the IFS, which divided the calcaneal tunnel into two compartments. The plantar nerves were ramified into two or three branches within each compartment. The IFS terminated around the talocalcaneonavicular joint, and the plantar nerves traveled into the sole. Clinical manipulation of the plantar nerves should be performed in consideration of the fact that they are clearly separated by the IFS. Clin. Anat. 32:877-882, 2019. © 2019 Wiley Periodicals, Inc.

Schwannoma of the plantarmedial aspect of the foot: A case report.

Schwannomas of the common medial plantar nerve branch are rare solitary nerve sheath tumors. Fewer than a dozen cases have since been described in the literature, most of which were initially misdiagnosed as ganglion cysts. The case of a 56-year-old male who developed a painful mass on the plantar medial hallux, misdiagnosed as a ganglion cyst, is presented. After surgical intervention and pathological analysis the patient was diagnosed as having a schwannoma. A schwannoma is a slowly growing neoplasm of Schwann cell origin. It is very rare for a schwannoma to transform into a malignant lesion and usually occurs in individuals between the ages for 20-50. Schwannomas usually have a predilection for the head and upper extremities and is very rare in the foot and ankle. The principal treatment of a schwannoma is surgical excision, which eliminates symptoms and can correctly diagnose the mass. Even though schwannomas of the foot have been reported in literature, this case demonstrates an abnormal location on a branch of the medial plantar nerve. Level of Clinical Evidence: Level 4 of Evidence.

Degenerative subtalar joints complicated by medial plantar intraneural cysts : cutting the cystic articular branch prevents recurrence.

AIMS: The pathogenesis of intraneural ganglion cysts is controversial. Recent reports in the literature described medial plantar intraneural ganglion cysts (mIGC) with articular branches to subtalar joints. The aim of the current study was to provide further support for the principles underlying the articular theory, and to explain the successes and failures of treatment of mICGs. PATIENTS AND METHODS: Between 2006 and 2017, five patients with five mICGs were retrospectively reviewed. There were five men with a mean age of 50.2 years (33 to 68) and a mean follow-up of 3.8 years (0.8 to 6). Case history, physical examination, imaging, and intraoperative findings were reviewed. The outcomes of interest were ultrasound and/or MRI features of mICG, as well as the clinical outcomes. RESULTS: The five intraneural cysts followed the principles of the unifying articular theory. Connection to the posterior subtalar joint (pSTJ) was identified or suspected in four patients. Re-evaluation of preoperative MRI demonstrated a degenerative pSTJ and denervation changes in the abductor hallucis in all patients. Cyst excision with resection of the articular branch (four), cyst incision and drainage (one), and percutaneous aspiration/steroid injection (two) were performed. Removing the connection to the pSTJ prevented recurrence of mIGC, whereas medial plantar nerves remained cystic and symptomatic when resection of the communicating articular branch was not performed. CONCLUSION: Our findings support a standardized treatment algorithm for mIGC in the presence of degenerative disease at the pSTJ. By understanding the pathoanatomic mechanism for every cyst, we can improve treatment that must address the articular branch to avoid the recurrence of intraneural ganglion cysts, as well as the degenerative pSTJ to avoid extraneural cyst formation or recurrence. Cite this article: Bone Joint J 2018;100-B:183-9.

Trifurcation of the tibial nerve within the tarsal tunnel.

The tibial nerve is the larger terminal branch of the sciatic nerve and it terminates in the tarsal tunnel by giving lateral and medial plantar nerves. We present a rare case of trifurcation of the tibial nerve within the tarsal tunnel. The variant nerve curves laterally after branching from the tibial nerve and courses deep to quadratus plantae muscle. Interestingly, posterior tibial artery was also terminating by giving three branches. These branches were accompanying the terminal branches of the tibial nerve.

Anatomic Delineation of Tarsal Tunnel Innervation via Ultrasonography.

OBJECTIVES: High-resolution ultrasonography (US) can play an important role in studying nerves, as it has several advantages. Entrapments of distal tibial nerve branches can be mapped out or diagnosed with selective anesthetic blocks, and US can guide therapeutic procedures, such as radiofrequency ablation and selective infiltrations of specific nerve branches. The aim of this study was to verify that US is an effective method for accurately locating the posterior tibial nerve and its terminal branches, such as the medial calcaneal branch, the first calcaneal branch, and the medial and lateral plantar nerves. METHODS: In this study, we analyzed the correlation between US mapping and real anatomy after cadaveric dissection, assessing the distribution and variability of the tibial nerve and its terminal branches. We used 12 fresh anatomic specimens of the foot and ankle, including the calf. A high-resolution US study of the tibial nerve and its branches was performed. RESULTS: The results of the US studies of the anatomic specimens were drawn as paper diagrams and in data collection tables. Both were completed twice per anatomic specimen, first using the results of the US study and second using the results from dissection of the anatomic specimens; this approach enabled us to compare the results and verify whether the US study and the dissection correlated on the topography of the tibial nerve and its terminal branches. We found almost total agreement between the US and dissection results, with no significant differences between the evaluations. CONCLUSIONS: On the basis of this work, we can conclude that high-resolution US is almost 100% effective as a tool for identifying the tibial nerve and its branches, enabling the specialist to make diagnoses or perform selective treatments on each nerve branch and even to design surgical interventions by observing the patient's anatomy before performing the dissection.

Hypertrophy of the abductor hallucis muscle: A case report and review of the literature.

OBJECTIVES: Muscle hypertrophy is a relatively rare condition that may cause nerve entrapment syndromes. We report the case of a 14-year-old girl with unilateral hypertrophy of the abductor hallucis muscle with entrapment of the medial plantar nerve and review the literature. METHODS: Computed tomography and magnetic resonance imaging revealed unilateral hypertrophy of the abductor hallucis muscle. RESULTS: Two injections of steroid and lidocaine at the point of tenderness resulted in resolution of the pain. CONCLUSIONS: We report a rare case of hypertrophy of the abductor hallucis muscle considered with entrapment of the medial plantar nerve. Treatment of this condition should be selected according to the pathological condition of each patient.

Diagnostic utility of distal nerve conduction studies and sural near-nerve needle recording in polyneuropathy.

OBJECTIVE: The electrodiagnosis of polyneuropathy (PNP) may benefit from examination using near-nerve needle technique (NNT) and from inclusion of distal nerves. This study compared the diagnostic utility of distal nerve conduction studies (NCS) and NNT recording. METHODS: Bilateral NNT and surface recording of the sural nerve and surface recording of the dorsal sural and medial plantar nerves were prospectively done in 91 patients with clinically suspected PNP. Distal NCS were additionally done in 37 healthy controls. Diagnostic reference standard was the final clinical diagnosis retrieved from the patients medical records after 1-4years. RESULTS: The clinical follow-up diagnosis confirmed PNP in 68 patients. Equally high sensitivities of the dorsal sural (72%), medial plantar (75%), and sural nerve with NNT recording (77%) were seen, while the sensitivity of conventional surface recording of the sural nerve was lower (60%). Sural NCS with both NNT and surface recording and dorsal sural NCS showed high specificities (85-95%) and positive predictive values (94-98%), while a lower specificity was seen for the medial plantar nerve (68%). CONCLUSION: NCS of distal nerves, especially the dorsal sural nerve, have high diagnostic power equalling sural NNT recording. SIGNIFICANCE: The electrodiagnostic evaluation of patients with suspected PNP benefits from NCS of distal nerves.

Medial plantar-to-radial amplitude ratio: does it have electrodiagnostic utility in distal sensory polyneuropathy?

PURPOSE OF THE STUDY: We proposed a new electrophysiological parameter medial plantar (MP)-to-radial amplitude ratio (MPRAR), similar to sural-to-radial amplitude ratio (SRAR), in the diagnosis of distal sensory polyneuropathy (DSP), based on the concept that distal nerves are affected more and earlier than proximal nerves in axonal neuropathies. We aimed to investigate the diagnostic sensitivity of this parameter in diabetic DSP, together with sensitivities of SRAR and MP nerve action potential (NAP) amplitude. MATERIALS AND METHODS: In 124 healthy controls and 87 diabetic patients with clinically defined DSP and normal sural responses, we prospectively performed sensory nerve conduction studies (NCS), and evaluated the MP NAP amplitude, MPRAR and SRAR values. We determined the lower limits of normal (LLN) of these parameters in the healthy controls and calculated their sensitivities and specificities in detecting DSP in diabetic patients. RESULTS: MP nerve amplitude and MPRAR values were significantly lower in the patient group, compared to controls. However, SRAR values did not differ significantly between the two groups. The LLN of MP NAP amplitude was found to be 4.1 µV. The cutoff values for SRAR and MPRAR were determined as 0.24 and 0.16, respectively. MPRAR was abnormal in 21.8% of patients. However, the most sensitive parameter in detection of DSP was MP NAP amplitude, which showed a sensitivity of 31% and a specificity of 100%. CONCLUSIONS: Although MPRAR is more sensitive than SRAR in detecting DSP, it does not provide additional diagnostic yield to the assessment of MP NCS alone in diabetic DSP patients with normal sural responses.